Question

Discuss the regulation of glycolysis. In your answer ensure you list the key reactions, clearly highlighting the metabolic intermediates, enzymes and hormones involved in the pathway and its regulation. You should also highlight where the regulation differs between muscle and liver cells 20 Marks

Answer 1

It is the glycolysis cycle above mentioned the enzymes that catalyses the irreversible reactions are the main regulatory enzyme of glycolysis which are hexokinase,phosphofructo kinase and pyruvate kinase.

The phosphofructokinase is the most important regulatory enzymes ATP and alanine inhibits it whereas the ADP and fructose-2,6-biphosphate an substrate produce by liver activates it.

The fructose biphosphate is positively regulated by insulin and negatively by glucagon.If the sugar levels are high then the insulin binds to fructose biphposphate substrate in liver and activates phospho fructo kinase which activates glycolysis which involves conversion of glucose to pyruvate hence the blood glucose level decreases.If the sugar level starts to fall opposite happens and glycogen is activated and inhibits the substrate and the glycolysis.Hence the enzyme of glycolysis PFK enzyme is regulated by the substrate as it is a regulatory enzyme and in turn that substrate has to sites and is so regulated by two hormones of our body.

In liver cells there is an extra enzyme known as glucokinase enzyme which can converts glucose to glucose 6 phosphate .This is important as hexokinase enzyme gets inhibited by large quantiies of glucose 6 phosphate itself though it catalyses the same reaction as glucokinase but glucokinase in the liver cells does not get inhibited So the proces of glycolysis can still be carried out in liver even if high glucose 6 phosphate accumultaes which is not possible in liver.