Final answer:
Pyruvate would accumulate in the cytosol if cells undergoing glycolysis could not carry out fermentation, as fermentation is necessary to recycle NAD+ for glycolysis to continue.
Step-by-step explanation:
If cells were undergoing glycolysis but could not carry out fermentation, the product that would build up in the cytosol is pyruvate. During glycolysis, glucose is broken down into two pyruvate molecules, generating a small amount of ATP and NADH in the process. However, without fermentation, there would be no way to recycle NAD+ from NADH, which is required for glycolysis to continue. This bottleneck would result in an accumulation of pyruvate and NADH in the cell.Red blood cells, which only perform glycolysis, would fail to generate ATP and die if glycolysis were blocked.
Human red blood cells rely solely on glycolysis for their energy needs as they do not have mitochondria and cannot perform aerobic respiration. If glycolysis were blocked, red blood cells could not generate the ATP necessary for functions such as maintaining sodium-potassium pumps, leading to cell death. Fermentation is critical for recycling NAD+; without it, a cell is limited to the ATP produced in glycolysis and cannot meet high energy demands.