Question

mini-quiz: substrate concentration and enzymes
how is enzyme activity at varying substrate concentrations different from enzyme activity at varying temperatures or ph levels?
i. the graph for substrate concentration shows the rate levelling off when substrate concentration is high, instead of declining when not in the optimal range.
ii. when increasing substrate concentration, it is apparent that the enzyme denatures but this is not seen when increasing temperature or ph.
iii. changes in substrate concentration do not cause the enzyme to denature, but changes in temperature and ph may cause the enzyme to denature.
a. i, ii and iii
b. i and iii only
c. ii and iii only
d. iii only

Explanation:

• Analyze Statement I: The enzyme - substrate concentration graph has a rate that levels off at high substrate concentrations (due to enzyme saturation), while temperature or pH - rate graphs decline outside the optimal range. So, Statement I is correct.
• Analyze Statement II: Increasing substrate concentration does not cause enzyme denaturation. Enzyme denaturation is caused by extreme temperature or pH, not substrate concentration. So, Statement II is incorrect.
• Analyze Statement III: Substrate concentration changes do not denature enzymes, but extreme temperature or pH can cause enzyme denaturation. So, Statement III is correct.

Since Statements I and III are correct, the answer is the option that includes only I and III.

Answer:

B. I and III only