Proteins are
macromolecules. They are constructed from one or more unbranched
chains of amino acids;
that is, they are polymers. A typical protein contains 200-300 amino acids
but some are much smaller (the smallest are often called peptides) and
some much larger (the largest to date is titin a protein found in
skeletal muscle; it contains some 27,000 amino acids in a single chain!).
Every function in the living cell depends on
proteins.
- Motion and locomotion of cells and organisms
depends on contractile proteins.
- The catalysis of all biochemical reactions is
done by
enzymes, which contain protein.
- The structure of cells, and the extracellular
matrix in which they are embedded, is largely made of protein. (Plants
and many microbes depend more on carbohydrates, e.g., cellulose, for
support, but these are synthesized by enzymes.)
- The transport of materials in body fluids depends
of proteins.
- The receptors for hormones and other signaling
molecules are proteins.
- Proteins are an essential nutrient for
heterotrophs.
- The transcription factors that turn genes on and
off to guide the differentiation of the cell and its later
responsiveness to signals reaching it are proteins.
- and many more - proteins are truly the physical
basis of life.
For detailed information regarding proteins to to
this page. |
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