Chapter 5 BIO PDF

Chapter 5 Membranes Diffusion Gases water THe process in which particles spread out from each other From high concentration to an area of low concentration ○ PARTICLE MOVES DOWN THE CONCENTRATION GRADIENT UNTIL IT IS...

Chapter 5 Membranes Diffusion Gases water THe process in which particles spread out from each other From high concentration to an area of low concentration ○ PARTICLE MOVES DOWN THE CONCENTRATION GRADIENT UNTIL IT IS EQUAL Diffusion seen throughout nature Much be dissolved and must have a concentration gradient Osmosis Just for water ○ Movement from a high concentration down the concentration gradient to low gradient Water molecules move at random There is movement to the more concentrated side to the less side ○ Until both sides are equal Plasmolysis of elodea cells Plants cells duo their cell wall and membrane below that ○ However, too much substance outside the cell Waters going to go from the inside of the plant to the outside GOing to shrink and go to the outside Membrane Structure Phospholipids arranged in a bilayer (2) ○ Include glycerol phospholipids and sphingolipids Apart of the cell membrane Globular proteins inserted in the lipid bilayer Fluid mosaic model – ○ mosaic of proteins floats in or on the fluid lipid bilayer like boats on a pond Why?  Mosaic because it has a lot of little structure like proteins floating in the lipid bilayer ( like boat floating in water) Cholesterol prevents the cellular membrane from freezing/ Slowing down Cellular Membranes Have Four Components Phospholipid bilayer ○ Flexible matrix, barrier to permeability. Cholesterol inside it Flexible, moveable Transmembrane proteins ○ Some proteins that are hollow for things to cross Integral membrane proteins. Interior protein network ○ Peripheral or intracellular membrane proteins. Cell-surface markers ○ Glycoproteins and glycolipids Freeze-Fracture Microscopy Visualizes the Inside of the Membrane HOW THEY KNOW WHen you freeze dry a cell, you can move in with a tiny knife ○ When you pry in the ice, cleave it apart, it comes apart where the tails are. Able to seperate the pholipid bilayer Membrane Lipids Lipidomics defines the number and biological function of lipids ○ Hydrophilic tails Exposed to water ○ Hydrophobic Tails Not exposed to water Why scientist are able to separate them 1000 distinct lipids in cells are divided into 3 classes ○ Glycerol phospholipids ○ Sphingolipids ○ Sterols Polar head exposed to water Stay outside Non-poplar tail not exposed to water Stay inside Phospholipids Two layers of proteins and lipids Spontaneously form a bilayer because of amphipathic structure ○ Polar head group is polar and hydrophilic Phosphate group attaches to the head. ○ Two fatty acids are roughly parallel to each other. Nonpolar and hydrophobic (“water-fearing” Folding because of the way of the bonding Phospholipid Bilayer (Cellular Membrane) Phospho= Protein lipid = fat Bilayers are fluid ○ Membrane is fluid Ice floating in a river or lake Proteins move around through there like the example above Hydrogen bonding of water to itself and to polar heads, holds the layers together ○ Individual phospholipids and unanchored proteins can move through the membrane Heads on top Tails underneath , Like getting a bunch of different colored balls, and because of the currently, they are going to randomly combines If the members were fluid, you’d see a half red/blue, but You didn't so it shows that its constantly in motion Proof it moves ○ (Shown through scattering) Influences on Fluidity of the Phospholipid Bilayer Has to remain flexible even when colled Saturated fatty acids make the membrane less fluid than unsaturated fatty acids. ○ Saturated = solid room temp ○ Unsaturated = liquid in room temp Hot would make it more fluid so it works more efficiently Warm temperatures make the membrane more fluid than cold temperatures. ○ Cold tolerance in bacteria due to fatty acid desaturases Can be killed with a too high temp or low Lipid composition of the ER membrane, Golgi stack & plasma membrane are distinct. ○ Composition affects fluidity, thickness, shape of membrane Cholesterol molecules help maintain its fluidity These have membranes around them Look somewhat alive but lipids look different ish  ER and the PM Proteins that cross all the way across ○ Endoplasmic reticulum More fluid at room temp Has saturated fat ○ Plasma Membrane Uses unsaturated fat  Membrane Proteins The membrane has proteins embedded everywhere, but mainly made out of lipids These proteins have various functions. Various functions: (usually ask these on test) 1. Transporters a. Transport substances b. Don't always require energy (transporters) 2. Enzymes a. Most enzymes are proteins i. Will speed up chemical reactions 1. By lowering the activation energy 3. Cell-surface receptors a. Receives 4. Cell-surface identity markers a. They're for cell to cell identification i. For cells to recognize: 1. Eachother 2. Foreign objects 5. Cell-to-cell adhesion proteins a. For cells to glue together 6. Attachments to the cytoskeleton a. SO the cell can communicate inwardly and outwardly 7. Affect membrane structure  Membrane Protein Functions Most of these transmembranes, proteins Some of these have channels where certain substance can or cannot cross Enzymes connect together like a key or lock Part of the cytoskeleton that interacts with the cell. Structure Relates to Function Diverse functions arise from the diverse structures of membrane proteins ○ Have common structural features related to their role as membrane proteins ○ Anchoring Molecules Anchoring molecules attach membrane protein to the membrane surface. Anchoring molecules are modified lipids with: ○ 1. Nonpolar regions that insert into the internal portion of the lipid bilayer Nonpolar Regions are inside the lipid bilayer and sometimes in a protein Water is polar ○ Meaning it cannot cross the membrane easily which means it needs a channel protein They are polar in the inside so they’ll be able to cross in Called Aquaporins ○ 2. Chemical bonding domains that link directly to proteins Like glycoproteins Transmembrane Proteins Span the lipid bilayer Nonpolar regions of the protein are embedded in the interior of the bilayer. (Why some things can and cannot pass) EX: Water Water molecules cannot pass through the lipid because its a fat so they find other alternatives ○ α helices Sometimes secondary structure like a spiral staircase ○ β pleated sheets Or they fold Polar regions of the protein protrude from both sides of the bilayer. ○ It would pop out because the cell is nonpolar means that the polar cell would reject it Some of these have polar regions but in the inside or outside Outside and inside polar but the middle isn't ○ Why you cannot push it through Transmembrane Domains Transmembrane domain is a membrane-spanning region. ○ Hydrophobic amino acids arranged in α helices. Some of these have hydrophobic amino acids that don't respond well to the lipids Proteins need only a single transmembrane domain to be anchored in the membrane. ○ Often have more than one such domain  ○ Classification of some types of receptors is based on the number of transmembrane domains present. Pores Extensive nonpolar regions within a transmembrane protein can create a pore through the membrane ○ Nonpolar regions that may be nonpolar in the inside but they have to be nonpolar in some regions because they wouldn't be able to span the membrane For it to accept inside of the membrane, some of the proteins need nonpolar membranes Cylinder of β sheets in the protein secondary structure called a β-barrel ○ Interior is polar and allows water and small polar molecules to pass through the membrane. Always ask this question Sometimes ○ Exterior of the same protein needs to be non-polar You have protein going through the membrane The outside of the protein has to be non-polar or they’d pop out ○ The inside could be polar because it's fine as long as the outside is. So some molecules could come in with charges Passive Transport Not Active (inactive) not doing anything No energy required Substances will go through it due to diffusion and osmosis Passive transport is movement of molecules through the membrane in which ○ No energy is required. ○ Molecules move in response to a concentration gradient. Diffusion is movement of molecules from high concentration to low concentration ○ Will continue until the concentration is the same in all regions. More molecules in one side of the membrane Contributes to osmosis ○ Movement of water to a high concentration to low concentration ○ Movement of particles to a high concentration to low concentration Reach equilibrium till both regions have to same material on both sides  Diffusion Ex: Think of Kool Aid Transport Across Membranes (passive diffusion) These transport proteins cross the membrane to the inside where the cytoplasm is Major barrier to crossing a biological membrane is the hydrophobic interior that repels polar molecules but not nonpolar molecules ○ Nonpolar molecules will move until the concentration is equal on both sides. Will simply move through the membrane ○ Limited permeability to small polar molecules. Tiny enough and poler they might be able to pass through Not like water ○ Very limited permeability to larger polar molecules and ions Ions smaller than water molecules The bigger ones cannot usually easily pass Proteins Allow Membrane Diffusion to be Selective (Passive Diffusion Cont.) Facilitated diffusion ○ Molecules that cannot cross membranes easily may move through proteins. ○ Move from higher to lower concentration Channel proteins. (same cases use this to do so) Hydrophilic channel when open. ○ Inside might be hydrophilic Membrane is for the most part hydrophobic ○ Carrier proteins. Bind specifically to molecules they assist (they cross) Membrane is selectively permeable because of channels and carriers ○ Some can pass but others cannot Channel Proteins Ion Channels (Charged particle) ○ Allow the passage of ions through nonpolar interior of plasma membrane Might be able to bust most cannot pass through the polar membrane ○ Gated channels – open or close in response to stimulus (chemical or electrical). Depends on a stimulus like chemical or electrical ○ Three conditions determine direction: 1) Relative concentration on either side of membrane a) Relative concentration comparing the outside and the inside 2) Voltage differences across membranes. a) Negative on one side and positive on the other. 3) Gated channels – is channel open or closed.  Some of these transmembrane proteins have to be nonpolar in the outside Otherwise it wouldn't be able to interact with the outside Carrier Proteins Can help transport both ions and other solutes, such as some sugars and amino acids. Movement is via diffusion, requires a concentration difference across the membrane ○ If happening via diffusion, you might end up with more on one side that that it can move ○ Must bind to the molecule they transport (SO they move through) Saturation – rate of transport limited by number of transporters TOo many of theme molecules binding to these different proteins, so they have to wait their turn because its too occupied ○ See Through enzymes Osmosis Cytoplasm of the cell is an aqueous solution ○ Water is solvent ○ Dissolved substances are solutes Osmosis - net diffusion of water across a membrane toward a higher solute concentration ○ Movement of water ○ Looking at the concentration of water molecules and Solutes ○ Talking about when mentioning solute concentration: When has less water on one side: means there more solutes on one side Solutes can be anything ○ Ions, sugars, proteins, carbohydrates, lipids, etc Move right to left because there are more solutes on the left Osmotic Concentration When two solutions have different osmotic concentrations: ○ Hypertonic solution = higher solute concentration If you put a cell in a water here it will shrink Because outside of the cell is hypertonic in respect to the inside ○ Move inside to outside If happens with water: Plants will lose water and shrivel up. ○ Hypotonic solution = lower solute concentration (Hippo) If you put a cell in a water here it will become bigger Water going from outside to inside  ○ Have plants and if the plant looks wilted, and fill the vacuoles, expanding the cell walls. Hypotonic = Stays the same (equilibrium) Plasmolysis = the cell did not shrink only the plasmas Became detached When two solutions have the same osmotic concentration, the solutions are isotonic Aquaporins, specialized channels for water in cell membrane, facilitate osmosis ○ Little pores in proteins that allow proteins to pass through Osmotic Pressure Force needed to stop osmotic flow Cell in a hypotonic solution gains water causing cell to swell – creates pressure ○ What causes a plant cell to look nice and healthy Plant would not burst ○ Cell wall protects the cell from getting too large and exploding Cause a cell to have hydrostatic pressure: ○ Water will go in to a certain point but then will finally escape Read a balance in there In a case of a cell or fish, they would explode Cell wall can reach balance of osmotic pressure driving water in with hydrostatic pressure driving water out ○ Prokaryotes, fungi, plants, many protists Four different kingdoms All animal kingdoms except animal kingdom have cell wall Can control, won’t explode ○ Some protist who don't have cell walls have this so they won't burst THrough protected vacuoles Plasma membrane is not as strong, may burst ○ Animal cells must be in isotonic environments Stay in homeostasis Animal cells explode Maintaining Osmotic Balance (DO to maintain their water balance, Take in or move out water) Through the cell membrane, they are used to eject waste Some cells use extrusion in which water is ejected through contractile vacuoles ○ Paramesium ○ Amoeba Both have contractile vacuoles which are used for water regulation Function as our kidneys do Isosmotic regulation involves keeping cells isotonic with their environment Have to keep entering environment stable (reach equilibrium) ○ Marine organisms adjust internal concentration to match sea water. They regulate their water in certain ways Fish that are osmoregulation SOme marine organisms can take in substances from their environment to help maintain water regulation ○ Terrestrial animals circulate isotonic fluid DOnt need to rely on external environment like marine do, we naturally can Plant cells use turgor pressure to push the cell membrane against the cell wall and keep the cell rigid ○ When the cell large vacuole fills and exerts pressure on the membrane and that membrane asserts pressure on the cell wall Keeps the cell rigid How plant looks healthy and pull (without they would look wilted) Active Transport Requires energy – ATP is used directly or indirectly to fuel active transport ○ Usually in form of ATP Moves substances from low to high concentration ○ Now the reverse is true Now you move stuff against the concentration gradient L-H We use energy which are dont by transport molecules Requires the use of highly selective carrier proteins ○ Use ATP to change form and move substances across the membrane in which they are imbedded. Carrier Proteins and Active Transport Carrier proteins that require energy Carrier proteins used in active transport include: ○ Uniporters – move one molecule at a time. Uni = one ○ Symporters – move two molecules in the same direction. Working together ○ Antiporters – move two molecules in opposite directions. Move two molecules in the opposite directions Terms can also be used to describe facilitated diffusion carriers Sodium-Potassium (Na*/K+) Pump (functions on the nervous system) One side sodium and one side potassium Direct use of ATP for active transport Uses an antiporter to move out of the cell and into the cell ○ Movement is against their concentration gradient. Like moving against current ATP is used to change the conformation of the carrier protein Affinity of the carrier protein for either changes so ions can be carried across the membrane ○ ATP used to change the shape of the carrier protein 1) Extracellular - outside a) ATP i) When its broken down to ADP, one of them is going to be detached and create energy 2) 2) a) ATP realise a phosphate i) Because its going to phospilate the molecule (1) Going to detach from the protein and go to the outside ( the NA) 3) J a) When phosphate comes in its going to remove the phosphate and then they're going to leave and restart the cycle. Coupled Transport Uses ATP indirectly ○ Have two molecules being transported across the membrane Uses the energy released when a molecule moves by diffusion to supply energy to active transport of a different molecule Symporter or antiporter can be used Glucose–Na+ symporter captures the energy from Na+ diffusion to move glucose against a concentration gradient ○ Glucose and sodium 1) Have to molecules moving in or out Bulk Transport (requires energy) Type of active transport Bulk Transport: Means cell eating, drinking and releasing waste Endocytosis (Inside) ○ Movement of substances into the cell. ○ Requires energy To move substances inside the cell ○ Happens in all cells ○ Phagocytosis – cell takes in particulate matter. ‘ to eat’ CELL EATING ○ Some cells in your body like macrophages, immune cells, can eat foreign things like bacteria If cell eats bacteria, it will be broken down into substances we can use in the cell for its own function (components) Can break down to carbs, ect. Sometime s ○ Pinocytosis – the cell takes in only fluid. CELL DRINKING ○ Receptor-mediated endocytosis – specific molecules are taken in after they bind to a receptor.  Markers on the cell that help identify different substances Little structure on the membrane which help the substances in after the membrane binds to it Exocytosis (Outside) Removing stuff from the cell waste products Or products that are used by other cells./ and or waste products the cell is getting rid of. ○ Movement of substances out of the cell. ○ Requires energy. Will merge with a lysosome which will combine and be let out as waste : Phago These travel on the cytoplasm (Travel on the microtubules and use little motors that take substances in) Phino Think of that video where its badly animated and the things are moving along the microtubules  Because they have receptor proteins that only accept certain molecules When these receptor proteins land, it'll make the catherines react and then the whole thing together will engulf the molecules coming in and will be taken in by the cell. Decides and dirtubes what is and can be taken in. Exocytosis Discharge of materials out of the cell. ○ Cells releasing waste products Used in plants to export cell wall material. ○ Golgi apparatus working with the endoplasmic reticulum is sometimes responsible for making cell wall material Can be exported to the surface and make some of the cell wall material Used in animals to secrete hormones, neurotransmitters, digestive enzymes