GCSE Biology
Questions
& Answers

1. Question 1·Cell biology and microscopy·1 mark

   Name the structure that controls what enters and leaves an animal cell.

   • Weaker0 marks

     The cell wall.

   • Middling1 mark

     The membrane.

   • Stronger1 mark

     The cell membrane.

   What separates them

   A one-mark Name question has no partial credit and no room to recover, which makes it the purest test of whether a fact is known or nearly known. The first answer is a plant structure given for an animal cell, and it is the commonest wrong answer here because both words begin with cell and both sit at the outside. The second is accepted: mark schemes credit the shortened form where no other membrane in the question could be meant. Note what the command does not ask for — no function, no explanation. Anything written after the name is time spent for nothing.

   The full-mark answer1 mark

   Cell membrane.

2. Question 2·Cell biology and microscopy·2 marks

   Give two structures found in a plant cell that are not found in an animal cell.

   • Weaker1 mark

     Chloroplasts and a nucleus.

   • Middling2 marks

     Cell wall and chloroplast.

   • Stronger2 marks

     A cell wall made of cellulose, and a permanent vacuole containing cell sap.

   What separates them

   One correct structure and one that both cells have, so it scores one. That is the shape of nearly every lost mark on this question: not ignorance of plant cells, but forgetting that the question is a difference question. A nucleus is in both, so naming it answers nothing. The third answer earns no more than the second — the detail is free — but it is worth seeing, because permanent vacuole is the word that separates it from the small temporary vacuoles an animal cell can have.

   The full-mark answer2 marks

   Cell wall and permanent vacuole. (Chloroplast is also accepted.)

3. Question 3·Cell biology and microscopy·2 marks

   Describe the function of the mitochondria.

   • Weaker0 marks

     They make energy for the cell.

   • Middling2 marks

     Mitochondria release energy from glucose. This happens by respiration.

   • Stronger2 marks

     Aerobic respiration takes place in the mitochondria. Glucose reacts with oxygen and the energy transferred is used by the cell for movement, warmth and building larger molecules.

   What separates them

   ‘They make energy’ is not badly expressed — it is scientifically wrong, and it is the single most common wrong answer in GCSE biology. Energy is not made. It is not created, produced or generated; it is transferred from one store to another, and a mark scheme that says reject 'produces energy' means the word costs the mark however good the rest of the sentence is. The middling answer earns both marks in eleven words. The stronger answer is worth reading not because it scores more — it cannot — but because it is what the same knowledge looks like when the question is worth four.

   The full-mark answer2 marks

   Aerobic respiration takes place in the mitochondria, releasing energy from glucose for the cell to use.

4. Question 4·Cell biology and microscopy·3 marks

   Describe how a light microscope and an electron microscope differ.

   • Weaker0 marks

     An electron microscope is better than a light microscope because you can see more with it.

   • Middling2 marks

     An electron microscope has a much higher magnification than a light microscope, so it can show smaller structures. It uses electrons rather than light.

   • Stronger3 marks

     A light microscope uses light and has a magnification of up to about ×2000; an electron microscope uses a beam of electrons and reaches around ×2,000,000. The electron microscope also has much higher resolving power, so two points close together are still seen as two points and sub-cellular structures such as ribosomes become visible. It is, however, large, expensive and cannot be used on living specimens.

   What separates them

   ‘Better’ is not a difference; it is a verdict, and a mark scheme cannot credit it because it does not say what is different. The middling answer scores well and stops one idea short of the mark that most students miss: resolution. Magnification and resolution are not the same property. Magnification makes an image bigger; resolution decides whether making it bigger reveals anything new. A photograph enlarged past its resolution is a larger blur, and that is precisely why a light microscope cannot show a ribosome however far you magnify it.

   The full-mark answer3 marks

   A light microscope uses light and magnifies up to about ×2000. An electron microscope uses a beam of electrons and magnifies up to about ×2,000,000. It also has a much higher resolving power, so it reveals sub-cellular structures such as ribosomes that a light microscope cannot resolve.

5. Question 5·Cell biology and microscopy·4 marks

   Describe what happens to the chromosomes during mitosis.

   • Weaker1 mark

     The chromosomes split in half and go into the two new cells, which are identical.

   • Middling3 marks

     The chromosomes line up in the middle of the cell and the copies are pulled to opposite ends by the spindle fibres. The cell then divides into two identical cells.

   • Stronger4 marks

     Before mitosis begins the DNA replicates, so each chromosome consists of two identical copies joined together. The chromosomes then line up along the centre of the cell, and the spindle fibres pull one copy of each chromosome to each pole. The nucleus divides, and finally the cytoplasm and cell membrane divide to form two genetically identical daughter cells.

   What separates them

   ‘Split in half’ is a specific and damaging error, not a loose phrase. Chromosomes are not halved in mitosis — they are copied, and each daughter cell receives a full set. A student who writes split here will write it again in meiosis, where it is closer to true, and never be able to tell the two processes apart. The middling answer has the sequence right but omits the replication happening before division, which is the step that makes the answer make sense: without it, two identical full sets appearing from one is impossible.

   The full-mark answer4 marks

   Before mitosis begins the DNA replicates, so each chromosome becomes two identical copies joined together. The chromosomes line up along the centre of the cell. Spindle fibres pull one copy of each chromosome to each end of the cell. The nucleus divides, then the cytoplasm and membrane divide, forming two genetically identical cells.

6. Question 7·Cell biology and microscopy·2 marks

   Convert 0.008 mm into micrometres.

   • Weaker1 mark

     0.008 ÷ 1000 = 0.000008 µm

   • Middling2 marks

     1 mm = 1000 µm, so 0.008 × 1000 = 8 µm

   • Stronger2 marks

     There are 1000 µm in 1 mm. A micrometre is smaller than a millimetre, so the number must get bigger: 0.008 × 1000 = 8 µm.

   What separates them

   Both wrong and right answers here used the same conversion factor. The only difference is the direction, and direction is decided by one question: is the new unit bigger or smaller than the old one? Smaller unit, bigger number — a rope is fewer metres long than it is centimetres. The first answer earns a mark for knowing the factor of 1000 and loses the second for multiplying the wrong way, which produced a length far smaller than an atom without the student noticing.

   The full-mark answer2 marks

   1 mm = 1000 µm, so 0.008 mm = 0.008 × 1000 = 8 µm

7. Question 8·Cell biology and microscopy·3 marks

   A cell lining the small intestine absorbs large amounts of glucose. Explain why this cell contains many mitochondria.

   • Weaker1 mark

     Mitochondria are where respiration happens, so the cell needs a lot of them.

   • Middling3 marks

     The cell absorbs glucose by active transport, which needs energy. Mitochondria release energy by respiration, so having many of them supplies the energy the cell needs.

   • Stronger3 marks

     Glucose is absorbed against its concentration gradient, from a lower concentration in the gut to a higher concentration in the cell, so it must move by active transport. Active transport requires energy, which is released by aerobic respiration in the mitochondria. Many mitochondria therefore release energy at the rate this cell needs it.

   What separates them

   Entirely true, and an answer to a different question. It says what mitochondria do, which is recall, and never mentions glucose, absorption or this particular cell — it would be exactly as true written on a page about a muscle cell or a root hair. That is the defining failure of an AO2 question: a correct sentence that does not touch the situation in front of it. The test is blunt. If the answer would be unchanged had the question described a different cell, it has not applied anything.

   The full-mark answer3 marks

   Glucose is absorbed against the concentration gradient, so it moves by active transport. Active transport requires energy. That energy is released by respiration in the mitochondria, so a cell doing a great deal of it needs many mitochondria.

8. Question 50·Homeostasis and response·3 marks

   Describe the effect of ADH on the kidney.

   • Weaker1 mark

     ADH makes the kidney produce less urine when you need to save water.

   • Middling3 marks

     ADH increases the permeability of the kidney tubules to water. More water is reabsorbed back into the blood, so a smaller volume of more concentrated urine is produced.

   • Stronger3 marks

     ADH is released by the pituitary gland when the water content of the blood is too low. It increases the permeability of the walls of the kidney tubules, so more water is reabsorbed from the filtrate back into the blood. A smaller volume of more concentrated urine is produced, and the water content of the blood returns towards normal.

   What separates them

   Outcome given, mechanism skipped — which is what happens when a topic is learned from what it achieves rather than from what it does. The word that carries the marks here is permeability: ADH does not pump water and does not create urine, it changes how easily water passes through a tubule wall. Everything else — less urine, more concentrated urine, more water in the blood — follows from that one change, and an answer that reaches the outcome without passing through it has described a result rather than an effect.

   The full-mark answer3 marks

   ADH increases the permeability of the kidney tubules to water. More water is therefore reabsorbed from the filtrate into the blood, and a smaller volume of more concentrated urine is produced.

Twelve more GCSE Biology questions, with answers, free