Anabolism is the building or creation of new compounds during metabolism. Catabolism is the opposite of anabolism, the breakdown of compounds during metabolism.
A synthesis reaction is when two or more stable compounds are combined to form one molecule. In decomposition reactions a compound is split into two or more stable compounds.
Anabolism and catabolism are frequently discussed in the study of protein nutrition. If you take amino acids and combine them the result is protein. During metabolism a protein that is broken down into its constituent parts yields amino acids.
Anabolism and catabolism are two processes within the body of humans and all other living organisms, and are collectively named as the process of metabolism. Metabolism is the chemical processes by which cells produce the materials and energy necessary for life.
In the process of anabolism, or constructive metabolism, cells combine molecules to assemble new organic materials. In this way it is a process of synthesis. In the process of catabolism, or destructive metabolism, cells break down molecules to obtain energy and release heat. This makes it a process of decomposition.
In humans during anabolism, cells combine amino acids to form structural proteins and functional proteins. These structural proteins are used for body repairs and growth. Functional proteins perform specific jobs such as speeding up chemical reactions; help in fighting disease; and regulating various body processes.
In the process of catabolism glucose, fatty acids, and amino acids are decomposed to obtain energy and produce heat. The compounds involved in catabolism come either from newly digested food, from the breakdown of stored glycogen or fat, or from the breakdown of body protein.