Carbohydrate catabolism

Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. The empirical formula for carbohydrates, like that of their monomer counterparts, is CX(H2YOY). Carbohydrates literally undergo combustion to retrieve the large amounts of energy in their bonds. Read more about mitochondria to find out more about the reaction and how its energy is secured in ATP.

There exist different types of carbohydrates, these are polysaccharide (e.g., starch, amylopectin, glycogen, cellulose), monosaccharides (e.g., glucose, galactose, fructose, ribose) and disaccharides (e.g., maltose, lactose).

Glucose reacts with oxygen in the following redox reaction, C6H12O6 + 6O2 → 6CO2 + 6H2O, the carbon dioxide and water is a waste product and the chemical reaction is exothermic.

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.

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.

Anaerobic respiration
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.

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 FADH 2 are converted into usable ATP molecules in the mitochondria by the mitochondrial electron transport chain.