7. Energy and Metabolism

How does pH affect enzyme-catalyzed reactions?

a. Protons serve as substrates for most reactions.

b. Energy stored in protons is used to drive endergonic reactions.

c. Proton concentration increases the kinetic energy of the reactants, enabling them to reach their transition state.

d. The concentration of protons affects an enzyme's folded structure and reactivity.

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to

a. Add more of the enzyme.

b. Heat the solution to 90°C.

c. Add more substrate.

d. Add a noncompetitive inhibitor.

Some bacteria are metabolically active in hot springs because

a. They are able to maintain a lower internal temperature.

b. High temperatures make catalysis unnecessary.

c. Their enzymes have high optimal temperatures.

d. Their enzymes are completely insensitive to temperature.

Enzymes usually function best at an optimal pH and temperature. The following graph shows the effectiveness of two enzymes at various temperatures.

From what you know about enzyme structure, explain why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C (140°F).

Enzymes usually function best at an optimal pH and temperature. The following graph shows the effectiveness of two enzymes at various temperatures. One of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria.

Which enzyme would you predict comes from which organism?

Enzymes usually function best at an optimal pH and temperature. The following graph shows the effectiveness of two enzymes at various temperatures.

At which temperature does enzyme A perform best?

At which temperature does Enzyme B?

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