Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.
Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains. There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function.
Proteins can be described according to their large range of functions in the body, listed in alphabetical order:
Examples of protein functions
|Antibody||Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body.||Immunoglobulin G (IgG)|
|Enzyme||Enzymes carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA.||Phenylalaninehydroxylase|
|Messenger||Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs.||Growthhormone|
|Structural component||These proteins provide structure and support for cells. On a larger scale, they also allow the body to move.||Actin|
Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. In animals, proteins are needed in the diet to provide the essential amino acids that cannot be synthesized. Digestion breaks the proteins down for use in the metabolism.