Question

A young animal has never had much energy. He is brought to a veterinarian for help 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.

Answer 1

b. His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.

Step-by-step explanation:

Splitting of glucose into pyruvate via glycolysis occurs in the cytoplasm. Pyruvate should enter the mitochondrial matrix where pyruvate dehydrogenase enzyme complex oxidizes it into acetyl CoA and acetyl CoA enters the Kreb's cycle. The given animal can produce energy from other nutrients which means that the electron transport chain of mitochondria is perfectly functional.

The animal has defective or nonfunctional transport proteins involved in the transport of pyruvate from the cytoplasm to the mitochondrial matrix. Since pyruvate can not enter the mitochondria, Kreb's cycle and oxidative phosphorylation are not performed. The pyruvate enters anaerobic respiration to produce lactate and to oxidize NADH to allow glycolysis to occur.