Question

Which of the following steps during glycolysis is associated with utilization of ATP?

• A. Glucose $\to$ Glucose-6-phosphate
• B. Fructose-6-phosphate $\to$ Fructose-1,6-bisphosphate
• C. PEP $\to$ Pyruvic acid
• D. Both (a) and (b)

Answer 1

The correct option is D Both (a) and (b)

In the initial phase (energy spending phase) of glycolysis, the hexoses (i.e glucose and fructose) are phosphorylated in a reaction that uses ATP at two steps: First in the conversion of glucose into glucose-6-phosphate and second in the conversion of fructose-6-phosphate to fructose-1, 6-biphosphate.
These reactions are catalysed by the hexokinase and phospho-fructokinase respectively.
$Glucose+ATP\underset{{Mg}^{2+}}{\overset{hexokinase}{\to }}Glucose-6-phosphate+ADP$
$Fructose-6-phosphate+ATP\underset{{Mg}^{2+}}{\overset{Phospho-fructokinase}{\to }}Fructose-1,6-biphosphate+ADP$.

So the correct answer is 'Both (a) and (b)'.