Protein

• Proteins

  • Made from hydrogen, oxygen and nitrogen
  • Some contain sulfur
  • Made of 20 monomers called amino acids
  • Found in living things
  • Joined by a condensation reaction to form a peptide bond
  • Variable nature of R group they fold
  • Have different shapes and functions
• Proteins

  • Some are structural and hormonal
  • Some are enzymes (biological catalysts)
  • Some are antibodies
• Amino acid

  • Monomer unit of proteins
  • Has an amine group, carboxyl group, and R group
• Protein structure

  1. Primary structure - number and order of amino acids

  2. Secondary structure - coils into alpha helix or folds into beta pleated sheet

  3. Tertiary structure - further coding into unique 3D shape

  4. Quaternary structure - more than one polypeptide chain
• Protein structure

  • Primary structure held by peptide bonds
  • Secondary structure held by hydrogen bonds
  • Tertiary structure held by ionic, hydrogen, and disulphide bonds
• Fibrous proteins

  Long chain, insoluble in water, usually for structure and support
• Globular proteins

  Spherical, compact, hydrophilic groups spaced out hydrophobic R groups, involved in many processes
• Enzymes

  • Biological catalysts that speed up reactions without being used up
  • Have a unique specific active site where substrate binds
• Enzymes

  • Affected by temperature and pH
  • Rate of reaction affected by substrate/enzyme concentration and inhibitors
• As temperature increases

  Enzyme activity increases initially as they gain more kinetic energy and collide more
• After 30°C

  Enzyme activity decreases as hydrogen and ionic bonds break and active site changes shape
• Enzyme action models

  • Lock and key - enzyme binds to active site as they are complementary
  • Induced fit - enzyme active site changes to fit around substrate
• Enzyme inhibitors

  • Competitive - similar shape to substrate, binds to active site preventing substrate binding
  • Non-competitive - not similar to substrate, binds to allosteric site changing enzyme activity
• Small change in pH

  Can alter charges on R groups of amino acids that make up the shape of the active site
• Larger pH change

  Can cause hydrogen and ionic bonds to break, preventing substrate from binding to the enzyme
• Substrate concentration

  Is the limiting factor - more substrate molecules means more enzyme-substrate complexes form
• Enzyme saturation point

  All enzyme active sites are in use, enzyme is at maximum rate
• Biuret test - turns blue to lilac to test for proteins