Lesson 3.2.4.1

3.2.4.1 Antigens and cell-surface recognition Quiz: AQA Biology, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.2.4.1, Antigens and cell-surface recognition: 20 multiple choice questions for the AQA Biology (7402), Unit 2: Cells, written with Revision Ninja.

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The 20 questions

  1. Which description best defines an antigen?

    • A molecule, often a protein on a cell surface, that the immune system recognises as foreign or non-self.
    • A protein secreted by plasma cells that binds to and neutralises free toxins in blood plasma.
    • A short sequence of three bases on mRNA that codes for a specific amino acid.
    • A type of white blood cell that engulfs and digests pathogens by phagocytosis in tissues.

  2. Which of these can the immune system identify using molecules on the surface of cells?

    • Only abnormal body cells, because toxins and pathogens carry no surface molecules.
    • Only pathogens, because all body cells carry the same surface molecules.
    • Pathogens, cells from other members of the same species, abnormal body cells and toxins.
    • Only cells from other species, because cells of the same species are always identical.

  3. Why does the influenza virus cause repeated infections in the same population over time?

    • Its antigens are identical each year, so immunity is never gained against it.
    • It is a prokaryote, so it divides by binary fission and avoids all immune responses.
    • Its DNA is copied by reverse transcription, so it cannot be recognised as a virus.
    • Its surface antigens vary, so antibodies from earlier infections may not bind effectively.

  4. Which feature of a foreign cell would be recognised as non-self by a person's immune system?

    • Different glycoproteins on the cell surface compared with the person's own cells.
    • Identical glycoproteins on the cell surface to the person's own cells.
    • A cell wall made of cellulose, which is found in all human tissues.
    • A nucleus that contains DNA, which is found in all human cells.

  5. An abnormal body cell, such as a cancer cell, can be recognised by the immune system. What is the basis of this recognition?

    • The cell releases large quantities of glucose, which signals an immune response.
    • Changed or abnormal molecules on the cell surface act as antigens.
    • The cell loses its nucleus, which is detected by antibodies in the blood.
    • The cell stops producing any proteins, which makes it invisible to the immune system.

  6. A toxin released by a bacterium acts as an antigen. Which response is most likely?

    • Red blood cells respond by producing toxins that neutralise the bacterium.
    • B lymphocytes respond by producing antibodies that bind to the toxin.
    • Neutrophils respond by producing haemoglobin that binds the toxin molecules.
    • Glucose is hydrolysed into toxins that are then absorbed by the liver.

  7. Which description of antigen variability best explains why vaccines may need to be updated regularly?

    • Vaccines lose their antigens within a few hours of being injected into the body.
    • Pathogens with changing antigens may no longer be recognised by the immunity from an earlier vaccine.
    • Vaccines cause the pathogen to replicate faster, reducing the immunity produced.
    • Pathogens lose their surface antigens when exposed to ordinary sunlight and air.

  8. Which molecule is most directly involved in identifying a cell as self or non-self?

    • A glycoprotein on the outer surface of the cell membrane.
    • A phospholipid molecule inside the hydrophobic core of the membrane.
    • A cellulose microfibril in the cell wall of the cell.
    • A tRNA molecule carrying an amino acid in the cytoplasm.

  9. A pathogen has an antigen that is not recognised by antibodies made against a previous strain. What is the most likely effect on disease?

    • The person may become ill again because the immune response to the new antigen starts slowly.
    • The antibodies from the earlier strain are converted into the new strain's antigen.
    • The person becomes immune to all strains at once, because antigens do not change.
    • The pathogen is destroyed immediately by lysozymes in the blood before any response.

  10. Phagocytes engulf pathogens. Which molecules are then used to destroy the ingested pathogens?

    • Lysozymes, which break down the cell walls of ingested bacteria.
    • Cellulose, which surrounds the pathogen and digests it into glucose.
    • Plasmids, which carry resistance genes that destroy the pathogen.
    • Histone proteins, which package the pathogen DNA into chromosomes.

  11. Which statement about antigens and the body's own cells is correct?

    • The body's own cells carry no antigens, so the immune system cannot identify them.
    • The body's own cells carry antigens that are identical to all pathogen antigens.
    • The body's own cells carry only foreign antigens, which the immune system attacks.
    • The body's own cells normally carry self antigens that the immune system does not attack.

  12. A researcher finds that two strains of a bacterium have different surface glycoproteins. What does this suggest about their immune recognition?

    • The strains cannot be recognised by any immune response because glycoproteins are lost.
    • The strains must be identical in antigenicity, because glycoproteins are never different.
    • The strains may be recognised as different antigens, so antibodies to one strain may not bind to the other.
    • The strains will always be destroyed by the same antibodies, because glycoproteins are shared.

  13. Which two activities of the immune system are described as involving antigen recognition by cell-surface molecules?

    • Phagocytosis of pathogens and the response of lymphocytes to foreign antigens.
    • Osmosis of water and active transport of sodium ions across membranes.
    • Transcription of mRNA and translation of polypeptides on ribosomes.
    • Digestion of starch in the mouth and absorption of glucose in the ileum.

  14. A vaccine contains antigens from a pathogen. Why does the vaccine not cause the disease itself?

    • The antigens are not able to cause disease, so they stimulate immunity without causing full infection.
    • The antigens are converted to glucose in the liver, which prevents the disease from spreading.
    • The antigens are removed from the membrane of the pathogen before injection occurs.
    • The antigens are digested by the stomach so they never reach the bloodstream at all.

  15. A researcher tests whether a surface molecule acts as an antigen. Which result would best support that it is an antigen?

    • The molecule is found in every cell in the body and is never recognised as foreign.
    • The molecule triggers antibody production in an immune response when introduced into the body.
    • The molecule is broken down by amylase in the mouth before it can enter the bloodstream.
    • The molecule dissolves in water and passes freely through the phospholipid bilayer.

  16. Which feature of a cell surface molecule allows the immune system to identify its owner?

    • Its specific shape and sequence of amino acids and sugars that is unique to the cell's type.
    • Its ability to hydrolyse ATP and release energy for the cell's metabolic processes.
    • Its ability to pass through the cell membrane by simple diffusion with no restriction.
    • Its ability to carry oxygen molecules to the mitochondria in the cell cytoplasm.

  17. Which statement explains why an antibody made against one antigen will not destroy a different pathogen?

    • Antibodies are made in red blood cells, which cannot reach pathogens in tissues.
    • Antibodies have binding sites that are specific to one antigen shape.
    • Antibodies are digested by lysozymes before they can reach any pathogen in the body.
    • Antibodies only destroy pathogens that have already been ingested by phagocytes.

  18. Abnormal cells are more likely to be destroyed by the immune system when which of these occurs?

    • They display altered antigens on their surface that differ from the body's normal self antigens.
    • They display identical antigens to all normal body cells in the same tissue.
    • They have no nucleus, so their DNA cannot be recognised by any antibody.
    • They lack any cell-surface glycoproteins, which makes them easier to identify.

  19. A student states that the immune system could never identify a cell from another person of the same species. Evaluate this claim.

    • The claim is correct, because only pathogens carry surface molecules that the immune system detects.
    • The claim is incorrect, because cells from other individuals can carry different surface molecules that act as non-self antigens.
    • The claim is correct, because all cells of one species carry exactly the same molecules.
    • The claim is partly correct, because only red blood cells can be identified by their surface molecules.

  20. A pathogen's antigen varies between strains. Which conclusion is best supported?

    • Antigen variation has no effect on vaccine protection because antibodies bind all antigens.
    • A vaccine against one strain gives complete protection against all strains of the pathogen.
    • Antigen variation only affects bacteria, not viruses, so vaccines always work equally well.
    • A vaccine against one strain may give reduced protection against a different strain of the same pathogen.

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