Glucose is the major food molecule for living cells. The breakdown of Glucose into energy in the form of molecules of ATP is therefore one of the most important biochemical pathways found in living organisms.

Anaerobic respiration is the metabolic pathway where glucose is broken down in the absence of oxygen. Aerobic respiration is the pathway where glucose is broken down in the presence of oxygen.

Anaerobic respiration

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Glycolysis

The six-carbon Glucose molecule is broken down into two three-carbon Pyruvate molecules yielding two ATP molecules and two high energy NADH molecules.

Fermentation

Without Oxidative phosphorylation, the NADH molecules cannot be converted to ATP. When all of the NAD+ molecules have been converted to NADH, glycolysis will stop unless the NAD+ is regenerated by Fermentation.

Aerobic respiration

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Glycolysis

The six-carbon Glucose molecule is broken down into two three-carbon Pyruvate molecules yielding two ATPmolecules and two high energy NADH molecules.

Pyruvate oxidation

The three carbon pyruvate molecule loses a carbon atom and is shepherded into the citric acid cycle by coenzyme A.

The Citric acid cycle (also known as the Kreb's cycle)

The acetyl group that came from pyruvate enters this biochemical cycle which releases carbon dioxide, water, and the high energy molecules ATP, NADH, and FADH₂.

Oxidative phosphorylation

The high energy molecules NADH and FADH₂ are converted into usable ATP molecules in the mitochondria by the mitochondrial electron transport chain.

See also

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• Anaerobic organism
• Cellular respiration
• Cell metabolism
• Metabolism
• Anabolism and Catabolism
• Carbohydrate catabolism
• Pentose phosphate pathway
• Anaerobic digestion