Proteins are an essential part of living organisms. They form part of the body’s structure and perform important functions such as distributing oxygen, clotting blood, fighting infections, and transmitting messages.
Proteins in Blood
- Hemoglobin – This protein is responsible for picking up oxygen from the lungs and delivering it to tissue cells.
- Fibrinogen – This protein is responsible for clotting blood. When a blood vessel is broken a chemical reaction takes place that converts fibrinogen into fibrin which them forms a mesh over the wound.
- Albumin – This protein is responsible for maintaining the proper amount of liquid in the blood. It also transports bilirubin to the liver.
Proteins in the Immune System
- Antibodies – Antibodies are responsible for fighting invaders.
- Complement System – This is a system that consists of over 20 different protein molecules that is activated during infections. They work together to attract phagocytes and cause bacteria to burst.
Proteins in the Muscle
- Actin – This protein is essential for cellular function – it maintains cell mobility, shape, and polarity and regulates transcriptions. It interacts with myosin to form the basis of muscle contraction.
- Myosin – This is a motor protein that interacts with actin and results in movement relative to each other.
- Myoglobin – This protein is similar to hemoglobin, it releaes oxygen to the muscle.
- Ferritin – This protein is responsible for storing and releasing iron. It can also be found in the liver, spleen, bone marrow, and other areas.
Cell Membrane Proteins
These proteins are responsible for forming channels that allow substances to move through the membrane, carrying substances, acting as enzymes, and acting as receptors (ex. insulin). There are three types of cell membrane proteins:
- Peripheral Proteins – These proteins sit on the surface and can be found in the outer and inner surface of the membrane. They are weak and usually temporary.
- Integral Proteins – These proteins extend all the way through the membrane and can be referred to as a transmembrane protein.
- Lipid-Bound Protein – These proteins can be found in the phospholipid bilayer.
Structural Proteins
- Cytoskeleton – This refers to a network of protein filaments and tubules in a cell that maintains cell shape.
- Keratin – This protein is found in skin, hair, and nails and serves structural and protective functions.
- Collagen – This protein helps provide strength.
- Elastin – This protein helps provide flexibility and elasticity to skin and organs. It typically functions with collagen.
Signaling Proteins
- Cytokines – These proteins communicate with other cells and stimulate the immune system.
- Erythropoietin – This is a hormone that stimulates red blood cell production in the bone marrow.
- HCG (Human Chorionic Gonadotropin) – This protein is responsible for maintaining the correct levels of estrogen and progesterone during pregnancy. It is also the basis for a lot of pregnancy tests.
Enzymes
Enzymes are proteins that function to speed up chemical reactions in the body. Without enzymes, many processes would occur too slowly to properly sustain life. There are many different enzymes, each with their specific function.
One common area where enzymes occur is along the digestive tract, these digestive enzymes are important for breaking down food and aiding digestion. For example, maltase is responsible for breaking apart maltose into glucose.
Proteins are an essential part of the body and performs various different functions. The body is able to take the proteins contained in food and convert them into amino acids that is tend used to produce proteins the body needs. Proteins are often targeted when developing new drugs and therapeutic treatments – especially since diseases can be the result of protein misfolding or proteins acting in a way that damages the body.
While the proteins listed above are not an exhaustive list of the proteins found in the body, they are some of the more important and well-known proteins that are vital to life.
Complement System. (n.d.). Retrieved from https://courses.washington.edu/conj/inflammation/complement.htm
Crampton, L. (2019, January 28). Protein Functions in the Human Body and in Cells. Retrieved from https://owlcation.com/stem/Essential-Functions-of-Body-Proteins
Dominguez, R., & Holmes, K. C. (2011). Actin Structure and Function. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3130349/
Lodish, H., Berk, A., & Zipursky, SL., et al. (2000). Myosin: The Actin Motor Protein. In Molecular Cell Biology (4th ed.). New York. Retrieved from
https://www.ncbi.nlm.nih.gov/books/NBK21724/
Brain, M. (2018, June 28). How Cells Work. Retrieved from https://science.howstuffworks.com/life/cellular-microscopic/cell2.htm
The Editors of Encyclopaedia Britannica. (2019, January 11). Keratin. Retrieved from https://www.britannica.com/science/keratin