everyone today I'll be going through the international AEV biology content for aexel for unit one this will include all the chapters uh I will link this PowerPoint Down Below in the description box feel free to use it if the quality isn't high enough or you want to go over anything carbohydrates lipids and proteins basically what you need to know is the structure of water and what it enables it to do so water has a d nature because the hydrogen atoms in the water are more positive than the oxygen atoms so they are attracted to each other as opposite charges attract so ions are able to dissolve in the water because of this dipole nature so for example uh ion like chloride is negative it will be attracted to the hydrogen atom and form bonds with it so it dissolves in the water and hyd hydrolysis is a reaction where water is used to break down molecules like carbohydrates lipids and proteins carbohydrates are composed of carbon hydrogen and oxygen um and you need to know that monosaccharides are the soluble carbohydrate monomers made of a single sugar unit they are soluble and they are the simplest sugar units two monosaccharides can join in a condensation reaction to form a disaccharide joined by glycidic bonds so a carbohydrate monomer joins by glycidic bonds a maltose is a disaccharide that's composed of two glucose sucrose is composed of a glucose monosaccharide and a fructose lactose is composed of glucose and gcto and polysaccharides are SE several monosaccharides joined together by glycosidic bonds for example glycogen in animals as an energy store and storage in plants lipids are non-polar molecules that are insoluble in water basically polar molecules have o groups that are polar and can form hydrogen bonds with water so they are able to dissolve in water but non-polar molecules do not so they cannot dissolve in water and they are hydrophobic lipids are used as long-term energy resers in organisms lipids can either be saturated with no carbon carbon double bonds or unsaturated with carbon carbon double bonds so basically there are two types of lipids saturated which actually cause uh cardiovascular disease and unsaturated which are basically the healthy kind of lipids uh we'll go over the differences between them later for example triglycerides it's an example of a liid it's made of Three fatty acids and one glycerol joined by Ester bonds fatty acids in the glycerol and the triglyceride or overall can defer in chain length presence a number of double bonds so a triglyceride can either be a saturated one or an unsaturated one just like any fatty acid could be proteins proteins are made of amino acid monomers joined by peptide bonds the primary structure is the amino acid sequence and the secondary structure is the folding the using hydrogen bonds the tertiary structure is the 3D folding by ionic bonds Etc uh the quinary involves more than one polypeptide chain getting bonded together here are some questions involving water they are all from past paper questions so first off explain how water is involved in the transport of molecules in living organisms because water is a polar solvent that dissolves ions to transport them and why is glucose more soluble in water than for example any other ion because glucose has more o groups so it can form more hydrogen bonds with water and why are fatty acids insoluble because they have nonpolar tails and cannot form hydrogen bonds with water explain how the properties of water molecules result in surface tension this is a three mark question water molecules are dipolar first Mark therefore they can form hydrogen bonds with each other resulting in cohesion between them which results in an inward for Force at the surface of the water water has a high specific heat capacity as there are many hydrogen bonds that would need a lot of energy to increase the temperature of the water this ensures Aquatic Life as temperature is Con constant for entic activity this is the answer to the question that would go anything from why it takes a lot of energy for water molecules to be broken down like a large body of water why it doesn't evaporate or why the temperature is mostly constant in water bodies this is very important because if it wasn't all the Aquatic animals inside the water would die this right here shows the dipolar nature of water you are often asked to draw it in past paper questions here are some questions for carbohydrates a very common one is described the structure of starch starch is a polysaccharide and it's made of two different polysaccharides it's made of Amo and amylopectin and Amo and amcon each have a different structure but they do have stuff in common you can add be asked to compare between Amo and amop pectin basically they are both a glucose like alpha glucose monomers and they are both joined by glycosidic bonds they both have 14 glycosidic bonds a 14 glycosidic bonds means that the first garbon is joined to the fourth gbon on the second alpha glucose but the difference is ailopin has one six glyc ayic bonds so it other than having 14 gly ayic bonds it also has alpha glucose monomers that are joined the first carbohydrate to the sixth carbohydrate okay so if you are asked to describe the structure of storage you will say that it's it is compact it is INS soluable so it doesn't have any osmotic effect if it was soluble the osmotic balance in the organism's body would be disrupted um AOS is also linear it is coiled if you are asked to compare between them okay you can be asked why aopc and glycogen are good energy stores okay so they are both branched so they are easy hyd hydrolized into glucose for energy and they are compact stores so you can store a lot of energy in a tiny bit of space and it is insoluble so has no osmotic effect and since they are polysaccharides they are energy stores since polysaccharides are stores of glucose or like the monomer is glucose basically here it shows the difference between alpha glucose and beta glucose in the alpha glucose the hydrogen is above the O group hydroxy group and in the B glucose the hydrogen is below the O group okay and you are also required to know what each disaccharide is composed of so maltose is composed of two glucose two alpha glucose sucrose is composed of one alpha glucose and one fructose lactose is composed of one alpha glucose and one galactose here we have questions about lipids and this is a very important diagram you often asked to show how a triglyceride is formed so you have one glycero and three fatty acids and they turn into a triglyceride this reaction is a condensation reaction you release three Hy water molecules here we have a few common questions about lipids and this is a very important reaction it's how triglycerides are formed it's important that you don't forget to draw the water molecule as there is a mark for it these are questions about proteins this is the most common question about proteins how the primary structure determines the 3D Shape of the protein and its properties here we have 1 B it's about circulation blood blood vessels hard and atheros atherosclerosis this um two very important questions why do mammals need the circular system like unlike insects for example and advantages of double circulation please memorize these before your final exam uh this is the blood clotting Cascade so first when a blood vessel is damaged the plists release throp plastin and with the presence of calcium ions um thromboplastin converts Pro thrombin into thrombin and thrombin cataliz the reaction of draining fibrinogen into fibrin which is insoluble fibrin forms a network of fibers that track platelets and blood cells into an insoluble mesh this is the bore curve uh it's important to do many questions about this the concept isn't quite hard you have to explain the shift of the curve the bore shift and here these are very important uh you are often asked to draw the structure of the artery you have to draw uh you have to label the Lumen inside and the layer of indial cells you have to label the tunic media the me the one in the middle it has muscles and elastic fibers and the layer on the outside Tunica externa that has col and fibers veins and capillaries aren't asked about as often but remember that capillaries are one cell thick and they are made of one layer of endothelial cells it's very important to remember how arteries are adapted to their function the last three points are specific to the aorta artery here we have structure of the hearts you have to remember what the names of each veins are the most commonly ason is the aarta and the Vana uh you have to also know the names of the vves here we have the cardiac cycle um the first step is the aroyo ventricular diol when the Atria contracts to push blood into the ventricles and then um ventricular systo when the ventricles contract to push blood out of the heart and here we have cardiac diol all Chambers are relaxed and blood flows into the heart atherosclerosis is the Harding of arteries caused by a build of plague or atheroma so how does this happen first the endothal lining in arteries is damaged due to high blood pressure or cholesterol or smoking and that leads to an inflammatory response causing white blood cells to move into the artery cholesterol calcium ions and uh blood cells build up on the artery wall into anoma uh and then um the aoma hardens into plaque and then that leads to the narrow further narrowing of the archery restricting blood flow increasing the blood pressure damaging IND lining all over again this uh is very dangerous if it happens in the coronary artery as it reduces blood supply to the heart muscle so deprives the heart muscle from oxygen nutrients needed for aerobic respiration so the muscle uh what was the word goes for anerobic respiration which produces lactic acid the pH um the pH gets too low the enzymes are denatured and the heart muscle die so no blood is pumped around the body and the person can get a heart attack and die one C you have to know the definition for correlation and cation and the definition of risk you have to know why each risk factor is an risk factor so why antioxidants reduce the risk they reduce the risk of cardiovascular disease because they reduce free radicals that damage indal lining that would otherwise cause an aoma and why age is a risk factor why gender is a risk factor and why diet is a risk factor why smoking is a risk factor why do people underestimate the risk of cardiovascular disease for example high salt diet or high cholesterol diet high energy diet or smoking on cardiovascular disease because cardiovascular disease takes so long to develop it has longterm effects and that takes a long time to develop people will think they're fine and won't notice an ual difference in their body until it's too late and um they see other people around them doing the same things and think they are fine so they just assume they are going to be fine too they mostly ask uh this question for three marks so you only know need to memorize three of those points and leave the rest okay if you want to uh if you want to plan an experiment on the effect of a risk factor on CBD like vitamin C you have to get a large sample of healthy volunteers why does it have to be a large sample for reliability and repeatability why do the individuals have to be healthy for validity because if the individuals already have cardiovascular disease or are at high risk of cardiovascular disease then it's too late to see if this Factor will increase the r risk or not uh the individuals have to be of similar age gender Mass lifestyle and diet you divide those individuals into two groups one is given for example a vitamin C supplement or A3 type of antioxidants and then the other group is given a placebo why is a placebo given so that um we know that the vitamin C is what is causing the change not the mental factor of it and then you monitor the incidence of heart disease over the group over a long period of time um this study might be unreliable why because not all factors can be controlled we can't have all the volunteers of the exact same mass of the exact same lifestyle of the exams same diet and then you might have an unreliable estimate there is no clear definition of a high salt diet and like if you have a group of smokers how many cigarettes are smoked by each person defer the treatments of cardiovascular disease and the risk of each one anti-hypertensives reduce blood pressure but they cause drowsiness heart palpitation swelling of the feet and ankles a persistent cup satin reduce levels of LDL cholesterol uh because it is a risk factor to have a high LDL to HDL ratio so we lower the LDL to HDL ratio using stens but it can uh cause things like diabetes or liver problems anti coogulant um it reduce the formation of the blood clots so it reduces atherosclerosis especially in the coronary artery can cause excessive bleeding if an injury occurs platelet Inhibitors work in a similar way they also reduce the formation of new blood clots so the risk of blood BL vessel blockage is reduced but can also cause excessive bleeding in case of an injury um an experiment you would have to describe is to compare the vitamin C contents for of three fruits so you have to collect fruit extracts from all three fruits get beakers with a certain volume of dcpip TI trade drops of fruit extract one the first fruit till the color changes from Blue to coloros of the cpip record the drops needed repeat for the other fruits on new DCP IP and Beaker of the same volume repeat the exper holy Experiment three times for all fruits use calibration curve to get the concentration and control the storage fright and age of fruit why the risk decreased over years so for example it gets you two graphs one from the '90s and one a new current one why is for the same risk factors why is the risk reduced for people because better healthare there are more pills developed new statins all of those and people are more aware of risks and lifestyle okay the difference between reli reliability and validity reliability is when you can repeat the experiment M multiple times and get similar results like here validity is when the results are correct to a we've got cell membranes and the transport across cell membranes so first the cell membrane controls the movement of substances into and out of cells it has proteins and glycoproteins embedded into the membrane has surface receptors to bind things like hormones the structure of the cell membrane is a phospholipid bilayer membrane it has phospho heads outside as they are hydrophilic and interact with polar acous environment while the fatty acid Sals are non-polar or hydrophobic so they orientate themselves away from the acous environment the fluid mosaic model is a model of the cell membrane uh the it's fluid du its fluid fluidity of phospholipid Bayer it allows molecules to flow within it and the phospholipids are constantly moving the um it's Mosaic because of the transport proteins receptor proteins that have various shapes and sizes embedded randomly into the cell membrane cholesterol is found in the membrane to give it stability and reduce the fluidity the non-polar for of the fatty acid taals is uh embedded into the fatty acids and the O group is is with the for fate heads to keep it in place here are the tri of Transport active which uses energy from ATP passive that doesn't use energy simple diffusion is for small non-polar molecules like CO2 and O2 and facility diffusion is for Polar ions that need a polar protein channel to go through it osmosis is for water endo and exocytosis both transport for large molecules an active transport is for molecules against their concentration gradient um you have to know the adaptations of gas exchange surfaces they have a thin Alvi wall that reduces diffusion distance they have many Alvi that increase the surface area for diffusion a capilary network to main maintain concentration gradient and good ventilation for uh concentration gradient explain the factors affecting the cell membrane permeability temperature because as temperature increases the rate of diffusion increases uh perity increases because the kinetic energy of molecules in the membrane increases so they move more the phospholipids move more a cholesterol reduces the movement of phospholipids as it combines with fatty acids holding the fatty acid chains together in place so phospholipids move less it's vital to say phospholipids move less I don't know why I didn't write that uh write that okay fatty acid ch are nonpolar and allow nonpolar substances to diffuse into cell polar ions need a polar channel to get into the cell through the cell membrane 2B talks about enzymes you have to know how to define an enzyme enzymes are biological catalysts that increase the rate of reaction by lowering the their activation energy of reactions they cataliz either intracellular reactions interactions in cells Mustafa how many times would I record the them and then how nucleotides join let's imagine this oh let's turn on the pen here those are the pentos sugars here's the phosphate group so to have the sugar backbone the two nucleotides join by phosphodiester bonds it's called phosphodiester because what's joining them is the phosphate group and then this just moves on to have a poly nucleotide chain this is the sugar backbone and then we have um hydrogen bonds between the bases so here we have those bases and then on the other side we'll have another poly peptide Cham here I'm showing you the structure all the images are from save my exams I hope they don't copyright me but anyways I forgot I put a diagram already I didn't have to draw it for you guys and um adenine and thyine they have two hydrogen bonds cytosine and guanine they have three hydrogen bonds and you can be asked to compare the structure of DNA and RNA DNA is double stranded it has thyine and uh DNA has deoxy ribos sugar uh while RNA it's single stranded has osol instead of thyine and it's a ribos sugar they both have pentos sugar ribos and deoxy ribos are both pentos sugar they have a phosphate group both have phosphodiester bonds between nucleotides and they both have the adenine and guanine bases here it's also showing you the structure this uh the Pines have a single carbon ring the pyramid pyramides have a double carbon ring structure now we have DNA replication DNA replication is described as semiconservative semiconservative because one DNA molecule will divide into two DNA molecules each DNA molecule has a new newly synthesized Strand and an old paternal strand from the old DNA it's shown here here we've got two strands one is purple one is blue and then one of the old blue strands is here on the left and then the new stand is on the right it's commonly asked to describe semiconservative replication or just um DNA replication and it's always semiconservative so you have to write the steps the double helix unwinds as DNA helicase breaks the hydrogen bonds one strand is used as a template Strand and complimentary base pairing occurs attaching fre nucleotides to template strand D polymerase moves along the Strand joining adjacent nucleotides by phosph foraster Bonds in condensation reaction to make the new DNA how do we know that it's semiconserved how did we prove that okay so two scientists called mesen and stall they proved it by growing bacteria and N15 it's uh I forgot the name all right isotope isotope is the word okay N5 is an isotope of nitrogen so it's a heavy nitrogen isotope oh it's right there I could have continued reading okay and then they transferred it to nitrogen 14 culture which is the normal light nitrogen to find out each DNA molecule has one Str with N15 and one Str with N4 so here we're showing the experiment cuz they looked at each one and each one has 1 N5 one N4 it means that when it was replicating it used one old Strand and generated one New Strand nature of genetic code the order of bases in DNA make up genetic code intron are the coding parts of DNA and Exon are the non-coding part uh so genetic code is a triplet code so three nucleotide bases make up a codon which codes for a particular amino acid um so three bases code for one amino acid so the first feature of the genetic code is that it's a a triplet code and then it's a non-overlapping code so each code is only read once and then and the amino acid is recruited and then the ribosome moves onto a new codon and so on it's a degenerate codes so different codons can code for the same amino acid for example the code on cuu and CC both code for the amino acid Lucine this means that some mutations will have no effect on the organisms since the same protein will still be produced so since the genetic code is degenerate that's a very huge Advantage for living organisms since silent mutations can mutate silent mutations can be undergone silent mutations oh can happen silent mutations can happen with no effect whatsoever and it's a universal code this isn't often in the mark scheme but it's still a point in the syllabus so we have we have to say it universal code so all organisms use the same genetic code bacteria bonobos and bananas all contain DNA made up of the four nitrogenous bases that are found in humans here um it shows you the transcription part of protein synthesis transcription is when oh sorry guys um it's the part where the DNA in the nucleus is turned into to mRNA here is the translation part of protein synthesis which happens at the ribosome so that mRNA code that has already been transcribed is translated into a protein or polypeptide you have to memorize the stps of transcription so first off the RNA polymerase enzyme attaches to the promoter region of the DNA and then unzips the gene RNA polymeres moves along the Gene and un wides the gene by breaking the hydrogen bonds between the nitrogenous bases the free ribon nucleotides and the nucleus bind with complimentary base pairs on the antisense strand of the gene the a uh binds with u and C with the G the free nucleotides are joined by condensation reaction to form phosph dither bonds this is um guys I'm kind of word actually the new mron a formed peels away from the coding strand coding Strand and the DNA rewinds which happens when the stop codone is reached translation mr& a moves from the nucleus into the cytoplasm and attaches to the ribosome TRNA Carri is an amino acid and attaches to the just memorize this it's there's no much explaining to do if you don't get it you can watch another YouTube video because I'm just summarizing I'm not doing much I think I think my brother is sick I don't know though to see to see the first lesson is about mutation mutation is a random change in DNA sequence coding for a polypeptide a point mutation is a mutation that involves a chain in the D base sequence at a single location so everything we have in the syllabus is a mutation that involves a change in the base sequence at a single point but some mutations take place in multiple place in the body or at the autosome cells so every single cell has that mutation in the whole body so for example substitution insertion and deletion insertion when is when an extra base is inserted into DNA sequin often results in a nonfunctional protein as all codons after insertion are affected this called frame shift as the code is non overlapping delation is when a b is removed from the sequence resulting also in frame shift and a likely nonfunctional protein as all codons after deletion or changed wait do I have a picture for this no I'll just draw for you guys so let's say we have a u c g a a t something and then you insert you know how those are tripx codes each three code for one if you add a little um let's think what would we add we add another a here okay so now we will probably have a nonfunctional protein because let's say this codes for like Lucine protein amino acid I mean and this codes for I don't have Amo name is memorized um we'll call it Melissa okay now after the mutation what happened is that this isn't the triplet code anymore that's going to be readed because those three AG G is going to be the new amino acid so it's going to translate into new amino acid and then after this let's say t a t instead of it being g a t and then the one after atg we have a new amino acid and each one after that will also have an amino acid so none of the amino acids after the frame shift will be correct and same with Del substitution mutation include silent mutations substitution is when um one single base is substituted by another replaced by another silent mutations the mutation does not alter the amino acid sequence of the Polar peptide this is due to the degenerate code of the nature of the genetic code so as we said genetic code is degenerate which means that multiple codons code for the same amino acid so basically there will be no difference because somehow by Chance the mutation caused a degenerate what okay moving on missense mutations the mutation Alters a single amino acid in the peptide chain for example cell anemia is caused by single substitution mutation chaining a single amino acid in the hemoglobin protein Amino is it Amino or is it Amino Amino right have I been saying amino acid the whole video Amino amino acid okay so um missense means a whole new amino acid will be produced nonsense is when the base is substituted replaced by a base which codes for for a stop codon a stop codon is the one that tells the MRNA to stop stop translating so the polypeptide or protein y will be shorter and yeah anything as say that will not be coded for since there are no complimentary tRNA molecules with anti-codons so basically the MRNA is coding at the ribosome and then the sub quotum comes and there is no thna with an amino acid for that so it just doesn't continue inheritance every cell contains two copies of each gene one from each parent we have 23 pairs of chromosomes and the chromosome in each pair are called homog homologous chromosomes in each pair one comes from the mother and one from the father you have to know these definitions very well they are often asked about very very very often um I don't know why I didn't write jeans but you also often about asked about what a gene means Gene is a part of DNA base sequence coding for poly peptide um genotypes is the combination of genes although combination of alal in the individual phenotypes is the characteristics expressed in an individual caused by a mix of genes and environmental factors alals are different forms of a gene a dominant alal is always expressed when it is present a recessive alal is only expressed when it is in homozygous form so both alas are recessive so you don't have any other Al to express so the recessive is expressed cystic fibrosis cystic fibrosis you have to memorize it very well it's often as to um so what causes Cystic Fibrosis cystic fibrosis is causing by mutation that causes a faulty CFT cftr uh transport protein in the surface membranes of epithelial cells the sft is a chloride ion transport channel so the chloride ions do not exit the cell so the chloride ions stay in the cell so water does not leave cell by osmosis since um the chloride ion concentration in the C is much higher than outside since no um channel protein is helping the chloride ions exit the cell so then um the mucus on the epithelial cells is not diluted by the water this results in thick sticky mucus It lines the tubes and ducts in the gas exchange tract the digestive tract and reproductive system this sticky mucus increases the chances of lung infection and makes gas exchange less efficient microorganisms become trapped in the sticky mucus causing illness Celia cannot move the mucus because it's is too sticky so the Celia cannot beat to move the mucus away so it's just stuck in the airway it reduces ventilation it reduces gas exchange since the airway is so inflamed low levels of oxygen in the mucus it's as harm so harmful bacteria can live in these condition uh Gases such as oxygen cross the walls of the Alvi into the blood system by diffusion the SE mucus makes it harder for diffusion to take place for the digestive system the cause the problems caused by stick fibrosis is that the pancreatic duct becomes blocked by that sticky mucus impairing the release of digestive enzymes the lower concentration of enzymes within the small intestine reduces the rate of digestion because of this the food is not fully digested and not all nutrients can be absorbed the pancreatic enzymes can also become trapped behind the meas blocking the pancreatic duct the enzymes damages the enzymes damage the pancreas damage to the cell walls and the pancreas that produce insulin insulin is involved in the control of blood sugar levels a form of diabetes can be the result so the main problem is that since pancreatic duct becomes blocked there are no enzymes in the small intestine to break down the large insoluble food molecules into small soluble ones that can be absorbed so it is not absorbed so that leads to Mal nutrition in the reproductive system we are mostly about mostly asked about females with cystic fibrosis they have a reduced chance of becoming pregnant because a mucous plug develops in the cervix and this stops sperms from reaching the egg so because the mucus is so sticky the sperm is stuck in that mucus before reaching the cervix or the fallopian tube so the egg cannot be fertilized genetic testing the DNA is tested to see whether it contains the known base sequin for the most common mutations that cause the genetic disease so uh genetic testing can be used in multiple ways it can be used to identify adult Carri they can choose to adopt or not have kids this is the answer to the question which asks you why because of the genetic testing less kids now have a genetic disease for example cystic fibrosis um genetic testing can be used for testing embryos am amniocentesis involves inserting a needle into the amniotic fluid to collect cells that have fallen of the placenta and fotus and then it is tested for the mutations cronic V sampling a small sample of placental tissue is removed either through the wall of the abdomen or through the vagina testing before implantation for IVF it is possible to test an embryo before it has been implanted into the urius a cell can be removed from an embryo the cell can then be analyzed and used to decide whether to place the embryo into the wimp or not problems with genetic testing if it's so convenient and you can eliminate people with such hard genetic diseases why do we not all get genetically tested before we implant kids because of Ethics there are religions that are against abortions as life is a sacred gift from God the baby has a right to live they view that discarding IVF embryos is like murder sick babies are less worthy of life and this caus a social stigma around illness if we abort every baby with the genetic illness people would think that they are less worthy of living than normal human beings this may cause a miscarriage of fetus and you can get false positive results and that would lead to a loss of a healthy baby oh we are done