proteins.

Question 1

Describe how a dipeptide is formed from two amino acids.

Answer 1

• Condensation reaction
• The OH of the carboxylic acid group in one amino acid bonds with a H atom from the amino group of the other amino acid
• This produces water
• Forms a peptide bond

Question 2

Define the term primary structure.

Answer 2

The sequence of amino acids in a polypeptide chain.

Question 3

Describe how the secondary structure of a protein is formed.

Answer 3

• The polypeptide chains coil to form an alpha helixes
• Or fold to form a beta pleated sheet

Question 4

Describe how the tertiary structure of a protein is formed (include details of the different bonds that hold the protein in its tertiary structure).

Answer 4

• The alpha helixes and beta pleated sheets coil and fold further.
• Held in place by lots of bonds:
  
  • Ionic bonds between amino acids of opposite charge
  • Hydrogen bonds between amino acids with slight charges
  • Disulphide bonds that form between sulphur atoms in two cysteine amino acids
  • Hydrophilic interactions – hydrophilic amino acids are found on the outside of the protein.

Question 5

Describe two examples of where the tertiary structure of a protein is crucial to its function.

Answer 5

1. Enzymes
   - Shape of active site is specific
   - And complementary to the substrate
   - If the tertiary shape is altered, the enzyme can’t hydrolyse the substrate
2. Hormones
   - Shape is specific and complementary
   - To the receptor
   - If the tertiary shape is altered the hormone won’t combine with the receptor

Question 6

Define the term quaternary structure.

Answer 6

A protein made up of different polypeptide chains

Question 7

Define the term conjugated protein.

Answer 7

• A protein with a non-protein group attached.
• The non-protein group is called a prosthetic group

Question 8

9. Describe the general structure of a globular protein.

Answer 8

• Spherical
• Amino acids with hydrophilic R groups are on the outside
• Soluble

Question 9

Structure of haemoglobin.

Answer 9

• Four polypeptide chains
• Each polypeptide chain has a haem group as a prosthetic group.
• Each haem group contains iron.

Question 10

Function of haemoglobin.

Answer 10

To carry oxygen in erythrocytes.

Question 11

Str