Question at position 32 The metabolic rate per kg of body weight is higher for a child than an adult since:A child’s brain is more metabolically active than an adult’s brain.All cells decrease metabolic activity in adulthood.The child may have more uncoupling proteins than the adult.The ratio of organs to body weight is higher in children than adults.

Question

BlackTom AI · Accepted Answer

The ratio of metabolically active organs to total body weight is higher in children, which raises metabolic rate per kg.

1) Relevant knowledge points and concepts
- Basal metabolic rate (BMR) is the sum of energy use of all tissues: highly metabolic organs (brain, heart, liver, kidneys) have much higher specific metabolic rates (energy per unit mass) than muscle or fat. 
- Metabolic rate per kg = (sum of each organ mass × its specific metabolic rate) / total body mass. 
- Children have proportionally larger brains and other organs relative to body mass and are also growing, both increasing energy demand per kg.

2) Step-by-step reasoning
- Represent total metabolic rate (R) = Σ(mi × ri), where mi = mass of organ i, ri = specific metabolic rate of organ i. 
- Metabolic rate per kg = R / Mtotal = [Σ(mi × ri)] / Mtotal.
- If the fraction of Mtotal composed of high-ri organs is larger, the numerator increases relative to Mtotal and the per-kg value is higher.

3) Illustrative calculation (intermediate steps)
- Choose illustrative specific rates: r_high (organs) = 200 units/kg, r_low (rest) = 20 units/kg (these are illustrative to show relative effects).
- Adult: Mtotal = 70 kg, high-organ mass = 7 kg (10%): R_adult = 7×200 + 63×20 = 1,400 + 1,260 = 2,660 units → per-kg = 2,660/70 ≈ 38 units/kg.
- Child: Mtotal = 20 kg, high-organ mass = 4 kg (20%): R_child = 4×200 + 16×20 = 800 + 320 = 1,120 units → per-kg = 1,120/20 = 56 units/kg.
- The child’s per-kg rate is higher because the high-metabolic organ fraction is larger.

4) Why the correct answer is correct
- The correct option states the ratio of organs to body weight is higher in children. Because high-metabolic organs represent a bigger fraction of body mass in children, energy use per kg is elevated. Growth-related metabolic demands further raise per-kg rates.

5) Why other options are incorrect
- “A child’s brain is more metabolically active than an adult’s brain.” Incorrect: specific metabolic rate per gram of brain tissue is similar; the key is the brain’s larger proportion of body mass in children, not a higher per-gram brain activity. 
- “All cells decrease metabolic activity in adulthood.” Incorrect: metabolic activity changes vary by cell type; this blanket statement is false. 
- “The child may have more uncoupling proteins than the adult.” Partly true for neonates (brown fat), but not the primary or general reason across childhood; UCPs are not the main explanation for higher per-kg metabolic rate in children.

6) Conclusion
The explanation shows that a higher organ-to-body-weight ratio in children raises metabolic rate per kg, confirming the provided correct answer: "The ratio of organs to body weight is higher in children than adults."

类似问题

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

Question at position 3 Resting metabolism is determined by cellular energy production and is directly proportional to: Lean body massNumber of uncoupling proteinsNumber of adipocytesBody weight

Taller individuals have a higher basal metabolic rate (BMR).

Which of the following is a safe way to increase BMR?

A major factor influencing BMR is:

Which of the following is the most important factor that influences basal metabolic rate?

Total energy expenditure declines as we age.

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