Enzyme Catalysis, Specificity, and Cellular Regulation

All flashcards

How does an enzyme affect a reaction’s overall $\Delta G$?

It does not change $\Delta G$ or the reaction’s thermodynamic favorability; it lowers activation energy and speeds the reaction.

What determines an enzyme’s substrate specificity?

The arrangement and chemical properties of amino acid residues in its active site.

What are four ways enzymes can lower activation energy?

They orient substrates, create a favorable chemical environment, strain bonds, or temporarily participate in the reaction.

How can extreme temperature or pH affect an enzyme?

It can disrupt active-site structure and reduce activity; extreme conditions may denature the enzyme.

Why can enzymes catalyze multiple reactions?

They are not permanently consumed and return to their original state by the end of catalysis.

Quiz questions

1. How does a competitive inhibitor reduce an enzyme’s activity?Answer: It competes with the substrate for binding at the active site.
2. How does an allosteric inhibitor typically affect an enzyme?Answer: It binds away from the active site and changes the enzyme’s shape or activity.
3. Which statement correctly distinguishes cofactors from coenzymes?Answer: Cofactors are inorganic helpers, whereas coenzymes are organic helpers.
4. When ATP is abundant, how can it regulate enzymes involved in sugar catabolism?Answer: It can act as an allosteric inhibitor and slow the pathway that produces ATP.
5. Why can an enzyme be reused after catalysis, even if it temporarily participates in a reaction?Answer: It returns to its original state by the end of the catalytic process.