Proteins (amino acids)

Question 1

describe/ draw strcuture of amino acid (2 marks)

Answer 1

• COOH carboxyl group
• R varibale group
  -H hydrogen
  -H2N amine group

Question 2

describe how amino acids join together (4 marks)

Answer 2

-condesnation reaction
-removing a water molecule
-between carboxyl group of one and amine group of other
-forming a peptide bond

Question 3

what are 2 and 3 or more amino acids joined together called (1 marks)

Answer 3

-dipeptide
polypeptide

Question 4

describe primary structure of protein (2 marks)

Answer 4

• sequence of amino acids in polypeptide chain
  -joined by peptide bond

Question 5

describe secondary structure of protein (3 marks)

Answer 5

• folding of polypeptide chain (alpha helix or beta pleats)
  -due to hydrogen bonding between amino acids
  -between NH of one amino acid and C=O group

Question 6

describe tertiary structure of protein (3 marks)

Answer 6

• 3-D folding of peptide chains
  -due to interactions between amino acid R groups
  -forming hydrogen, ionic and disulphide bonds

Question 7

what are foldings in secondary structures called (2 marks)

Answer 7

-alpha helix
-beta pleated sheets

Question 8

describe test for proteins (2 marks)

Answer 8

-add biuret reagent
-positive result= purple colour- shows presence of peptide bonds