Proteins

Question 1

Describe the structure of a protein.

Answer 1

Made up of amino acid monomers joined together through a series of condensation reactions to form a polypeptide. An -OH from the carboxyl group of one amino acid is combined with the -H from the amino group of another to release water and form a peptide bond.

• Primary structure = linear sequence of amino acids
• Secondary structure = hydrogen bonds form between amino acids in the chain causing it to fold into an alpha-helix or beta-pleated sheet
• Tertiary structure = the secondary structure is further folded and twisted to form a 3D shape held in place by hydrogen bonding, ionic bonding and disulphide bridges.
• Quaternary structure = some proteins contain multiple polypeptide chains and non protein groups.

Question 2

How many amino acids are there and how many of these are essential?

Answer 2

• 20 amino acids

- 9 essential amino acids

Question 3

How are proteins broken down?

Answer 3

Peptidases hydrolyse proteins into amino acids.

Question 4

What are complete proteins? Give some sources.

Answer 4

Foods that contain all 9 essential amino acids in adequate proportions.
- Meat, dairy, eggs, soya, quoin, quinoa.