Practice Questions

A competitive inhibitor binds directly to the active site. This inhibition is overcome by high substrate concentrations; Vmax remains unchanged but apparent Km increases.

Ribozymes are biologically active RNA molecules that possess catalytic activity, proving that biocatalysis is not exclusively the domain of proteins.

Km is the substrate concentration at half of Vmax. A low Km indicates high affinity, requiring only a low concentration to reach effective catalytic rates.

Enzyme specificity results from the chemical complementarity between the active site and the substrate's transition state.

At saturating substrate concentrations, the reaction rate is limited by enzyme concentration. Increasing the amount of enzyme creates more active sites and increases Vmax.

Enzymes accelerate reactions by stabilizing the transition state and providing an alternative reaction pathway with a lower activation energy.

Feedback inhibition is a regulatory mechanism where the end product of a pathway inhibits an enzyme acting earlier, preventing overproduction.

The complete, active enzyme (holoenzyme) consists of the protein part (apoenzyme) and a cofactor. Removing the cofactor leaves the inactive apoenzyme.

Turnover number represents the maximum number of chemical conversions of substrate molecules per second that a single catalytic site executes.

Many coenzymes are vitamin derivatives, such as pyridoxal phosphate (vitamin B6) which is required for aminotransferases.