Question

What happens during gluconeogenesis?

Answer 1

Gluconeogenesis:

1. Gluconeogenesis is a process by which glucose is produced from noncarbohydrate sources like glycerol, pyruvate, lactase, and amino acids.
2. It occurs when the dietary intake of carbohydrates is low or at the time of fasting to maintain glucose level.
3. Gluconeogenesis occurs generally in the kidney and liver.
4. Non-carbohydrate sources are firstly converted to pyruvate or other intermediates of glycolysis.
5. Gluconeogenesis also mainly occurs in the liver.

Procedure of gluconeogenesis:

Conversion of pyruvate to phosphoenolpyruvate (PEP):

1. Converting pyruvate to a PEP requires multiple steps and multiple enzymes.
2. Pyruvate carboxylase, PEP carboxykinase, and malate dehydrogenase are the three enzymes involved in this conversion.
3. Pyruvate carboxylase is present in mitochondria and converts pyruvate to oxaloacetate.
4. Oxaloacetic acid cannot cross the mitochondrial membrane and must first be converted to malic acid by malate dehydrogenase.
5. Malic acid then crosses the mitochondrial membrane and reaches the cytoplasm, where it is converted to oxaloacetate using another malate dehydrogenase.
6. Finally, oxaloacetate is converted to PEP via PEP carboxykinase.
7. The next step is the same as glycolysis, except that the process is reversed.

Conversion of fructose-1,6-bP to fructose-6-P using the enzyme fructose-1,6-phosphatase:

The conversion of fructose-6-P to glucose-6-P uses phosphoglucoisomerase, the same enzyme as glycolysis.

Conversion of glucose-6-P to glucose by the enzyme glucose-6-phosphatase.

This enzyme is in the endoplasmic reticulum.