AQA A-LEVEL BIOLOGY STUDY GUIDE
EXAM 2026 COMPLETE QUESTIONS WITH
SOLUTIONS GRADED A+
◉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
◉what do enzymes do?. Answer: lowers the activation energy of the
reaction it catalyses
◉activation energy. Answer: minimum energy required for a
reaction to start
◉induced fit model. Answer: a change in the shape of an enzyme's
active site occurs, enhancing the fit between the active site and
substrate(s)
EXAM 2026 COMPLETE QUESTIONS WITH
SOLUTIONS GRADED A+
◉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
◉what do enzymes do?. Answer: lowers the activation energy of the
reaction it catalyses
◉activation energy. Answer: minimum energy required for a
reaction to start
◉induced fit model. Answer: a change in the shape of an enzyme's
active site occurs, enhancing the fit between the active site and
substrate(s)
