what's going on besties this is everything you are going to need to know all in one place for the ait's version 7 portion of the exam specifically the life and physical sciences let's get started so when we think about biological systems they're structured across multiple layers each one is integral to understanding the entirety of life processes the first level that we're going to explore is the cell it's the most Elementary unit of life but is there anything smaller than a cell well yes indeed there is within cells that house organel these organel are smaller than the cells themselves moreover we have biomolecules which play crucial roles within the cell and are tinier than the cells themselves and even further down as we have atoms we can break those down further into subatomic particles which are again even smaller than the cells however for the te's we're going to begin at at the cellular level which is the fundamental unit of life this is the universal truth regardless if you're a bacterium a fungus protus plant or animal all living things are going to be Cellular in nature when these numerous cells collaborate to perform unified functions they form what is known as tissues marking the subsequent level of biological organization cardiac muscle tissue for example consists of cardiac muscle cells working in concert together to make our heartbeat these tissues can then combine to compose organs representing that third tier of our hierarchy of biological structures your body is composed of numerous organs such as your heart your lungs and your kidneys when these organs collaborate inside of our body they are going to form what we call an organ system let's take the digestive system for example it encompasses various organs including our St stomach our small intestine large intestine and liver they all work together in harmony to Aid the digestion of food and the conversion of that food into energy necessary for cellular processes the digestive system is merely one instance of an organ system when you interconnect all of these organ system together what emerges an individual an organism just like you there are additional biological hierarchies including population community ecosystem biomes and biospheres but for the purposes of the aits this is the group that you should focus on our first practice question is in the context of biological organization which of the following sequence correctly orders the hierarchy from simplest to the most complex is it A B C or D and the correct answer is a cells tissues organ organ systems and organisms as we we know the correct answer is always going to start with our cells that's the basic unit of life cells group together to form tissues which combine to create organs these organs work together in organ systems and then of course multiple organ systems are going to create the organism that is what we are our next question states which statement accurately describes the relationship between organ systems and organisms and biological hierarchy is it a organ systems exist independently of organisms and do not interact with each other is it B an organism is composed of multiple cells bypassing the need for an organ system is it C organ systems are composed of organs that work independently to support an organism's life or is it D organisms are comprised of multiple organ systems working together to ensure survival and the correct answer is D organisms are comprised of multiple organ systems working together to ensure survival if these systems did not work together we wouldn't really survive very long long so yes the correct answer is going to be D now that we have a basic understanding of biological hierarchy let's get down and dirty when it comes to cells modern cell theory encompasses several key principles firstly it states that cells represent the most fundamental unit of life across all organisms secondly it asserts that every living entity is composed of cells which may be singular like we see with bacteria which is a unicellular organism or could be made up of multiple cells making them multicellular like humans the third principle states that cells arise only from existing cells highlighting their capability to replicate when you think about it cells are complex entities that house genetic material and are capable of division they have internal structures or organel that perform various functions and processes on Earth cells are categorized by two principal types reflecting the diversity of life cellular foundations within the cellular world you are classified as either procaryotes or eukaryotes bacteria and ARA all both fall within the procaryote category while fungi protus animals and plants all fall within the UK carot category both of these categories share common features such as genetic materials cytoplasm and ribosomes each are small organel responsible for protein synthesis additionally they both have cell membranes that regulate the passage of substances in and out of the cell however the distinction between them is pretty significant procaryotes suggest that with the prefix pro meaning no that's going to be a memory trick for you to remember for the atits is that they lack a nucleus that houses and manages genetic information furthermore they do not have membranebound organel which are more complex structures like a nucleus mitochondria and ggia apparatus like we find with our UK Cario cells so whenever I'm trying to remember which one has a nucleus and which one has membrane bound organel I use this pneumonic Pro means no which means they don't have those and youu means do which means that they do have those you might now be curious about the roles of organel what functions do they serve well let's begin by talking about the cell membrane also referred to as the plasma membrane this barrier has selective permeability which means that it allows only specific materials in and out of the cell The Selective entry and exit Point helps maintain stability within the cell and state known as homeostasis once we get inside the cell we are immersed with a jellylike substance known as the cytoplasm this substance envelops all of the cell's internal structures and it's present in both procaryotes and ukar contrary to what one might assume the organel floating within the cytoplasm receive substantial support this support comes from the cytoskeleton it's an intricate network of fibers that not only provides structural support for the cell but it also plays a crucial role in cellular movement navigating our way through the cytoplasm we encounter ribosomes first notably ribosomes are not enclosed by membranes and are found in both procaryote and ukar cells their primary function is protein synthesis this is a critical process since a significant portion of genetic material also known as DNA is dedicated to coating for proteins ribosomes May either float freely within the cytoplasm or it can be anchored to another organel which is a topic we're going to discuss very soon shifting our attention to organel exclusive to UK carots we now EXP exp or those that are encased in membranes this ultimately brings us to our key player the nucleus often considered the control center of UK carotic cells it's here within the nucleus that our DNA is housed and stored while all cells do possess DNA and UK carots it's neatly contained inside the nucleus the nucleus oversees the cell's operations and houses the nucleos which is a specialized area where ribosomes are assembled next up the endoplasmic reticulum adjoining to the nucleuses membrane or nuclear envelope plays a crucial role in the cell's operations this organel is going to be instrumental in processing molecules such as the folding of proteins and serves as the primary conduit when it comes to transporting throughout the cell much like a cellular Highway the endoplasm reticulum comes in two forms we have rough ER which is studed with ribosomes lending to the name rough in its appearance and we have smooth ER which is going to lack those ribosomes the rough ER is particularly active in the synthesis and transport of proteins it's a direct consequence of its association with ribosomes which are the cellular Machinery responsible for protein synthesis molecules exiting this ER is often enclosed in vesicles that bud from the ER itself on the other hand our smooth has a much broader range of functions including detoxification which is a vital process especially abundant in liver cells due to their high content of having smooth ER additionally to detoxification the smooth ER is involved in synthesis of certain types of lipids further diversifying its functional portfolio moving on to the gold G apparatus often regarded as the cell's Premier packaging and Distribution Hub it accepts materials from transport vesicles that have detached from the ER employing enzymes to modify these receiving molecules and organizing them accordingly the Gogi apparatus also decides the destination of these molecules including directing some of the cell membrane for secretion effectively expelling them from the cell amidst all of these cellular activities that are taking place you might begin to question what exactly is fueling them enter the mighty monondach condre if we're referring to just one these organel function like cellular power plants generating ATP energy through a process known as cellular respiration unlike conventional power plants mitochondria operates on glucose it's a type of sugar and requires oxygen to produce ATP energy efficiently in addition to mitochondria plant cells boast remarkable organel known as chloroplasts chloroplasts are capable of synthesizing glucose through the process of phot photosynthesis which harnesses light energy their green appearance is attributed to the pigment that they absorb from light energy reflecting green light back giving plants their colorful characteristic lomes often dub the cells waist deposal system are membranebound organel filled with enzymes that break down biomolecules such as proteins lipids and carbohydrates they play a crucial role when it comes to digesting cellular debris unwanted materials as well as invasive organisms like bacteria maintaining cellular cleanliness and recycling materials that are reused by the cell vacul on the other hand are large fluid-filled sacks find predominantly in plant cells though they are also present in some animal and fungal cells their functions are going to vary including storing nutrients and waste products to maintaining internal hydrostatic pressure within the cell and sequest uring harmful materials in plants vacul are pivotal when it comes to growth because they absorb water and expand enabling the cell to grow larger with minimal investment of new biomass now let's do some practice on everything we just learned which of the following cell components is primarily responsible for assembling proteins using instructions encoded in mRNA is it the nucleus ribosomes ggia apparatus or mitochondria yeah and the correct answer is B our ribosomes so again our ribosomes are those cellular structures responsible for protein synthesis so they actually read the sequence of mRNA and assemble amino acids into proteins based on what was coated in the instructions the nucleus houses that DNA the gogia apparatus modifies and packages the proteins and the mitochondria are involved in energy production But ultimately it's those ribosomes that're going to be directly related to syn synthesizing proteins which organel is known as the PowerHouse of the cell due to its role in producing ATP which is the cell's main energy currency is it the chloroplast the nucleos mitochondria or endoplasmic reticulum and the correct answer is C mitochondria like we talked about before that mitochondria is responsible for producing ATP also known as adenosine triphosphate they do this through a process of cellular respiration ation which is why they're often referred to as the PowerHouse of the cell our cor paaths are involved in photosynthesis when it comes to plant cells our nucleos is involved in ribosome production inside our nucleus and of course our endoplasmic reticulum is involved in protein and lipid synthesis as well as processing so let's talk about the differences between mitosis and meiosis initially I approached learning about mitosis and meiosis say two distinct topics a direct comparison laid out side by side would have been significantly better and aided me in understanding it which is why I'm going to teach it like this today so what are the key differences well mitosis is actually going to lead to the formation of somatic cells also known as body cells while meiosis is going to produce reproductive cells known as gtes which is sperm and egg cells let's consider the initial state of a cell involved in both processes both are going to start off as a diploid cell designated by 2 N this just simply means that they contain two complete sets of chromosomes for humans this means that one set of 23 chromosomes were inherited from their mother and the other set of 23 chromosomes was inherited from their father totaling a total of 46 chromosomes during the interface stage the cell replicates its chromosomes even after duplicating 46 chromosomes the chromosom count is still referred to as 46 because the copies known as chromatids remain joined at the region called the centrom miror effectively doubling the chromatid number to 92 and although interface does proceed both mitosis and meiosis is not technically part of their process however it is a crucial phase for chromosome duplication setting the stage for the ultimate cell division that we're going to discuss and by the way illustrating a full 46 human chromosomes can be a little challenging so for the sake of clarity and ease visualization of our diagrams we're only going to use six chromosomes to help us understand these Concepts so in order to help us understand cell division we're going to use the acronym Pat which stands for the sequences of both mitosis and meiosis however the only difference is is that meiosis includes these stages twice resulting in each phase being de designated with a numerical suffix like we see with prophase 1 metaphase 1 so on and so forth while we're going to outline the basic events that occur during the pmat stages for the aits it's really important for you to understand that everything we're talking about is barely scratching the surface of all the intricate details that are taking place when it comes to the aits this is what you're going to need to know so during mitosis prophase is going to be that initial stage when it comes to division it's indicated by the prefix of pro which means before this is when chromosomes become more visible as they condense ultimately becoming thicker in contrast prophase one of meiosis features not only chromosome condensing but they're also going to start pairing up in homog chromosomes these hogus chromosomes are roughly equal in size Gene type and location one came from the mother and one came from the father this stage is going to allow for the exchange of genetic material between chromosomes through a process called crossing over this is going to lead to the creation of recumbent chromosones which are essential for genetic diversity next up we have metaphase so in mitosis that nuclear envelope that was previously enclosed in the nucleus has already been dismantled by the time that this face begins a pneumonic when it comes to metaphase is we remember that m stands for Middle as during this phase the chromosomes are going to a line in the cell center forming a single Row in contrast in metaphase 1 of meiosis while chromosomes are gathering in the cell's Central Area they're going to remain in those pair of their homologous counterparts therefore the alignment is not going to be a single row but rather a pair of chromosomes standing together in the middle during anaphase of mitosis a helpful pneumonic to remember that is to associate a with a away at this phase the chroma are going to be separated and Drawn to opposite ends of the cell by spindle fibers in the context of meiosis anaphase 1 is going to mirror this concept but with a crucial distinction it is the chromosomes rather than the chromatids they're going to be moved away to opposite ends of the cell in both mitosis and meiosis specifically telease one of meiosis chromosomes are going to reach the opposite sides of the cell and the process of forming new nuclear envelopes around these chromosome sets are going to begin setting the stage for the creation of two brand new cells each new nuclei is going to encapsulate the chromosomes on each side Paving the way for the cell to eventually divide into two separate entities following that nuclear division stage is cyto kinesis that is the partitioning of the cytoplasm is going to finalize that cell division process thus at the conclusion of mitosis and cytokinesis two genetically identical diploid cells are going to be produce both having 46 chromosomes in humans this process is crucial for an organism's growth as generating more cells is going to be essential for development and for the repair and replacement of damaged cells well that's it for mitosis let's move on to meiosis part two so in prophase 2 we observe that the chromosomes are condensing within both cells this phase is less eventful compared to prophase 1 primarily because there's no homologous pairs anymore undergoing crossing over in this stage during metaphase 2 the pneumonic M for the middle applies once again however in this phase the chromosomes are going to align in a single roll down the middle similar to the arrangement that we saw in metaphase of mitosis in anaphase 2 the pneumonic a for away is going to happen and in this stage the chromati SS are going to separate themselves and are going to be drawn to opposite sides of the cells remember during the first stage they were still chromosomes now they are separating their chromosomes into chromatids so this is huge when it comes to meiosis anaphase part two during telophase 2 chromosomes are going to be moved to the furthest opposite ends of the cell and the formation of new nuclear envelopes are going to begin to encapsulate these new divisions leading to the creation of new cells following the completion of meiosis 2 cytokinesis is going to occur dividing the cytoplasm entirely this is going to Mark the conclusion of meiosis resulting in four genetically distinct cells or gtes in this process males are going to produce sperm and females are going to produce egg cells all of them being haid cells carrying half the chromosome count of the original cell for humans each of these gametes contained 20 23 chromosomes notably the fusion of sperm and an egg cell creates a diploid cell or a fertilized egg known as a zygote this zygote is going to undergo numerous mitotic divisions leading to the development of a new organism let's do some practice questions during which phase of meiosis does crossing over occur contributing to genetic diversity by exchanging genetic material between homologous chromosomes is it a prophase 1 B metaphase 2 C anaphase 1 or D telophase 2 and the correct answer is a prophase 1 that crossing over occurs during prophase 1 of meiosis this is when those homologous chromosomes pair up and exchange segments of genetic material leading to genetic variation in resulting gametes which of the following statements accurately distinguishes between mitos is and meiosis in terms of genetic outcomes is it a mitosis results in two genetically identical diploid daughter cells while meiosis produces four genetically unique haploid cells is it B both mitosis and meiosis result in four genetically identical daughter cells is it C mitosis produces four genetically unique diploid daughter cells whereas meiosis results in two genetic genetically identical hloy cells or is it D both mitosis and meiosis produces two genetically unique diploid daughter cells and the correct answer is a mitosis results in two genetically identical diploid daughter cells while meiosis produces four genetically unique haid cells we talked about this a little bit before that mitosis when it comes to Cellular division is going to result in those two genetically identical diploid daughter cells essential for growth and repair and with biosis on the other hand that is a two-step division process that's going to result in those four genetically diverse haid cells also known as gtes which is going to be crucial for sexual reproduction in meiosis homologous chromosones segregate during anaphase 1 what is the significance of this event in terms of genetic variation is it a it ensures that each gami inherits an exact copy of each chromosome reducing genetic diversity is it B it results in the duplication of chromosomes increasing the chromosome number of gametes C it allows for the random assortment of chromosomes contributing to genetic diversity among Offspring or is it D it eliminates the need for crossing over as a means of generating genetic variation and the correct answer is C it allows for the random assortment of chromosomes contributing to genetic diversity among Offspring so during anaphase 1 of meiosis homologous chromosomes are pulled apart to each end of the cell this segregation allows for that random assortment of chromosomes meaning that each gam is going to receive a mix of maternal and paternal chromosomes this is really significant when it comes to assortment because this random assortment is going to contribute to that genetic diversity Among The Offspring as it produces a variety of potential genetic combinations so let's talk about her so heredity explores the transmission of traits from parents to their offspring a complex process that cannot be fully appreciated without a fundamental grasp of DNA chromosones genes and traits let's consider each one of us whose physical characteristics such as body patterns and size are determined by the genetic information coded in our DNA in addition to DNA environmental factors can also influence inherited traits for example our growth could have been impacted with insufficient nutrition contrary to the idea that DNA is a singular hidden code it's actually a widespread code present in the nuclei of almost all of our cells inherited from both our mother and our father another important note is that some animals have the ability to reproduce asexually meaning that an animal could haveed all of its genetic material from just one parent if that were the case for some species nevertheless the essence Remains the Same DNA is responsible for coding the traits that Define us it's essential for self function and it influences everything we've come to know such as our height eye color risk for certain diseases and hair color let's talk about the structure of DNA it's not only beautiful but it's also pivotal in understanding the mechanism of inheritance DNA which also stands for deoxy ribonucleic acid falls into the category of nucleic acids one of our essential biomolecules composed of building blocks known as nucleotides nucleic acids feature three critical components a sugar named deoxy ribos a phosphate group collectively forming what is often referred to as the sugar phosphate backbone of DNA and most importantly we have a base it is the sequence of these bases that encode the genetic information that we've come to know Direct correlating to the traits an organism exhibits in DNA we have four types of bases commonly abbreviated as a T C and G A stands for adenine T stands for thyine C stands for cytosine and G stands for guanine these bases pair up in a specific Manner and a well-known pneumonic can assist in Remembering these pairings we have apples in the tree stands for adenine is going to pair with thum sine and then cars in the garage means that cytosine is going to pair with guanine this base pairing rule of these DNA bases is universal applying to all living entities from animals to plants protest as well as humans however the total number of DNA bases as well as the sequence in which these bases are arranged is going to vary depending on the different species and even individuals within those species underpinning the diversity of life DNA consists of two strands with nucleotides aligned along each side of them in the center the bases of opposite strands are going to pair up connected by hydrogen bonds the structure of DNA is going to twist into what we know as a double helix shape segments of DNA constitutes genes which means specific regions of DNA correspon to individual genes capable of encoding proteins we call these structural genes these proteins are going to play a crucial role when it comes to trait expression take human eye color for example it's a complex trait influenced by multiple genes which direct the production of proteins responsible for the pigmentation that we have in our eyes however proteins are going to influence far beyond just eye color it's also going to Encompass transport structural support enzymatic activity which is facilitating the synthesis of various substances defense mechanisms and so much more it's also important to note that not every Gene is going to be involved in protein synthesis DNA also contains non-coding regions these are what we like to call regulatory genes despite each of our body cells containing a complete DNA code only specific Gene segments may be utilized with certain genes being activated and deactivated through various mechanis isms this process is known as Gene regulation so your body contains a vast amount of DNA which when compacted is organized into structures we know as chromosomes this organization is particularly useful during cell division as it simplifies the process of Distributing DNA into new cells chromosomes consist of DNA coiled around a protein scaffold humans possess 46 chromosomes which means that almost every C within our body carries the same number of chromosomes however when we talk about human gametes which is our sperm and our egg cells these particular cells only carry 23 chromosomes each consequently you inherit 23 chromosomes from your mother and another 23 chromosomes from your father which gives you a complete set of 46 chromosomes this constitutes your unique genetic code let's do some practice which of the following best explains the Rel relationship between DNA genes and chromosomes within the context of heredity is it a genes are made up of chromosomes which are specific segments of DNA that code for proteins B chromosomes are composed of DNA and genes are specific segments of chromosomes that dictate individual traits is it C DNA replicates to form genes which then organize into chromosomes to be expressed as traits or is it D chromosomes replicate to produce genes which are then transcribed into DNA to determine hereditary information and the correct answer is B chromosomes are composed of DNA and genes are specific segments of chromosomes that dictate individual traits so remember chromosomes are very long strands of DNA wrapped around proteins called histones genes which are segments of DNA are located on these chromosomes and they're going to act as instructions to produce proteins these proteins are going to determine the characteristics or traits that can be passed from parents to offspring through heredity which of the following best describes the function of regulatory genes in gene expression is it a they encode for proteins that are directly involved in metabolic reactions is it B they provide the code for structural components of the cell membrane is it C they produce proteins that help in the replication of DNA or is it D they produce proteins or RNA that can controls the expression of other genes and the correct answer is D they produce proteins or rnas that control the expression of other genes so regulatory genes are responsible for producing proteins and rnas and they play a crucial role when it comes to controlling the expression of those genes within an organism so these regulatory molecules can either enhance or inhibit the transcription of Target genes thereby regulating gene expression in response to the cell's needs or external stimuli DNA often seems to hog the spotlight with its stunning double helix structure resembling that spiral laded appearance indeed DNA is crucial for storing genetic information and determining traits yet the significance of RNA frequently goes underappreciated RNA is essential for conveying genetic instructions to cells for protein production a process explored in depth when discussing protein synthesis ultimately it's a biomolecule just as pivotal as DNA and according to RNA World hypothesis RNA might have even predated DNA When comparing DNA and RNA it's notable that both are found across all forms of life in eukaryotic cells DNA is typically located inside of the nucleus whereas RNA is going to be present inside and outside of the nucleus Unlike DNA which has a double stranded appearance RNA is typically single single stranded presenting with only one strand of nucleotides the sugar component differs between the two as well DNA contains deoxy ribos which aligns with its name deoxy ribonucleic acid indicating the absence of an oxygen molecule that's where the deoxy at the front of deoxy ribonucleic acid comes from in contrast RNA sugar is ribos reflecting in its name ribonucleic acid when it comes to Nitro genus bases RNA is going to include adenine urel cytosine and guanine did you notice something different ell replaces thyine found in DNA this substitution is going to call for a little bit of a tweak from The Familiar pneumonic that we learned about base pairings so instead of apples in the tree we're going to say apple under the tree that way it lets us know that adenine is going to pair with urel when it comes to RNA when it comes to car in the garage that's still going to remain the same because we still have C cytosine and quanin pairs that are going to pair together when it comes to RNA it's crucial to understand that while DNA does hold the instructions for your traits it cannot be expressed without rna's intervention RNA plays a key role when it comes to translating DNA's genetic code into proteins that carry out numerous functions within our bodies there are three different types of RNA that's going to be important for you to know because of their roles mRNA also known as messenger RNA conveys genetic instructions derived from DNA in eukaryotic cells while DNA predominantly resides in the nucleus mRNA possesses the unique capability of exiting the nucleus this allows it to transport the genetic blueprint to the ribosome the cellular site for protein synthesis notably RNA is also significant structural component of ribosomes C RNA found in ribosomes is known as R RNA short for ribosomal RNA another crucial type of RNA is TNA which stands for Transfer RNA whose primary function is to fery amino acids to the ribosome ensuring that they align correctly with the corresponding mRNA codons as these amino acids are sequentially linked they form a polypeptide chain proteins which play a marod of rol within an organism are composed of one or more polypeptide chains protein synthesis unfolds through two principal phases transcription and translation a useful pneumonic to recall the sequence and steps involves noting the letters c in transcription and L in Translation since C precedes l in the alphabet it's easy to remember that trans transcription is going to occur before translation so starting with transcription it's going to to involve converting DNA into a messenger strand this process is going to take place within the nucleus where the DNA is going to reside during transcription the enzyme RNA polymerase attaches matching RNA bases to the DNA templates these RNA bases are then linked together to create a single stranded molecule of mRNA messenger RNA is composed of an RNA sequence that mirrors the DNA template it's important to note that mRNA typically under goes substantial editing before it's ready for action this editing process is both intriguing and essential when it comes to the correct functioning of the protein synthesis mechanism as we had previously noted one of the most notable advantages of being mRNA especially in eukariotic cells is the ability to exit the nucleus mRNA is going to travel from the nucleus into that cytoplasm where they going to associate themselves with r romes ribosomes which are responsible for protein synthesis are comprised of R RNA which the r remember stands for ribosomal RNA making that pneumonic pretty straightforward the next phase we encounter is translation and this is where the ribosome is going to assemble the protein so let's simplify the essentials of what occurs in the cytoplasm there you're going to find numerous tRNA molecules at the ready TR RNA which stands for Transfer RNA na is responsible for carrying amino acids which are the fundamental building blocks of proteins as we're in the process a synthesizing proteins these amino acids are crucial for construction the Assembly of a protein requires the aggregation of these amino acids which is a task orchestrated by our TRNA but exactly how does tRNA know which amino acid to collect this is where the role of mRNA becomes crucial the mRNA is going to serve as a guide determining which TRNA needs to be brought to the ribosome and consequently which amino acids need to be assembled to form our protein so each TRNA molecule is going to search for bases that match its own mRNA strand aiming to find a set that is going to be complementary upon locating these matching bases of the MRNA the TRNA is going to contribute its amino acid to the growing protein chain this matching process is going to involve reading that mRNA sequence in groups of three bases at a time not individually these groups of three are known as codons for instance tRNA molecules are going to encounter a codon of au U of the MRNA while having a corresponding anti-codon of UA any TRNA with its anticodon is designated to carry the amino acid acid isoline when a TRNA possesses that UAG anti-codon pairs with a UAC codon on the MRNA it donates that isoline to the polypeptide chain after the transfer that TNA is going to depart leaving behind its amino acid to incorporate into the protein this marks the addition of one amino acid before proceeding to interpret our next codon you might be wondering how do we determine that a TRNA matching the UAC codon is going to carry isoline well there's actually a codon chart that's going to become invaluable when you're trying to figure this out it's not necessary knowledge for you to know for the atits but it is important for you to understand the mechanism and the keys that are taking place when we're talking about protein synthesis revisiting our mRNA sequence let's to code the next codon which is G Au according to a codon chart the sequence specifies that the next amino acid should be aspartic acid the TRNA with its complimentary anti-codon which would have been CUA is going to bind to the codon this TRNA is going to deliver that aspartic acid and after the transfer it's going to detach and connect to our original amino acid forming our polypeptide chain typically at some point the MRNA sequence is going to conclude with a stop codon so stock codons don't correspond with any amino acid instead they signal the ribosome to tell them that protein synthesis process is done incomplete and they can release their amino acid the outcome of the translation process is the creation of that amino acid chain it's going to be assembled in a specific sequence that was dictated by our mrna's code however it's crucial to remember that the sequence of mRNA is complementary to that of the DNA making being DNA The Ultimate Guide when it comes to protein synthesis despite DNA playing a pivotal role the process cannot proceed without the crucial contribution of our mRNA rrna and TRNA after that amino acid is assembled the protein May undergo further folding and modifications it might need to be transported to a different location inside of the cell these subsequent steps depending on the protein specific structure and function will take place so practice question which component is essential for initiating the transcription of a gene into mRNA in eukariotic cells is it a DNA ligase B RNA poase C helicase or D ribosome and the correct answer is B RNA polymerase RNA polymerase is crucial when it comes to the transcription process in eukariotic cells which reads the DNA sequence of a gene and synthesizes a comp complimentary R mRNA strand DNA ligase is more involved in DNA replication and repair not necessarily transcription helicase unwinds our DNA Helix during replication and ribosomes are the site of protein synthesis during translation not involved in the transcription process initiation so what is the role of mRNA and protein synthesis is it a it brings amino acids to the ribosome is it B it replicates DNA segments before protein synthesis is it C it serves as a template for assembling amino acids into proteins or D it transports proteins to different parts of the cell and the correct answer is C it serves as a template for assembling amino acids into proteins so during protein synthesis mRNA carries that genetic code from DNA during the transcription process to the ribosome here is where it's going to serve as a template for the sequence of amino acids and a protein during translation TRNA not mRNA is responsible for bringing amino acids to the ribosome so option A would be wrong and then DNA replication and option b is a separate process from protein synthesis so again that doesn't make sense and then lastly with option D transporting proteins to different parts of the cell is a function of other cellular components like our endoplasmic micula and our GGI apparatus not mRNA for my entire life growing up I've always been intrigued by the idea of owning a sphinx cat while they're available at select breeders they're actually quite rare their survival in the wild ultimately seems unlikely consider picturing a sphinx cat shivering out in the cold it's a true Testament about their Specialized Care needs however the genetics Behind These hairless cats are utterly captivating just like the cats themselves unlike their furry counterpart Sphinx cats lack hair a trait determined by their genetic makeup genes which are segments of DNA are passed down from the Sphinx kittens from both their mother and their father dictating everything from their hairlessness to their distinctive appearance an alil is a variant of a gene often recognized by letters for our discussion we're going to use the letter F to represent fur a sphinx cat known for its lack of fur is going to possess two recessive alals for the fur trait recessive alals are typically indicated by the lowercase letter being recessive implies that this trait will only manifest if there are no dominant alals present dominant alals marked by their uppercase letter are traits that are expressed in essence they dominate over the others therefore the Sphinx cat la the dominant fur Gene allowing the recessive trait of being fur less to be expressed so if we take a look at our guide here we can see that a sphinx cat is going to have two recessive alals conversely a long-hairs cat genotype can either be two dominant alals meaning we have two uppercase letter FS or they can have one dominant Al and one recessive alil meaning they'll have one uppercase F and one lowercase f because of that presence of just one dominant alil that uppercase F it's sufficient for that free trait to be expressed effectively masking that recessive alil as we dive deeper into genetics we come across a few terminology genotypes capital F capital F or lowercase f lowercase f are labeled homo zycus genotypes the prefix homo suggesting sanness due to both alals either being upper C or lowercase respectively if we break this down even further our uppercase F uppercase F is termed homo zyus dominant reflecting that uppercase notation while our lowercase f lowercase f is homo zus recessive given its lowercase notation a genotype with an uppercase F and a lowercase f is called hetero zagis where hetero in the the beginning of that word means different indicating that alal are of different notations one is uppercase and one is lowercase if you were to observe a cat with hair its genotype could either be homo zakus dominant or it could be heterozygous it's IND discernible just by their appearance however if we wanted to we could test to clarify what the exact genotype is in contrast the genotype of a hairless Sphinx cat is always going to be homo zyus recessive since the present of any dominant alil which would be our uppercase F would ultimately Resort in a furry phenotype let's tackle a monoh hybrid cross where mono signifies the focus of a single trait in this instance fur to analyze this we are going to construct what we know as a punet square it's divided into four sections and in this instance we're going to look at two heterozygous cats being crossed together our initial step step one is we want to identify the parents genotypes in this case we have two hetero zagustin square and the other parents genotype on the side of our punet Square then for step three we're going to proceed by Crossing them ensuring that whenever we have a dominant alil that would be our capital F we're going to list that first for consistency so this is how we are going to cross them we are going to multiply the top of the square by the side of the square so our first example we have F multiplied by capital F so we'd have a capital f capital F for our next again we're going to multiply the top of this Square by the side of this square and that is going to give us capital F lowercase f then we're going to multiply the top of this Square by the side of this square and that is going to give us capital f lowercase f and then lastly we're going to multiply the top of this Square by the side of this square and that is going to give us lowercase f lowercase f the resulting squares are going to reveal the potential genotypes of these cats Offspring if you were asked on your te's what the offsprings genotypes would be you could say that you have one cat that is going to be homozygous dominant you're going to have two cats that are going to be heteros zagis and you're going to have one cat that is going to to be homozygous recessive this outcome can also be expressed as a 1:2:1 ratio or 25% capital F capital F 50% capital F lowercase f and 25% lowercase f lower case f now we're going to shift our Focus to phenotype but what exactly is a phenotype the term phenotype can be remembered by associating pheno with physical appearance so p and pheno p and physical that's how I like to remember that this is a observable characteristic of an organism in this scenario the trait in question is the presence or absence of fur given that the presence of at least one dominant alil that would be our capital F results in fur Offspring with the genotypes capital F capital F or capital F lowercase f are going to indeed have fur thus three of our offspring are going to display that furry fenale type our homo zagis recessive kitten which is our lowercase f lowercase f ultimately lacks that dominant a so this cat is going to result in a hairless phenotype therefore we can describe the phenotype distribution as three furry to one fur less or we can even break it down into percentages 75% are going to have fur and 25% are going to be hairless it's crucial to remember that punet squares offer predictions based on prod probabilities not certainties they're ultimately going to indicate potential outcomes rather than guaranteeing specific results for instance while there's theoretically a 50 to 50% chance of a child being born male or female many of us are familiar with families that have only daughters or only Sons these outcomes show the nature of probabilities as they forecast the possible events adding an element of unpredictability until now we we've concentrated on only one single Al pairs which is why we have been talking about monoh hybrid crosses mono standing for one however cats possess a multitude of traits Beyond just their first status each influenced by their own alals when we examine a cross involving two different pairs of alals we often refer to this as dihybrid cross the prefix die indicates two so we're looking at two distinct traits so I I want you to picture this there's a cat named Oreo named for its black and white patched appearance reminiscent of a cookie or admittedly we just couldn't come up with a more original name now imagine beginning your day walking into the living room to relax with your morning cup of coffee only to find that your cat Oreo meticulously knocked your favorite mug off the coffee table as you attempt to tidy up you notice that Oreo is now pushing your pen off your desk it's clear that not all cats are going to share in this behavior of playful disruption but Oreo is irresistibly drawn to it day or night he's irresistibly engaging in little gravity experiments the origin of this Behavior intrigues us is it genetic probably not but let's practice di hybrid squares IM imagining if playful disruption towards objects were genetic traits let's suppose that the enjoyment of causing playful disruptions is a dominant trait denoted by the alal capital D and its absence which is is a more preference for calm is a recessive trait symbolized by the alil lowercase D imagine that we have a cat that is heterozygous for both the fur trait and the playful disruption traits being heterozygous for both traits would leave them with a genotype of capital F lowercase f capital D lowercase D we're going to cross this cat with another cat that is both hairless and prefers calm environments this means that they're going to have homozygous recessive Dr tra so they're going to have a lowercase f lowercase f for the fur trait and they're going to have a lowercase D lowercase D for the playful disruption traits now in Mendel's Law of Independent Assortment it suggests that traits are inherited independently of one another indicating there's no genetic link between having fur and enjoying playful disruptions for example this means that a cat may enjoy playful disruptions regardless if they have fur or they don't we're going to apply this principle to two die hybrid cross here we have a setup of a 16 square Punit Square our very first step is we want to begin by establishing the parents genotypes for our cross which we have in our example here on the left hand side of our screen like we discussed before step number two is we want to determine the gam combinations from each parent and place them alongside the top and the side of our punet square but ultimately how do we determine what letters to place there we employ the foil method which helps us figure out the possible gami combinations the foil acronym stands for first Outside Inside and last let's take a look at each of these of how we determine our gami combinations starting with our first cat we are going to multiply the first letter of each one of our traits this would be our capital F and our capital D which would give us capital F capital D next we are going to multiply the outside of each one of our traits that would be our capital F and our lowercase D ultimately giving us this gam formation then we have the inside so we're going to multiply the inside of our formation here which would give us lowercase f capital D and then lastly we would multiply the last traits which would be our lowercase f lowercase D ultimately giving us our final gambi combination if you take a look at our last example because everything is homo zous recessive we don't have to do a whole lot of ground workor here because our gam combinations are always going to be lowercase f lowercase D now we're going to place these alongside our punet Square the uniformity of these combinations are going to highlight The Limited Al variation that the parents contribute and for step three we're going to merge the gametes to forecast the potential genetic outcomes that we're going to see with these cats Offspring just like we did with monohybrid cross we want to maintain consistency when it comes to formatting so if we have a capital f or a capital D first we always want to make sure that we list those before our lowercase letters we also want to make sure that we list our FS before our D's because when we're looking at our combination of our gametes that is how it's listed with each one of these CS ultimately this method is going to ensure Clarity and uniformity by interpreting the punet squares results so just to give you an example for our first Square we have capital F capital D here and we have lowercase F lowercase D here we are going to cross these two traits together so we always want to start with f so we have a capital f and a lowercase f we want to make sure that capital F becomes comes before the lowercase and the same thing with our D we have a capital D and a lowercase D so we want to list the uppercase letter first and the lowercase letter last so one more example we have here same thing we're going to cross the top of this square with the side of this Square so we have a capital F lowercase f we list that in order and then look here we have two recessive alals we have two lowercase D's so we're going to list lower case D and lowercase D you're going to do this the entire time throughout this the entirety of this di hybrid cross Punit Square so we always want to know our genotypes and our phenotypes so we're going to start with our genotypes what genotypes are we going to have with these Offspring so if we take a look at our example the distribution is as follows we're going to have four out of six 16 when it comes to capital F lowercase f capital D lowercase D we are going to have four out of 16 when it comes to capital F lowercase f lowercase D lowercase D we're also going to have four out of 16 of lowercase f lowercase f capital D lowercase D and again four out of 16 when it comes to lowercase f lowercase f and lowercase D lowercase D so the potential genotypes that we could see with these cats is a 1: one: one: one ratio now let's shift our Focus to phenotypes so in this scenario we see that about half of our cats are going to be furry and the other half of our cats are going to be fur lless however that's not the only thing that we're going to be testing with dihybrid cross we also wanted to see the likelihood that the kitten was going to be born with characteristics similar to Oreo or not so listen here with the use of polka dots we can see that our pink polka dots which is in this column and this column show that there's going to be an 8 and 16 chance that they're going to be like Oreo and with our blue pokka dos in this column and this column there's an 8 and 16 chance that they're going to be calm if we break this down by their two traits we can see that 25% are going to be furry and playful 25% is going to be furry and calm 25% are going to be F Less in playful and another 25% are going to be F Less in calm this ultimately leaves us with another ratio of one to one to one to one when it comes to our cat's phenotypes it's crucial to note that in this particular case the genotype and the phenotype ratios align but this is not always the case whenever we're mixing two heterozygous cats together we usually see a ratio of 9 to 3 to 3: one but in this case we had one heterozygous cat and one homozygous recessive cat the key takeaway from this is that punet squares serve as a tool for estimating the probabilities of Offspring inheriting specific genotypes or phenotypes it's going to offer a glimpse of the Intriguing dynamics of genetics one links the color of flowers and human height together they both serve as Prime examples of non- mandelian inheritance this term refers to genetic traits that defy the conventional mandelian principles where the presence of a dominant alil guarantees that expression of the dominant traits let's take a look at roses with the following three phenotypes red white and an immediate Hue of pink this phenotype is known as incomplete dominance in cases of incomplete dominance there's a Twist the alil typically seen as dominant doesn't fully overshadow our so-called recessive alil when they coexist in fact the concept of dominant alals becomes a little murky here for instance when the red flower genotype capital r capital r and the white flower genotype lowercase R lowercase R result in offspring that are both capital r and lowercase R they don't conform to that mandelian expectation instead of that dominant R overpowering the recessive R to produce red flowers it now actually manifests our pink flowers this blending effect signifies incomplete dominance should two pink flowers we cross like we see here in our last example this blending effect signifies incomplete dominance should we cross two pink flowers like we see here in our last punet Square The Offspring could be red they could be pink or they could even be white showcasing the diverse outcomes when it comes to incomplete dominance and lastly we have co-dominance so the prefix Co in co-dominant suggests cooperation are working together which apply describe how the alals interact in this scenario unlike with incomplete dominance where one Al's expression is not entirely masked by the other co-dominance involves both alals being expressed equally and independently to illustrate this let's consider the genetic Crossing of certain chickens when a black chicken with the genotype capital b capital B is crossed with a white chicken with the genotype capital W capital W the resulting offspring are going to exhibit the genot type capital b capital W these capital b capital W chickens are going to display both black and white feathers with a speckled pattern this simultaneous expression of both traits without blending or dilution amplifies Co dominance a situation where both alals contribute to the phenotype in a distinctly visible manner so let's take a moment to consider our favorite food while we all have our unique preferences food fundamentally serves as a source of critical large molecules necessary for Life known as biomolecules or macro molecules these can include things like carbohydrates lipids proteins and nucleic acids each found in varying quantities across different foods for instance my favorite peanut butter is rich in both proteins as well as lipids although this video is going to reference examples of food containing biom molecules our Focus isn't going to be on nutrition but understanding the major classes of those biomolecules and their critical roles in cellular structure and function after all these cells make up the organisms themselves before we Deep dive into each one of these four different types of biomolecules we must introduce an essential term the monomer the monomer acts as a building block the smaller units composing any large molecule is termed monomers as we explore each class of biomolecules we'll discuss their respective monomers if they apply before we move on let's take a moment to appreciate the stunning structure of biomolecules as we review each one of these let's think about how we might remember the primary and most common elements that they contain there's a handy pneumonic called cho cho Chan and chump where instead of an M we actually use an N this helps us actually recall the elements in each each one of these biomolecules carbon is our C hydrogen is our H oxygen is our o nitrogen is our n and phosphorus is our P so you may question does this imply these are the only elements that we're going to find in these biomolecules certainly not however understanding the common Elemental composition and their Arrangements Within These biomolecules is crucial because their structural configurations significantly influence their functions let's be by exploring the class of biomolecules known as carbohydrates common sources like bread pasta fruits and vegetables are all typically very rich in carbohydrates the basic building block or monomer of a carbohydrate is known as a monosaccharide a prime example of a monosaccharide is glucose glucose plays a critical role when it comes to cellular respiration where it produces ATP which is often referred to as the cell's energy currency when two monosaccharides link together they form what is known as a disaccharide here's a memory trick for you you'll notice many sugars share a common suffix o e like glucose maltose lactose sucrose and fructose which helps indicate that these are carbohydrates when many monosaccharides are linked together they create a polysaccharide which represents a more complex form of carbohydrate if you're having any difficulty remembering which saccharide is which I use the memory trick mono die and poly because mono stands for one Dy stands for two and poly stands for many carbohydrates plays a crucial role in the structure and function of cells across various organisms for instance plant cells have cell walls composed of specific carbohydrates called cellulose similarly fungi have cell walls made of a carbohydrate known as kiten which interestingly is also the material that forms the exoskeletons of insects a vital function of carbohydrates such as glucose is its role in energy production like we talked about before glucose is instrumental in generating ATP the primary energy carrier in cells making carbohydrates a rapid and accessible energy source furthermore this energy can be stored in the form of polysaccharide es complex carbohydrates like starch and plants and glycogen and animals which serve as an energy Reserve to be utilized when needed next let's discuss lipids which Encompass fats and oils common sources include items like butter and olive oil and they represent a remarkably diverse category of biomolecules encompassing several types including triglycerides phospholipids and steroids just to name a few well many lipids are composed of glycerol and fatty acids this isn't universally true for all lipids lipids also do not have a true monomer because they do not have repeating units like we saw with carbohydrates however a common characteristic when it comes to most lipids is their hydrophobic nature meaning that they tend to repel water this hydrophobic nature means that lipids generally do not dissolve in water unlike most other biomolecules which makes them unique in their interaction with water and their role in the biological systems lipids play a crucial role in their structure and function of organisms and their cells the cell membrane is the fundamental structures in all cells whether it's plants animals or other organisms this essential barrier is largely composed of phospholipids arranged in a phospholipid bilayer thanks to their structural properties Beyond structural roles lipids are vital in long-term energy storage while carbohydrates do provide quick energy lipids store energy for longer periods which organisms can tap into when carbohydrate sources are depleted lipids also play a significant role in insulation this includes electrical insulation such as the milin sheath surrounding many neurons which enhances the speed of electrical impulse transmission thermally lipids are integral for temperature regulation evident in the thick layers of blubber like we see in marine animals such as the harp seal or even in an oversized kitty cat which helps them retain heat and frigid temperatures another significant function of lipids is hormonal activity many lipids act as hormones serving as key chemical Messengers that regulate various biological processes throughout the body next up we have proteins common protein sources include meat nuts beans and even eggs proteins are polymers made up of amino acids which serve as their monomers there are various types of amino acids which link together to form proteins proteins are crucial for both structure and function of an organism and their cells structurally proteins are major components of tissues such as muscles they are also found in other body structures such as hair and collagen proteins play an essential role in cell membrane Integrity by forming protein channels and receptors which are vital for transporting substances across the cell membrane and for cell signaling enabling these cells to communicate and coordinate their actions functionally most enzymes are proteins enzymes catalyze biochemical reactions in the body aiding in both the synthesis and breakdown of substances during metabolical processes proteins are also fundamental to the immune system antibodies produced by immune cells are proteins that play a key role in defending the body against pathogens furthermore several critical hormones including insulin are also proteins highlighting their role in regulating physiological processes when it comes to genetics although genes are composed of DNA many genes encode for proteins underlying the genetic basis for building and regulating the body's proteins this brings us to our final category nucle acids which Encompass both DNA and RNA we'll explore nucleic acids in Greater detail when we talk about genetics the monomer of a nucleic acid is known as a nucleotide in terms that conveniently resemble nucleic acids making it much easier to remember nucleotide nucleic acids nucleic acids are essential across all life forms whether it's plants animals fungi or even bacteria as they contain the genetic instructions necessary for introducing cellular activities in terms of their importance inside of your cells nucleic acids hold all your genetic information in the form of DNA and RNA this genetic content is crucial for coding your traits that Define your structure and your function influencing everything from physical appearance to psychological processes so our first practice question what is the monomer of carbohydrates is is it a nucleotide B amino acids C fatty acid or D monosaccharide and the correct answer is D monosaccharide remember monosaccharides are the simplest form of carbohydrates and they serve as the monomers for those more complex carbohydrates what type of lipid is primarily used by the body for long-term energy storage is it a steroids b phospholipids c triglycerides or D waxes and the correct answer is C triglycerides remember triglycerides are the main form of stored energy in your body and are found in a lot of your fat cells which type of Macro Molecule plays a key role in forming cellular membranes is it a nucleic acids B carbohydrates C lipids or D proteins and the correct answer is C lipids lipids specifically phospholipids are fundamental components of cell membranes now we're going to discuss infectious agents often referred to as microorganisms however it's crucial to note that not all agents that we're going to cover today qualify as living organisms some actually aren't even alive at all they're neither cells nor considered life forms so for clarity we're going to refer to them as infectious agents instead of microorganisms these agents can enter our bodies which act as hosts and potentially cause injury disease or even death when discussing anything that can cause disease or injury we're going to use the term pathogenic this term can be broken down into two parts patho which means disease and genic which means causes thus pathogenic refers to an infectious agent capable of inducing disease another term that you might encounter when you're taking the teas is virulence which describes IES the severity or harmful potential of a pathogen it's important to understand that virulence doesn't necessarily correlate with more damaging outcomes so for instance a more virulent strand of a virus may not always cause more severe disease but could be more Adept to invading immune systems more transmissible and it could even be more capable of circumventing vaccines or in the case of bacteria antibiotics so in summary pathogenic means capable of causing disease while virulent refers to the potential severity or nastiness of a pathogen so let's start off with our favorites viruses familiar to many and very significant in the study of microbiology viruses are tiny entities ranging from anywhere between 20 to 400 nanometers in size notably viruses are not cells and they're not actually considered alive they remain motionless on surfaces like bench tops or the ground outside of a host organism to be active a virus has to enter a host whether it's an animal or it's a plant and once it's inside it behaves as an intracellular obligate parasite this means that it's compelled to reside within a whole cell to function specifically to replicate and perform activities viruses are classified based on structural components as well as genetic material the outside shell of a virus is known as a capsid and the genetic core inside is referred to as a genome thus viruses can be categorized by their capsid structure and whether their genome consists of DNA or RNA additionally some viruses have an envelope which is derived from the host cell's membrane as the virus exits the cell enveloping itself for protection and aiding an infection the impact of a cell on the body and its pathogenicity depends on where it infects different virus Target specific regions such as the respiratory tract your gastrointestinal tract systemic skin central nervous system just to name a few for instance the common cold influenza and covid affect the respiratory system while Rota virus and Ms is prevalent in your GI tract especially in children systemic infections like chickenpox and HIV can affect the entire body and skin specific viruses like we see with HPV can cause cervical warts or even worse cervical cancer due to that cellular mutation induced by viral genetic material integration viruses attached to a host cell via structures like Spike proteins on their capsid which bind to specific receptors on the cell membrane upon attachment the virus injects its genetic material into the host cell hijacking the cell's Machinery to replicate new viruses this is often going to lead to the host cell's death contributing to the disease in some cases like we see with HPV that integration and mutation of viral DNA can lead to cancer fortunately though for many of these viruses vaccines are available providing protection by priming the immune system against these infectious agents moving on let's talk about bacteria which marks a significant jump in scale bacteria can range anywhere from 0.2 to 15 microns in size to put this into perspective 0.2 microns is equivalent to 200 nanom and 15 microns is equivalent to 15,000 nanometers from here until the rest of our examples of microorganisms unlike viruses we're dealing with living organisms cells that are very much alive bacteria are classified as procaryote meaning that they have DNA but it's not contained within a membranebound nucleus instead it resides in an area called a nucleoid unlike eukaryotic cells most bacterial organel are not enclosed by membranes a key structural feature of bacteria is their cell membrane it's similar to that of other cells but more permeable which means that they are more susceptible to swelling and bursting under fluid pressure fortunately bacteria have a protective cell wall which helps maintain its structural Integrity against such pressures this cell wall is crucial for the bacteria's survival and is composed of a network of proteins and sugars bacteria can be further categorized based on the composition of these cell walls into two types gr positive and gram negative our gr positive bacteria have a thick cell wall while gram negative bacteria has a thinner cell wall but an additional outer membrane additionally bacteria can be categorized by their shape cockeye is more several and bili is more of a rod shape the organization of these shapes can be indicative for example cocky that group in a grap like structure can be known as Stafa caky and those that form in long chains are known as stripto cocky one disease example could be chlamidia which is a bacteria that requires intracellular environments to access energy and carry out its functions effectively as a result they can also lead to Cellular damage ultimately causing scarring such scarring can occur in the reproductive tract especially in females potentially leading to infertility in the eyes the scarring can actually impair vision and lead to various types of visual dysfunctions another example would be micoplasma notably one of the primary causes of community acquired pneumonia micoplasma is unique because it lacks a typical bacterial cell wall which allows it to live both inside and outside of host cells we also have bacteria like streptococus which can cause conditions such as strep throat primarily affecting the respiratory tract stfa coccus orus orus meaning golden which is a common cause of skin infections additionally there is Clum tetani which is a particularly interesting because it produces exotoxins Grand positive bacteria like cluster ridium tetani release exotoxins that can cause severe damage by infecting motor neurons with skin wounds leading to tetanus this condition is lifethreatening and it can cause muscles to stiffen uncontrollably in contrast gram negative bacteria produce endotoxins which are part of their outer membrane when these bacteria die and break down they release those endotoxins triggering int inflammation as well as other serious health issues to the host as we progress to larger cellular structures we encounter fungi which range in size from 2 to 200 microns fungi like the cells we find within our body are UK carots meaning they possess membranebound organel including nuclei unlike bacteria fungi have cell walls made up of kiten which is a polysaccharide also found in the exoskeletons of insects like spiders fungi has the capability to reproduce both sexually and asexually often relying on spores which function similarly to seeds to spread and propagate when fungi causes diseases the condition is referred to as mosis which can manifest as superficial or deep infections superficial fungal infections primarily affect the skin typically arising from fungi that releases enzymes irritating the skin and causing symptoms like itching and redness a common example is Tena which is known as ring worm thought to not be actually a worm but a fungal infection depending on the affected area Tania may be called Tena capitus if it's on the scalp or Tena Pettis if it's on the foot like we see with athletes foot fungal infections can also impact mucous membranes leading to a condition known as thrust which can encourage in our mouth we have oral thres or it can occur into the genital area known as vaginal thres more severe and deep fungal infections may involve internal organs like the lungs or bloodstream particularly in immunocompromised individuals in such cases fungal infections can lead to serious health complications and are a common cause of mortality in people with weakened immune systems such as those with HIV protozoa also referred to as protus range in size from 1 to 50 microns these organisms are eucaryotic and usually unicellular like we see with fungi or they're typically multicellular protozoa possess all the organel necessary for metabolic functions similar to those found in our cells including nuclei and mitochondria examples of diseases caused by protozoa include malaria and gr diasis malaria begins with the protozoan life cycle inside the mosquito's gut and saliva when a mosquito bites it injects what can be similar to cyst into the bloodstream which then travels down into our liver here they mature within the hepatocytes before bursting out and infecting red blood cells within these cells the protozoa reproduces asexually leading to the typical symptoms we see with malaria once released from the red blood cells the protozoa enter a gamet form ready to be picked up by another mosquito continuing that transmission cycle it's important to note that the mosquito only serves as a vector the actual infectious agent is the protozoa Gard diasis on the other hand is a Digestive Disease which enters the body through contaminated food and water the cysts are ingested and travel to the upper digestive tract where they hatch and multiply through mitosis they then attach to the Digest tract walls absorbing nutrients and causing irritation and inflammation this process often results in symptoms like severe watery and sometimes bloody diarrhea eventually the protozoa produces more cysts which are excreted in feces and often contaminate food and water sources perpetuating the cycle of infection finally we move on to animals that can be classified as helmets which are worms or ectoparasites helmets are multicellular eukaryotic organisms that range significantly in size from as small as 3 millit all the way up to as large as 10 m in terms of classification helmets can be divided based on their shape they can be round worms flat worms or flukes round worms such as hookworms typically inhabit the gastrointestinal track and have a crosssection circular appearance flat worms like tap worms are often very long and have a ribbon-like shape flukes such as liver flukes are typically leaf-shaped as for Ecto parasites these include organisms like mites fleas and bed bugs these parasites are primarily known for causing skin irritation and inflammation they attach to the skin feeding off the host and often leading to discomfort and allergic reactions if we consider creatures like ticks they can transmit bacteria through their bites known as Lyme disease a tick bite introducing bacteria into the skin can potentially lead to significant health issues which of the following is characteristic of fungi is it a they are photosynthetic B they reproduced by binary fision C they have a cell wall made of kiten or D they are typically motile and the correct answer is C they have a cell wall made of kiten remember fungi have that cell wall and it's going to distinguish them from Plants who have cell walls made of cellulose which type of microorganism causes malaria is it virus bacteria protozoa or fungi and the correct answer is C protozoa malaria is caused by protozoa which is transmitted to humans from a bite of an infected female mosquito what is a unique feature of viruses compared to other microorganisms is it a they contain both DNA and RNA B they require a host cell to replicate C they have a rigid cell wall or D they can undergo photosynthesis the correct answer is B they require a host cell to replicate remember viruses are unique in that they cannot replicate on their own they have to invade a host cell and use its Machinery to produce new virus particles infectious and non-infectious diseases represent two broad categories of illnesses each with the distinct causes and mechanisms infectious diseases are caused by pathogenic microorganisms such as bacteria viruses parasites or fungi and these diseases can spread directly or indirectly from one person to another for example covid-19 primarily spreads through respiratory droplets when an infected person either coughs sneezes or talks it can also spread by touching surfaces contaminated with the virus and then touching your face although it is less common similarly influenza is caused by various strands of the flu viruses and is highly contagious spreading through respiratory droplets chickenpox is another highly contagious disease most commonly affecting children this virus spreads through direct contact with a rash or through the air by respiratory droplets when that infected person coughs or sneezes non-infectious disease dises also known as non-communicable diseases are not caused by infectious agents and cannot be transmitted between people or other organisms these diseases are often the result of genetic environmental or lifestyle factors examples can include diabetes which results from the body's inability to produce or effectively use insulin heart disease is often caused by a combination of dietary genetic and lifestyle factors leading to the buildup of black in our coronary arteries cancer can have various causes as well including genetic predisposition environmental exposures and lifestyle choices such as smoking and diet understanding the distinctions between these two types of diseases is crucial for Effective prevention treatment and management strategies next we're going to examine the various ways diseases are transmitted and often referred to as modes of transmission the first category we are going to to discuss is going to be direct transmission this occurs when infectious agents are immediately transferred from a source or Reservoir such as an infectious person directly into a susceptible new host direct transmission can occur in two primary ways either through direct contact or droplet spread direct contact is going to involve physical interaction with bodily fluids from an infected individual which might include oral secretion blood or other fluids like we see with skin lesions semen or vaginal secretions this type of transmission can result from activities like touching biting kissing or sexual intercourse droplet spread another form of direct transmission requires droplets from respiratory droplets containing those infectious agents this typically happens when an infected person coughs or sneezes projecting droplets directly onto someone nearby diseases like prusis also known as the whooping cough is often spread this way for droplet transmission to occur close proximity is necessary generally less than 2 m such as sharing a small space like a car or a room it's important to understand that both direct contact and droplet spread are considered direct transmission methods next we'll discuss indirect transmission which which includes several mechanisms one of which is Airborne transmission Airborne transmission involves infectious agents that are carried on Dust particles are within droplet nuclei that remains suspended in the air due to their small size and lightweight these droplet nuclei can linger in the air for extended periods of time allowing them to be inhaled into a host respiratory system with Airborne transmission neither direct contact nor or close proximity is necessary for the disease to spread the droplet nuclei can travel and disperse widely across an environment and can infect a host without any direct interaction with the person who was infected indirect transmission involves objects and items often referred to as fomite Transmissions they occur when infectious agents are transferred from an infected person to an object or a surface these objects like door handles tabletops utensils or electrical devices can then Harbor the Infectious agents for varying lengths of time when another individual touches these contaminated surface and then touches their face eyes nose or mouth they can inadvertently introduce that pathogen to their body leading to an infection the risk of fomite Transmissions depends on several factors including the type of pathogen the environment and the material of the object for example heart surfaces like plastic stainless steel can retain some viruses for days whereas more porous materials like fabric are less conducive to long-term survival of viruses regular cleaning and disinfection of frequently touched surfaces are effective strategies to reduce the risk of disease spread through fomites hand hygiene is also crucial in preventing the acquisition and spread of infections through in direct contact with contaminated objects and lastly we have Vector born diseases they are transmitted when an infected person passes a pathogen to a vector typically an insect which then spreads the infection to another person without this Vector the disease cannot pass directly between individuals due to their complex transmission Dynamics these diseases are among the most challenging to prevent and control for example preventive strategies in the fight against malaria which is spread by mosquitoes includes vaccinations and environmental tactics these environmental methods often involve using mosquito Nets or removing standing water to disrupt the mosquitoes breeding grounds finally let's talk about microscopes to start it's essential to grasp a few key terms when understanding how microscopes work magnification is the primary concept often associated with microscopes highlighting their ability to enlarge small objects into observable sizes another critical term you're going to need to know is resolution and that's the ability of a microscope to distinguish between two closely positioned objects as separate entities without adequate resolution two proximate objects might appear as a single blurred entity for instance a microscope with a resolution of 0.2 microns requires objects to be at at least 0.2 microns apart in order for them to be distinct from one another let's explore various types of microscopes each designed with both magnification and resolution in mind to effectively visualize and study specimens first up we have the light microscope which is the type of microscope you typically see in biology classroom settings as the name suggests these microscopes utilize light to visualize specimens the most common type type of light microscope is the bright field light microscope which typically displays a darker image against a light background alternatively there are dark field light microscopes which includes a component known as a light stop this element blocks most of the direct light that we see through the light source and because of this the only light that reaches your eyes is the light that has been reflected or refracted by structures within the specimen themselves this technique creates a visual effect where lighter images appear against a dark background enhancing the contrast and detail of the specimen light microscopes utilize light to visualize specimens but not all microscopes are going to operate by this principle for instance to observe extremely small entities like viruses which are typically smaller than your average bacterium more advanced technology is necessary to enhance magnification and resolution this is where electron microscopes are going to come into play electron microscopes use beams of electrons instead of light to create images of the specimens among electron microscopes we have two we have transmission electron microscopes known as Teem which are particularly effective in examining the internal structions of a specimen and on the other hand we have scanning electron microscopes known asem which are better suited for detailed visualization of threedimensional structures of a specimen let's finish off with some practice questions which microscope would be best reviewing the detailed external morphology of a microorganism is it a light microscope B Transmission electron microscope C scanning electron microscope or D fluorescence microscope and the correct answer is C scanning electron microscope remember our scms are ideal for examining surface structures and high detail as they scan the surface with a focused beam of electrons providing us with a threedimensional image what type of transmission involves infectious particles suspended in the air over time and distance is it a direct contact B droplet Transmission C Airborne transmission or D fite transmission and the correct answer is C Airborne transmission remember our air airborn transmission refers to the spread of infectious agents through droplet nuclei that are going to remain infectious and suspended in the air over a distance and time Beyond 1 meter which disease is known to be transmitted through droplet spread is it a HIV B hepatitis C C measles or D influenza and the correct answer is D influenza influenza is well known to be transmitted through droplets that are EXP spelled from an infected person either coughing or sneezing requiring close proximity to spread and that's everything you're going to need to know biology right as always if you have any questions make sure that you leave them down below I love answering your questions head over to nurse chunk store.com there is a ton of additional resources available to you to help you Ace those ait's exams and as always I'm going to catch you in the next video bye