Question

which statement may be applied to enzymes?
a. they are not specific.

b. they are unaffected by ph changes.

c. they remain attached to substrate molecules.

d. they may speed up or slow down a reaction.

e. they are not found in animals.

Explanation:

• A: Enzymes are specific (lock - key model), so A is wrong.
• B: pH affects enzyme activity (optimum pH exists), so B is wrong.
• C: Enzymes are not permanently attached to substrates (they are reusable), so C is wrong.
• D: Enzymes are catalysts; they can speed up (most common) or in some cases, regulate (slow down) reactions.
• E: Enzymes are found in animals (e.g., digestive enzymes), so E is wrong.

Answer:

D. They may speed up or slow down a reaction.