Protein Functions

The Functions of Proteins

Protein has many important roles in our body. Proteins work as enzymes, hormones, precursors, antibodies, structures (eg: muscles, tendons), buffers, fluid balance, transport, blood clotting and the can provide us with energy.

Enzymes are molecules that speed up reactions in our cells. A series of chemical reactions occur constantly throughout the body and enzymes are necessary for these reactions to occur. Hormones are chemical messengers that are made and released into the bloodstream by glands. These chemical messengers then travel to specific organs to help regulate bodily functions, such as digestion, sleep, stress, growth and development. Not all hormones are made from amino acids, some are made from cholesterol and called steroid hormones.

Amino acids act as precursors, compounds necessary to create another compound. For example, the amino acid tryptophan is necessary to create serotonin. Antibodies, also known as immunoproteins, are Y-shaped proteins designed to recognize and remove foreign invaders such as viruses and bacteria. Probably best known for their structural function, proteins make up muscle, skin, tendons, ligaments, cartilage, bone, teeth and blood vessels. Proteins serve as buffers, regulating the body's pH and aiding in fluid balance. The body maintains a balance of fluid in the bloodstream, the tissues and the cells.

Protein Functions

Enzymes

Hormones

Precursors

Antibodies

Structural

Buffers

Fluid balance

Transport

Blood clotting

Energy

The presence of protein in the bloodstream pulls fluid into, and maintains fluid in, the bloodstream. Without protein in the bloodstream, fluid leaks out into the tissues, resulting in edema. These fluid balancing proteins are also transport proteins, carrying substances from one part of the body to the other. The transport protein albumin carries nutrients such as zinc, calcium and vitamin B6. The complex mechanism of blood clotting is regulated by protein coagulation factors. Lastly, protein can be used to provide the body with energy.

Using Protein for Energy

The body does not want to use protein for energy when it is needed for other essential functions. But, the body does use some protein for energy on a regular basis, and can use protein for energy to a greater extent when necessary. If there is inadequate energy intake, the first step the body takes is to breakdown structural proteins in the body (eg: muscle, blood proteins) to use as energy. Proteins are not stored like carbohydrates and fats in the body. Instead, there is a pool of amino acids that result from the breakdown of proteins or from dietary intake. Some protein is constantly being built up from amino acids in this pool and other protein is constantly being broken down, adding to the pool. This amino acid pool acts as a source of building blocks from which the body can draw from.

When an amino acid is not used to build a protein for the body (not used for ligaments, enzymes, hormones, etc) the amino acid is broken down, using the carbons and hydrogen for energy and the nitrogen is excreted. This is called wasting an amino acid. Think of it as wasting an important building block needed for structures and compounds in our body.