Protein in the body
Protein comprises approximately 20% of the human body composition and is present in every cell. Protein is a Greek word for "of the utmost importance." Proteins are also called the workhorses of life because they provide the body with structure and perform various functions.
Protein is the major component of muscle. Protein is also required for proper immune system function, digestion, nail and hair growth, and many other body functions.
This chapter will discuss protein's roles within the body, how the body uses protein, and where to find healthy protein sources in our diet.
Protein is an essential group of macronutrients required by our bodies. The functions of protein in our bodies are summarized as the following:
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Protein builds and maintains the body, and protein acts as a structural component of the body.
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Protein is a component of many enzymes, hormones, and antibodies.
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Protein helps transport iron, fats, minerals, and oxygen.
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Protein helps maintain fluid and acid-base balance.
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Protein helps blood clot when bleeding.
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Protein provides energy as a last resort. The body’s primary energy source is carbohydrates and fat; protein is the last energy resort.
​The proteins we eat in food only become part of proteins in our bodies once they are broken down into single amino acid units during digestion and then used by our cells to make new proteins.
Protein digestion starts in the stomach when stomach acid uncoils the proteins enough to allow enzymes to enter them to do their work. An enzyme in the stomach begins splitting apart amino acids in proteins.
In the body, the instructions to make proteins reside in the cell's core, or nucleus, in each of your cells. The genetic material instructing the protein synthesis present in the nucleus of the cell is DNA. DNA is the abbreviation of deoxyribonucleic acid. Every human cell contains the same DNA, the master plan for cell function and reproduction. The exception is the mature red blood cells, which have no nucleus in them.
Segments of each DNA molecule are called genes. A gene carries instructions that allow a cell to produce something, often a protein. There are thousands of genes in each of your cells with instructions to make many different proteins.
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​The supply of amino acids in the blood and the body's cells comprise the amino acid pool. Amino acids from foods and those from body proteins that have been disassembled stock this pool. Suppose your body makes a protein and can not find an essential amino acid. In that case, the protein production process can not be completed, and the uncompleted protein is degraded. In this manner, the human body recycles its proteins.
Protein is part of most body structure: build and maintain the body; is part of many enzymes, hormones, and antibodies; transport substances around the body; maintain fluid and acid-base balance; can provide energy for the body; and helps in blood clotting.
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Proteins function as part of the body’s structure. Protein can be found in the skin, bones, muscles, hair, nails, blood vessels, digestive tract, and blood. Proteins also give structure to individual cells. Collagen, the most abundant protein in the body, is the major protein in bones, ligaments (which hold bones together), and tendons that attach muscles to bones. To a certain extent, collagen is the glue that keeps us together.​
​Proteins are used for building and maintaining body tissues. Worn-out cells are replaced throughout the body at regular time intervals. For instance, A skin cell lives only about one month. Skin is constantly being broken down and rebuilt, like most body cells. The cells that line the gastrointestinal tract are replaced every few days.