CIE A Level Biology
CIE A Level Biology Topic 1: Cell Structure Exam Questions
Free CIE A Level Biology exam questions for Topic 1: Cell Structure, with a mark scheme for every pack. Covers light and electron microscopy, magnification and calibration, eukaryotic and prokaryotic cell ultrastructure, organelle functions, ATP and viruses.
Topic 1: Cell Structure exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About CIE A Level Biology Topic 1: Cell Structure
Cell structure is the first topic in the Cambridge International AS and A Level Biology (9700) syllabus and underpins almost everything that follows. You need to be confident using a light microscope, calculating magnification and actual size, and calibrating an eyepiece graticule against a stage micrometer. The topic then moves to the ultrastructure of animal and plant cells seen with an electron microscope, the functions of each organelle, and the differences between eukaryotic and prokaryotic cells. Viruses are included as non-cellular structures. Examiners often give an electron micrograph to identify organelles, or ask for a calculation of size from an image with a scale bar.
What you need to know
- Microscopy Magnification = image size / actual size. Resolution is the ability to distinguish two points as separate; electron microscopes have higher resolution because electrons have a much shorter wavelength than light.
- Units and calibration 1 mm = 1000 µm and 1 µm = 1000 nm. An eyepiece graticule has no units, so it must be calibrated against a stage micrometer (each division usually 0.01 mm, or 10 µm) at each objective.
- Eukaryotic organelles Know the structure and function of the nucleus, nucleolus, rough and smooth ER, Golgi body, mitochondria, ribosomes (80S in cytoplasm, 70S in mitochondria and chloroplasts), lysosomes, centrioles, microtubules, chloroplasts, cell wall, plasmodesmata and large permanent vacuole.
- ATP ATP is the universal energy currency; it is made in mitochondria and chloroplasts and hydrolysed to release energy for processes such as active transport and protein synthesis.
- Prokaryotic cells Prokaryotes have no nucleus or membrane-bound organelles, a circular DNA molecule with no histones, 70S ribosomes, a peptidoglycan cell wall and are much smaller (often 1 to 5 µm).
- Viruses Viruses are non-cellular: a nucleic acid core (DNA or RNA) surrounded by a protein capsid, sometimes with a phospholipid envelope. They can only replicate inside host cells.
Common mistakes in Topic 1: Cell Structure
- Mixing up magnification and resolution: increasing magnification does not increase the detail you can see unless resolution also improves.
- Forgetting to convert units before calculating magnification; always put image size and actual size in the same unit first.
- Saying the cell wall of bacteria is made of cellulose; prokaryote walls are made of peptidoglycan (murein).
- Describing ribosomes as membrane-bound organelles; ribosomes have no membrane and are made of rRNA and protein.
- Stating that an eyepiece graticule division is a fixed length; its value changes with every objective lens, so it must be recalibrated.
Try three Topic 1: Cell Structure exam-style questions
1. An image of a mitochondrion is 45 mm long. The actual length of the mitochondrion is 15 µm. Calculate the magnification of the image. (2 marks)
Show the mark scheme answer
Convert 45 mm to 45 000 µm; 45 000 / 15 = x 3000.
2. Forty eyepiece graticule divisions line up with ten stage micrometer divisions. Each stage micrometer division is 0.01 mm. Calculate the length of one eyepiece division in µm. (2 marks)
Show the mark scheme answer
10 divisions x 10 µm = 100 µm; 100 / 40 = 2.5 µm per eyepiece division.
3. Explain why an electron microscope can show the internal structure of a mitochondrion but a light microscope cannot. (3 marks)
Show the mark scheme answer
Electrons have a much shorter wavelength than light; so resolution is much higher (about 0.5 nm compared with about 200 nm); structures such as cristae are smaller than the resolution of a light microscope so cannot be distinguished.
Topic 1: Cell Structure FAQs
What does Cambridge International A Level Biology Topic 1 Cell structure cover?
It covers microscopy, magnification and calibration, the ultrastructure and functions of organelles in plant and animal cells, ATP, prokaryotic cells and the structure of viruses.
Which paper is Cell structure examined in?
It is AS Level content, so it is assessed in Paper 1 (multiple choice) and Paper 2 (AS Level structured questions), with related practical skills tested in Paper 3. A Level candidates can also meet it again in Paper 4 and Paper 5, which assume AS knowledge.
Which calculations do I need for Cell structure?
You need magnification = image size / actual size rearranged to find any value, unit conversions between mm, µm and nm, and eyepiece graticule calibration using a stage micrometer.
