Unformatted text preview: e 4.7 B. Factors Influencing Enzyme Activity
1. 2. 3. 4. 5. Coenzymes and cofactors Allosteric regulators Temperature pH Salt concentration 3 1. Allosteric Control Activator or inhibitor binds to an enzyme Binding changes enzyme shape Change hides or exposes active site Feedback inhibition Product of pathway binds to and inhibits enzyme in the pathway Allostery
allosteric activator vacant allosteric binding site enzyme active site allosteric inhibitor allosteric binding site vacant; active site can bind substrate active site cannot bind substrate active site altered, can bind substrate active site altered, can't bind substrate can' Allosteric activation Allosteric inhibition 4 Feedback Inhibition
enzyme 2 enzyme 3 enzyme 4 enzyme 5 enzyme 1 A cellular change, caused by a specific activity, shuts down the activity that brought it about
END PRODUCT (tryptophan) SUBSTRATE 3. Effect of pH
Pepsin trypsin Depends on protein! But tightly restricted 5 2. Effect of Temperature Small increase in temperature increases molecular collisions, reaction rates High temperatures disrupt bonds and destroy the shape of active site Denaturation!! Denaturation!! III. Membrane Transport: Concentration Gradient Means the number of molecules or ions in one region is different than the number in another region a substance moves from a region where it is more concentrated to one where it is less concentrated: "down" gradient (High down"
oxygen, carbon dioxide, and other small, nonpolar molecules; some water molecules Low concentration)
glucose and other large, polar, water-soluable molecules; ions water(e.g., H+, Na+,...
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