Rebecca DavenportBIOL 1406 BW110/3/16Ch. 7 blueprint1. Cell membranes- a.i. Phosolipid bilayer- foundation of cell membrane.ii. Amphipathic molecules1. Hydrophobic (water-fearing) region faces in. (TAILS)2. Hydrophilic (water-loving) region faces out. (HEAD)iii. Contain proteins, other lipids and other molecules.1. Everything except Nucleic Acids.2. Carbohydrates on outside of membrane are how cells identify each other. iv. Fluid-mosaic model:1. Membrane exhibits properties that resemble a fluid because lipids and proteins can move relative to each other within the membrane.a. They spin, sway, and rarely flip.2. It’s considered a mosaic because of lipid, protein, and other molecules that make each membrane unique from one another. v. Factors affecting fluidity:1. Length of fatty acid tails- a. Shorter tails are less likely to interact so the membrane is more fluid, because they won’t get tangled.2. Presence of double bonds in tails-a. The double bonds create a kink in the fatty acid taili. Saturated less fluidii. Unsaturated more fluid3. Presence of cholesterol-a. Cholesterol tends to stabilize membranes (less fluid)b. The cholesterol molecules stack up in the membrane and don’t allow much movement.c.vi. Proteins associated with membranes:1. Integral membrane proteins-a. One or more regions that are physically embedded in the hydrophobic region of the phosolipid bilayer1. Transmembrane: protein goes through the entire membrane.2. Non-transmembrane: protein does not go all the way through the membrane.2. Peripheral membrane or extrinsic proteins-a. Found on one side of the membrane or the other b. Is not integrated in the membraneb. Transportation across the membranei. Selectivity permeable plasma membrane1. Essential molecules enter2. Metabolic intermediates remain3. Wastes products exitii. Gases and small nonpolar molecules move easilyiii. Barrier to most hydrophilic substances1. Small polar molecules move slowly2. Ions and large polar molecules can’t penetrate the phosolipid bilayer directly.iv. Cells maintain gradients:1. Living cells maintain a relativity constant internal environment different form their external environment.2. Concentration gradient-a. Concentration of a solute is higher on one side of a membrane than the other.Passive Activev. No EXTRA energy required vi. Regular extra energy (typically ATP)vii. DOWN gradient (High to low)viii. AGAINST gradient (low to high)ix. Passive diffusion- small, phobic/nonpolar molecules wiggle x. Primary Active transport- lowto high concentration, uses ATPacross membrane barrier. energy to help carrier change shape, only use carrier proteins.xi. Facilitated diffusion- small philic/polar molecules being transported by carrier proteins.xii. Secondary active transport- low to high concentration, Pre-existing concentration gradient (will piggy back so you don’t have to use ATP)xiii. Diffusion of water- high concentration of “free h2o” to low concentration of “free h2o” aka like to go from low solute to high solute (h2o likes to work aka dissolve solute)xiv.xv.xvi. Passive transportation: movement of molecules through a membrane.1. No energy is required- because molecules are moving from high concentration to low concentration.2. Molecules move in response to a concentration gradient.3. Types of passive transportation-a. Diffusion- movement of molecules from high concentration to low concentration.i. Osmosis- a type of diffusion1. Diffusion of water across a semipermeable membrane.2. Water diffuses through a membrane from an area with more free water to an area with less free water. 3. Tonicity- ability of a solution to cause a cell to gain or lose water. a. Compare solute concentration inside and outside the cell.b. Hypertonic (more) c. Hypotonic (less)d. Isotonic (equal)e.ii.b. Facilitated diffusion- movement of a molecule from high to low concentration with the help of a specific transport protein.1. Is specific2. Is passive3. Saturates when all carriers are occupiedii. A protein is facilitating the transport of a molecule.iii. Transport proteins: provide passageway for the movement of ions and hydrophilic molecules across membranes.1. Some move molecules passively and others actively2. 2 classes based on manner of movementa.b. Channels- form passageway for direct diffusion of ions or molecules across themembrane. (Like a toilet paper roll)c. Carriers- principal pathway for the uptake of organic molecules.i. Conformational change- changing shape.ii. -------lock and key fit, bind and release.iii. Uniporter- single molecule or ioniv. Symporter/cotransporter- 2 or more ions or molecules transported in same direction.v. Antiporter- 2 or more ions or molecules transported in opposite directions.xvii. Active transportation- movement of a solute across a membrane against its gradient from a region of low concentration to higher concentration.1. Energetically unfavorable and requires the input of energy.2. Only uses carrier proteins- cause they can change shape to move molecules over.3. Primary active transport- moving low concentration to high concentration by ATP.a. Use ATP get protein pump to transport soluteb. Ion pumpc.4. Secondary active transport-a. Use pre-existing gradient to drive transport of soluteb. One molecule moving down its gradient while it pulls the second along (2nd is moving up its gradient).xviii. Bulk transport- transport larger molecules such as proteins and polysaccharides and even very large particles.1. Exocytosis (EXIT) - material inside the cell packaged into vesicles and excreted into the extracellular medium.a.2. Endocytosis (ENTER)-a. Phagocytosis- plasma membrane extended outward to engulf a particle.i. Particle will eventually be broken down by lysosome.b. Pinocytosis- plasma membrane folds inward to “gulp” the extracellular fluid.i. Nonspecific- all solutes from extracellular fluid are takeninto the cell.ii. Regions of plasma membrane that form vesicle are linedwith coat proteins. c. Receptor- mediated endocytosisi. Specialized form of pinocytosis.ii. Specific for certain molecules due to presence receptorson the plasma
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