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Structure and bonding: OCR A‑Level Chemistry B questions

Every OCR A-Level Chemistry B exam question on PL Structure and bonding (specification points PL(a)–(e)), 2016–2025, with its mark scheme and examiner’s report.

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2,049 questions

  1. Q1

    June 2025 · Paper 1

    1 markPL Structure and bonding
    The whole paper ↗
    June 2025 Paper 1, question 1: Part of a protein structure can be represented as: –CONHCH(CH3)CONHCH2CONHCH(CH3)– What is correct about this part of the protein structure? A All its amino aci

  2. Q4(a)(i)

    June 2025 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2025 Paper 2, question 4(a)(i): Vancomycin has a polypeptide chain. The area shaded grey represents the primary structure. In order for vancomycin to function, the primary structure must be he

  3. Q4(a)(ii)

    June 2025 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2025 Paper 2, question 4(a)(ii): The part of the peptide shown at the bottom of Fig. 4.1 is made from a repeat of the same amino acid. Give the structure of this amino acid. [1]

  4. Q4(a)(iv)

    June 2025 · Paper 2

    2 marksPL Structure and bonding
    The whole paper ↗
    June 2025 Paper 2, question 4(a)(iv): In the peptides from some bacteria, the circled NH in Fig. 4.1 is replaced by an oxygen atom, O. These bacteria are resistant to vancomycin. Suggest why vancomy

  5. Q4(b)

    June 2025 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2025 Paper 2, question 4(b): The binding of vancomycin is an example of molecular recognition. Many medicines have part of their molecule that interacts in this way. Name this part of a med

  6. Q4(c)

    June 2025 · Paper 2

    3 marksPL Structure and bonding
    The whole paper ↗
    June 2025 Paper 2, question 4(c): Molecular recognition occurs in the formation of proteins from messenger RNA. Explain this process. [3]

  7. Q3(a)(i)

    June 2024 · Paper 2

    2 marksPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(a)(i): The ‘R-groups’ for alanine and serine are –CH3 and –CH2OH. Draw a possible structure for this dipeptide. [2]

  8. Q3(a)(iii)

    June 2024 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(a)(iii): Explain why the reaction between the amino acids is not called addition. [1]

  9. Q3(b)

    June 2024 · Paper 2

    6 marksPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(b): Enzymes are proteins made up of amino acids. (b)* The students boil the dipeptide from (a) with 6 mol dm–3 hydrochloric acid. They want to show that the resulti

  10. Q3(c)(i)

    June 2024 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(c)(i): What name is given to the helix part of the protein structure? [1]

  11. Q3(c)(ii)

    June 2024 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(c)(ii): Name the main bonds that hold the helix in shape. [1]

  12. Q3(d)(i)

    June 2024 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(d)(i): Fig. 3.1 shows the structure of a DNA chain. Fig. 3.1 O T NH N O O CH2 O H2N A O N O N P N O N O− CH2 O H2N A O N O N P N O N O− CH2 O O Draw an arrow on Fig. 3

  13. Q3(d)(ii)

    June 2024 · Paper 2

    1 markPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(d)(ii): Give the general name of the parts in Fig. 3.1 labelled A and T. [1]

  14. Q3(e)(ii)

    June 2024 · Paper 2

    2 marksPL Structure and bonding
    The whole paper ↗
    June 2024 Paper 2, question 3(e)(ii): Suggest why the removal of incorrectly coded DNA helps to maintain the accurate replication of genetic information. [2]

  15. Q23

    June 2023 · Paper 1

    1 markPL Structure and bonding
    The whole paper ↗
    June 2023 Paper 1, question 23: What is correct about the structure of DNA? A Guanine is paired with Adenine. B The repeating units in the backbone are deoxyribose-phosphate-deoxyribose-phosph

  16. Q35(a)

    June 2023 · Paper 1

    2 marksPL Structure and bonding
    The whole paper ↗
    June 2023 Paper 1, question 35(a): One section of mRNA contains the sequence .....GGUGCC.... that codes for glycine and alanine. Explain how this mRNA sequence enables these two amino acids to fo

  17. Q35(c)

    June 2023 · Paper 1

    2 marksPL Structure and bonding
    The whole paper ↗
    June 2023 Paper 1, question 35(c): The primary structure of a protein is the order in which the amino acid residues are bonded together. Draw a structural formula to show a dipeptide that can be

  18. Q35(e)

    June 2023 · Paper 1

    3 marksPL Structure and bonding
    The whole paper ↗
    June 2023 Paper 1, question 35(e): The secondary structure of a protein is held together by hydrogen bonds. Fig. 35.1, shows hydrogen bonding between neighbouring peptide chains in a sheet-type s

  19. Q16

    June 2022 · Paper 1

    1 markPL Structure and bonding
    The whole paper ↗
    June 2022 Paper 1, question 16: What is correct about the linking of DNA strands? A Adenine forms three hydrogen bonds with thymine. B Guanine forms three hydrogen bonds with cytosine. C Guani

  20. Q20

    June 2022 · Paper 1

    1 markPL Structure and bonding
    The whole paper ↗
    June 2022 Paper 1, question 20: GCC is a mRNA triplet code for alanine. What is correct? A Alanine has a transfer RNA with the code CGG. B GCC is the only code for alanine. C Other amino acids
All 52 questions on Structure and bonding, as a list
  1. June 2025, Paper 1, Q1 (1 mark): Part of a protein structure can be represented as: –CONHCH(CH3)CONHCH2CONHCH(CH3)– What is correct about this part of the protein structure? A All its amino aci
  2. June 2025, Paper 2, Q4(a)(i) (1 mark): Vancomycin has a polypeptide chain. The area shaded grey represents the primary structure. In order for vancomycin to function, the primary structure must be he
  3. June 2025, Paper 2, Q4(a)(ii) (1 mark): The part of the peptide shown at the bottom of Fig. 4.1 is made from a repeat of the same amino acid. Give the structure of this amino acid. [1]
  4. June 2025, Paper 2, Q4(a)(iv) (2 marks): In the peptides from some bacteria, the circled NH in Fig. 4.1 is replaced by an oxygen atom, O. These bacteria are resistant to vancomycin. Suggest why vancomy
  5. June 2025, Paper 2, Q4(b) (1 mark): The binding of vancomycin is an example of molecular recognition. Many medicines have part of their molecule that interacts in this way. Name this part of a med
  6. June 2025, Paper 2, Q4(c) (3 marks): Molecular recognition occurs in the formation of proteins from messenger RNA. Explain this process. [3]
  7. June 2024, Paper 2, Q3(a)(i) (2 marks): The ‘R-groups’ for alanine and serine are –CH3 and –CH2OH. Draw a possible structure for this dipeptide. [2]
  8. June 2024, Paper 2, Q3(a)(iii) (1 mark): Explain why the reaction between the amino acids is not called addition. [1]
  9. June 2024, Paper 2, Q3(b) (6 marks): Enzymes are proteins made up of amino acids. (b)* The students boil the dipeptide from (a) with 6 mol dm–3 hydrochloric acid. They want to show that the resulti
  10. June 2024, Paper 2, Q3(c)(i) (1 mark): What name is given to the helix part of the protein structure? [1]
  11. June 2024, Paper 2, Q3(c)(ii) (1 mark): Name the main bonds that hold the helix in shape. [1]
  12. June 2024, Paper 2, Q3(d)(i) (1 mark): Fig. 3.1 shows the structure of a DNA chain. Fig. 3.1 O T NH N O O CH2 O H2N A O N O N P N O N O− CH2 O H2N A O N O N P N O N O− CH2 O O Draw an arrow on Fig. 3
  13. June 2024, Paper 2, Q3(d)(ii) (1 mark): Give the general name of the parts in Fig. 3.1 labelled A and T. [1]
  14. June 2024, Paper 2, Q3(e)(ii) (2 marks): Suggest why the removal of incorrectly coded DNA helps to maintain the accurate replication of genetic information. [2]
  15. June 2023, Paper 1, Q23 (1 mark): What is correct about the structure of DNA? A Guanine is paired with Adenine. B The repeating units in the backbone are deoxyribose-phosphate-deoxyribose-phosph
  16. June 2023, Paper 1, Q35(a) (2 marks): One section of mRNA contains the sequence .....GGUGCC.... that codes for glycine and alanine. Explain how this mRNA sequence enables these two amino acids to fo
  17. June 2023, Paper 1, Q35(c) (2 marks): The primary structure of a protein is the order in which the amino acid residues are bonded together. Draw a structural formula to show a dipeptide that can be
  18. June 2023, Paper 1, Q35(e) (3 marks): The secondary structure of a protein is held together by hydrogen bonds. Fig. 35.1, shows hydrogen bonding between neighbouring peptide chains in a sheet-type s
  19. June 2022, Paper 1, Q16 (1 mark): What is correct about the linking of DNA strands? A Adenine forms three hydrogen bonds with thymine. B Guanine forms three hydrogen bonds with cytosine. C Guani
  20. June 2022, Paper 1, Q20 (1 mark): GCC is a mRNA triplet code for alanine. What is correct? A Alanine has a transfer RNA with the code CGG. B GCC is the only code for alanine. C Other amino acids
  21. June 2022, Paper 1, Q35(a) (1 mark): Local anaesthetics work by binding to certain receptors in cells in order to inhibit pain. Name the part of a molecule that binds to a receptor in a cell in the
  22. June 2022, Paper 2, Q4(b)(i) (2 marks): In the boxes below, draw the structural formulae for the two dipeptides. [2]
  23. June 2022, Paper 2, Q4(b)(ii) (1 mark): Explain, with a reason, whether the reaction to form the dipeptides is condensation or addition. [1]
  24. June 2022, Paper 2, Q4(c)(i) (1 mark): What name is given to the amino acid sequence of a protein? [1]
  25. June 2022, Paper 2, Q4(c)(ii) (2 marks): What name is given to the α-helical structure and how is it held together? [2]
  26. November 2021, Paper 1, Q12 (1 mark): What is correct about DNA? A The backbone consists of a phosphate – base – phosphate sequence. B The bases cytosine and guanine join by condensation reactions.
  27. November 2021, Paper 1, Q18 (1 mark): Some triplet base codes for mRNA are shown on the Data Sheet. What is correct about RNA codes? A An anticodon for glutamine is GTT. B Each amino acid has only o
  28. November 2021, Paper 1, Q34(e)(ii) (1 mark): A polypeptide is a small portion of a protein chain. Explain how the reactions shown above can lead to the formation of a polypeptide. [1]
  29. November 2021, Paper 3, Q2(a) (3 marks): A protein can be described in terms of its primary, secondary and tertiary structure. Explain the terms primary, secondary and tertiary in this context. Primary
  30. November 2021, Paper 3, Q2(c)(i) (1 mark): Salbutamol and salmeterol are medicines used in the treatment of asthma. They contain the same pharmacophore. Explain the term pharmacophore. [1]
  31. November 2021, Paper 3, Q2(c)(iii) (2 marks): One of the enantiomers of salbutamol is nearly seventy times more effective at treating asthma than the other. Suggest why this is the case. [2]
  32. November 2020, Paper 1, Q18 (1 mark): Insulin is a protein consisting of two chains. Parts of both chains are helical. The two chains are held together by covalent bonds. Which statement about insul
  33. November 2020, Paper 2, Q1(e)(i) (4 marks): Describe the rest of their method, including how they could tell whether hydrolysis has occurred. You may include a diagram in your answer. [4]
  34. November 2020, Paper 2, Q5(c)(i) (1 mark): What is the name of the base in Fig. 5.1? Use the Data Sheet to help you. [1]
  35. November 2020, Paper 2, Q5(c)(ii) (1 mark): What is the name of the type of bond at B in Fig. 5.1? [1]
  36. November 2020, Paper 2, Q5(e) (6 marks): This question refers to the Advance Notice Article ‘Platinum metal complexes in medicine’ that is included inside this document. (e)* Give the disadvantages of
  37. June 2019, Paper 1, Q32(a) (3 marks): Use the Data Sheet to draw a section of DNA. The section of DNA must consist of two phosphate units, one deoxyribose sugar unit and one thymine unit, all joined
  38. June 2019, Paper 1, Q32(b) (3 marks): The double helix of DNA is formed by the bases pairing using hydrogen bonds. Complete the diagram to show all the hydrogen bonds between guanine and cytosine. S
  39. June 2019, Paper 1, Q32(c) (2 marks): The sequence of bases in DNA determines the primary structure of the protein synthesised. Draw the structural formula for a section of a protein molecule formed
  40. June 2018, Paper 1, Q32(a) (1 mark): State the meaning of the term tertiary structure of a protein. [1]
  41. June 2018, Paper 1, Q32(c)(ii) (4 marks): Give the organic products of the complete hydrolysis of this protein section with hydrochloric acid. [4]
  42. June 2018, Paper 1, Q32(d) (6 marks): Enzymes catalyse the breakdown of protein molecules in the digestive system. The tertiary structure of enzymes enables the substrate to bind to them. (d)* The s
  43. June 2018, Paper 2, Q5(a) (1 mark): One reason arsenic is poisonous because it reacts with –SH groups in amino acids. Suggest how the removal of –SH groups might interfere with the way these amino
  44. June 2018, Paper 2, Q5(b) (2 marks): Arsenate(V) can replace phosphate(V) in nucleic acids. Draw the skeletal formula of a DNA nucleotide containing thymine and with As instead of P. [2]
  45. June 2017, Paper 1, Q8 (1 mark): Which statement about DNA is not true? A DNA is a condensation polymer. B Adenine and uracil join by 2 hydrogen bonds in DNA. C Guanine and cytosine join by 3 h
  46. June 2017, Paper 1, Q9 (1 mark): Which statement describes the secondary structure of a protein? A the types of amino acids present B the sequence of the amino acids C attractions between group
  47. June 2017, Paper 2, Q3(b) (2 marks): In DNA, deoxyribose is always present as the ring form. The primary alcohol group in the ring form of deoxyribose and the alcohol group on the adjacent carbon c
  48. June 2017, Paper 2, Q3(c)(i) (2 marks): What single term describes guanine, adenine and cytosine? How and where do they attach to the sugar-phosphate backbone? term [2]
  49. June 2017, Paper 2, Q3(c)(ii) (1 mark): Give the DNA sequence that would produce the CUG sequence in RNA. [1]
  50. June 2017, Paper 2, Q3(c)(iii) (1 mark): The sequence given in (c)(ii) codes for an amino acid in a protein chain. Name the amino acid. Use the Data Sheet to help you. [1]
  51. June 2017, Paper 2, Q3(c)(iv) (2 marks): Explain how a sequence in DNA codes for an amino acid. [2]
  52. June 2017, Paper 3, Q1(c) (6 marks): A group of students decide to analyse a commercial sweetener. The major component is listed as the dipeptide aspartame. (c)* The students wanted to confirm that

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