Proteins may be defined as compounds of high molar mass consisting largely or entirely of chains of amino acids. Their masses range from several thousand to several million daltons (Da). In addition to carbon, hydrogen, and oxygen atoms, all proteins contain nitrogen and sulfur atoms, and many also contain phosphorus atoms and traces of other elements. Proteins serve a variety of roles in living organisms and are often classified by these biological roles. Muscle tissue is largely protein, as are skin and hair. Proteins are present in the blood, in the brain, and even in tooth enamel. Each type of cell in our bodies makes its own specialized proteins, as well as proteins common to all or most cells.
Proteins are present in the foods we eat, both plant- and animal-based. The digestion of food is dependent upon the action of many proteins within the body called enzymes.
Note: The dalton is a unit of mass used by biochemists and biologists. It is equivalent to the atomic mass unit. A 30,000 Da protein has a mass of 30,000 amu.
Table 18.1 Classification of Proteins by Biological Function
|Enzymes||accelerate biological reactions||α-amylase breaks down starch and glycogen|
|Structural||provide strength and structure||gluten provides structure to breads and other baked goods|
|Contractile||muscle contraction, cell division||myosin is one protein found in muscle tissue that is necessary for the contraction of muscles|
|Transport||transport substances from one place to another||hemoglobin transports oxygen from the lungs throughout the body|
|Regulatory||regulates the function of other proteins||insulin regulates the activity of specific proteins in the body|
|Storage||provide storage of essential nutrients||ovalbumin stores amino acids in the egg white|
|Protection||protect cells or the organism from foreign substances||immunoglobulins recognize and break down foreign molecules|
We begin our study of proteins by looking at the properties and reactions of amino acids, which is followed by a discussion of how amino acids link covalently to form peptides and proteins.
This page is based on “Chemistry 2e” by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD, Openstax which is licensed under CC BY 4.0. Access for free at https://openstax.org/books/chemistry-2e/pages/1-introduction
This page is based on “The Basics of General, Organic, and Biological Chemistry” by David W Ball, John W Hill, Rhonda J Scott, Saylor which is licensed under CC BY-NC-SA 4.0. Access for free at http://saylordotorg.github.io/text_the-basics-of-general-organic-and-biological-chemistry/index.html