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What are proteins and what do they do?

Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.

Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains. There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function.

Proteins can be described according to their large range of functions in the body, listed in alphabetical order:

FunctionDescriptionExamples
AntibodyAntibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body.Immunoglobulin G (IgG) (illustration)
EnzymeEnzymes carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA.Phenylalanine hydroxylase (illustration)
MessengerMessenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs.Growth hormone (illustration)
Structural componentThese proteins provide structure and support for cells. On a larger scale, they also allow the body to move.Actin (illustration)
Transport/storage moleculeThese proteins bind and carry atoms and small molecules within cells and throughout the body.Ferritin (illustration)

For more information about proteins and their functions:

Information about proteins and what they do is available from the National Institute of General Medical Sciences publication Genetic BasicsThis link leads to a site outside Genetics Home Reference.. Refer to the section “From Genes to Proteins” in Chapter 1 (How Genes Work).

Additional discussion of the role of proteins can be found in the NCBI Science PrimerThis link leads to a site outside Genetics Home Reference. under the heading “Proteins.”

Next Topic: How does a gene make a protein?

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Published: October 8, 2004
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