Lesson 3.3.13.2

3.3.13.2 Proteins Quiz: AQA Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.13.2, Proteins: 20 multiple choice questions for the AQA Chemistry (7405), Unit 3: Organic chemistry, written with Revision Ninja.

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The 20 questions

  1. What links amino acids together in a protein?

    • Peptide links
    • Disulfide links only
    • Glycosidic links
    • Ester links

  2. What is the structure of a peptide link?

    • -CONH-
    • -SO2-
    • -CH2-
    • -COO-

  3. What is the primary structure of a protein?

    • The arrangement of several chains together
    • The coiled helix formed by hydrogen bonds
    • The sequence of amino acids in the chain
    • The folding of the chain into a globular shape

  4. Which bonding maintains the alpha-helix secondary structure?

    • Hydrogen bonds between C=O and N-H groups in the chain
    • Metallic bonds between backbone carbons that link the chain into a rigid coil
    • Disulfide bonds between cysteine residues, which hold the chain in a fixed fold
    • Ionic bonds between side groups that carry opposite charges at the active site

  5. Which bonds hold the tertiary structure of a protein together?

    • Metallic bonds only, which form between the sulfur atoms in the folded chain
    • Peptide links only, which hold the amino acids in a single chain in the right order
    • Van der Waals forces between water molecules that surround the protein in solution
    • Hydrogen bonds, ionic attractions and S-S (disulfide) bonds

  6. What is produced by complete acid hydrolysis of a peptide link?

    • Esters and water
    • Alkenes and carbon dioxide
    • The constituent amino acids
    • Ketones and hydrogen

  7. What is the product of hydrolysing a dipeptide?

    • One amino acid and one ester
    • Two amino acids
    • A nitrile and water
    • Two alkenes

  8. How many peptide links are present in a tripeptide?

    • 3
    • 1
    • 2
    • 4

  9. What is the Rf value when a spot moves 3.0 cm and the solvent front moves 6.0 cm?

    • 2.0
    • 0.33
    • 1.0
    • 0.5

  10. Which developing agent is used to make colourless amino acids visible on a TLC plate?

    • Fehling's solution
    • Bromine water
    • Ninhydrin
    • Silver nitrate solution

  11. Why must Rf values be compared with standards under identical conditions?

    • Rf values depend only on the molar mass
    • Rf depends on the solvent, plate and temperature used
    • Rf values are the same for all compounds
    • Rf values change with the colour of the sample only

  12. A change in a single amino acid alters which structural level of a protein?

    • Only the quaternary structure, never the primary
    • Primary structure, which can change folding and function
    • Only the colour of the protein
    • None of the structural levels

  13. Which bonds hold adjacent polypeptide strands together in a beta-pleated sheet?

    • Hydrogen bonds between C=O and N-H groups on neighbouring strands
    • Ionic bonds between all amino acid side groups in the sheet, which hold it flat
    • Disulfide bonds between the same strand only, which hold each strand in a fixed shape
    • Metallic bonds across the sheet, which give it electrical conductivity in solution

  14. How many amino acids are released by complete hydrolysis of a tripeptide made of three different amino acids?

    • 1
    • 2
    • 3
    • 6

  15. Which factor separates amino acids on a thin-layer chromatography plate?

    • Different affinities for the stationary phase and the moving solvent
    • Different densities of the amino acids, which make some sink faster in the solvent
    • Different melting points of the amino acids, which make some melt on the plate
    • Different colours of the amino acids, which make some spots easier to see on the plate

  16. A chromatogram shows solvent front 8.0 cm, amino acid A at 2.0 cm and amino acid B at 6.4 cm. Which has the higher Rf value?

    • B, at 0.80
    • They have the same Rf
    • A, at 0.25
    • Neither can be calculated

  17. What happens to the tertiary structure of a protein when it is heated strongly?

    • The protein becomes a sugar, which is then broken down by the enzymes in the cell
    • It is disrupted, while the primary sequence is unchanged
    • The protein gains extra peptide links, which stabilise its shape at high temperature
    • The peptide links are always broken first, which splits the chain into amino acids

  18. Which feature describes an alpha-helix correctly?

    • A coiled structure held in place by hydrogen bonds between backbone C=O and N-H groups
    • A flat sheet held by disulfide bonds between every residue in the chain
    • A sphere held together by ionic bonds only, with no hydrogen bonding in the structure
    • A straight chain with no hydrogen bonding, which keeps the polypeptide fully extended

  19. What is the quaternary structure of a protein?

    • The arrangement of two or more polypeptide chains together
    • The coil formed by hydrogen bonds between backbone groups within one chain only
    • The order of amino acids in one chain, which is the sequence of the polypeptide
    • The sugar unit attached to a glycoprotein, which forms the outer part of the molecule

  20. Which name describes an S-S link between two cysteine residues in a protein?

    • Peptide link
    • Disulfide bond
    • Ester link
    • Glycosidic link

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