plumiAmino acids: Edexcel International A Level Chemistry questions
Edexcel International A Level Chemistry past-paper questions on 19.2.2 Amino acids, 2019–2025, with mark schemes and examiner’s reports where available.
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Open the full PDFYour answerQ19(a)(ii)
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All 24 questions on Amino acids, as a list
- June 2025, Unit 5, Q9 (1 mark): At what pH would the amino acid phenylalanine have the structure shown? O– O H N+ H H A pH 2 B pH 6 C pH 10 D pH 14
- June 2025 (A), Unit 5, Q19(a)(ii) (3 marks): Explain why alanine has a much higher melting temperature than butanoic acid, which has a similar relative molecular mass. Detailed descriptions of the bonding
- June 2025 (A), Unit 5, Q19(b)(i) (2 marks): Draw a possible structure of E. (2)
- June 2025 (A), Unit 5, Q19(c)(i) (1 mark): F is not optically active. Suggest a structure for F. (1)
- June 2025 (A), Unit 5, Q19(c)(ii) (2 marks): G has two chiral centres. Suggest a structure for G. (2)
- January 2025, Unit 5, Q16(a) (1 mark): Which compound is an optically active amino acid? (1) A compound W B compound X C compound Y D compound Z
- January 2025, Unit 5, Q17(a) (1 mark): What will be the structure of asparagine in an aqueous solution at pH 2? (1) O NH2 C CH2 A H2N C COOH H O NH2 C CH2 B + COO– H3N C H H+ O NH2 C C CH2 + H3N C CO
- October 2024, Unit 5, Q8(b) (1 mark): Which is the organic product of the reaction between serine and sodium hydroxide solution? (1) H H O N C C A H O–Na+ CH2 OH H H O N C C B O–Na+ H CH2 O–Na+ H H
- June 2024, Unit 5, Q10(a) (1 mark): Which form of aspartic acid is formed at pH 12? (1) NH+ 3 H O– O A C C C C OH O H H NH2 H HO O B C C C C O– O H H NH2 H O– O C C C C C O– O H H NH+ 3 H HO O D C
- June 2024, Unit 5, Q10(b)(i) (1 mark): Which is a correct structure when aspartic acid forms a dipeptide with glutamine? (1) H2N H O O H H H OH O C C C C C C C C C N O A OH H H H H H2N H HO O C H H N
- January 2024, Unit 5, Q7 (1 mark): Peptides are short chains of amino acids linked by peptide bonds. COOH NH COOH O O O O H H H N N N H2N N N N N COOH H H H H O O O COOH COOH COOH How many differ
- January 2024, Unit 5, Q8 (1 mark): Which shows the structure of the amino acid lysine as a solid, and in solution at high pH? Solid High pH solution O O H2N H2N O– OH A NH2 NH2 O O H3N+ H2N O– O–
- January 2024, Unit 5, Q9 (1 mark): A dipeptide has the molecular formula C7H12N2O3 . The dipeptide is hydrolysed to form two amino acids. One of the amino acids produced does not have a chiral ce
- October 2023, Unit 5, Q13 (1 mark): The amino acid 2-aminopropanoic acid exists as a zwitterion at pH 6.0 What will be the structure of 2-aminopropanoic acid at pH 9.0? A H2NCH(CH3)COOH B H2NCH(CH
- June 2023, Unit 5, Q19 (1 mark): Four amino acids are dissolved in deionised water to form separate 0.05 mol dm–3 solutions. Which amino acid will give the solution with the lowest pH? O A HO O
- January 2023, Unit 5, Q13 (1 mark): A student hydrolysed a section of a protein and then used thin-layer chromatography to analyse the amino acids produced. The chromatogram is shown. solvent fron
- January 2023, Unit 5, Q19(c)(i) (1 mark): Complete the structure of the zwitterion of phenylalanine. (1)
- January 2023, Unit 5, Q19(c)(ii) (1 mark): Draw the structure of the dipeptide formed from phenylalanine. (1)
- October 2022, Unit 5, Q12(b) (1 mark): What is the structure of isoleucine in a solution of pH = 2? (1) O O A O− B OH + NH2 NH3 O O C D OH2 + O− NH2 + NH3 Use this space for any rough working. Anythi
- June 2022, Unit 5, Q10(a) (1 mark): Which ion is most likely to form if serine is dissolved in sodium carbonate solution? (1) O A HO OH +NH3 O B HO O− +NH3 O C −O O− NH2 O D HO O− NH2
- June 2022, Unit 5, Q10(b) (1 mark): Serine has a melting temperature in the region of 200–300 °C. This high melting temperature is mainly due to the formation of (1) A hydrogen bonds B ionic bonds
- October 2021, Unit 5, Q15 (1 mark): How many different amino acids form the repeat unit of the polymer shown? O O O A 3 B 4 C 5 D 6
- June 2021, Unit 5, Q13(a) (1 mark): Which structure best represents alanine at high pH? (1) NH2 OH A H3C C C O H NH2 O– B H3C C C O H NH3 + OH C H3C C C O H NH3 + O– D H3C C C O H
- June 2021, Unit 5, Q13(b) (1 mark): Alanine is a crystalline solid at room temperature. What are the main forces broken when alanine melts? (1) A London forces B hydrogen bonds C covalent bonds D
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