Copy of 6. Cell Membrane and Transport 2023.pdf

SBI 4U0 CELL MEMBRANE  Cell (Plasma) Membrane Intracellular fluid Extracellular (cytoplasm; fluid (ECF) cytosol) Cell Membrane Structure Cell (Plasma) Membrane ◻ aka. phospholipid bilayer ◻ is selectively permeable, allowing so...

SBI 4U0 CELL MEMBRANE  Cell (Plasma) Membrane Intracellular fluid Extracellular (cytoplasm; fluid (ECF) cytosol) Cell Membrane Structure Cell (Plasma) Membrane ◻ aka. phospholipid bilayer ◻ is selectively permeable, allowing some substances cross through the membrane ◻ is a “fluid mosaic” fluid = proteins and phospholipid are free to move lipids and proteins that form membranes constantly move, shifting and rearranging themselves to serve the cell's needs mosaic = proteins and carbs are randomly placed The Fluid Mosaic Model phospholipid bilayer: made of polar phosphate Cholesterol heads (hydrophilic) & hydrophobic fatty Membrane lipids are held together by acid tails weak intermolecular forces (pg. 69) Cell Membrane Exploration Structure of Phospholipid Membrane Proteins (loosely bound on the surface) (embedded in the membrane) Function of Membrane Proteins Proteins allow molecules (hydrophilic/large) to pass through. These proteins have receptors that recognize molecules (i.e. glycoproteins) These proteins send signals to cells Function of Carbohydrates in the Membrane ◻ Used for cell to cell recognition ◻ Basis of immune response. Ex. WBC and T-cell response ◻ carbohydrates are usually branched oligosaccharides with fewer than 15 sugar units  Function of Cholesterol in the Membrane ◻ ¨At warm temp., intermolecular forces weaken, phospholipids want to move apart BUT cholesterol restrains the movement ◻ ◻ ¨At cool temp., intermolecular forces strengthen, phospholipids become rigid; BUT cholesterol keeps membrane fluid by preventing tight  Factors that affect membrane fluidity: 1. Temperature: high temp = bilayer is extremely fluid; low temp = bilayer solidifies like gel 2. Presence of double bonds in fatty acid “tails”: kinks result in a fluid membrane 3. Fatty acid “tail” length: longer fatty acid ‘tails’ have more intermolecular attractions & hold together more tightly 4. Presence of cholesterol: at low temp., it prevents phospholipids from packing tightly making membrane more fluid; at high temps. Cholesterol attracts & stabilizes phospholipids. (only in eukaryotic cells)  Cell Membrane Questions 1. Why wouldn’t life be possible without cell membranes? (Hint: look at the function of cell membranes!) 2. Why are cell membranes described as fluid mosaic? Why this characteristic is important? 3. How do phospholipids make cell membranes “semipermeable”. Don’t forget to define “semi-permeable”? 4. What is the role of cholesterol in cell membranes? 5. What type of molecules can easily pass through the cell membrane? Give examples. 6. What type of molecules need protein channels? Why? Give Examples. 7. Proteins in the membrane control a wide variety of cellular processes. List and explain at least 4. 8. Why do phospholipids spontaneously form lipid bilayers when placed in water. Draw and label a diagram of a phospholipid bilayer to support your answer. 9. How do double bonds in fatty acids and fatty acid tail length affect membrane fluidity? Explain with the aid of a diagram. 10. Watch “Soap Kills Covid.” With the aid of a diagram, explain how soap kills covid 19. Cell Membrane Transport Movement of molecules across a membrane CELL TRANSPORT ◻ A cell requires a constant supply of raw materials to keep it alive. And it also needs a transportation system to get rid of wastes and move out finished goods. There are specific ways to move material in and out of the cell.  What are some things that cells would need to transport? proteins Glucose (move in of cell through (active transport) special openings in cell membrane – active transport oxygen (diffusion) Water (osmosis) proteins Carbon dioxide (move out of cell through (diffusion) special openings in cell membrane – active transport )  Terms ◻ Solute: substance to be dissolved (ie. sugar, salt) ◻ Solvent: substance that DOES the dissolving (i.e water)  Terms ◻ Concentration Gradient: difference of concentration between 2 areas area with more area with less molecules molecules 2 Types of Cell Membrane Transport Passive Transport Active Transport ◻ is the movement of molecules ◻ is the movement of down the concentration molecules against the gradient (high to low) concentration gradient (from low to high WITHOUT using energy concentration) with the use (ATP) of energy (ATP). ◻ Types of passive transport: ◻ Types of active transport: Diffusion Primary Active Osmosis Secondary Active Facilitated Diffusion Vesicle Transport Exocytosis Farts, Water Farts, & Elephant Doors Endocytosis  DIFFUSION ◻ movement of particles from an area of high concentration to an area of low concentration (down the concentration gradient). DIFFUSION example Oxygen gas diffuses from lungs to blood while carbon dioxide diffuses from blood to lungs (alveoli). ◻ In cells, oxygen gas diffuses from blood to cells while carbon dioxide diffuses from cells to blood. DIFFUSION example ◻ CO2 (in high concentration in the air) moves into the leaf (where the concentration is lower) OSMOSIS ◻ Movement of water across membranes Which side did the water move to? Why? OSMOSIS Three types of solutions in osmosis [solute] is the same [solute] outside [solute] outside both in and outside cell is high cell is low the cell * Water ALWAYS follows solute!* Tonicity in Animal vs. Plant Cell (crenation) Carrot Slices Under Microscope: http://teachertube.com/viewVideo.php?video_id=16606 OSMOSIS example In freshwater, solute In saltwater, solute concentration is concentration is higher inside higher outside fish, so water moves fish, so water moves in. Fish out. Fish regulate water by actively regulate water by pumping out absorbing solutes so water can solute so excess water can exit. move back in.  Examples of Osmosis Plant roots absorb water and minerals from soil.  What am I? solvent ◻ When you place a drop of ◻ When you place a cell in a food colouring in a glass, the salty solution, it shrinks colour spreads ◻ When you place a cell in ◻ When you cook in your pure water, it swells and kitchen, the smell travels to bursts your room FACILITATED DIFFUSION ◻ is the movement of molecules across the membrane WITH THE HELP A MEMBRANE PROTEIN. ◻ is needed for large or hydrophilic molecules (ex. glucose)  FACILITATED DIFFUSION ◻ A channel protein some stay open all time and allow a specific molecule to cross. Look carefully - For example: aquaprorin is a channel protein that allows massive amounts of water to move into or out of the cell ◻ A carrier protein opens and closes. It moves large molecules like glucose or amino acids. - For example: GLUT1 is a carrier protein found in all animal cell membranes that transports glucose. CYSTINUREA Cystinurea is a hereditary disease caused by the inability of carrier proteins to remove the amino acid cystine. If cystine is not removed from urine, it crystallizes into painful stone that can block the flow of urine in the urinary tract. Active Transport Active Transport ◻ is the movement of molecules against the concentration gradient (from low to high concentration) with the use of energy (ATP). ◻ Types of Active Transport: Primary active transport Secondary active transport Vesicle (Bulk) Transport Exocytosis Endocytosis Primary Active Transport: PROTEIN PUMPS ◻ Direct use ATP to move material against the [gradient]. ◻ example: sodium-potassiu m pump uses the energy of 1 ATP to pump 3 Na+ ions out and 2 K+ ions in against the gradient. Secondary Active Transport ◻ indirect use of ATP ¨to move material against the [gradient]. ◻ Transport proteins are used, but they do not get phosphorylated by ATP, instead, the energy used to power these proteins come from concentration gradients created by proteins pumps that do use ATP Several types of protein pumps… Membrane Assisted TRANSPORT ◻ Really big molecules (proteins & macromolecules) are transported in/or of cells by vesicles ◻ also known as bulk or vesicle transport ◻ Two types of vesicle transport: Endocytosis & Exocytosis VESICLE/ BULK TRANSPORT  Endocytosis ◻ portion of the cell membrane pinches Receptor-mediated in, breaks off from the membrane endocytosis and forms a vesicle. ◻ allows the cell to engulf target substances from their Phagocytosis Pinocytosis extracellular environment. These substances bind to ◻ “cell eating” ◻ “cell drinking” receptors on the cell ◻ involves solids membrane which cause a ◻ Involves liquids coated pit to form which turns into a coated vesicle. Exocytosis ◻ used to export very large molecules out of the cell; ◻ vesicles fuse with the membrane and release their content