Question

under anaerobic conditions, i.e. during vigorous exercise, when hemoglobin is not able to supply adequate amounts of oxygen to your tissues, your muscles accumulate lactate derived pyruvate. This reaction is very favorable, thus the reversal would not be favorable. However, in the liver the reaction can easily be reversed and lactate can serve as a substrate for gluconeogenesis. Explain how this is accomplish

Answer 1

Gluconeogenesis is a metabolic pathway in which glucose is synthesized from non-carbohydrate substrates such as pyruvate, lactate, glycerol, and glucogenic amino acids. This process occurs to maintain blood glucose level. It occurs majorly in liver and to very lesser extent in cortex of kidneys.

The gluconeogenesis mostly occurs during fasting, starvation, low-carbohydrate diets or intense exercise. The liver in mammals uses lactate, alanine, and glycerol, while kidneys use lactate, glutamine, and glycerol as the substrates for glucose production by gluconeogenesis.

The lactate produced in the muscle during strenuous exercise is transported to liver. In the liver, lactate is converted into pyruvate by Cori cycle. The enzyme lactate dehydrogenase (LDH) is involved in conversion of lactate to pyruvate.

The LDH is found in most of the cells. It can reversibly convert pyruvate to lactate and vice versa. The excess concentration of LDH in liver inhibits conversion of pyruvate to lactate and activates lactate to pyruvate conversion. Thus, only in liver lactate is easily reversed to form pyruvate.

The produced glucose is released into blood to maintain blood glucose level. This glucose serves as the energy source for performing the exercise.