Proteins

• Proteins contain the atoms; carbon, oxygen, hydrogen, nitrogen and sometimes sulfur
• Two amino acids join to form a dipeptide
• A chain or more than two amino acids is called a polypeptide
• Monomers are amino acids
• Plants can make their own amino acids
• Animals can only make some amino acids. Some must come from the diet – essential amino acids
• Proteins are made up of one or more polypeptide chains
• The R-group is different in each amino acid
• Amino acids contain an Amine group and Carboxyl group
• Amino acids contain an Amine group and what other group?

  Carboxyl
• Primary Structure of a protein is the specific sequence of amino acids in a polypeptide chain
• The secondary structure of a protein is the coiling or folding of the polypeptide chain due to the formation of hydrogen bonds
• Two main 3D shapes formed in secondary structure are:

  • Alpha helix
  • Beta pleated sheet
• Tertiary structure is the overall 3D shape of a protein molecule
• There are four types of bonding involved:

  1. Hydrogen bonds

  2. Ionic bonds

  3. Disulphide bonds

  4. Hydrophobic and hydrophilic interactions
• The quaternary structure of a protein is the way that two or more polypeptide subunits are arranged to give a final specific shape. E.g insulin and collagen
• Quaternary structure

  Refers to the arrangement of multiple polypeptide chains (or subunits) in a protein complex (e.g. insulin, collagen)
• Secondary structure

  Refers to the local spatial arrangement of the polypeptide backbone (e.g. alpha helix, beta sheet)