The electron transport chain<span> occurs across the inner membrane of the </span>mitochondria<span>.
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Answer:
Facilitated diffusion require no energy and travels down the gradient of concentration. On the other hand, active transport takes energy and travels up the gradient of concentration.
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Answer - A. Deep because there is less O2 exchange
Reasoning - Bacteria has been known to only use half a percentage which is .5 percent of O2.