Ayoung animal has never had much energy. he is brought to a veterinarian for and is sent to the animal hospital for some tests. there they discover his mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. of the following, which is the best explanation of his condition?

a. his cells contain something that inhibits oxygen use in his mitochondria.
b. his mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
c. his cells cannot move nadh from glycolysis into the mitochondria.
d. his cells have a defective electron transport chain, so glucose goes to lactate instead of to acetyl coa.
e. his cells lack the enzyme in glycolysis that forms pyruvate.

On a backpacking trip, kenny hikes all day at a steady pace, covering 30 kilometers and burning 4000 calories. at the school track, janelle runs the 100-meter sprint in 13.5 seconds, burning 10 calories. afterward, janelle’s leg muscles are aching and she is breathing hard, while kenny maintains normal breathing all day, even though he burns 400 times more calories than janelle. which two statements offer the best explanation for this phenomenon? a. if the aerobic pathway—cellular respiration—cannot meet the energy demand, then the anaerobic pathway—lactic acid fermentation—starts up, resulting in lactic acid buildup and "oxygen debt." b. aerobic cellular respiration produces more energy, but its use is limited because of lactic acid buildup in the muscles and the resulting "oxygen debt." c. after about 90 seconds of intense exercise, the muscles become depleted of oxygen, and anaerobic respiration can no longer function to produce atp, resulting in "oxygen debt." d. the rate of energy demand determines how the muscles will obtain energy, either from cellular respiration or from lactic acid fermentation if not enough oxygen is present.