Question

Reduced coenzyme NADPH $\left( {{H}^{+}} \right)$ is produced in respiration during
A. Glycolysis
B. PPP
C. Krebs cycle
D. Terminal Oxidation

Answer 1

PPP or pentose phosphate pathway produces the enzyme NADPH $\left( {{H}^{+}} \right)$ during respiration. Respiration is a biochemical process.

Complete answer: The pathway has two phases: oxidative and non-oxidative phase. The steps involved in the oxidative phase are as follows:
1. Glucose-6-phosphate is converted into 6-phosphogluconolactone, and $\text{NAD}{{\text{P}}^{+}}$ is converted to NADPH $\left( {{H}^{+}} \right)$ using the enzyme glucose-6-phosphate dehydrogenase.
2. 6-Phosphogluconolactone is converted to 6-phosphogluconate. The conversion is facilitated by the enzyme gluconolactonase. Water is converted into hydrogen ions.
3. 6-Phosphogluconate undergoes an oxidation, followed by decarboxylation. Carbon dioxide gas is released. In this step $\text{NAD}{{\text{P}}^{+}}$ is converted into NADPH $\left( {{H}^{+}} \right)$. The rest of the carbon atoms form the compound, ribulose-5-phosphate. The dehydrogenation is facilitated by the enzyme, 6-phosphogluconate dehydrogenase.
The non-oxidative phase succeeds in the oxidative phase. The reactions are as follows:
1. Ribulose-5-phosphate isomerizes into ribose-5-phosphate by the enzyme ribulose-5-phosphate isomerase or epimerizes into xylulose-5-phosphate by the enzyme ribulose-5-phosphate-3-epimerase.
2. Ribose-5-phosphate and xylulose-5-phosphate then undergo reactions, facilitated by enzymes, transketolase. This result is the transfer of carbon atoms and the formation of fructose 6-phosphate and erythrose-4-phosphate.
3. Glyceraldehyde-3-phosphate and fructose 6-phosphate are formed from erythrose-4-phosphate and fructose 6-phosphate again facilitated by the enzyme transketolase.
So, the correct answer is option B.

Note: All the processes mentioned in the question are interconnected and work for one main objective which is to form ATP. ATP is the reason for the survival of creatures. It is the energy all chemical processes in the body require. Glycolysis and PPP take place in the cytoplasm whereas the Krebs cycle and terminal oxidation occur in mitochondria, the powerhouse of the cell.