These twelve original questions cover naming structures, magnification, scale bars, specialised cells and drawings. They are ordered from easier to harder. All data are invented for practice and are not taken from any examination paper.
Write your own answer before opening the worked solution. For calculation questions, write the units next to every number, and check that a magnification above 1 makes sense for an enlarged image. The topic is explained in cells and microscopy.
Part A: Structures
1. State the job of the nucleus.
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The nucleus contains the genetic material (DNA) and controls the activities of the cell.
2. A cell has a cell wall, a large vacuole and chloroplasts. A second cell has none of these but does have a nucleus and mitochondria. Name the type of cell each is.
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The first cell has features found only in plant cells: it is a plant cell. The second has none of those features: it is an animal cell.
3. Explain the difference between the cell wall and the cell membrane in a plant cell.
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The cell wall is the thick, rigid outer layer made of cellulose. It supports the cell and lets water and dissolved substances through. The cell membrane is a thin layer just inside the wall that controls what enters and leaves the cell.
Part B: Magnification and sizes
4. The real length of a cell is 0.06 mm. A drawing of it is 24 mm long. Calculate the magnification.
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Both lengths are in mm. Magnification = image ÷ actual = 24 ÷ 0.06 = 400.
Check: 24 mm = 24 000 µm and 0.06 mm = 60 µm, and 24 000 ÷ 60 = 400.
×400
5. A photomicrograph is at ×900. A cell on it measures 54 mm. Calculate the actual length of the cell in µm.
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Actual size = image ÷ magnification = 54 ÷ 900 = 0.06 mm. Convert to µm: 0.06 × 1000 = 60.
Check: 60 µm × 900 = 54 000 µm = 54 mm.
60 µm
6. A cell is 25 µm long. A student draws it at ×200. How long is the drawing in mm?
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Image size = magnification × actual size = 200 × 25 µm = 5000 µm. Convert to mm: 5000 ÷ 1000 = 5.
5 mm
7. Convert 0.4 mm to µm, and 350 µm to mm.
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mm to µm: multiply by 1000. 0.4 × 1000 = 400 µm.
µm to mm: divide by 1000. 350 ÷ 1000 = 0.35 mm.
8. A micrograph has a scale bar labelled 10 µm. The bar is 10 mm long on the page. A cell on the micrograph is 35 mm long. (a) Find the actual length of the cell. (b) Find the magnification.
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(a) The cell is 35 ÷ 10 = 3.5 bars long. Each bar is 10 µm, so 3.5 × 10 µm = 35 µm.
(b) Magnification = bar image ÷ bar actual = 10 mm ÷ 10 µm = 10 000 µm ÷ 10 µm = ×1000.
Check: 35 µm × 1000 = 35 000 µm = 35 mm, which matches the measured cell.
9. A red blood cell is 7 µm across. A textbook diagram shows it 35 mm across. Calculate the magnification of the diagram.
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Convert the image to µm: 35 mm = 35 000 µm. Magnification = 35 000 ÷ 7 = 5000.
×5000
Part C: Specialised cells and drawings
10. Explain how the structure of a sperm cell helps it carry out its function.
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The sperm has a tail, which allows it to swim to the egg. It has many mitochondria, which release the energy needed for movement. It has an acrosome containing enzymes, which help it break into the egg.
11. A student measures a cell drawing at 48 mm. The magnification is ×600. (a) What is the actual length of the cell in µm? (b) How many of these cells would fit end to end across a length of 2 mm?
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(a) Actual size = 48 ÷ 600 = 0.08 mm. Convert: 0.08 × 1000 = 80 µm.
(b) 2 mm = 2000 µm. Number of cells = 2000 ÷ 80 = 25.
Check: 25 × 80 µm = 2000 µm.
12. Describe three faults in this drawing: it is small, it is shaded with coloured pencils, and the label lines are curved and cross each other. Say how to correct each.
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Small drawing: enlarge it so the detail is clear and there is space for labels. Shading and colour: remove them and use sharp single pencil lines, because shading hides outlines. Curved, crossing label lines: redraw them with a ruler, so each is straight, touches the structure and does not cross another.
If you got these wrong
Use the pattern of your errors to choose what to revise.
| If the error was in | Go to |
|---|---|
| Questions 1 to 3, naming or explaining a structure | Identify structures from an original cell diagram |
| Questions 4, 5, 6, 7 or 9, calculating or converting | Calculate magnification with consistent units |
| Questions 8 or 11, scale bars or swapped values | Distinguish image size from actual size |
| Question 10, explaining a cell’s adaptation | Relate a specialised cell shape to its role |
| Question 12, drawing faults | Evaluate a labelled drawing for clarity rather than artistry |
Record each miss with a short note on what went wrong in the mistake log and retest queue, and try a similar question a few days later.
If the same type of question keeps slipping, a teacher working one-to-one can trace the step where your reasoning changes course, in online one-to-one Biology tuition.