Why is the formation of fructose-1,6-bisphosphate the committed step in glycolys
ID: 211865 • Letter: W
Question
Why is the formation of fructose-1,6-bisphosphate the committed step in glycolysis? 2. What is the metabolic advantage of having both hexokinase and glucokinase to phosphorylate glucose? 3. What is the difference between an isomerase and a mutase? 4. High levels of glucose-6-phosphate inhibit glycolysis. If the concentration of phosphate decreases, activity is restored. Why would this be advantageous to glucose-6 the cell? If lactic acid is the buildup product of strenuous muscle activity, why is solium lactate often given to hospital patients intravenuously?Explanation / Answer
1 Fructose-1,6-bisphosphate can undergo the reactions of glycolysis only. The reaction in which fructose-6-phosphate is phosphorylated to give fructose- 1,6-bisphosphate is the reaction in which the sugar is committed to glycolysis. fructose-1,6-bisphosphate does not play roles in other pathways, but Glucose-6-phosphate and fructose-6-phosphate can. After the formation of fructose-1,6-bisphosphate from the original sugar, no other pathways are accessible, and the molecule needs to go through the rest of the reactions of glycolysis.2 The two enzymes can have separate tissue locations and kinetic parameters. The value of km for glucose is higher for glucokinase than hexokinase. Thus, when the concentration of glucose is low, the liver does not convert glucose to glucose-6-phosphate. When the glucose concentration is higher, glucokinase helps phosphorylate glucose so that it can be stored in the form of glycogen.
3 Isomerase is a class of enzymes. It changes the structure of one molecule into other structures by rearrangement of atoms inside a molecule. Isomerase can be racemase, epimerase, cis-trans isomerase, etc.Mutase is a member of isomerase. Mutase catalyses reactions in which there's a change in the position of a group in a molecule which changes it to some other form.
4 Glucose-6-phosphate inhibits hexokinase, the enzyme responsible for its own formation. Because Glucose-6-phosphate is used up by additional reactions of glycolysis, the inhibition is relieved.
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