Question

1. What is the purpose of gluconeogenesis? How do gluconeogenesis and glycolysis differ? Why is regulation of these pathways important, and what is the role of ATP in regulation?

Answer 1

The main purpose of gluconeogenesis is to maintain the blood glucose level in our body. Constant supply of glucose is mandatory for brain cells, RBC, cornea,etc. The primary source of energy i.e., glucose is supplied through glycogen. when glycogen amount decreases, to supply enough glucose gluconeogenesis takes place. It is an essentail process in which non carbohydrate reactants such as lactate, glucogenic amino acid,  glycerol are used to produce glucose products- the reverse of glycolysis.

Gluconeogenesis is anabolic reaction--> 2 pyruvate moelcules join to form one moelcule of  glucose whereas glycolysis is a catabolic reaction---> glucose breaks down into 2 pyruvate molecules. they may look like exact reverse of a metabolic process. Yes, it is but with changes in the enzymes and regulation. No two metabolic process can be same, they will have unique regulations. Gluconeogenesis only takes place in the liver cells whereas glycolysis happens in cytoplasm of all the cells

Regulation of both these pathways are important because if both the pathways are working continuosly, the net result will only be waste of ATP molecules. If production of glucose is continued by its breakdown continuously, then its a waste. So regulation in the irreversible reactions of both the pathways are done inorder to make the process utile. Presence of ATP promotes gluconeogenesis and inhibits glycolysis and reduced level of ATP promotes glycolysis and inhibits gluconeogenesis. The logic is that purpose of glycolysis is ATP production, so when already ATP is present there is no need of glycolysis. it is allosterically regulated. The reverse happens when ATP level gets reduced in the cells