Q. In which of the following steps of aerobic respiration of glucose, carbon dioxide is evolved?
I. Glycolysis
II. Link reaction
III. Krebs cycle
IV. Electron transport system

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Solution:

In the link reaction pyruvic acid is converted into acetyl coenzyme A also producing reduced coenzyme NADPH + and carbon dioxide in the presence of enzyme pyruvate dehydrogenase. In the Kreb's cycle, carbon dioxide is evolved at two points:
a. During the conversion of isocitric acid to oxalosuccinic acid.
b. During the conversion of alpha-ketoglutaric acid to succinyl co-A