8.2: Enzymes and Energy - Reaction Rates

how are reaction rates measured

decreasing substrate concentration and increasing product concentration = both measure rate of change

Michaelis-Menten Model

describes the rate of enzyme-catalyzed reactions based on substrate concentration and enzyme affinity.

v = velocity of reaction

Vmax =maximum rate achieved by system

S = concentration of substrate

Km = Michaelis constant

Michaelis constant

a value that represents the substrate concentration at which the reaction velocity is half of Vmax, indicating enzyme affinity for the substrate.

factors which effects enzymes

enzymes have optimal temp and pH in which they are most active. Rate of reactions decrease when outside optimal range

inhibitor

Substance that makes an enzyme inactive by interfering with its ability to react with a substrate.

competitive inhibitor

molecule with similar structure to substrate and inhibits enzyme activity by competing with substrate for active site - can be reversed by increasing substrate concentration

noncompetitive inhibitor

doesn’t resemble substrate and binds to enzyme not at active site and alters enzyme’s shape preventing substrate binding - not reversed by increasing substrate concentration but still reversible

irreversible inhibitor

molecule that causes enzyme to lose all activity such as pesticides, antibodies, toxins or poisons. Usually forms covalent bonds with amino acid side chain that prevents catalytic activity