Difference between Krebs cycle and Electron Transport Chain (Citric acid vs ETC)

Difference between Citric acid cycle and Electron Transport Chain

Cellular Respiration is a catabolic process where respiratory substrates like glucose is broken down or oxidised to form carbon dioxide and water with release of energy as ATP. This energy is used to drive all cellular activities.

Stages of Cellular respiration

1. Glycolysis: glucose broken down to two pyruvate molecules

2. Link reaction: Pyruvate transported to mitochondria and converted to Acetyl CoA with the release of CO2

3.Krebs cycle: Acetyl CoA enters krebs cycle by combining with oxaloacetate to form citrate; the first compound formed in Krebs cycle (therefore krebs cycle also called as citric acid cycle)

4. Electron transport chain and oxidative phosphorylation: NADH and FADH2 produced in Krebs cycle enters electron transport chain, creating a proton motive force and finally produces ATP with O2 as terminal electron acceptor forming H2O.

Krebs Cycle vs Electron Transport Chain (ETC)

Krebs Cycle	Electron Transport Chain (ETC)
Krebs cycle occurs in the mitochondrial matrix	Electron transport chain occurs in the mitochondrial inner membrane (cristae)
Net gain of ATP per glucose molecule is 2	Net gain of ATP per glucose molecule is 34 (1 NADH=3 ATP & 1 FADH2=2 ATP)
Reduced NAD and FAD are produced as NADH and FADH2 (6 NADH & 2FADH2 per glucose molecule)	NADH and FADH2 are reoxidised to NAD and FAD
The phosphorylation for ATP synthesis is substrate level phosphorylation	The phosphorylation for ATP synthesis is oxidative phosphorylation
CO2 release or decarboxylation occurs at various steps	No decarboxylation
Chemiosmosis; not involved in ATP production	Chemiosmosis (proton gradient formation and associated ATP synthesis) involved in ATP production
Aerobic process, but oxygen not directly involved. It needs byproducts from ETC like NAD and FAD	Aerobic process; oxygen directly involved as terminal electron acceptor
Carbon dioxide is released as a waste product of these reactions.	Water is released as a waste product of these reactions.