3.1.4.1 General properties of proteins

Question 1

Protein definition

Answer 1

Molecules made up od more than one polypeptide chain

e.g. enzymes, antibodies, transport proteins, structural proteins

Question 2

Amino acid definition

Answer 2

The monomers from which proteins are made

Question 3

Amino acid structure

Answer 3

C= carbon chain 
H2N =amino group 
R= variable group (contains carbon minus glycine)
H= hydrogen 
COOH= carboxyl group

Question 4

Peptide bond

Answer 4

Condensation reaction between 2 amino acids
└with the elimination of a water molecule
-between the carboxyl group of one and the amine group of another

Question 5

Biuret test for proteins

Answer 5

-add biuret reagent

(+) light purple

Question 6

Primary structure

1ᵒ

Answer 6

• sequence of amino acids

- 1ᵒ peptide bonds

Question 7

Secondary structure

2ᵒ

Answer 7

• the way in which the primary structure/polypeptide chain folds
  e. g. alpha helix, beta pleated sheets
• 1ᵒ peptide bonds
• 2ᵒ hydrogen bonds

Question 8

Tertiary structure

3ᵒ

Answer 8

• the final 3D shape of the protein
• Tertiary structure depends on the primary structure
• 1ᵒ peptide bonds
• 2ᵒ hydrogen bonds
• 3ᵒ ionic bonds, disulphide bridges

Question 9

Quaternary structure

4ᵒ

Answer 9

-proteins formed from more than one polypeptide chainm may contain a prosthetic group (an inorganic component)

• 1ᵒ peptide bonds
• 2ᵒ hydrogen bonds
• 3ᵒ ionic bonds, disulphide bridges
• hydrophobic/hydrophilic interactions

e.g. Antibodies (3 chains), Haemoglobin (4 chains)