Question

What enzymes are necessary in gluconeogenesis to bypass the irreversible enzymes in glycolysis and what is the basic reaction they are catalyzing? How is their activity regulated, so glycolysis and gluconeogenesis are not occurring simultaneously?What tissues convert lactate back to pyruvate, which can then enter the citric acid cycle?

Answer 1

Gluconeogenesis is the process in which glucose is generated from non carbohydrate precursors such as pyruvic acid, amino acids etc. It occurs in the liver and the kidneys.

Whereas glycolysis is the process of breakdown of glucose into pyruvate producing high energy molecules.

• The enzymes required in gluconeogenesis to bypass the enzymes catalyzing the irreversible steps of glycolysis are glucose 6 phosphatase, fructose 1,6 bisphosphatase and oxaloacetate. To understand the reactions they catalyse I have inserted an image along with this.
• The process which converts lactate to pyruvate is commonly known as Cori cycle. Pyruvate from liver is transported to muscle and converted to lactate in the muscle tissues. This lactate enters the liver and is converted back to pyruvate. Thus the tissue which convert lactate to pyruvate is liver tissue.
• Gluconeogenesis and glycolysis doesn't occur simultaneously because there will be the hydrolysis of four nucleotide triphosphates per reaction cycle. Hence their activity should be regulated. Their activity is regulated by reciprocal regulation in liver