During gluconeogenesis, which of the following substrates can be converted into glucose?

During gluconeogenesis, both lactic acid and amino acids serve as crucial substrates for the synthesis of glucose.

Lactic acid, produced in anaerobic metabolism, can be converted back into glucose through a process known as the Cori cycle. In the liver, lactic acid is re-oxidized to pyruvate, and then pyruvate is utilized in gluconeogenesis to form glucose.

Amino acids, particularly the glucogenic amino acids like alanine and glutamine, can also be transformed into glucose. The transamination process converts these amino acids into intermediates that feed into gluconeogenesis. For example, alanine can be converted into pyruvate, which then enters gluconeogenesis.

Thus, both lactic acid and amino acids are important substrates that can be effectively converted into glucose during gluconeogenesis, making the choice of both as correct. Fructose, on the other hand, enters glycolysis and does not serve as a gluconeogenic substrate in a direct manner, which differentiates it from the other options presented.