What are the functions of proteins?

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Proteins are considered macromolecules because of their size. Large molecules made up of repeating units are called polymers. The small units or monomers that make up proteins are called amino acids. There are 20 different amino acids. Since proteins are made up of many amino acids there can be an...

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Proteins are considered macromolecules because of their size. Large molecules made up of repeating units are called polymers. The small units or monomers that make up proteins are called amino acids. There are 20 different amino acids. Since proteins are made up of many amino acids there can be an unlimited number of combinations (much like the many different words that can be made out of only 26 letters in the alphabet). Because of this the functions of different proteins can be as varied as their structures.

Proteins can be categorized as either structural or functional.


The jobs of structural proteins are to build or construct tissues of living organisms. For example, the protein myosin and actin are necessary for the building of muscle tissue. Other proteins are structural components of steroid hormones. In addition, proteins are structural components of antibodies whose job is to recognize foreign invaders and protect organisms against it.

Functional proteins do something other than "build". For example, enzymes are proteins whose job is to catalyze chemical reactions. They can do this by lowering the activation energy needed to start the chemical reaction. Hemoglobin is a protein in red blood cells to which oxygen binds and then gets transported to other cells. Embedded in the cell membrane of virtually all cells are proteins sometimes referred to transport proteins that help molecules move across the cell membrane.

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