Respiration and Energy Transfer — Biology STD 11 Science — Question
Maharashtra BoardEnglish MediumSTD 11 ScienceBiologyRespiration and Energy Transfer4 Marks
Question
How are glycolysis, TCA cycle and electron transport chain-linked$?$ Explain.
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Answer
Glycolysis, TCA cycle and electron transport chain are linked in the following manner:
The coenzymes are initially present in the form of $NAD^+$ and $FAD^+$ which latter get reduced to $NADH+H^+$ and $FADH+H^+$ by accepting the hydrogen from organic substrate during glycolysis, link reaction and Krebs cycle.
During glycolysis, glucose is oxidised to two molecules of pyruvic acid with net gain $2$ molecules of $NADH+H^+.$
This pyruvic acid undergoes link reaction to form two molecules of acetyl $CoA$ and two molecules of $NADH+H^+.$
Acetyl $CoA,$ thus formed enters into the Krebs cycle and it gets completely oxidised to $C0_2$ and $H_20;$ with a net gain of $6$ $NADH+H+$ and $2$ $FADH+H^+$ are formed.
During ETS, reduced coenzymes are reoxidized to $NAD^+$ and $FAD^+$ with a net gain of $34$ ATPs. The ATPs thus formed are used during glycolysis.
The oxidized $NAD^+$ and $FAD^+$ will again accept the hydrogen from organic substrate. Thus, reduced coenzymes are converted back to their oxidized forms by dehydrogenation to keep the process going.
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