Lesson 3.1.4.1.1

3.1.4.1.1 Amino acids and peptide bonds Quiz: AQA Biology, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.4.1.1, Amino acids and peptide bonds: 20 multiple choice questions for the AQA Biology (7402), Unit 1: Biological molecules, written with Revision Ninja.

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The 20 questions

  1. Which two functional groups are present in every amino acid?

    • An aldehyde group and a ketone group
    • A phosphate group and an ester group
    • A hydroxyl group and a phosphate group
    • An amine group and a carboxyl group

  2. What distinguishes one amino acid from another?

    • The length of the carbon chain in the glycosidic bond
    • The side chain, or R group, attached to the central carbon
    • The type of bond holding the amine group to the carboxyl group
    • The number of phosphate groups attached to the carboxyl group

  3. How many amino acids are commonly found in all living organisms?

    • 64
    • 10
    • 4
    • 20

  4. What type of bond joins two amino acids together?

    • Hydrogen bond
    • Peptide bond
    • Glycosidic bond
    • Phosphodiester bond

  5. Which groups react together in a condensation reaction to form a peptide bond?

    • The side chains of two amino acids only
    • The two amine groups of two amino acids
    • The hydroxyl group of one amino acid and the phosphate group of another
    • The amine group of one amino acid and the carboxyl group of another

  6. What is a dipeptide?

    • A molecule of two amino acids joined by a glycosidic bond
    • A molecule formed by the condensation of two glucose units
    • A chain of many amino acids that is always folded into a helix
    • A molecule formed by the condensation of two amino acids

  7. Which definition of a polypeptide is correct?

    • Two amino acids joined by a single hydrogen bond
    • A chain of many amino acids joined by peptide bonds
    • A chain of many glucose units joined by glycosidic bonds
    • A chain of nucleotides joined by phosphodiester bonds

  8. A chain of 4 amino acids is formed by condensation. How many water molecules are released?

    • 1
    • 4
    • 2
    • 3

  9. How many peptide bonds are present in a linear polypeptide of 300 amino acids?

    • 300
    • 299
    • 298
    • 301

  10. What is the relative molecular mass of a dipeptide formed from two glycine molecules (75 each)?

    • 93
    • 114
    • 132
    • 150

  11. Which molecule is released when two amino acids form a dipeptide?

    • Oxygen
    • Carbon dioxide
    • Water
    • Ammonia

  12. How many peptide bonds are present in a linear chain of 12 amino acids?

    • 11
    • 12
    • 24
    • 10

  13. Why do proteins differ in properties even though they are all built from the same 20 amino acids?

    • Proteins are built from different monosaccharides that change their shape
    • The number, type and order of amino acids differ, changing the sequence of R groups
    • Proteins contain different numbers of phosphate groups in each chain
    • Proteins use different types of bonds between the same amino acids

  14. Which statement describes the R group of an amino acid?

    • It is always a double-bonded oxygen atom that is responsible for forming the peptide bond between units
    • It is always a carboxyl group that reacts with the amine group of a second amino acid in a condensation
    • It is the variable part of the molecule and can be a hydrogen atom or a more complex group
    • It is always a phosphate group that makes the amino acid molecule carry a negative electrical charge overall

  15. A student says that the amine group of an amino acid is the part that reacts to form a peptide bond. What is the best evaluation?

    • Partly correct: the amine group reacts, but only with the carboxyl group of another amino acid
    • Incorrect: the R group, rather than the amine group, always forms the peptide bond between two units
    • Correct: the amine group reacts with any functional group that is present on the second amino acid
    • Incorrect: the amine group never takes part in a condensation reaction, so it is always left unchanged

  16. A polypeptide of 5 amino acids with average relative mass 110 each is formed by condensation. What is its approximate relative molecular mass?

    • 478
    • 532
    • 550
    • 514

  17. How many different tripeptides can be formed from 20 amino acids if any amino acid can be used more than once in each position?

    • 400
    • 6840
    • 60
    • 8000

  18. Explain why an amino acid can act as both an acid and a base.

    • The R group can donate a proton and the amine group can donate a hydroxyl
    • The peptide bond can donate a proton and the glycosidic bond can accept one
    • The amine group can accept a proton and the carboxyl group can donate one
    • The carboxyl group can donate a phosphate and the amine group can donate an electron

  19. Why is the peptide bond rigid and largely planar, restricting rotation about the C-N bond?

    • The C-N bond has partial double-bond character because of delocalisation of electrons around the C=O group
    • The bond contains an ionic interaction that holds the two atoms in a fixed position relative to each other
    • The bond contains a phosphate group that forms a rigid ring with the carboxyl group of the amino acid
    • The bond is a hydrogen bond that is simply too weak to allow the two atoms to rotate freely about it

  20. An amino acid chain is hydrolysed completely. What is the most accurate description of the products?

    • Individual amino acids, with one water molecule used for each peptide bond broken
    • Glucose and amino acids, with two water molecules used for each peptide bond
    • Individual nucleotides, with one water molecule used for each phosphodiester bond
    • Individual amino acids, with one water molecule produced for each peptide bond broken

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