Functions of Proteins in the Human Body

Genes are expressed through proteins. Proteins are involved in almost all biological functions. Proteins are synthesized or produced in every living cell through the instruction given out by the genes. There are different kinds of proteins found in the human body and each of these proteins has specific functions to do. There are human proteins that function as enzymes, as structural proteins, as hormonal proteins, as storage proteins, or as transport proteins. Continue reading to learn the specific functions of proteins in the human body.

Proteins Function as Enzyme

Enzymes are proteins that accelerates the  rate of biochemical reactions taking place in the body. Without enzymes, biological activities such as digestion, DNA replication, DNA transcription, energy production, and even protein synthesis would be tremendously slow that life could not be possible.

Digestive enzymes such as lactase, pepsin, salivary amylase are all made up of proteins. Lactase is the enzyme that the breaks down the sugar lactose, an abundant protein found in milk. Pepsin breaks down large proteins into tiny molecules (amino acids) in the stomach during digestion; the body cannot absorb large proteins unless they are broken down to tiny pieces. Salivary amylase is the enzyme found in the saliva. It breaks down starch into its constituent parts.

The enzymes mentioned above are among the thousands of enzymes found in the human body. A defect to even a single enzyme can cause disease to human.

Proteins Function as Hormones

Hormones function in coordinating body activities by acting as messenger proteins. Hormones are produced by different tissues and organs in the body. There are different hormones found in the human body and each of these hormones has specific function. A particular hormone can influence the activity of a cell, a tissue, an organ, or all the whole body.

An example of hormone is insulin produced by specialized cells in the pancreas. Insulin regulates glucose level in the blood. Inadequate amount of hormone insulin in the human body can cause diabetes: one of the major human diseases today.

Rennin is an enzyme that coagulates milk (milk curdling) in the stomach of young mammals. Milk curdling allows the milk to stay longer in the stomach for proper digestion by proteases.

Other hormones are the oxytocin and somatotrophin. The former stimulates vaginal contraction during childbirth while the latter promotes growth by stimulating the production of more muscle cells.

Proteins as Structural Protein

Fibrous and stringy proteins provide support to biological entities. The cell has shape because of the structural protein cytoskeleton. The cytoskeleton functions just as what the human skeleton do in providing the shape and framework to the body. Without the cytoskeleton, everything in the cytoplasm is disorganized and cell functions cannot be carried out.

Other structural proteins are the collagen and elastin. These proteins are the major components of connective tissues such as cartilage, tendons, ligaments, and bones.

Keratin is the major protein found in nails and hairs.


Proteins Function in Movement

Muscles are able to contract and produce movement because of motor proteins. Motor proteins found in muscle include the myosin, kinesin, and dynein. These proteins coordinate to each other to produce mechanical forces that will result in muscle contraction.

The human sperm uses motor protein to swing its flagellum to swim. The sperm should swim to reach and fertilize the egg waiting in the fallopian tube.

Proteins as Transport Proteins

Transport proteins function in carrying molecules in various parts of the human body. Hemoglobin is the protein found in red blood cells. It binds to oxygen molecules in the lungs and transports them to the cells of the body. It also binds to carbon dioxide molecules and transports them to the lungs for release.

Transport proteins are also found in biological membranes. The cell membrane has transport protein embedded into it that function in transporting molecules (e.g. nutrients, oxygen) from the outside environment to the cytoplasm. The mitochondrial membrane also contains carrier proteins (e.g. cytochromes) that transport molecules involved in energy production from the cytoplasm towards the mitochondrion and vice versa.

Proteins as Storage Protein

Proteins store molecules for future use. For example, the protein ferritin forms a complex with iron in the liver. The iron is released when the body needed it.

Proteins Function in Cell Signaling

Cell signaling is a process where cells transmit signals to distant and adjacent cells. It is a form of communication among cells in the body. For example, the hormone insulin produced in pancreatic beta-cells travel in various parts of the body through the bloodstream to transmit the signal relating to glucose metabolism.

If there are proteins that act as signaling molecule, there are also proteins that act as receptors for signaling molecules. These receptor proteins that are usually found in the surface of cell membrane bind to the signaling molecule and then induce biochemical responses inside cell.

Proteins Function as Antibodies

Antibodies are proteins that bind to antigens or foreign substances in the body such as bacterial antigens. When antibodies detect the presence of foreign substances, they stimulate the immune system to respond. Antibodies are usually found in the extracellular membrane or attached in the surface of specialized B cells (lymphocytes) and other plasma cells.