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Amino acids, peptides and proteins: Eduqas A‑Level Chemistry questions

Every Eduqas A-Level Chemistry exam question on OA3.2 Amino acids, peptides and proteins, 2016–2025, with its mark scheme and examiner’s report.

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1,513 questions

  1. Q11(c)(i)

    June 2025 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2025 Component 2, question 11(c)(i): Give the structure of the species formed from methionine in a strongly alkaline solution. [1]

  2. Q11(c)(ii)

    June 2025 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2025 Component 2, question 11(c)(ii): Give the structure of one of the dipeptides formed between methionine and glycine (aminoethanoic acid). [1]

  3. Q11(d)

    June 2025 · Component 2

    2 marksOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2025 Component 2, question 11(d): H O H3C C C OH NH2 Explain why this compound has a very high melting temperature. [2]

  4. Q6(a)

    June 2024 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2024 Component 2, question 6(a): Give the formula for the zwitterion of phenylalanine. [1]

  5. Q6(b)

    June 2024 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2024 Component 2, question 6(b): Give the structure of the dipeptide produced from two molecules of phenylalanine. [1]

  6. Q6(d)(i)

    Autumn 2021 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    Autumn 2021 Component 2, question 6(d)(i): Write the displayed formula for cysteine. [1]

  7. Q6(d)(ii)

    Autumn 2021 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    Autumn 2021 Component 2, question 6(d)(ii): Cysteine reacts with hydrochloric acid to give the salt cysteine hydrochloride, which is used in flour processing. Suggest a skeletal formula for this salt. [1

  8. Q6(a)(i)

    Autumn 2020 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    Autumn 2020 Component 2, question 6(a)(i): In an aqueous solution tyrosine exists largely as the zwitterion. Give the structure of this zwitterion. [1]

  9. Q6(a)(ii)

    Autumn 2020 · Component 2

    2 marksOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    Autumn 2020 Component 2, question 6(a)(ii): The melting temperature of tyrosine is 314 °C. Explain how the structure of tyrosine contributes to this high melting temperature. [2]

  10. Q6(a)(iii)

    Autumn 2020 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    Autumn 2020 Component 2, question 6(a)(iii): Give the structure of one of the dipeptides formed between tyrosine and aminoethanoic acid. [1]

  11. Q10(b)(i)

    June 2019 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2019 Component 2, question 10(b)(i): At pH 5.1 the α-amino acid cysteine exists as the zwitterion. +NH3 O HS CH2 C C O– H Write the structure of the organic species present when cysteine is added t

  12. Q10(b)(iii)

    June 2019 · Component 2

    1 markOA3.2 Amino acids, peptides and proteinsOA1.1 Stereoisomerism
    The whole paper ↗
    June 2019 Component 2, question 10(b)(iii): Cysteine is an α-amino acid that contains a chiral centre. Write the displayed formula of an α-amino acid that does not contain a chiral centre. [1]

  13. Q13(a)

    June 2018 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2018 Component 2, question 13(a): Explain why amino acids are amphoteric compounds. [1]

  14. Q13(b)(ii)

    June 2018 · Component 2

    5 marksC2.1 Simple equilibria and acid-base reactionsOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2018 Component 2, question 13(b)(ii): Use appropriate titration values to calculate the relative molecular mass of the amino acid. [5] Mr =

  15. Q13(b)(iii)

    June 2018 · Component 2

    2 marksOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2018 Component 2, question 13(b)(iii): Assuming that the amino acid in part (ii) is a straight chain aliphatic α-amino acid deduce its structure. [2]

  16. Q13(c)(iii)

    June 2018 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2018 Component 2, question 13(c)(iii): State which of these amino acids would not be able to form two different dipeptides with either of the other two amino acids. Explain your answer. [1]

  17. Q4(b)

    June 2018 · Component 3

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2018 Component 3, question 4(b): Give the structural formula of one of the dipeptides that may be formed from serine and leucine. [1]

  18. Q10(a)(i)

    June 2017 · Component 2

    2 marksOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2017 Component 2, question 10(a)(i): Explain why the melting temperature of hydroxyproline is about 240 °C, which is much higher than expected from the formula given. [2]

  19. Q10(a)(ii)

    June 2017 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2017 Component 2, question 10(a)(ii): Give the displayed formula of the compound formed when hydroxyproline has acted as a base. [1]

  20. Q10(b)

    June 2017 · Component 2

    1 markOA3.2 Amino acids, peptides and proteins
    The whole paper ↗
    June 2017 Component 2, question 10(b): The formula of a dipeptide formed between 2-aminopropanoic acid and another amino acid is shown below. H O H HO CH2 C C N C CH3 NH2 H COOH Give the displayed fo
All 21 questions on Amino acids, peptides and proteins, as a list
  1. June 2025, Component 2, Q11(c)(i) (1 mark): Give the structure of the species formed from methionine in a strongly alkaline solution. [1]
  2. June 2025, Component 2, Q11(c)(ii) (1 mark): Give the structure of one of the dipeptides formed between methionine and glycine (aminoethanoic acid). [1]
  3. June 2025, Component 2, Q11(d) (2 marks): H O H3C C C OH NH2 Explain why this compound has a very high melting temperature. [2]
  4. June 2024, Component 2, Q6(a) (1 mark): Give the formula for the zwitterion of phenylalanine. [1]
  5. June 2024, Component 2, Q6(b) (1 mark): Give the structure of the dipeptide produced from two molecules of phenylalanine. [1]
  6. Autumn 2021, Component 2, Q6(d)(i) (1 mark): Write the displayed formula for cysteine. [1]
  7. Autumn 2021, Component 2, Q6(d)(ii) (1 mark): Cysteine reacts with hydrochloric acid to give the salt cysteine hydrochloride, which is used in flour processing. Suggest a skeletal formula for this salt. [1
  8. Autumn 2020, Component 2, Q6(a)(i) (1 mark): In an aqueous solution tyrosine exists largely as the zwitterion. Give the structure of this zwitterion. [1]
  9. Autumn 2020, Component 2, Q6(a)(ii) (2 marks): The melting temperature of tyrosine is 314 °C. Explain how the structure of tyrosine contributes to this high melting temperature. [2]
  10. Autumn 2020, Component 2, Q6(a)(iii) (1 mark): Give the structure of one of the dipeptides formed between tyrosine and aminoethanoic acid. [1]
  11. June 2019, Component 2, Q10(b)(i) (1 mark): At pH 5.1 the α-amino acid cysteine exists as the zwitterion. +NH3 O HS CH2 C C O– H Write the structure of the organic species present when cysteine is added t
  12. June 2019, Component 2, Q10(b)(iii) (1 mark): Cysteine is an α-amino acid that contains a chiral centre. Write the displayed formula of an α-amino acid that does not contain a chiral centre. [1]
  13. June 2018, Component 2, Q13(a) (1 mark): Explain why amino acids are amphoteric compounds. [1]
  14. June 2018, Component 2, Q13(b)(ii) (5 marks): Use appropriate titration values to calculate the relative molecular mass of the amino acid. [5] Mr =
  15. June 2018, Component 2, Q13(b)(iii) (2 marks): Assuming that the amino acid in part (ii) is a straight chain aliphatic α-amino acid deduce its structure. [2]
  16. June 2018, Component 2, Q13(c)(iii) (1 mark): State which of these amino acids would not be able to form two different dipeptides with either of the other two amino acids. Explain your answer. [1]
  17. June 2018, Component 3, Q4(b) (1 mark): Give the structural formula of one of the dipeptides that may be formed from serine and leucine. [1]
  18. June 2017, Component 2, Q10(a)(i) (2 marks): Explain why the melting temperature of hydroxyproline is about 240 °C, which is much higher than expected from the formula given. [2]
  19. June 2017, Component 2, Q10(a)(ii) (1 mark): Give the displayed formula of the compound formed when hydroxyproline has acted as a base. [1]
  20. June 2017, Component 2, Q10(b) (1 mark): The formula of a dipeptide formed between 2-aminopropanoic acid and another amino acid is shown below. H O H HO CH2 C C N C CH3 NH2 H COOH Give the displayed fo
  21. June 2017, Component 2, Q10(c) (2 marks): Secondary protein structure is concerned with hydrogen bonding between certain groups. State the groups present that take part in this hydrogen bonding and expl

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