Question

1. Explain why the step you identified is rate limiting.

2. Three reactions in glycolysis operate far from equilibrium and are potential sites for major flux control. List the three enzymes and explain why each enzyme is or is not the major control site of glycolysis.

3. Explain how insulin signaling can be impaired by inhibition of the glycolytic pathway

1. What is the goal of glycolysis? Provide a succinct summary of glycolysis. Be sure to distinguish between the ATP investment and ATP earnings stages.

Answer 1

3. The three rate-limiting steps of glycolysis are-

a. Glucose + ATP Glucose 6 phosphate + ADP

catalyzed by Hexokinase. It is inhibited by its immediate product ie glucose 6 phosphate.

b. Fructose 6 phosphate + 2ADP Fructose 1,6 diphosphate + 2ATP

catalyzed by phosphofructokinase 1. Its activators are AMP and fructose 2,6 bisphosphate and inhibitors are ATP, citrate and free fatty acids.

c. Phosphoenolpyruvate + ATP pyruvate + ADP

catalyzed by pyruvate kinase. It is inhibited by ATP and 3` 5` AMP

2. The insulin transduction pathway is a biochemical pathway by which insulin increases the uptake of glucose into fat and muscle cells and reduces the synthesis of glucose in the liver and hence is involved in maintaining glucose homeostasis. When the blood-glucose levels are too high, the pancreas is signalled to release insulin. Insulin is delivered to the liver and other tissues throughout the body. Now when glycolysis is impaired that means glucose is unable to get converted into pyruvate, insulin signalling is also affected as there is more glucose present and it is signalled to produce more insulin to balance that extra glucose present.

3. glycolysis produces two pyruvate molecules, a net gain of two ATP molecules, and two NADH molecules from a single molecule of glucose.

Glycolysis-