LSU Bio 1201 exam 2 Questions With 100% Correct Answers.

LSU Bio 1201 exam 2 Questions With 100% Correct Answers. what is meant by membrane fluidity? - ANSWER -not too solid, not too fluid why is fluidity an important property? - ANSWER -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? - ANSWER - 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? - ANSWER -small nonpolar molecules, gases, steroid hormones, and water what is simple diffusion? - ANSWER -down the concentration gradient; does not require supplied energy; does not use a carrier molecule what is facilitated diffusion? - ANSWER -down the concentration gradient; employs carrier molecule; does not require supplied energy what is active transport? - ANSWER -work must me done; must use supplied energy; employs carrier molecule for which transport processes are carrier molecules involved? - ANSWER -facilitated diffusion and active transport which transport processes require the input of additional energy? - ANSWER -active transport what is a semi-permeable barrier? - ANSWER -only some types of molecules pass through when equilibrium is reached in diffusion: does movement of molecules stop? - ANSWER -no when equilibrium is reached in diffusion: does the net movement of molecules stop? - ANSWER -yes what is meant by hypertonic? - ANSWER -lower water potential; more solutes dissolved; tend to gain water via osmosis what is meant by hypertonic? - ANSWER -higher water potential; fewer solutes dissolved; will tend to lose water via osmosis isotonic - ANSWER -equivalent water potential; equal number of solutes; no note movement of water in which direction does water flow? - ANSWER -osmosis and the direction of net water movement what are aquaporins? - ANSWER -channel proteins which facilitate water diffusion through the membrane marine bony fish are...? - ANSWER -hypotonic to seawater how do enzymes work? - ANSWER -they position the reactants in a conformation more favorable for the chemical reaction to occur what aspects of the energetics do enzymes change? - ANSWER -enzymes lower activation energy barrier ΔG⧧ what aspects of energetics do enzymes not affect? - ANSWER -they do not reverse an energetically unfavorable reactions; they do not make a reaction go uphill how are substrates lured into the active site? - ANSWER -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? - ANSWER -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? - ANSWER -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? - ANSWER -Able to remain stable and function at high temperatures Proteins can be denaturation by physical factors such as temperature and pH - ANSWER -Environment can alter enzyme's functional properties: denaturation -Temperature -Hydrogen ion concentration -Solutes -Hydrostatic pressure What sets the upper temperature limit for life - the presence of liquid water or the stability of biological molecules? - ANSWER -Stability of biological molecules At high temperatures biological molecules, such as protein and DNA, break down very rapidly Why is there an upper limit? - ANSWER -It is energetically too costly to make biological molecules that breakdown that quickly You can't build them faster than they are broken down why are membranes called phospholipid bilayers? - ANSWER -phospholipids have hydrophilic head and hydrophobic tail, hydrophobic face inside of cell making 2 layers what is meant by fluid mosaic? - ANSWER -Mosaic of proteins drifting laterally in fluid bilayer of phospholipids how are membranes adjusted for different temperatures? - ANSWER -membrane fluidity adjusted by changing the ratio of unsaturated to saturated fatty acids how do the relative amounts of saturated and unsaturated fats change? - ANSWER -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 Enzyme homologs - what are they? - ANSWER -Comparable enzymes from different organisms Enzyme homologs from cold- and warm-adapted species - how do they differ in order to adapt to the different thermal energy in their environments to maintain adequate catalytic rates? - ANSWER -At their respected temperatures the enzymes catalyze the reaction at similar rates At a common temperature, the enzyme from cold-adapted species converts substrate to product a faster rate Coenzymes - ANSWER -NAD (oxidized form) NADH (reduced form) NADP (oxidized form) NADPH (reduced form) FAD+ FADH2 What do we mean by "reducing power?" - ANSWER -The addition of electrons or hydrogen to a molecule (adds energy) Oxidation= the removal of electrons or hydrogen from a molecule (reduces energy) There is a constant pool cycling between the reduced and oxidized forms. Competitive enzyme inhibition - ANSWER -Substrate and inhibitor compete for binding ot the active site of the enzyme Inhibitor is structurally similar to the substrate Most apparent at low [substrate]