Proteins

• What is a protein

  a long chain polymer made up of amino acids
• draw an amino acid and label the groups

  
• What reaction takes place to join two amino acids to from a dipeptide

  Condensation reaction - water is removed
• What bond forms between 2 amino acids

  peptide bond
• Draw a dipeptide and label the groups and the bond

  
• What is the primary structure of a protein? what bonds are involved?

  The sequence of amino acids in the polypeptide chain, held together by peptide bonds
• What is the secondary structure of a protein? what bonds are involved?

  When the sequence of amino acids has caused the molecule to bind into either an alpha helix or a beta pleated sheet. These are held in place by hydrogen bonds
• Where do the hydrogen bonds in the secondary structure form

  Between the C=O group of the carboxyl group and the H in the amino group of another amino acid. There form between the O and H
• how does the alpha helix structure and the beta pleated sheet structure differ

  In the alpha helix the hydrogen bonds form within the peptide chain to form the spiral, the hydrogen bonds in a beta pleated sheet are between 2 or more beta strands

  therefore alpha helix can be a single chain polypeptide, beta pleated sheets must contain at lest 2 peptide chains
• What is the tertiary structure of a protein? What bonds are involved?

  3D structure formed by further folding of the secondary structure. It is held together by more hydrogen bonds, ionic bonds and disulphide bonds
• Where do the ionic and disulphide bonds form

  Both between the R group

  Ionic- between oppositely charged molecules within the r group

  Disulphide- between sulphur atoms on the r group
• What type of bonds are disulphide bonds

  covalent
• What is the quaternary structure of proteins?
• What is the quaternary structure of a protein?

  two or more tertiary (polypeptide) structures held together. they are either fibrous or globular
• what is a fibrous e protein?

  structural proteins, filament looking long thin structures with a particular function. they are made from many amino acids with hydrophobic R groups so are insoluble in water.

  eg keratin and collagen
• what is a globular protein?

  3D round structures, they have hydrophobic parts that fold inwards with the hydrophilic parts staying external so are soluble in water.

  Their structure relates to their function, there functions include enzymes, transport proteins and messenger proteins.

  they may contain a prosthetic group (ion) eg haemoglobin contains two ahem groups with the ion Fe2+