Proteins

Proteins -

> 1. Proteins are biopolymers (called polypeptides) of L-amino acids.

> 2. Amino acids in proteins are joined to each other via peptide bonds.

> 3. Only L-amino acids are used to make proteins (rare exceptions of proteins in bacterial cell wall, which contain some D-amino acids)

> 4. The process of putting amino acids together to make proteins is called translation.

> 5. Translation relies on the genetic code, in which three nucleotides in mRNA specify one amino acid in protein.

> 6. The order or sequence of amino acids distinguishes different proteins from each other. The sequence of amino acids determines the 3-dimensional shape of the protein. Alterations to the amino acid sequence of a protein changes its 3D shape.

> 7. The difference between a polypeptide and a protein is that the term polypeptide refers simply to a chain of amino acids. The term protein refers to the chain of amino acids after it folds properly and is (in some cases) modified. Proteins may consist of more than one polypeptide chain.

> 8. Proteins are sometimes described as the "workhorses" of the cell because they do so many things - catalyze reactions, provide structural integrity, transport molecules, provide movement, bind molecules, and others.

See also: Amino Acids, Peptide Bonds, Translation, Genetic Code, Polypeptides, Nucleic Acids, RNA, Translation Overview (from Chapter 27), The Genetic Code, Polyampholytes