PROTEINS

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  • Proteins
    • Peptides are polymers made up of amino acids
      • Proteins are one or more polypeptides arranged as complex macromolecules.
    • Carbon, hydrogen, oxygen and nitrogen
    • AMINO AIDS
      • Same basic structure
        • Different R groups
          • These result in different amino acids
      • Twenty different amino acids are found in cells
        • 5 are non essential
        • Nine are essential and can only be obtained by what we eat
        • Six are conditionally essential as they are only needed during childhood growth.
    • SYNTHESIS OF PEPTIDES
      • Amino acids and carboxylic groups connected to the central carbon atoms react.
      • The hydroxyl in the COOH group of one amino acid reacts with the hydrogen in the amino group of another amino acid
        • PEPTIDE bond is formed
          • Form of condensation reaction
          • FORMS A DIPEPTIDE
      • Many amino acids joined = POLYPEPTIDE
        • Catalysed by the enzyme peptidyl transferase (in ribosomes for protein synthesis)
        • Polypeptides
          • Proteins
            • Different structures of amino acids means proteins vary.
      • Different R groups are able to interact with each other forming different types of bond.
        • Polypeptides
          • Proteins
            • Different structures of amino acids means proteins vary.
    • CHROMATOGRAPHY
      • Rf value = distance traveled by component / solvent front
      • Capillary action moves solutes up the chromatography paper
      • Larger molecules don't move as far as smaller molecules
    • LEVELS OF PROTEIN STRUCTURE
      • PRIMARY STRUCTURE
        • sequence of amino acids
        • Particular amino acids in the sequence influence how the polypeptide folds to give the proteins final shape
          • Determines its structure and function
        • ONLY PEPTIDE BONDS
      • SECONDARY STRUCTURE
        • Oxygen, Hydrogen and nitrogen atoms of the basic repeating structure of amino acids interact
        • HYDROGEN bonds may form in the amino acid chain = alpha helix
        • Lie parallel joined by hydrogen bonds forming beta-pleated sheets
        • RESULT OF HYDROGEN BONDS
      • TERTIARY STRUCTURE
        • Folding the protein into the final shape
        • Coiling or folding of sections of proteins into their secondary structures brings R groups of different amino acids close enough to interact
          • Hydrophobic and hydrophilic interactions
          • Hydrogen bonds
          • Disulfide bonds
          • Ionic bonds
      • QUATERNARY STRUCTURE
        • Two or ore protein structures called subunits
          • Same interactions as tertiary structure except they are between different protein molecules rather than within one molecule
    • HYDROPHOBIC AND HYDROPHILIC INTERACTIONS
      • Proteins are assembled in the aqueous environment of the cytoplasm.
      • Hydrophobic groups are on the inside of the molecule
      • Hydrophilic groups are on the outside of the molecule
    • TYPES OF PROTEINS
      • GLOBULAR
        • Compact
        • Water soluble
          • Essential for regulating many processes necessary for life
            • Chemical reasction
            • Immunity
            • Muscle contraction
        • form when proteins take their tertiary structure so hydrophobic R groups on the amino acid are kept away from the cytoplasm
          • Water soluble
            • Essential for regulating many processes necessary for life
              • Chemical reasction
              • Immunity
              • Muscle contraction
        • INSULIN
          • hormone involved in the regulation of blood glucose concentration
          • transported in the bloodstream
            • Soluble
          • Fit in specific receptors on cell surface membranes so have precise shapes
      • CONJUGATED
        • Globular proteins that contain a non-protein component called a prosthetic group
          • Haem groups are an example of a prosthetic group
            • Contain an iron II ion
            • Catalase and haemoglobin both contain haem groups
              • CATALASE
                • Enzyme
                • quaternary protein containing four haem prosthetic groups
                • Interact with hydrogen peroxide and speed up its brekdown
                  • Common byproduct of metabolism reactions but is damaging to cells
              • HEAMOGLOBIN
                • Quaternary  structure made of four polypeptides, two alpha and two beta subunits
                • Each subunit contains a prosthetic haem group
        • Lipids or carbohydrates can combine with proteins forming lipoproteins or glycoproteins
      • FIBROUS
        • Long
        • Insoluble
        • high proportion of amino acids with hydrophobic R groups in primary structures
        • Limited range of amino acids and usually have small R groups
        • Amino acid sequence is usually quite repetitive
        • Organised structures
        • KERATIN
          • Hair, skin and nails
          • Sulfur containing amino acid - cystiene
          • Many strong disulfide bonds forming strong, inflexible, insoluble materials
        • ELASTIN
          • Present in the walls of blood vessels and in the alveoli in the lungs
            • Give flexibility to expand and return to their normal size
          • Quaternary protein made of molecules called tropoelastin.
        • COLLAGEN
          • Tendons, ligaments, and the nervous system
          • 3 polypeptides wound together in a long rope-like structure.
          • flexible

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