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Secondary Biology: Cell Structure and the Microscope (Paper 3)
Secondary Biology: Cell Structure and the Microscope (Paper 3)
Ten original questions on scale bar arithmetic, millimetre to micrometre conversion, how red blood, root hair and muscle cells suit their jobs, resolution against magnification, and the mistaken belief that the highest power is always clearest.
Direct answer Use the scale bar to find the value of one millimetre, and keep resolution separate from magnification.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: Secondary Biology: Cell Structure and the Microscope |
| Level | 4 basic, 3 advanced, 2 challenge and 1 redo question |
02 Questions (10 items)
- FoundationWhich structure is missing from a mature red blood cell, so that it cannot divide?
- FoundationHow many micrometres are there in one millimetre?
- FoundationWhich stain is commonly used when observing cheek cells?
- FoundationWhat is the function of the long hair-like extension at the end of a root hair cell?
- IntermediateOn a drawing a scale bar of 8 mm stands for 20 micrometres. A cell in the same drawing measures 40 mm. What is its actual length?
- IntermediateMuscle cells contain many mitochondria. How does this relate to their function?
- IntermediateAmoeba is a single cell. Why does it not need organ systems?
- ChallengeWhat is the difference between resolution and magnification?
- ChallengeAt the same magnification, cell A measures 60 mm on the image and cell B measures 15 mm. What is the ratio of their real sizes?
- Error redoA pupil says that the highest magnification always shows every cell most clearly. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The nucleus. | A maturing red blood cell expels its nucleus to make room for oxygen, so it cannot divide. |
| 2 | One thousand micrometres. | Microscopy uses micrometres; one millimetre equals one thousand micrometres. |
| 3 | Methylene blue solution. | Methylene blue stains the nucleus deep blue while the membrane and cytoplasm stay pale. |
| 4 | It increases the surface area for absorbing water and mineral salts. | Shape fits function: a larger surface area means faster water uptake. |
| 5 | 100 micrometres (40 divided by 8, multiplied by 20). | First find how many micrometres one millimetre stands for, then multiply by the image length. |
| 6 | Muscle contraction needs a lot of energy, which mitochondria release through aerobic respiration. | The number of organelles matches the energy demand of the cell. |
| 7 | One cell already carries out feeding, respiration, excretion and reproduction. | A unicellular organism divides the work among organelles rather than tissues and organs. |
| 8 | Resolution is the ability to tell two very close points apart; magnification only enlarges the image and a higher value does not mean better resolution. | A blurred image stays blurred when enlarged, so the two ideas must be kept apart. |
| 9 | 4 to 1 (60 divided by 15). | At equal magnification, the ratio of image lengths equals the ratio of real sizes. |
| 10 | Magnification only sets the image size. Seeing detail depends on resolution, and beyond the resolution limit the image simply becomes blurrier. | Magnification and resolution are two separate ideas. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.
