the peptide chain

• Glycine

  • Glycine is an example of an amino acid.
  • Glycine has a hydrogen atom in its R group.
  • Glycine is the only amino acid that does NOT have a carbon atom in its R group.
• Essential amino acids

  • There are 20 different types of amino acids that are common in all organisms.
  • 10 of these are essential amino acids in humans because the human body cannot produce them and they are obtained from the diet.
• R groups

  • The R group is different in each amino acid.
  • The R group determines how the amino acid interacts and bonds with other amino acids in the polypeptide.
• Structure of amino acids

  • Each amino acid has a central carbon atom (alpha carbon).
  • There are four atoms or groups of atoms bonded to the central carbon atom:
  • NH2 (an amine group).
  • COOH (a carboxyl group).
  • H (a hydrogen atom).
  • R (a side group).
• Structure of proteins

  • Proteins are made up of amino acids.
  • Dipeptides are formed from the condensation of two amino acids.
  • Polypeptides are formed by the condensation of many amino acids.
• Polypeptides

  • Polypeptides are made from chains of amino acids.
  • There are amino acids at each end of the polypeptide chain.
  • These amino acids form the two end terminals:
  • The N-terminal (amine terminal).
  • The C-terminal (carboxyl terminal).
• The peptide bond

  • When two amino acids react together, a bond forms between the carboxyl group of one amino acid and the amine group of a second amino acid.
  • One water molecule is released as a by-product.
  • The bond formed between two amino acids is a covalent bond called a peptide bond.
• functions of proteins

  Antibodies

  • Antibodies are made up of polypeptide chains.
  • Antibodies are used in the immune response.
  • Antibodies are diverse proteins.
  • Each antibody has a different sequence of amino acids.
• functions of proteins:

  Transport proteins

  • Transport proteins include channel proteins.
  • Channel proteins transport molecules across the cell membrane.
  • Channel proteins transport molecules that are too large to diffuse freely or molecules that carry a charge.
• functions of proteins

  Structural proteins

  • Structural proteins are long, strong polypeptide chains.
  • Structural proteins are connected by cross-links that hold the chains parallel to each other.
  • E.g. Collagen and keratin.
• functions of proteins

  Enzymes

  • Enzymes are biological catalysts.
  • Enzymes increase the rate of a reaction without being used up in the reaction.
  • The enzymes are usually tightly folded, complex proteins that are soluble.