Question

Explain how lipids lead to ATP production?

Answer 1

Lipids are the molecules having hydrocarbon chains and they form the structural and functional building blocks of the cells. They are water-insoluble molecules as they are non-polar and so soluble in non-polar solvents. Examples of lipids are fats, waxes, oils, hormones, etc.

Complete answer:
The hydrocarbons in the lipids are present in the most reduced form, thus they form an excellent source of stored energy. When these hydrocarbons oxidize, they release a large amount of energy. The lipids are formed when carbohydrates in the diet are present in excess by the process known as lipogenesis. This process takes place in the endoplasmic reticulum. The lipids enter the cell through channels and then the lipase converts them into fatty acid and glycerol. The glycerol formed is used to make the pyruvic acid which is then used to form the ATP. For this purpose, glycerol can be phosphorylated to form glycerol-3-phosphate which is then converted into glyceraldehyde-3-phosphate which enters the glycolysis cycle. If an excess amount of glycerol is produced, then it is stored in the form of glucose.

The fatty acids produced are catabolized through the process of beta-oxidation. In this process, two carbon acetyl groups are removed from the ends of the fatty acid chains which reduces NAD+ and FAD to produce NADH and FADH2. The electrons thus produced are utilized for the production of ATP. Additionally, the acetyl groups can be used in the Krebs cycle that will also lead to the production of ATP.

Note: Mostly, the lipids which are used for energy production are found in the fat cells as triglyceride, which is an ester produced from glycerol and fatty acids.