3.1.4.1 Protein properties

• Amino acids- the monomers which join together in a condensation reaction to make proteins
• Dipeptides- two amino acids bonded together by a peptide bond, formed in a condensation reaction
• Polypeptides- long chains of amino acids that are joined together by peptide bonds, formed in a condensation reaction
• Structure of amino acid:

  A) COOH

  B) carboxyl

  C) R

  D) variable

  E) amine

  F) NH2

  
• Reactions of amino acids and dipeptides:

  A) peptide

  B) peptide

  C) condensation

  D) hydrolysis

  E) dipeptide

  F) used

  G) released

  
• Primary structure- the sequence of amino acids in a chain, held by peptide bonds
• Secondary structure- hydrogen bonding between amino acid chains causes folding, forming an alpha helix or a beta pleated sheet
• Tertiary structure- formed by interactions between R-groups, forming a 3D protein structure, held by ionic and hydrogen bonds and disulphide bridges
• Quaternary structure- the 3D structure of a protein that is formed by the interaction of multiple polypeptide chains
• Test for proteins:

  • Add sodium hydroxide to sample- to make it alkaline
  • Add copper sulphate solution
  • Positive result= colour change from blue to purple
• Functions of proteins:

  • Transport proteins- allows movement of large molecules across cell membrane
  • Structural proteins- provides strength and support
  • Antibodies- diverse proteins
  • Enzymes- tightly folded proteins