LSU Bio 1201 Exam 2 Study Questions and Answers Graded A 2024

why are membranes called phospholipid bilayers? - phospholipids have hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2 layers what is meant by fluid mosaic? - Mosaic of proteins drifting laterally in fluid bilayer of phospholipids how are membranes adjusted for different temperatures? - membrane fluidity adjusted by changing the ratio of unsaturated to saturated fatty acids how do the relative amounts of saturated and unsaturated fats change? - if you are in a cold environment you want more saturated fats for your membranes to be fluid; warm environment you want more saturated fats to make your membranes more solid what is meant by membrane fluidity? - not too solid, not too fluid why is fluidity an important property? - preserves membrane function Henrique and Hanson performed experiments with pigs and examined the effects on the relative amounts of saturated and unsaturated fats. What did they find? - found that membrane fluidity can acclimate to temperature; pigs raised wearing underwear in a hot room had subcutaneous fats with higher melting point what types of molecules can move easily across the membrane? - small nonpolar molecules, gases, steroid hormones, and water what is simple diffusion? - down the concentration gradient; does not require supplied energy; does not use a carrier molecule what is facilitated diffusion? - down the concentration gradient; employs carrier molecule; does not require supplied energy what is active transport? - work must me done; must use supplied energy; employs carrier molecule for which transport processes are carrier molecules involved? - facilitated diffusion and active transport which transport processes require the input of additional energy? - active transport what is a semi-permeable barrier? - only some types of molecules pass through when equilibrium is reached in diffusion: does movement of molecules stop? - no when equilibrium is reached in diffusion: does the net movement of molecules stop? - yes what is meant by hypertonic? - lower water potential; more solutes dissolved; tend to gain water via osmosis what is meant by hypertonic? - higher water potential; fewer solutes dissolved; will tend to lose water via osmosis isotonic - equivalent water potential; equal number of solutes; no note movement of water in which direction does water flow? - osmosis and the direction of net water movement what are aquaporins? - channel proteins which facilitate water diffusion through the membrane marine bony fish are...? - hypotonic to seawater how do enzymes work? - they position the reactants in a conformation more favorable for the chemical reaction to occur what aspects of the energetics do enzymes change? - enzymes lower activation energy barrier ΔG⧧ what aspects of energetics do enzymes not affect? - they do not reverse an energetically unfavorable reactions; they do not make a reaction go uphill how are substrates lured into the active site? - positively charged arginine sidechain lures the negatively charged substrate into the active site what are the analogs to these characters in the binding of substrates to enzymes? - Siren song= positively charged arginine sidechain Negatively charged substrate= Odysseus' men Circe= active site how do temperature changes affect the rates of reactions catalyzed by enzymes? - temperature is a measure of how many molecules will have achieved activation energy; low temp= low energy associated with molecule what is meant bby the thermostability of an enzyme? - Able to remain stable and function at high temperatures