BIOL 1361 1nd Edition Lecture 6 Outline of Last Lecture I. Understanding Correlation TableII. Cell Membranes and Membrane TransportIII. Structure of Cell MembraneOutline of Current Lecture I. Unsaturated Fatty AcidII. PhospholipidsIII. ProteinsIV. Function: Selective PermeabilityV. OsmosisVI. Water Balance in Cells (problem)VII. Passive TransportCurrent LectureI. Unsaturated Fatty Acida. Side chain has 1 or more double bondsi. Carbons NOT fully saturated with Hb. Double bond causes a kinkc. Cant pack tightlyd. Liquid at room temperatureII. Phospholipidsa. Form a bilayer in aqueous solutionb. Hydrophobic tails associate with each otherc. Hydrophilic heads interact with aqueous solutiond. Form organelle and cell membranese. Cells can change fluidity of membranei. More unsaturated fatty acids = more fluid membraneii. More saturated fatty acids = less fluid membranef. Steroidi. Carbon skeleton = 4 ringsii. Animal cell membranes contain cholesterolg. Cholesterol in membrane changes viscosity (a fluids resistance to flow)i. Low temp: cholesterol prevents too much phospholipid packingii. Warmer temp: cholesterol prevents too much phospholipid movementThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. Proteinsa. Transmembrane proteins = integral proteins span the phospholipid bilayerb. Peripheral proteins attach to inner (cytoplasmic) or outer (extracellular) ends of integral proteinsIV. Function: Selective Permeabilitya. Permeabilityi. Property of being porous and allowing something to pass throughb. Cell membranes are selectively permeable: some molecules can cross and other cantc. Diffusioni. Movement of molecules from high to low concentrationii. Spontaneous process, no cellular energy requirediii. Molecules have kinetic energy and are constantly movingiv. At equilibrium, molecules are distributed equally across membranev. But molecules continue to move back and forthd. Molecules that Cross Cell Membranes by Simple Diffusioni. Non-Polar substances1. Can dissolve in phospholipid bilayer2. O2, Co2, hydrocarbons can crosse. Diffusion Ratei. Depends on physical factorsii. Fick’s Law of Diffusioniii. Qs = (t)DA(C2=C1)/x1. Qs – quantity of substance2. D – diffusion constant3. A – area of surface4. C2-C1 – concentration gradient5. x – thickness of surface6. t – timeiv. What if?1. How will Qs change is the value of each variable is large?2. If the value of each variable is small?If ___ is large QsD Get largerA Get largerC2-C1 Get largerx Getsmallert Get largerIf ___ is smallQsD Get smallerA Get smallerC2-C1 Get smallerx Get largert Get smallerV. Osmosisa. Diffusion of waterb. Water molecules move from high to low water concentrationVI. Water Balance in Cells (problem)a. Cell without cell wall placed in hypotonic solution – a solution containing fewer solutes that the cytosoli. Result: cell will swell and burstb. Cell with cell wall place in a hypotonic solution i. Result: cell swells, but cant burstVII. Passive Transporta. No cellular worki. Example: Simple Diffusion1. Non-polar substances move across cell membrane from high to low concentrationii. Example: Facilitated Diffusion1. Hydrophilic substances cross cell membrane via transport proteinsa. Move from high to low concentration2. Mechanisms of Facilitated Diffusiona. Channel Proteins – hydrophilic tunnels through cell membranei. Transport small polar or charged molecules: H20, ionsb. Carrier Proteins – integral membrane proteinsi. Polar molecule attaches to one side of the protein, protein changes shape, moves substance across thecell membraneii. Ex. Glucose transporter protein in basolateral membrane of intestinal epithelial
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