Respiration in Plants
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For each ATP produced, 2H+ passes through F0 from the inter-membrane
space to the matrix down the electrochemical proton gradient.
THË RËSPÏRÅTØRÝ BÅLÅÑÇË SHËËT
Net gain of ATP from each glucose molecule is calculated based on the
following assumptions.
All steps in Glycolysis, TCA cycle & ETS occur sequentially and orderly.
The NADH synthesised in glycolysis is transferred into mitochondria and
undergoes oxidative phosphorylation. Intermediates in the pathway are
not used to synthesize other compounds.
Only glucose is being respired. Other alternative substrates are not
entered in the pathway at any stages.
Such assumptions are not valid because,
All pathways work simultaneously and do not
take place one after another
Substrates enter the pathways and are
withdrawn from it as and when necessary.
1
2
ATP is utilised as and when needed.
3
Enzymatic rates are controlled by multiple
means.
4
Such calculations are useful to appreciate the efficiency of the living
system in extraction and storing energy.
Net gain of ATP molecules from one glucose molecule
Glycolysis
2 ATP directly
2 ATP
2 molecules of NADH
6 ATP
Oxidative decarboxylation
2 NADH
6 ATP
TCA cycle
6 NADH
18 ATP
2 FADH2
4 ATP
2 GTP
2 ATP
TOTAL
38 ATP
If 2 ATP molecules are spent for transporting 2 NADH molecules formed
during glycolysis to the mitochondria, then the net gain = 36 ATP molecules.