Proteins

Proteins

1. amino acid

   • Are buiding blocks of protein
   • Contains
     • Carbon
     • hydrogen
     • Oxygen
     • nitrogen
     • sometimes sulphur
   • Each amino acid consist of the central alpha carbon some grups are attached
     • Hydrogen atom
     • a carboxyl (COOH)
     • An amino (NH2)
     • a unique R group or side chain
       • determines amino acid prpperties
   • amino acids have tow funtional grups
     • an amino functional group
     • a carboxyl functional group
   • Properties of amino acid R groups
     • non polar
     • polar
     • some amino acid have charged R groups

2. General functions of proteins

   • enezymes
     • Digestion
     • metabolism
   • Transport and storage
     • Oxigen transports
     • fatty acids transport
     • iron storage
   • structural support
     • Skin and bone ( collagen)
     • Elastic Ligamenst ( elatin)
   • Immune protection
     • antibodys
   • movement
     • muscle contractions (actin and myosin)
   • Hormones
     • Blood glucose relulation (insulin and glycogen)

3. Protein structure

   • Primary Structure
     • Each amino acid is linked by peptide bond
     • The sequence of amino acids in the polypeptide chain
     • dislphide bridges are also part of the primary structure
   • Secondary structure
     • Allpha helices
     • Beta pleated sheets
     • The areas of finding or coiling within a protein
     • Amino acids interact non-covalent between thr amino acids side chains
     • hydrogen bonding coils the polypetide into a stabilised secondry structure
   • Tertiary Structure
     • the final 3D shape of a protein
     • the function of a protein depends on thethe function of a protein depends on the
     • the forces which give rise to and stabilise the tertiary structure are
       • ionic bonds
         • salt bridges and electrostatic interactions between side chains of amino acids
       • hydrogen bonding
         • occurs between side chains between the hydrogens on one amino acid and the hydrogens on another amino acid
       • hydrophobic interactions
         • in water soluble proteins non-polar amino acids are located on the hydrophobic inside of the molecule away from the hydrophilic medium surrounding the protein
         • hydrophobic regions are further stabilised by Van der Waals forces
   • Quaternary structure
     • involves the clustering of several individual polypeptide chains into a final and precise 3D shape
     • polypeptide chains into a final and precise 3D

4. formation of a protein

   • the alpha carboxyl group is joined to the alpha amino group another amino acid by a peptide bond
   • froms a peptide bond
   • condensation reaction
   • leads to the formation of a chain of amino acids called a peptide bond

5. Main categories of proteins

   • Fibrous
     • provide mechanical support to cells and to entire organisms
     • insoluble in water and physically tough
     • polypeptide chains form a single repetitive structure which is twisted regularly and arranged in bundles or sheets
     • elongated molecules whose secondary structure is the dominant structural feature
   • Globular proteins
     • are relatively sepherical

6. Proteins are molecules composed of amino acids

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