AQA AS BIOLOGY 7401/2 PAPER 2 MARK
SCHEME JUNE 2021 EXAMINATION TEST
2026 COMPLETE QUESTIONS AND
SOLUTIONS GRADED A+
⩥ protein. Answer: polymer of amino acids linked by peptide bonds
⩥ dipeptide. Answer: product of the condensation of two amino acids
⩥ polypeptide. Answer: long chain of amino acids joined by peptide
bonds
⩥ disulphide bridges. Answer: a strong covalent bond formed with the
sulfur of cysteine monomers
⩥ R group. Answer: a variable/functional group that defines an amino
acid
⩥ primary structure. Answer: sequence of amino acids, coded by DNA
⩥ secondary structure. Answer: local folding of the chain to form either
an α-helix or β-pleated sheet
, ⩥ tertiary structure. Answer: further folding involving interactions
between R-groups.
⩥ quaternary structure. Answer: many polypeptide chains and
sometimes an associated prosthetic group
⩥ fibrous proteins. Answer: long, insoluble, structural proteins (collagen
in bone, keratin in hair, actin in muscle etc)
⩥ globular proteins. Answer: spherical, water-soluble proteins (enzymes,
membrane proteins, haemoglobin, insulin etc)
⩥ strength of bonds in proteins (weak to strong). Answer:
hydrophobic/phillic interactions, hydrogen bonds, ionic bonds, disulfide
bridges
⩥ what is the test for proteins?. Answer: biuret test
⩥ describe the biuret test. Answer: add biuret reagent to the sample,
turns purple in the presence of peptitde bond ∴ protein is present; if not
it stays blue.
⩥ enzyme. Answer: protein that is a biological catalyst
SCHEME JUNE 2021 EXAMINATION TEST
2026 COMPLETE QUESTIONS AND
SOLUTIONS GRADED A+
⩥ protein. Answer: polymer of amino acids linked by peptide bonds
⩥ dipeptide. Answer: product of the condensation of two amino acids
⩥ polypeptide. Answer: long chain of amino acids joined by peptide
bonds
⩥ disulphide bridges. Answer: a strong covalent bond formed with the
sulfur of cysteine monomers
⩥ R group. Answer: a variable/functional group that defines an amino
acid
⩥ primary structure. Answer: sequence of amino acids, coded by DNA
⩥ secondary structure. Answer: local folding of the chain to form either
an α-helix or β-pleated sheet
, ⩥ tertiary structure. Answer: further folding involving interactions
between R-groups.
⩥ quaternary structure. Answer: many polypeptide chains and
sometimes an associated prosthetic group
⩥ fibrous proteins. Answer: long, insoluble, structural proteins (collagen
in bone, keratin in hair, actin in muscle etc)
⩥ globular proteins. Answer: spherical, water-soluble proteins (enzymes,
membrane proteins, haemoglobin, insulin etc)
⩥ strength of bonds in proteins (weak to strong). Answer:
hydrophobic/phillic interactions, hydrogen bonds, ionic bonds, disulfide
bridges
⩥ what is the test for proteins?. Answer: biuret test
⩥ describe the biuret test. Answer: add biuret reagent to the sample,
turns purple in the presence of peptitde bond ∴ protein is present; if not
it stays blue.
⩥ enzyme. Answer: protein that is a biological catalyst
