Question

1. What would occur if the body could no longer produce lactate?
   1. In the presence of oxygen, acetyl CoA would build up and be converted back to fatty acids.
   2. In the absence of oxygen, ATP production would increase.
   3. In the absence of oxygen, pyruvate would build-up, causing glycolysis to slow down.
   4. Lactose would no longer be digested properly, leading to increased bloating

Answer 1

Lactate is produced from pyruvate when there is oxygen deprivation. Due to lack of oxygen, pyruvate is not converted to acetyl CoA. This is because of electron transport chain being non-functional.

Pyruvate is converted to lactate by lactate dehydrogenase when oxygen is absent. Hence, if lactate production is inhibited, pyruvate will accumulate in the cell. There is no NAD+ produced for glycolysis to continue, thereby causing inhibition of glycolysis.

Aerobic respiration is not affected as no lactate production occurs there. Thus, acetyl CoA can be broken down by TCA cycle. Lactose is broken down mostly by the lactic acid bacteria present in the intestine. Lactase of body (brush border enzyme) breaks down lactose to its monosaccharide sugars, glucose and galactose, which can be absorbed by small intestine. Thus, lactate defect will not affect lactose metabolism.

Right choice: In the absence of oxygen, pyruvate would build-up, causing glycolysis to slow down.