Question at position 49 What can account for individual variations in basal metabolic rate even with the same amount of lean body mass?differences in activitydifferences in food intakedifferences in heightdifferences in number of uncoupling proteins单项选择题
A
differences in activity
B
differences in food intake
C
differences in height
D
differences in number of uncoupling proteins

Question

Question at position 49 What can account for individual variations in basal metabolic rate even with the same amount of lean body mass?differences in activitydifferences in food intakedifferences in heightdifferences in number of uncoupling proteins单项选择题

A

differences in activity

B

differences in food intake

C

differences in height

D

differences in number of uncoupling proteins

BlackTom AI · Accepted Answer

Uncoupling proteins (UCPs) in the inner mitochondrial membrane increase proton leak and convert the mitochondrial proton-motive force to heat rather than ATP, so differing amounts or activity of UCPs cause different resting energy expenditure even when lean mass is equal.

1) Relevant knowledge points and concepts
- Basal metabolic rate (BMR) is the energy expended at rest in a post-absorptive state and is primarily determined by metabolically active lean tissues (organs, muscle).
- Mitochondrial proton leak and non-shivering thermogenesis (mediated by UCPs, especially UCP1 in brown adipose tissue) raise resting energy expenditure independent of gross lean mass.
- Factors such as recent activity or food intake affect total daily energy expenditure or transiently raise metabolism, but BMR is measured under standardized resting/fasted conditions.

2) Step-by-step reasoning
- Start from the premise: two individuals have the same amount of lean body mass.
- Because lean mass is equal, differences in organ and muscle mass are controlled for, so gross tissue mass cannot explain BMR differences.
- Mitochondrial efficiency differs between individuals: greater expression or activity of UCPs increases proton leak, reducing ATP per substrate oxidized and increasing heat production, thereby raising oxygen consumption and BMR.
- Therefore, variation in number/activity of UCPs provides a plausible mechanism for different BMRs given identical lean mass.

3) Intermediate steps (conceptual)
- Equal lean mass → equal baseline potential for metabolic activity.
- Add variable: UCP expression/activity → variable proton leak.
- Result: variable resting energy expenditure (BMR).

4) Why the correct answer is correct
Differences in number or activity of uncoupling proteins directly alter mitochondrial efficiency and resting heat production, producing interindividual BMR variation independent of lean mass.

5) Why other options are incorrect
- Differences in activity: Acute or chronic activity affects total daily expenditure or increases lean mass, but BMR is defined at rest in the fasted state and is not directly set by recent activity.
- Differences in food intake: Food intake causes diet-induced thermogenesis; however BMR is measured post-absorptive, so immediate food intake should not account for resting BMR differences.
- Differences in height: If lean mass is the same, height per se does not change the metabolic rate contributed by those tissues.

6) Conclusion
Variation in uncoupling proteins best explains differing basal metabolic rates with identical lean body mass; this matches the provided correct answer: differences in number of uncoupling proteins.