What are precursor metabolites? Where do they come from and what are they used for?

Answer 1

The precursor metabolites are molecules used in essential chemical reactions within organisms. These chemical reactions either result in the formation of large molecules that are useful to the body (such as polysaccharides, lipids, proteins, and DNA) and/or create ATP (energy molecule). In this way, the precursor metabolites are like building blocks.

Catabolism is the breaking down of macromolecules into smaller molecules, a process which also results in conversion of ADP to ATP, which the body can use for more reactions. On the other hand, anabolism is the formation of larger molecules from smaller ones and requires the use of ATP. The precursor metabolites are formed from the breakdown of molecules like proteins, but can be used to create more macromolecules. Therefore, the precursor metabolites link catabolism and anabolism in the body.

Here is an example. Glucose 6 phosphate (G6P) can be formed from the breakdown of glycogen (glycogenolysis). It is also constructed from simple glucose which organisms either get from consuming complex sugars and breaking them down, or by photosynthesis in plants. G6P can then be used in energy-consuming processes (the pentose phosphate pathway and glycolysis). to make other important structures such as pyruvate, NADPH, and ribose (to form nucleotides).

There are 12 proposed precursor metabolites - there are a few tables online listing them, and they are probably listed in your textbook. It is helpful in biochemistry to be familiar with the precursor metabolites, what reactions they are involved in, and the steps required to form them or to build other molecules.