Proteins

• What do AMINO ACIDS contain?

  • AMINO GROUP

  • CARBOXYL GROUP

  • R GROUP
• How many AMINO ACIDS does a DIPEPTIDE contain?

  • 2 AMINO ACIDS
• How many AMINO ACIDS do POLYPEPTIDES contain?

  • 3 or MORE AMINO ACIDS
• What is PRIMARY STRUCTURE of a PROTEIN?

  • PRIMARY STRUCTURE: SEQUENCE of AMINO ACIDS in a PROTEIN
• What is SECONDARY structure in a PROTEIN?

  • SECONDARY STRUCTURE: 2D arrangement of the CHAIN of AMINO ACIDS - (either ALPHA HELIX or BETA PLEATED SHEET )
• What is the TERTIARY structure of a PROTEIN ?

  
  

  • the 3D FOLDING of the SECONDARY structure into COMPLEX SHAPE
  • The shape is determined by the type of BONDING present, namely: HYDROGEN BONDING(forces of attraction between partially charged atoms in R groups), IONIC BONDS (salt bridges, form between oppositely charged groups on the R groups) and DISULPHIDE (covalent bonds between sulphur atoms in cysteine)
• What is the QUATERNARY structure of a PROTEIN?

  • the 3D ARRANGEMENT of MORE than one POLYPEPTIDE
  • Not all proteins have all levels of structure
• What are the characteristics of FIBROUS PROTEINS ?

  • LONG PARALLEL POLYPEPTIDES

  • Very little TERTIARY/QUATERNARY structure

  • Occasional CROSS-LINKAGES which form MICROTUBILES for TENSILE STRENGTH

  • INSOLUBLE

  • Used for STRUCTURAL PURPOSES - such as collagen
• What are the characteristics of GLOBULAR PROTEINS?

  • Complex TERTIARY/QUATERNARY structures
  • Form COLLOIDS in WATER
  • Many uses e.g. HORMONES,ANTIBODIES, CARRIER PROTEINS for example HAEMOGLOBIN