welcome to the passionate minds course content review today we'll be covering cell structures and will have a focus on specific eukaryotic cell structures you'll also review how these structures help in the functioning of the cell so let's first talk about the plasma membrane so plasma membrane is found in all types of cells such as prokaryotes eukaryotes plants and animal cells so the plasma membrane is a very thin barrier that consists of a lipid bilayer so a lipid layer like we discussed in the lipid like uh lecture and it consists of proteins as well that we will see in the fluid mosaic model and that will separate the exterior environment from the interior environment so we see that there's two very different environments so the plasma membrane consists of a semi permeable barrier which allows for the passage of small molecules like oxygen nutrients and waste to support the cell volume in general and it also has a very key role in cell communication cell adhesion and cellular structure so the cell part is made up of a lipid bilayer like i said over here and specific associated proteins and a dysfunction results in cystic fibrosis so the endomembrane system is a continuous uh sort of system and it's connected indirectly via vesicles and it plays a big role in the cell's compartmental organization right so the endomembrane system where so endo the term endo means within so it is a group of members and organelles in the eukaryotic cells that works together to modify package and transport lipids and proteins it's all it also includes a variety of organelles such as the nuclear envelope lysosomes and vesicles endoplasmic reticula and the golgi apparatus which we'll cover shortly in the next slides technically it's not a part of the cell uh but the plasma membrane is part of the endomembrane system so we'll see that the plasma membrane interacts with other endomembrane organelles and it's the site usually where specific things like proteins are secreted so uh for example the in the pancreas uh you you have enzymes that are secreted note that the endomembrane system however does not include the mitochondria chloroplasts and peroxisomes so these aren't involved so the nucleus is found in all eukaryotes so not prokaryotes but eukaryotes which includes animal cells and plant cells particularly so the cell part is found within the cytoplasm and it's the most visible organelle so when you see under a microscope usually that's the most visible structure that you'll see within the cell so the cell part uh it contains most of the cell's genetic material and you'll see that the dna it is organized into chromosomes it's tightly wound up and then it's organized into chromosomes which uh play a role in storing the genetic information the cell part consists of a double membrane nuclear envelope so i'll write that here nuclear envelope uh and i will enclose the nucleus so you have these nuclear pores like we see over here these nuclear pores will regulate the entry and exit of molecules from the nucleus and finally you have a nuclear lamina which is present and the nuclear lamina is uh is what helps regulate the nucleus's shape so it's a protein matrix that'll help regulate the shape of the nucleus a dysfunction uh leads to hereditary diseases just because it's genetics related so like down syndrome for example so trisomy 21 the nucleolus is found in eukaryotes it is found inside the nucleus that's key it's found inside the nucleus but it is not membrane bound all right so it's not membrane brown uh membrane bound basically what it is is it's a sort of visible density that's within the nucleus and the appearance of the nucleolus differs across the cell cycle so at various stages it looks different so the main role of the nucleolus is that it is the site of rrna synthesis and ribosome assembly so the cell part is made up of rrna genes rrna as well and the associated proteins present with it so a dysfunction of the nucleolus leads to programmed cell death which is essentially cancer the rough endoplasmic reticulum is found in all kinds of eukaryotic cells uh it is found in uh specifically it's found in the cytoplasm as a membranous structure and the purpose of the rough endoplasmic reticulum is that it acts uh it synthesizes proteins and glycoproteins so synthesizes proteins and glycoproteins so glycoproteins are basically uh proteins that are modified with covalently linked carbohydrates so you think of a protein like this and then let's just say you have these carbohydrates that link from it uh so what is synthesized is i've what proteins are synthesized are include the proteins of the endomembrane system proteins that are embedded to the outer cell membrane and proteins that are secreted from the cell so these include protein hormones and enzymes additionally it can produce transport vesicles which distributes lipids and proteins to other components of the endomembrane cell so it can produce transport vesicles uh which can be used for other components of the endomembrane cell and endomembrane system or eventually end up the plasma membrane so this is why uh the the rough endoplasmic reticulum is given the name membrane factory so the cell part is made up of uh it's just continuous with the nuclear envelope it's a membranous structure uh and combined with the smooth endoplasmic reticulum it accounts for half the total membranes in many eukaryotic cells it also has an internal component uh called the er lumen and the surface of the rough endoplasmic reticulum is studded with ribosomes so that's one of the key features that we see over here the surface of uh the rough endoplasmic reticulum is studded with ribosomes a dysfunction leads to improper protein folding because a rough endoplasmic reticulum is responsible for a lot of proteins synthesis and production as we talked about uh with in terms of its purpose the smooth endoplasmic reticulum is also found in all kinds of eukaryotic cells uh it is a membranous structure found within the cytoplasm uh similarly to the rough endoplasmic reticulum but the difference is is that it is a smooth meaning that there's no ribosomes that are embedded onto the surface so the smooth endoplasmic reticulum has uh four main roles so we refer to it generally as a biosynthetic factory of the cell so what it does is it can synthesize lipids it metabolizes carbohydrates it detoxifies drugs and proteins and it stores calcium ions additionally the smooth endoplastic reticulum doubles in size when detoxifying but after a waste has been processed uh it returns to a normal size so the cell part is once again it is continuous with the nuclear envelope it continues with the rough endoplasmic reticulum as well and it also accounts for half of the total membranes in many eukaryotic cells combined with the rough endoplasmic reticulum it accounts for half of the total membranes the internal compartment once again is also known as the er lumen but the surface is smooth and it's lacking ribosomes just like i've mentioned a dysfunction results in huntington's disease ribosomes are found in all types of cells so this includes prokaryotes eukaryotes plants and animal cells so the cell part is found either in the cytosol as uh free cytosolic ribosomes so this is in all cells so all cells uh all cell types in particular consists of ribosomes that are free and the site is also free cytosolic ribosomes but in eukaryotes specifically what happens is uh they're found in the surface of the e the rough endoplasmic reticulum so this only occurs in eukaryotes uh it is also found in mitochondria and chloroplasts which are also found in which are specific to the eukaryotes so the main goal of ribosomes is to carry out protein synthesis through the translation so there's a process called translation which we'll talk about in molecular genetics so translation of rna into protein so the cell consists of small complexes both made up of rrna plus proteins and it is not membrane brown that's really important detail not membrane bound okay so we see that there's two complexes over here you have a small subunit and you have a large subunit uh additionally a dysfunction in the ribosome leads to uh something called dyskeratosis congenita so the golgi apparatus is found only in eukaryotic cells uh it is in close proximity to the endoplasmic reticulum but it's found it's basically found in the cytoplasm just like every other part that we're looking at the main role of the golgi apparatus is that is it is involved in shipping and receiving so it's a shipping and receiving center of the cell and it is able to modify uh products that come from the er so it modifies products from the endoplasmic reticulum a main modification is called glycosylation so glycosylation and this is basically when you add carbohydrate groups to proteins and lipids another function of the golgi apparatus is that it manufactures some macromolecules such as carbohydrates so what it'll do is that it can sort and package material these materials like carbohydrates into transport vesicles thirdly the there's also another important distinguishing that we must consider here you have a cis face and a trans face so the cis face is where it uh the the receiving side of the golgi apparatus and the trans face is the shipping side of the golgi apparatus so that is where vesicles will butt out so let's go through a little uh process here so the transport vesicles from the endoplasmic reticulum will first fuse with the cis face and then they'll empty their contents into the lumen of the golgi apparatus so you see that the lumens are these little the spaces uh between here so then will happen is that proteins and lipids they'll travel through the golgi and they're modified and then they'll be packed and sorted accordingly and then finally uh vesicles will butt out from the trans uh face of the golgi apparatus and they'll be sent to their destination the golgi apparatus basically consists of flattened membranous sacs that are called cisternae like we see over here these look like sort of pancakes in a way finally a dysfunction in the golgi apparatus leads to a chondrogenesis the lysosome is found in all eukaryotes we're currently questioning whether it is found in plant cells but it is uh will currently say that it is found in all eukaryotes the cell part is uh basically what it is is it's a membrane-bound compartment that is found in the cytoplasm of the cell now there's three main functions here as to what the cell part does we'll go through each one so the first the first function is enzymatic hydrolysis of various macromolecules so these macromolecules include lipids fats proteins and nucleic acids so it performs digestion using enzymes so the lysosome contains specific enzymes uh that if it will fuse it will break down components so it'll fuse with food vacuoles for example and it will absorb all the contents and then it'll digest it breaking it down to a part that could be useful useful for the cell lysosomes are also able to engulf another cell by phagocytosis by forming something called a food vacuole so lysosome will fuse with the food vacuole and digest the molecules inside of it so that's how some cells can engulf another cell finally lysosomes can also recycle the cell's own organelles and macromolecules in a process that is called auto so this so auto phagy refers to self eating the cell part is made up of uh a lysosomal membrane so the specific properties to the lysosomal membrane which allows the lysosomal compartment to be uh more acidic than the rest of the cell so this is like an enhanced environment so that you can have more variety of enzymes that are involved here the size number and shape of the lysosome are often variable though dysfunction in the uh in the uh lysosome can lead to something called eye cell disease vacuoles are found in all eukaryotes so plants and animal cells uh vacuoles are you are a membrane bound structure that is found within the cytoplasm and it is derived from the endoplasmic reticulum and golgi through the endomembrane system so that's how you form a vacuole so it is a result of the endomembrane system and the interactions within the various the previous organelles that we've talked about it is predominantly for storage but it varies by the cell types so food vacuoles are formed by phagocytosis so phagocytosis produces food vacuoles uh you have contractile vacuoles which is done by protists so protists have contractile vacuoles to pump out excess water from their cells and finally you have a scent uh you have so plants they have a central vacuole so central vacuole helps to hold organic compounds and water so in plants particular they have one large central vacuole but in animal cells there's many smaller vacuoles that are present so you see this example over here we have the plant cell there's this one large central vacuole here um additionally if you have a dysfunction in the vacuole you're going to have something that's called danan's disease peroxisomes are found in all eukaryotic cells and they're found within the cytoplasm just like all the other cell parts the cell part consists of having specialized metabolic compartments to break down organic molecules by oxidation so it breaks down uh organic molecules by oxidation and as a result of this oxidation you're going to produce hydrogen peroxide so hydrogen peroxide is unstable so what will happen is that it is converted to water and oxygen then peroxisomes also perform reactions with different metabolic functions so they can break down fatty acids so it breaks down fatty acids and amino acids necessary to produce other biomolecules such as cholesterols and phospholipids so these can be reused uh the cell part is made up of a single member so it's basically a single membrane with a single crystalloid enzyme core so that's this is called a crystalline core acts it has a enzyme function the mitochondria is found in all eukaryotes so this includes plants and animal cells it is found within the cytoplasm and it carries out a function that is called uh oxidative metabolism what does that mean it means that it is a metabolic process that converts energy from macromolecules to atp using oxygen so it will ultimately produce atp using oxygen cell part consists of a double membrane so we see one membrane here and then we see a second membrane over here and the outer membrane is very smooth but the inner membrane it folds into these little folds here that are called cristae so the reason why they're full folded into cristae is to increase its surface area the inner membrane will create these two aqueous compartments so you have the the outer compartment which is the inter membrane space and then you have the mitochondrial matrix which is the internal compartment over here a dysfunction in the mitochondria leads to congenital lactic acidosis chloroplasts are found in plants and algae and they're found within the cytoplasm the main function of chloroplasts is to carry out photosynthesis so photosynthesis is a process which uses sunlight to fix carbon dioxide so to fix carbon from carbon dioxide uh to generate organic molecules that are energetically rich such as glucose so the chloroplasts are surrounded by two membranes so you have an internal compartment like we see in this diagram here there's an internal compartment that is filled with an aqueous solution and this aqueous solution is called stroma so stroma uh the internal thylakoid membrane so we see these thylakoids over here so the internal thylakoid membranes that's what contains chlorophyll and they form these membranous sacs you call each one of these disks that are stacked they're called grana and inside the thylakoid is the thylakoid lumen a dysfunction results in leaf chlorosis now let's talk about the structural components of the structural parts of the cell the cytoskeleton is found in all types of cells so prokaryotes and eukaryotes they all have a cytoskeleton uh this the cytoskeleton is found as protein fibers so protein fibers that are extended through the cytoplasm like we see in this diagram over here so the cytoskeleton has many functions it's able to organize the cells structures and activities by anchoring many organelles so it organizes by anchoring organelles uh it helps to support the cell and maintain its shape so maintains cell shape it is also able to interact with motor proteins to enable motility and finally the cytoskeleton enables vesicles to travel along its tracks the cell part is made up of actin filaments microtubules and intermediate filaments and a dysfunction leads to alzheimer's so before we talk about centrosomes let's first go through a little bit of vocabulary here so this is a centriole and this is a centriole a centrosome consists of a pair of centrioles at right angles to one another so you can see how this forms a right angle because it's perpendicular so when you have two centrioles in this arrangement you form a centrosome so let's answer the first question so a centriole is found only in animal cells uh in plant cells they have their own version where they have microtubules that originate from a small nucleation site the cell part is found near the nucleus and microtubules are able to grow out from the centrosomes so it looks something like this so you see in a cell diagram uh we see microtubules that are extending they're projecting out so there's two main functions over here so the first function is that the microtubule portion of the cytoskeleton is involved in chromosome separation during cell division so the ana in anaphase what happens is that you have the cell over here and then we have one centrosome here we have another centrosome here we have the mitotic spindle fibers over here here let's just say this is a chromosome these are chromosomes so in anaphase you have them pulling towards the poles of the cell and that is a result of the centrosome working in action secondly the microtubules from the animal cell are involved as microtubule organizing centers so like i said before microtubules grow out from a centrosome near the nucleus in animal cells and a dysfunction leads to cancer cilia flagella are found in prokaryotes mostly but they're also found in some eukaryotic cells like sperm um the cell part basically what it is is that it has microtubules that control the beating of the cilia and flagella so they're locomotor appendages that's the term to describe them local motor appendages basically they're these extensions of the cell the cell part what it does is it basically acts in propulsion propulsion key for movement uh of the cell it basically works to move around various locations from point a to point b uh the cell part is made up of microtubules and then i'll talk about the specific associated proteins so uh cilia and flagella they have a common structure so they have a core of microtubules that are encased by plasma membrane and then they have this basal body that anchors that that anchors the uh so you have a basal body that will anchor the the celial flagella and then you have a protein that is called dinin so this is a motor protein that can that drives the bending movements finally what is what differs flagella from celia is a protein that is called flagellin flagellin is what enables the flagella to move in a rotary pattern so it's able to move in the circular fashion so that is what differentiates the prokaryotic flagella from cilia a dysfunction leads to male factor infertile infertility so cell walls are found in all types of cells so prokaryotes eukaryotes plants and animal cells and this is what distinguishes plant cells from animal cells prokaryotes and fungi they also have cell walls too the cell part basically what it is is is a very very thin barrier that consists of a lipid bilayer and proteins that separates the exterior environment from the interior environment just like i talked about for the plasma membrane but in this case i'll be more specific to plants because this is what distinguishes plant cells from animal cells in particular so the function of a cell wall is to protect maintain the shape and prevent the excessive uptake of water in plant cells so protect maintains the shape and it will prevent the excessive uptake of water so prevents the excessive uptake of water and plant cells particularly okay so the cell part is made up of peptidoglycan peptidoglycan uh if it is prokaryotic so peptidoglycan is a polymer of sugar and amino acids and this is notably found in only prokaryotic cells plant cell walls are made up of cellulose and cellulose which is embedded in other polysaccharides and proteins so this is specific to plants a dysfunction leads to bacterial soft rot