Proteins

• Proteins

  • carbon, hydrogen, oxygen, nitrogen, sometimes sulfur
• amino acid

  A) AMINE GROUP

  B) R GROUP

  C) CARBOXYL GROUP

  
• Peptide bonds

  A) OH

  B) H

  C) H2O

  
• Primary structure

  • sequence of amino acids in the polypeptide chain
• Secondary structure

  • hydrogen bonds form between amino acids in the chain
  • coils into an alpha helix
  • OR folds into a beta pleated sheet
• Tertiary structure

  • further bonds within the polypeptide chain
  • to form their final 3D structure
  • bonds
  • ionic
  • hydrophobic/hydrophilic interactions
  • disulphide bonds
  • hydrogen bonds
• Quaternary structure

  • association of 2 or more polypeptide chains
  • to form final 3D structure
  • bonds
  • ionic
  • hydrophobic/hydrophilic interactions
  • disulphide bonds
  • hydrogen bonds
• Globular proteins

  • hydrophilic R groups are pushed outside of the molecule
  • they are now soluble
  • compact
  • easily transported in fluids
• Haemoglobin - globular and conjugated

  • carries oxygen around the body in red blood cells
  • conjugated protein - haem prosthetic group
  • Haem contains iron for oxygen to bind to
  • contains four polypeptide chains
• Insulin - globular

  • a hormone secreted by the pancreas
  • regulates blood glucose level
  • soluble to be transported in the blood
  • consists of 2 polypeptide chains - disulphide bonds
• Amylase - globular

  • an enzyme that breaks down starch
  • one polypeptide chain
  • both alpha helixes and beta pleated sheets in its secondary structure
• Fibrous proteins

  • insoluble
  • strong
  • unreactive
  • repetitive arrangement of R-groups
  • smaller R-groups, limited range
  • high proportion of hydrophobic R-groups
• Collagen - fibrous

  • in animal connective tissues
  • minerals can bind to it to increase rigidity
  • very strong
• Keratin - fibrous

  • external animal structures
  • skin, hair, nails, feathers, horns
  • can be flexible, hard or tough
• Elastin - fibrous

  • elastic connective tissue
  • skin, large blood vessels, some ligaments
  • elastic - can return some tissues to their original shapes after being stretched