Question

1. many poisons can enter the active site of enzymes essential for brain functioning. these poisons are never broken down and remain attached to the enzyme. which best describes the effect this would have on the enzymes activity?

a the enzyme activity would continue at its normal rate.
b. the enzyme would take longer to perform its normal functions.
c. the enzyme would be rendered useless since its active site was blocked.
d. the enzyme would transfer its active site to another location and continue its normal activity.

1. when a student drops a piece of liver into a beaker of hydrogen peroxide, the peroxide bubbles vigorously as the peroxide decomposes into water and oxygen. however, if the student cooks the liver first, the reaction fails to occur. what is the best explanation for these results?

a boiling the liver altered the shape of the enzyme in the liver so that it could not interact with the peroxide.
b. heating the liver killed the germs that caused the bubbling reaction.
c. lower temperatures result in a higher rate of enzyme activity.
d. heating the liver removed the water and oxygen from the hydrogen peroxide.

1. how does an enzyme speed up chemical reactions?

a by absorbing energy
b. by releasing energy
c. by decreasing the energy needed
d. by increasing the energy needed

Explanation:

• Question 18: Enzymes work by having substrates bind to their active sites. If a poison binds to the active site and doesn't leave, the enzyme can't bind to its normal substrate. So, it can't perform its function.
• Question 19: Enzymes are proteins. High temperatures (like boiling) can denature proteins, changing their shape. If the enzyme's shape (especially the active - site shape) is changed, it can't interact with the substrate (hydrogen peroxide in this case).
• Question 20: Enzymes are biological catalysts. Catalysts speed up reactions by lowering the activation energy (the energy needed for the reaction to start).

Answer:

1. C. The enzyme would be rendered useless since its active site was blocked.
2. A. Boiling the liver altered the shape of the enzyme in the liver so that it could not interact with the peroxide.
3. C. by decreasing the energy needed