Question

1. in muscle cell x, the breakdown of sugar happens very quickly, releasing energy that the cell can use right away. in muscle cell y, the same breakdown process is much slower and produces less energy. what could be the reason?

a. muscle cell y uses a different type of sugar molecule.
b. muscle cell x contains an enzyme that speeds up the reaction.
c. muscle cell x has more mitochondria to store energy.
d. the sugar molecules in muscle cell y are too small to react efficiently.

Explanation:

• Option A: The problem states "the same breakdown process", implying the same sugar, so A is incorrect.
• Option B: Enzymes speed up chemical reactions (like sugar breakdown). If Cell X has an enzyme speeding the reaction, it would break down sugar faster (releasing energy quickly) compared to Cell Y without or with a less effective enzyme, matching the scenario.
• Option C: Mitochondria are for energy production (via respiration), not "storing energy". Their number relates to energy production rate, but the option's reasoning about storage is wrong.
• Option D: Smaller sugar molecules would react more easily (not less efficiently), so D is illogical.

Answer:

B. Muscle Cell X contains an enzyme that speeds up the reaction.