Proteins - these large molecules are polymers of amino acids.

o      Proteins contain a significant amount of nitrogen in addition to the carbon, hydrogen and oxygen they contain.

o      Proteins serve many essential purposes in the cell. They can be structural proteins such as collagen and keratin.

o      Most other proteins such as the enzymes, the antibodies, the cell surface receptors and the various carrier molecules are actively involved in many of the biochemical reactions of the cell or the multicellular organism. Each of these proteins has the ability to specifically recognize and bind to its unique substrate.

• Proteins or polypeptides are polymers of amino acids.
• Each different amino acid has a unique R-group which gives each amino acid an unique chemistry.
• The amino acids are covalently linked to each other via peptide bonds.
• Once polymerized, the R-groups of the various amino acids interact with each other.
• This then causes the polypeptide to assume a shape or conformation.

Therefore the amino acid sequence determines the conformation of the protein and this in turn determines the function of the protein.

It is important to remember that protein shape is sensitive to pH, temperature and dissolved salts.

By changing these variables the activity or function of the protein will be altered.

If the protein's shape is altered so severely that the protein no longer functions, the protein is said to be denatured.

Review

Proteins are made of amino acids. Polymers.

How many aa's are there? What is the basic structure? How are amino acids classified?

Hydrophobic (non-polar), hydrophilic (polar), basic (+ charge), acidic (- charge).

What do proteins do? Name some categories of proteins.

35% of the dry weight of bacteria is ribosomes -- big investment in protein synthesis machinery.

Proteins have a shape -- a conformation. This is determined by the amino acid sequence. The shape is sensitive to physical and chemical conditions around the protein molecule: pH, ionic strength and temperature will affect protein conformation. Binding and interaction with other molecules (substrate, cofactors, other proteins) will also alter protein conformation.

If the conformation is altered too drastically, the protein molecule may lose function -- it breaks -- it becomes denatured. Some proteins have more stable conformations if they are stabilized by disulfide bonds.

Review Non-covalent interactions

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