Biochemistry: Enzymes & Kinetics

Which class of enzymes catalyzes the transfer of electrons from one molecule to another, often involving NAD+ or FAD?

Oxidoreductases

Which model of enzyme-substrate binding suggests that the enzyme's active site undergoes a conformational change to better fit the substrate upon binding?

The Induced Fit Model

What does the Michaelis constant (Km) represent in terms of substrate concentration?

Km is the substrate concentration at which the reaction rate is exactly half of the maximum velocity (Vmax).

What is the term for organic non-protein molecules, often derived from vitamins, that are required by enzymes for catalytic activity?

Coenzymes

What kinetic parameter represents the maximum possible rate of an enzyme-catalyzed reaction when the enzyme is fully saturated with substrate?

Vmax

Which specific coenzyme, derived from niacin, serves as a primary electron carrier in redox reactions like glycolysis and the TCA cycle?

NAD+ (Nicotinamide adenine dinucleotide)

How do lyases differ from hydrolases in their mechanism of breaking chemical bonds?

Hydrolases break bonds by adding water, whereas lyases break bonds by elimination reactions that often form double bonds or rings without water.

Why is the ratio kcat/Km used to define the 'catalytic efficiency' of an enzyme?

It accounts for both the rate of product formation (kcat) and the enzyme's affinity for the substrate (1/Km), reflecting how well an enzyme performs at low substrate concentrations.

What is the Michaelis-Menten equation that relates the initial reaction velocity (v0) to the substrate concentration ([S])?

v0 = (Vmax * [S]) / (Km + [S])

In a double-reciprocal Lineweaver-Burk plot (1/v vs 1/[S]), what are the physical meanings of the x-intercept and the y-intercept?

The x-intercept is -1/Km and the y-intercept is 1/Vmax.