Proteins

• What bond are amino acids joined by?

  Peptide bonds
• Describe the primary structure of a protein

  A sequence of amino acids, joined by peptide bonds
• Describe the secondary structure of a protein

  Hydrogen bonds form to make alpha helices and beta pleated sheets
• Describe the tertiary structure of a protein

  Hydrogen, ionic bonds and disulphide bridges form between R groups in specific places
• Describe the quaternary structure of a protein

  More than one polypeptide linked together
• What are the two causes of protein denaturation?

  -pH above or below the optimum

  -Temperature above the optimum
• What is the effect of protein denaturation?

  Hydrogen and ionic bonds break which changes the shape of the protein
• What is the biochemical test for a protein?

  -Add Biuret Reagent

  -Mix well

  -A purple colour change occurs in a positive result
• What must be present in a protein for a positive test to occur?

  At least two peptide bonds must be present for a positive result