Zoology 101: Animal BiologyLast Lecture Outline Lecture 5 1.Cholesterol• LDL• HDL2. Fats and Oils (Triglycerides)3. Phospholipids• Membrane remodeling4.What do membrane proteins do?Current Outline1. Simple Diffusion2. Facilitated diffusion• Channel Proteins• Carrier proteins3. Osmosis4. Active Transport5. Vesicular (Bulk Transport)Simple Diffusion • Def: movement down the concentration gradient• No energy needed (ex: cup of tea) • Moves from high concentration to low; moves to become in most stable state • Membrane accepts small, uncharged, hydrophobic molecules (estrogen) • Gases and water take part in simple diffusion• doesn't accept large polar molecules or ionsFacilitated Diffusion• Also movement down the concentration gradient, No energy required• movement aided by transmembrane proteins • Channel Proteins◦ pore-forming transmembrane proteins; “straw through membrane”◦ gated; open-close in response to specific signals◦ signal molecule, binds to channel and opens◦ chamber is hydrophobic◦ selective ◦ rapid response• Carrier Proteins◦ change shape upon binding to a substance they transport (in one side, out the other)◦ specific shape◦ Major example: process of low blood sugarOsmosis• Passive transport of water• water moves down its concentration gradient• no energy• proteins are and aren't used• Hypertonic: lots of solute, makes the cell shrivel up and die because water is trying to equilibration its surroundings → water goes out of the cell• Isotonic: surroundings are at an equal amount, water in and water out• Hypotonic: the there is a high concentration outside the cell, water moves into the cell causing cell to burst• is a combination of both simple diffusion and facilitated diffusion • aquaporins: water channels ◦ frog egg experiment Active Transport• movement against the gradient• energy is required • ATP (adenosine triphosphate) , energy comes from the phosphate bonds • proteins are required • Types of protein◦ Pumps (something active happening); sodium/potassium pump▪ binds phosphate from ATP, changes shape, pushes Na out to fit the shape of K, the phosphate group will get removed and then picks up K, changes shape again, dumps out KVesicular (Bulk) Transport• Movement of substance in and out of cell by vesicle • Vesicle- membrane- bound sac• exocytosis: substance released from the cell• Endocytosis: substance taken in by the cell (BIG)◦ Phagocytosis: “ cell eating;” brings food into the cells, food vacuole surrounds food, non-selective◦ pinocytosis: “cell drinking;” vesicle surrounds dissolved molecule, nonselective ◦ receptor mediated endocytosis: highly selective coated pit vesicle surrounds ligands ◦ receptor: membrane protein with binding site that is specific shape for signal to bind (LDL)◦ uptake of LDL cholesterol into cells by receptors (apo protein binds to receptors)• Familial hypercholesterolemia◦ inherited disorder of high LDL◦ LDL cant be removed from circulation◦ defect in apo protein or defect in LDL receptors (High blood
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