Section 14.8 What is the Primary Structure of Proteins? By Jon Stetler

 Primary Structure of a protein describes the linear sequence of amino acids in the polypeptide chain.  Peptide and protein molecules in biological organisms have different sequence of amino acids~this allows the protein to carry out its functions.

 There are 20 different amino acids. There are 20 possibilities for the N-terminal amino acid in the chain, and 20 for the C- terminal amino acid in the chain. 20x20=400 dipeptides  For each of the 400 dipeptides you can choose from 20 amino acids for the tripeptides in the chain 400x20=8000  8000 is the possible structures for the tripeptide.

 The assignment of positions of the amino acids in the sequence begins at the N-terminal.  The order of the amino acids on the chain allows the entire chain to fold and curl to assume its final shape.  Without its particular 3-D shape a protein can’t function.

 Changing just one amino acid may or may not matter  Humans and chimps have the exact same amino acid sequence for Cytochrome c (a terrestrial vertebrate protein) This chain has 104 amino acid residues. It performs the same in humans, sheep, chimps, and other animals.  However, sheep cytochrome c differs in 10 positions out of the 104.  Human insulin has 2 chains with a total of 51 amino acids.  People with diabetes have to take insulin injections. Humans have to use cattle, hog, or sheep insulin instead of human insulin because there is only a small amount of human insulin available.  These insulin's have differences in 4 of the amino acid residues. They all function the same though, but not as effective as human insulin.

 This is used to produce human insulin from bacteria.  Many people still use hog or sheep insulin because it is less expensive  When changing from animal to human insulin people with diabetes may have a reaction called hypoglycemia.  Hypoglycemia is where a persons blood sugar drops due to insulin level being too high. They can experience sweating, coordination problems, and hunger sensations (hypoglycemic awareness). These issues can be made better by eating some sugar.  Some diabetics have stated that the symptoms of hypoglycemic awareness from the recombinant DNA is not as bad as from the insulin from animals.

 Normal human hemoglobin has 2 alpha chains and 2 beta chains. With sickle cell the only difference is in the beta chain in the 6 th position.  Sickle Cell Anemia is when the red blood cells become sickle shaped and have decreased oxygen.  This shape clogs the capillaries and causes the body to destroy the clogged cells and this causes anemia.  There is a high death rate from this disease, and no known cure.