AQA GCSE Combined Science: Biology: Cell Biology
6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
A scientist studies a sample of pond water under a microscope and finds two types of cell: a bacterial cell and a single-celled algal cell (a eukaryote with a chloroplast).
Compare the structures of a bacterial (prokaryotic) cell and an algal (eukaryotic) cell. In your answer you should describe both similarities and differences, and refer to named sub-cellular structures. (6 marks)
A student views a plant cell using a light microscope. In the image, one chloroplast measures 8 mm across. The student is told that the real (actual) width of the chloroplast is 5 μm.
(Remember: 1 mm = 1000 μm.)
(a) Calculate the magnification of the image. Show your working. (3 marks)
(b) The student then uses a more powerful objective lens and records the magnification as ×400. A mitochondrion in this new image appears 2 mm long. Calculate the real length of the mitochondrion, in micrometres (μm). (1 mark)
Stem cells can be obtained from human embryos and from the bone marrow of adults.
(a) Give one difference between an embryonic stem cell and an adult stem cell in terms of the range of cell types each can produce. (1 mark)
(b) Describe one potential medical use of stem cells. (1 mark)
(c) Suggest one reason some people object to using embryonic stem cells in medical treatments. (1 mark)
A student investigated osmosis using cylinders cut from a potato. Five cylinders of equal starting mass were each placed in a different concentration of sugar solution for 30 minutes, then reweighed. The percentage change in mass was calculated for each.
| Sugar concentration / mol dm⁻³ | Percentage change in mass / % |
|---|---|
| 0.0 | +12 |
| 0.2 | +5 |
| 0.4 | 0 |
| 0.6 | −7 |
| 0.8 | −15 |
(a) Explain why the cylinder in the 0.0 mol dm⁻³ solution gained mass. (2 marks)
(b) State what the data tell you about the concentration inside the potato cells. (1 mark)
Root hair cells absorb mineral ions from the soil. The concentration of mineral ions is usually higher inside the root hair cell than in the surrounding soil water.
Explain why active transport, rather than diffusion, is needed for the root hair cell to absorb these mineral ions. (2 marks)
During the cell cycle, a cell divides by mitosis.
Name the type of cell (in terms of how many of each chromosome it contains) that is produced by mitosis. (1 mark)