Hexokinase and Glucose Phosphorylation — NEET Biology
✅ Asked in NEET 2019The conversion of glucose to glucose-6-phosphate is catalyzed by: NEET 2019
The conversion of glucose to glucose-6-phosphate is catalyzed by: NEET 2019
Answer & NCERT explanation
Correct answer: C — Hexokinase
Hexokinase catalyzes the first step of glycolysis by phosphorylating glucose to glucose-6-phosphate using ATP. This is the rate-limiting step that traps glucose in the cell. Other enzymes have different roles: phosphofructokinase acts on fructose-6-phosphate, aldolase cleaves fructose-1,6-bisphosphate, and enolase converts 2-phosphoglycerate to PEP.
Read more NCERT concept on the PYQ
Sucrose is converted into glucose and fructose by the enzyme, invertase, and these two monosaccharides readily enter the glycolytic pathway. Glucose and fructose are phosphorylated to give rise to glucose-6-phosphate by the activity of the enzyme hexokinase. This phosphorylated form of glucose then isomerises to produce fructose-6-phosphate. Subsequent steps of metabolism of glucose and fructose are same. The various steps of glycolysis In glycolysis, a chain of ten reactions, under the control of different enzymes, takes place to produce pyruvate from glucose. While studying the steps of glycolysis, please note the steps at which utilisation or synthesis of ATP or (in this case) NADH + H+ take place.
NTA tests whether students understand that hexokinase phosphorylates glucose to glucose-6-phosphate, which is the first committed step of glycolysis. Students often confuse hexokinase with other enzymes or forget that glucose-6-phosphate is an activated form that cannot easily leave the cell. The key trap is mixing up which enzyme catalyzes which phosphorylation step. Remember: hexokinase is the enzyme, glucose is the substrate, and glucose-6-phosphate is the product. This is crucial because glucose-6-phosphate is the entry point into glycolysis and cannot be directly transported out, trapping glucose in the cell.
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