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Correct answer for mcat
The correct answer is C. Animal cell is without cell wall.
Here's the reasoning:
The question asks why animal cells have more mitochondria than plant cells, despite having the same rate of metabolism.
- Plant cells have a cell wall (made of cellulose) in addition to their cell membrane. Maintaining and building the cell wall requires energy, but the wall itself is largely a passive structure - it does not consume ATP continuously.
- More importantly, plant cells can produce ATP via photosynthesis (chloroplasts) in addition to cellular respiration, so they have an additional energy source.
- Animal cells rely solely on mitochondria (aerobic respiration) for ATP production - they have no cell wall and no chloroplasts.
- To meet the same metabolic rate without the benefit of photosynthesis, animal cells must compensate by having more mitochondria.
The absence of a cell wall is not the direct reason - the key logic is that animal cells lack chloroplasts and depend entirely on mitochondria. However, among the given choices:
- A - "Animal cell is very dynamic" is vague and not a mechanistic explanation.
- B - "Only one source of energy" is actually the most biologically accurate reason (no photosynthesis), but looking at the answer choices again...
- C - "Without cell wall" - plant cells need energy to synthesize/maintain the wall, but this is a weaker reason.
Re-evaluating: Option B - "Animals is having only one source of energy" is actually the best biological explanation. Animal cells rely solely on mitochondrial respiration for ATP, whereas plant cells also use photosynthesis. To sustain the same metabolic rate with only one energy-generating pathway, animal cells need more mitochondria.
The correct answer is B.
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