Enzymes: Catalysts in Biochemistry

A biological catalyst that speeds up biochemical reactions.

The reactant in an enzyme-catalyzed reaction.

Enzymes are typically highly specific, reacting only with their particular substrate.

Non-protein molecules or ions that help an enzyme function.

Organic cofactor that helps in catalysis.

An enzyme with all its necessary cofactors bound to it.

Enzymes without their cofactors.

The part of the enzyme where the chemical reaction occurs.

Where the substrate binds to the enzyme.

The highest-energy species in a reaction pathway.

A thermodynamic function that predicts if a reaction will proceed spontaneously. A negative ΔG means the reaction will proceed to the right, while a positive ΔG means it will proceed to the left.

Indicates a spontaneous reaction; the reaction will proceed to the right.

Indicates a nonspontaneous reaction; the reaction will proceed to the left.

A reaction where the rate is directly proportional to the concentration of one reactant.

The substrate concentration at which the reaction rate is half of its maximum value.

The maximum rate of an enzyme-catalyzed reaction, achieved when the enzyme is saturated with substrate.

Turnover number, the number of substrate molecules converted to product per enzyme molecule per unit time when the enzyme is saturated.

Biological catalysts that speed up chemical reactions in living organisms.

The minimum energy required to initiate a chemical reaction.

State in which the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of reactants and products.

A model describing how enzyme activity depends on substrate concentration, characterized by a maximum velocity (Vmax) and a Michaelis constant (Km).

A double-reciprocal plot of enzyme kinetics, where 1/V is plotted against 1/[S].

Michaelis constant; the substrate concentration at which the reaction velocity is half of the maximum velocity (Vmax).

Maximum velocity; the theoretical upper limit of enzyme activity.

Regulation of enzyme activity by binding of a molecule (activator or inhibitor) to a site other than the active site

The site on an enzyme where a regulator molecule binds to control enzyme activity.

Enzymes with multiple active sites located on different protein subunits. The activity of one active site can be affected by the binding of a molecule to another active site or allosteric site.

A form of inhibition where the inhibitor competes with the substrate for the active site of an enzyme.

A form of inhibition where the inhibitor binds to a site on the enzyme other than the active site, changing the enzyme's shape and reducing its activity.

A form of allosteric regulation where binding of a substrate enhances the binding of additional substrates to other enzyme subunits.

A linear plot of enzyme kinetics, where velocity (V) is plotted against velocity divided by substrate concentration (V/[S]).