Enzymes — Flashcards & Quiz

Q1: Explain how enzymes function as biological catalysts.

Enzymes are proteins that lower the activation energy of biochemical reactions, increasing the reaction rate without being consumed. They have a specific 3D shape with an active site complementary to their substrate (lock-and-key or induced-fit model). The enzyme-substrate complex forms, the reaction proceeds, and products are released.

Q2: What factors affect enzyme activity?

Temperature: increasing temperature increases kinetic energy and reaction rate up to the optimum; beyond this, the enzyme denatures (tertiary structure unfolds). pH: each enzyme has an optimal pH; extreme pH causes denaturation. Substrate concentration: rate increases until all active sites are saturated (Vmax). Enzyme concentration: more enzyme = more active sites = faster rate (if substrate is not limiting).

Q1: Enzymes are consumed in the reactions they catalyse.

Answer: FALSE

Enzymes are biological catalysts that are NOT consumed — they lower activation energy, speed up reactions, and are recycled to catalyse further reactions.

Q2: Increasing temperature beyond an enzyme's optimum causes denaturation and loss of function.

Answer: TRUE

Excessive heat disrupts hydrogen bonds and other interactions maintaining the enzyme's tertiary structure, altering the active site shape and preventing substrate binding.