Proteins

• What are the roles of proteins?

  • Enzymes
  • Antibodies
  • Transportation
  • Structural components
  • Hormones
  • Muscle contractions
• What is the structure of a protein?

  H H --O

  H -N - C - C

  R OH
• What are the two reactions of dipeptide synthesis and breakdown?

  • Condensation - making water with products
  • Hydrolysis - using water to break reactants
• Whats the test for proteins?

  • Biuret Test
  • Blue = negative
  • Purple/lilac = positive
• What are the 4 3D complex structures of proteins?

  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• Whats features of primary proteins?

  • They have a unique sequence of amino acids in a polypeptide chain
  • The particular amino acid sequence will determine how the polypeptide folds to give the proteins final shape
• What are features of a secondary protein?

  • Beta pleated sheet
  • Alpha Helix
  • Hydrogen bonds form between amino group and the COOH group of another amino acid further down the group
  • The polypeptide chain coils into alpha helix or beta-pleated sheet
• What are some features of a quantenary protein?


  • Two or more polypeptide chains help together by same bonds in tertiary
  • Ionic bonds
  • Disulfide bridges
  • Hydrogen bonds
  • Peptide bonds
• What are features of a tertiary protein?

  • Folding of protein to its final shape
  • Coiling or shaping the protein in the secondary structure makes the R-groups of other amino acids closer together so they can react
  • Hydrogen bonding - typically weak but are strong in large numbers
  • Ionic bonds - Form between the negative and positive R-groups
  • Disulfide bridges - form between R-groups with sulfur in them
  • Hydrophobic and hydrophilic
• What are the metabolic roles that globular proteins have?

  • Enzymes
  • Hormones
  • Antibodies
• What are some globular proteins also known as?

  • Non-protein known as a prosthetic group
  • Conjugated Protein
  • Lipids, carbohydrates, metal ions
• What are 3 examples of globular proteins?

  • Haemoglobin
  • Insulin
  • Amylase
• What are some features of haemoglobin?

  • 2 alpha chains
  • 2 beta chains
  • Made up of 4 polypeptide chains (quanternary)
  • Known as conjugated as it has a polypeptide chain that each contains a haem group with an iron atom
  • The ion atom can irreversibly bind with one O2 molecule
• What are some features of insulin?

  • Globular protein known as a hormone
  • Used to regulate blood in glucose concentrations
  • Hormones travel in the blood and needs to be soluble aswell a specific shape to fit with receptors
  • Insulin is made up of two polypeptide chains held together by disulfide bonds
• What are some features of amylase?

  • Globular protein known as an enzyme
  • Responsible for the breakdown of starch into maltose
  • Made up of single polypeptide chain folded using both a-helix and b-pleats
• What is a fibrous protein and what are some of its roles?

  • Form long strands and are not usually soluble in water and have many structural roles in the body
• What are 3 examples of fibrous proteins?

  • Keratin
  • Collagen
  • Elastin
• What are some features of keratin?

  • Found in skin, hair and nails
  • Can be either flexible or rigid depending on the number of disulfide bonds it contains
  • Contain a large number of amino acid cysteine which allows disulfide bonds to form
  • This creates strong insoluble molecules
• What are some features of elastin?

  • Fibrous protein found in elastin connective tissue such as walls of blood vessels
  • Allows tissue to expand and return to original shape
• What are some features of collagen?

  • Fibrous protein used as a structural componment in skin, cartilage, bone, teeth and blood vessels
  • Collagen is made up of 3 polypeptide chains wound each other in a rope-like structure
  • This provides strength and flexibility