Most people have a fairly basic knowledge of proteins. We need to consume them to stay healthy, and eating meat or nuts is a good way to get more of this protein. However, your body produces a number of proteins on its own, and their functions are truly fascinating.
What Are Proteins?
Proteins are very large, often complex molecules made up of many amino acids attached to each other in long chains. Scientists differentiate proteins by studying the types of amino acids and their sequence, which affects the way the amino acids attach to each other and make the structure of the protein.
Proteins' jobs in the body vary so widely that they are usually categorized by their primary function. Overall, there are nine types of proteins:
Enzymes: This group of proteins trigger the building up and breaking down of molecules. These chemical reactions are responsible for cell growth, digestion, and many other cell processes. Proteins considered enzymes include lactase which helps with the digestion of lactose, the primary sugar in milk and DNA polymerase, which reads the structure of DNA and inserts the proper nucleotides to build the strand.
Structural proteins: These proteins make up the support structure of various body tissues. One example of a structural protein is collagen, which makes up the structure of skin, bone, ligaments, cartilage, and tendons. Another is tubulin, which makes up the hollow microtubules that support cell structure.
Signaling proteins: Signaling proteins allow cells to communicate with one another. Together signals, receptors, and relay proteins work to move the messages across the cell boundaries. One example is insulin, which activates insulin receptors so muscle and fat cells can store blood sugar. Another is the klotho protein, which is involved in signaling pathways that can help reduce oxidation and cell death.
Regulatory proteins: These proteins bind themselves to DNA strands to turn genes on and off. Regulatory proteins instruct cells what to become during development. An example of a regulatory protein is the hormone receptor proteins that accept androgen and estrogen to begin the onset of puberty.
Transport proteins: Transport proteins bind to molecules to move substances and nutrients in and out of cells and to move nutrients around the body. A well-known transport protein is hemoglobin in our red blood cells, which binds to oxygen in the lungs and transports it to the rest of the body.
Storage proteins: Sometimes grouped with transport proteins, storage proteins function in much the same way. These proteins bind with ions and amino acids to reserve them for later use. Examples include casein, which is a milk protein that stores amino acids, and ferritin, which stores iron.
Sensory proteins: These proteins, true to their name, support our senses. Sensory proteins aid in smell, touch, taste, sight, and hearing. Examples include opsins, which help convert light entering your eye into chemical signals which the brain interprets as images.
Motor proteins: Motor proteins help cells move. They also help cells move components internally, as well as change shape. One of the best-known motor proteins is kinesin. This protein attaches to a vesicle and walks down a pathway by attaching and detaching from microtubules.
Defense proteins: Defense proteins help protect the body from invaders by fighting off infection or helping heal damages that could let bacteria in. Antibodies are well-known defense proteins, otherwise known as immunoglobulins. They attach to invading antigens to remove them from the body.
As you can see, our bodies are host to numerous proteins that serve these functions and more. In fact, there are tens of thousands of proteins, many of which have not yet been identified. Scientists continue to map more proteins with functions we have yet to discover.