Question

Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the glycolytic pathway that are highly exergonic and essentially irreversible. Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway? 1) Hexokinase 2) Phosphoglycerate kinase 3) Phosphofructokinase-1 4) Pyruvate kinase 5) Triosephosphate isomerase

Answer 1

Gluconeogenesis is the process in the metabolic pathways by which an organism, let´s say the human body, is able to generate glucose out of non-carbohydrate sources, like amino acids and lipids.

This process of glucose generation initiates when blood levels of glucose are too low and both glycogen stores are depleted and there are no direct source providers of glucose (dietary carbs). When this happens, the body takes up other molecules, such as lipids and proteins, and through a pretty complex series of steps, that are the reverse of glycolysis (one of the three metabolic pathways for the energetic use of glucose), transforms them into glucose molecules that can then be fed into the regular cycle to produce energy.

Usually glycolysis and any other of the metabolic pathways is mediated by the presence and activities of different enzymes, who will be the ones responsible for carrying out the chemical reactions that will lead to the production of energy from glucose. If these enzymes are not bypassed during the process of gluconeogenesis, then the process cannot be carried out. These enzymes are: 1) Hexokinase, 3) Phosphofructokinase-1 and 4) Pyruvate kinase. All of these are part of the glycolytic pathway and must be circumvented, or "bypassed" for gluconeogenesis to be successful.