Proteins are mainly subdivided into what two categories?

Proteins are primarily categorized into essential and nonessential categories based on the body's ability to synthesize them. Essential proteins are those that the body cannot synthesize on its own and must be obtained through diet. These include amino acids that are crucial for various bodily functions such as tissue repair, enzyme production, and hormone regulation. On the other hand, nonessential proteins can be synthesized by the body and are not required to be consumed from external sources.

This classification helps in understanding the dietary needs for protein intake. For instance, individuals must ensure they receive adequate amounts of essential amino acids from their diet, which are typically derived from food sources such as meat, dairy, and some plant-based proteins.

Other classifications, such as complete and incomplete proteins, refer to the presence of all essential amino acids in the protein source rather than the essentiality of the amino acids themselves. Similarly, animal and plant-based classifications focus more on the origin of the proteins rather than their biological necessity and synthesis by the body. Thus, understanding the distinction between essential and nonessential proteins is fundamental in nutrition to grasp the role proteins play in health and dietary planning.