Overview of Metabolism

Metabolism can be divided into catabolism and anabolism.

Catabolism is a process where complex food molecules like polysaccharides, lipids, and proteins are broken down into simple molecules, such as sugars, fatty acids, and amino acids.

These simpler molecules are then processed inside a cell via various biochemical pathways to produce ATP, the energy currency of the cell.

For example, starch, a complex carbohydrate, is broken down by digestive enzymes into  glucose, which is then metabolized to produce pyruvate and ATP via glycolysis.

Anabolism is the reverse of catabolism. Here, small and simple precursors use energy from ATP hydrolysis to synthesize complex polymers.

For example, in glycogenesis, glucose monomers are bonded together to form glycogen, an energy storage molecule in animals. 

Since cells need to generate energy to maintain cellular metabolism, it is important to keep an adequate pool of ATP in the cell by modifying rates of ATP producing and utilizing reactions.

Such balance in the cellular metabolism is achieved via various regulatory systems present in the body like the endocrine system, regulatory enzymes, feedback inhibition loops, and modulation of gene expression patterns.