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AS Level Biology MCQs with answers

Practise AS Level Biology (9700) with 289 exam-style MCQs, each with the answer and a short explanation. Every test is marked the moment you finish and shows your score chapter by chapter, so you know what to revise next. It is free and needs no sign-up.

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AS Level Biology MCQs with answers

Practise AS Level Biology (9700) with 289 exam-style MCQs, each with the answer and a short explanation. Every test is marked the moment you finish and shows your score chapter by chapter, so you know what to revise next. It is free and needs no sign-up.

289 questions · 11 chapters · 23 Cambridge past papers · 5 mock exams

What each chapter covers 11 chapters

The questions follow the syllabus chapter by chapter. You can test the whole subject or one chapter at a time.

  1. Cell structure 26 questionsThe microscope in cell studies, Cells as the basic units of living organisms
  2. Biological molecules 49 questionsTesting for biological molecules, Carbohydrates and lipids, Proteins, Water
  3. Enzymes 24 questionsMode of action of enzymes, Factors that affect enzyme action
  4. Cell membranes and transport 25 questionsFluid mosaic membranes, Movement into and out of cells
  5. The mitotic cell cycle 21 questionsReplication and division of nuclei and cells, Chromosome behaviour in mitosis
  6. Nucleic acids and protein synthesis 26 questionsStructure of nucleic acids and replication of DNA, Protein synthesis
  7. Transport in plants 24 questionsStructure of transport tissues, Transport mechanisms
  8. Transport in mammals 35 questionsThe circulatory system, Transport of oxygen and carbon dioxide, The heart
  9. Gas exchange 12 questionsThe gas exchange system
  10. Infectious diseases 22 questionsInfectious diseases, Antibiotics
  11. Immunity 25 questionsThe immune system, Antibodies and vaccination
Sample AS Level Biology MCQs with answers 12 questions

12 questions from the test, one or two from each chapter. Try each one, then open the answer.

1. Which structure is found in a typical animal cell but not in a typical plant cell?

  1. A
    Golgi body
  2. B
    mitochondrion
  3. C
    centriole
  4. D
    cell surface membrane
Show answer

Answer: C. Centrioles are found in animal cells but not in the cells of flowering plants. Both cell types have a Golgi body, mitochondria and a cell surface membrane.

2. A solution gives a negative Benedict's test. To test for a non-reducing sugar, what should be done to a fresh sample before repeating the Benedict's test?

  1. A
    boil with dilute hydrochloric acid, then neutralise it
  2. B
    add sodium hydroxide, then boil with copper(II) sulfate solution
  3. C
    boil with iodine solution, then cool it under cold running water
  4. D
    shake with ethanol, then pour the ethanol into a beaker of water
Show answer

Answer: A. Boiling with acid hydrolyses glycosidic bonds, releasing reducing sugars. The acid is then neutralised so the Benedict's reagent can work.

3. What is an advantage of using an enzyme immobilised in alginate beads rather than free in solution?

  1. A
    the enzyme works faster at all temperatures because it is protected
  2. B
    the enzyme can be reused and separated easily from the product afterwards
  3. C
    the enzyme can no longer be denatured by high temperatures
  4. D
    the substrate no longer has to diffuse to reach the enzyme
Show answer

Answer: B. Beads are easily separated from the product and used again. Immobilised enzymes can still denature, and substrate must diffuse into the bead.

4. A hormone travels in the blood to every part of the body but only some cells respond to it. Why?

  1. A
    the hormone is broken down by enzymes in all cells except the target cells
  2. B
    only target cells have receptors with a shape that is complementary to the hormone
  3. C
    the hormone can only pass through the membranes of target cells
  4. D
    only target cells receive a blood supply that carries the hormone
Show answer

Answer: B. Responding requires a specific receptor. Cells without a complementary receptor are exposed to the hormone but do not respond.

5. Cells in a culture contain either 6 pg of DNA, 12 pg, or an amount in between. A cell containing 9 pg of DNA is in which phase of the cell cycle?

  1. A
    S phase
  2. B
    G2 phase
  3. C
    anaphase
  4. D
    G1 phase
Show answer

Answer: A. DNA doubles from 6 pg to 12 pg during S phase, so an in-between amount such as 9 pg means DNA replication is under way. A cell in G1 has 6 pg and one in G2 or anaphase has 12 pg.

6. A double-stranded DNA fragment has 100 base pairs, of which 30 are A–T pairs. How many hydrogen bonds hold the two strands together?

  1. A
    250
  2. B
    300
  3. C
    230
  4. D
    270
Show answer

Answer: D. 30 A–T pairs × 2 = 60; 70 C–G pairs × 3 = 210; 60 + 210 = 270.

7. Radioactive sucrose is injected into the phloem of a mature leaf of a healthy plant. Some days later radioactivity is found in the root tips and in developing seeds, but not in the other mature leaves. What does this show?

  1. A
    the root tips and seeds are sinks that use or store sucrose, while mature leaves are sources
  2. B
    sucrose moves only downwards in the phloem, so it cannot reach the seeds
  3. C
    the root tips and seeds are sources that make sucrose by photosynthesis
  4. D
    sucrose was carried to the roots and seeds in the xylem by transpiration pull
Show answer

Answer: A. Assimilates move in the phloem from sources (such as mature photosynthesising leaves) to sinks (such as growing roots and developing seeds). Other mature leaves make their own sucrose, so they do not import it.

8. What is the chloride shift?

  1. A
    movement of chloride ions from the plasma into the tissue fluid as CO2 enters the blood
  2. B
    movement of chloride ions out of red blood cells as oxygen enters
  3. C
    binding of chloride ions to haemoglobin so that it releases more oxygen
  4. D
    hydrogencarbonate ions move out of red cells as chloride ions move in
Show answer

Answer: D. HCO3− diffuses out of the red cell into the plasma, and Cl− moves in to maintain electrical neutrality.

9. What is the function of the cartilage rings in the trachea?

  1. A
    to secrete mucus that traps dust and bacteria before they reach the alveoli
  2. B
    to allow rapid diffusion of oxygen through the wall of the trachea into the blood
  3. C
    to support the trachea and stop it collapsing when air pressure inside falls
  4. D
    to contract and narrow the trachea, so that less air enters when dust is inhaled
Show answer

Answer: C. Cartilage keeps the trachea open during inspiration, while the gap at the back allows food to pass down the oesophagus.

10. How does penicillin kill bacteria?

  1. A
    it breaks down the bacterial DNA, so the bacterium cannot replicate and eventually dies
  2. B
    it prevents ATP synthesis in bacterial mitochondria, so the cell cannot make cell wall
  3. C
    it inhibits the enzymes that form cross-links in the cell wall, so the weakened wall bursts as water enters
  4. D
    it binds to the ribosomes of the bacterium and stops them making proteins, so the cell dies slowly
Show answer

Answer: C. Without cross-links, new wall is weak; water enters by osmosis and the cell bursts (osmotic lysis).

11. A town has 12 000 people. A vaccine is given to 9 000 of them and is protective in 80% of the people who receive it. What percentage of the town is protected by the vaccine?

  1. A
    20%
  2. B
    60%
  3. C
    75%
  4. D
    80%
Show answer

Answer: B. The number protected is 9 000 × 0.80 = 7 200, and 7 200 ÷ 12 000 × 100 = 60%. 75% is the proportion vaccinated, forgetting that the vaccine does not work in everyone. Immune people also protect the unvaccinated by reducing the spread (herd immunity).

12. A drawing of a cell is 36 mm long. The actual length of the cell is 12 µm. What is the magnification of the drawing?

  1. A
    ×30
  2. B
    ×300
  3. C
    ×3000
  4. D
    ×30 000
Show answer

Answer: C. Convert to the same unit first: 36 mm = 36 000 µm, and 36 000 ÷ 12 = ×3000. Forgetting the conversion gives a wrong power of ten.

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Ways to practise 7 ways

When you get a question wrong, a short note called "The idea behind this" explains the topic it belongs to, with the rules to remember and a worked example.

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Is this AS Level Biology test free?

Yes. Every test and every explanation is free, and you do not need an account. If you sign in, your results are kept across your devices.

Are these past paper questions?

The 289 MCQs are our own, written to the syllabus in the style of the exam. The 23 Cambridge past papers are listed separately inside the test.

How is the test marked?

Instantly. You get your score, the right answer and an explanation for every question, and a list of the topics to work on.

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