Question

The balance sheet for ATP production in glycolysis has been given below. Select the option which correctly fills up the blanks for $P,\,Q,\,R$ and $S$ \[ [\text{'X' stands for ‘nil’}]\].

Sl.No	Steps	ATP utilization	ATP production
1.	${\text{Glucose}} \to {\text{Glucose}} - 6 - {\text{phosphate}}$	$P$	$X$
2.	${\text{Fructose}} - 6 - {\text{phosphate}} \to {\text{Fructose}} - 1,6 - {\text{bisphosphate}}$	$1$	$Q$
3..	$1,3 - {\text{bisphosphoglyceric}} \to 3 - {\text{Phospho}} - {\text{glyceric acid}}$	$X$	$R$
4	$2 - {\text{Phosphoenolpyruvicacid}} \to {\text{Pyruvic Acid}}$	$S$	$2$

(A) $P - 1;Q - X;R - X;S - 2$
(B) $P - 1;Q - X;R - 2;S - X$
(C) $P - 2;Q - 1;R - X;S - 1$
(D) $P - 1;Q - 1;R - 2;S - X$

Answer 1

Hint: Glycolysis is the first process in the respiration in which the complex food molecules like glucose are converted into the pyruvate. This pyruvate then moves to the process of citric acid cycle or Krebs’s cycle for the further functions. In the conversion process of glucose, various ATPs are involved in the utilization and also released.

Complete Answer:
From the given table,
(1) In the process of conversion of glucose into the ${\text{Glucose}} - 6 - {\text{phosphate}}$ , one ATP molecule is utilized for the conversion. At the end of the conversion no ATP molecules are released. Similarly, in the process of the transformation of ${\text{Fructose}} - 6 - {\text{phosphate}}$ to the ${\text{Fructose}} - 1,6 - {\text{bisphosphate}}$, One ATP molecule is used and no ATP molecule is liberated. Hence the value of $P$ is $1$ and the value of $Q$ is $X$.

(2) In the process of conversion of $1,3 - {\text{bisphosphoglyceric}}$ to the $3 - {\text{Phospho}} - {\text{glyceric acid}}$ and in $2 - {\text{Phosphoenolpyruvicacid}}$ to${\text{Pyruvic Acid}}$, two ATP molecules are used and no such ATP molecules are liberated. Hence the value of $R$ is $2$ and the value of $S$ is $X$.

Thus, the option (D) is correct.

Note: Glycolysis is also known as EMP pathway. At the end of the process ATP and NADH molecules are produced. Hence totally two ATPs are produced from the EMP pathway which is used in the breakdown of further process in the cellular respiration.