Question

oxygen consumption can be used as a measure of metabolic rate because oxygen is

a necessary for atp synthesis by oxidative phosphorylation

b necessary to replenish glycogen levels

c necessary for fermentation to take place

d required by all living organisms

e required to break down the ethanol that is produced in muscles

Explanation:

• Option A: In oxidative phosphorylation, oxygen acts as the final electron acceptor. The process of oxidative phosphorylation is a major way to synthesize ATP. The rate of oxygen consumption is closely related to the rate of ATP synthesis through oxidative phosphorylation, so it can reflect the metabolic rate.
• Option B: Glycogen replenishment is mainly related to carbohydrate metabolism pathways like glycogenesis, and oxygen is not directly the key factor for replenishing glycogen levels in a way that makes oxygen consumption a measure of metabolic rate.
• Option C: Fermentation is an anaerobic process, meaning it does not require oxygen. So oxygen is not necessary for fermentation, and this option is incorrect.
• Option D: While many organisms require oxygen, there are anaerobic organisms that do not. Also, just the requirement of oxygen by an organism does not directly explain why oxygen consumption is a measure of metabolic rate. The key is its role in ATP synthesis (as in oxidative phosphorylation).
• Option E: Ethanol is mainly produced in yeast (in alcoholic fermentation) or in some plants under anaerobic conditions. In human muscles, lactic acid is produced during anaerobic respiration, not ethanol. And oxygen is not mainly for breaking down ethanol in a context related to metabolic rate measurement as described in the question.

Answer:

A. necessary for ATP synthesis by oxidative phosphorylation