proteins

• what are proteins?


  protein is a greek word meaning of first importance.
• what elements do proteins always contain?

  carbon, hydrogen and nitrogen but may also contain others
• what are some examples of protein functions?

  -structure-receptors-transport
• what are proteins made from?

  one or more polypeptides
• what are the monomers that make up polypeptides to form proteins?

  amino acids
• what are formed when 2 amino acids join together, and what happens when more than 2 amino acids are joined together?

  when 2 amino acids join together they form a dipeptide.when more than 2 join together they for a polypeptide
• what is the structure of amino acids?

  they have a carboxyl group, an amine group, and an R group (variable side group) attached to a carbon atom
• how are dipeptides formed?

  dipeptides are formed by a condensation reaction between 2 adjacent amino acids forming peptide bonds.
• how are polypeptides formed?

  polypeptides are formed when many amino acids join together by condensation reactions.
• how are dipeptides and polypeptides broken down?

  hydrolysis reaction
• what is the primary structure of proteins?

  • it is the sequence of amino acids that make a polypeptidechain held by peptide bonds
  • it determines the ultimate shape of protein
  • there is a limitless number of combinations as proteinshave wide variations
• what bonds maintain the primary structure of proteins?

  peptide bonds
• what is the secondary structure of proteins?

  • the way primary polypeptide chains fold and coil-form either a-helix or b-sheets.
  • a-helix = polypeptide chains wind into helix which is verystable
  • b-sheet = polypeptide chains zig zag forming a pleatedsheet
• what are the bonds that maintain the secondary structure?

  hydrogen bonds (position is important)
• what is the tertiary structure of proteins?

  • this describes the way the polypeptide folds into a uniqueand specific 3D shape.
  • the shape is determined by the primary structure
  • limitless number of possibilities
• what are the bonds maintain the tertiary structure?

  -hydrogen bonds-ionic bonds-disulphide bonds
• what is the quaternary structure of proteins?

  -some proteins are made of more than one polypeptides (with their own tertiary structure) linked togethereg. haemoglobin and antibodies
• what bonds maintain the quaternary structure?

  -hydrogen bonds-ionic bonds-disulphide bonds