Why does a plant cell produce only 36 ATP whereas an animal cell produces 38?

36 ATPs are produced in Aerobic Respiration involving the complete breakdown of glucose molecule into carbon-dioxide and water using oxygen as final electron aceptor

Complete oxidation of glucose molecule takes place in 3 sequential reactions -

1.Glycolysis occuring in cytoplasm

2.Kreb cycle occuring in mitochondrial matrix

3 Electron transport chain (ETC )and oxidative phosphorylation occuring in inner mitochondrial membrane .

In glycolysis ,if we see the overall reaction 1 glucose molecule is converted into 2 molecules of pyruvate with the release of 2 molecules of NADH2 (Nicotinamide adenine dinucleotide -reduced form) and 4 ATPs synthesized by substrate level phosphorylation (SLP) .As we know , NADH2 molecule will enter ETC and from 1 molecule of NADH2 ,3 or 2 ATPs are synthesized depending upon the shuttle system operating ,shuttle system works to tranfer the NADH2 synthesized in cytoplasm to the mitochondrial matrix so they can enter ETC and finally undergoes oxidative phosphorylation leading to the production of ATPs.There are 2 types of shuttle systems operating in cell ,I’m not going into too much detail but remember that one shuttle system leads to the production of 2 ATPs while other produces 3 ATPs per NADH2 molecule .

And moreover ,in first 2 reactions of glycolysis 2 ATPs are used so there is net gain of only 2 ATPs through SLP .

So,net ATPs synthesized in glycolysis are -

2NADH2- 6ATPs or 4 ATPs

SLP-2ATP

TOTAL ATPs -8 / 6 ATPs

LINK REACTION AND KREB CYCLE -

Under aerobic conditions or in the presence of oxygen ,pyruvate will enter link reaction that occurs in mitochondrial matrix and connects glycolysis with kreb cycle .In link reaction ,2 pyruvate molecules undergo oxidative decarboxylation to form 2 molecules of acetyl-coA with the release of carbon dioxide and 2 molecules of NADH2 .

After this , 2 molecules of acetyl-coA enters kreb cycle and undergoes complete oxidation leading to the release of 2 FAD molecules ( flavin dinucleotide ) ,6 molecules of NADH2 and 2 ATPs /GTPs by SLP .

And from 1 molecule of FAD ,2 ATPs are produced .So total ATPs produced in link and kreb cycle are

Total 8 NADH2 -24ATPs (No shuttle system operates as link and kreb cycles operates within mitochondrial matrix)

2FAD- 4ATPs

SLP- 2 ATPs

Total ATPs - 30 ATPs

So,total number of ATPs produced in aerobic respiration are

Glycolysis - 6/8 ATPs

Link reaction and kreb cycle - 30ATPs

Total -36/38 ATPs