GCSE Biology Cell Biology — Questions and Answers
Question 1: Which structure is found in plant cells but NOT in animal cells?
- Mitochondria
- Cell wall (Correct answer)
- Ribosomes
- Cell membrane
Correct answer: Cell wall
Plant cells have a cellulose cell wall; animal cells do not.
Animal and plant cells both contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells additionally have a cell wall made of cellulose, which strengthens the cell, plus chloroplasts and a permanent vacuole. The cell wall is a key distinguishing feature that examiners frequently ask you to identify.
Question 2: What is the function of ribosomes in a cell?
- Site of aerobic respiration
- Control the activities of the cell
- Site of protein synthesis (Correct answer)
- Store cell sap
Correct answer: Site of protein synthesis
Ribosomes are where proteins are made (protein synthesis).
Ribosomes are tiny structures found in the cytoplasm and on the rough endoplasmic reticulum. They read the mRNA code and join amino acids together to build proteins. Respiration happens in mitochondria, the nucleus controls the cell, and the vacuole stores cell sap in plant cells.
Question 3: A cell has a diameter of 0.05 mm. What is this in micrometres (µm)?
- 0.5 µm
- 5 µm
- 500 µm
- 50 µm (Correct answer)
Correct answer: 50 µm
1 mm = 1000 µm, so 0.05 mm × 1000 = 50 µm.
To convert millimetres to micrometres you multiply by 1000 because a micrometre is one thousandth of a millimetre. 0.05 × 1000 = 50, so the cell is 50 µm across. Unit conversions like this are a standard maths skill tested in GCSE Biology papers.
Question 4: Which of the following is a feature of a prokaryotic cell?
- Genetic material is free in the cytoplasm and not enclosed in a nucleus (Correct answer)
- It contains mitochondria
- It has a membrane-bound nucleus
- It is generally larger than a eukaryotic cell
Correct answer: Genetic material is free in the cytoplasm and not enclosed in a nucleus
Prokaryotes such as bacteria have no nucleus; their DNA is a single loop free in the cytoplasm.
Prokaryotic cells, such as bacteria, are much smaller than eukaryotic cells and lack membrane-bound organelles including a nucleus and mitochondria. Their genetic material is a single circular strand of DNA lying free in the cytoplasm, often with additional small rings called plasmids. Eukaryotic cells (animal, plant, fungal) keep their DNA inside a nucleus.
Question 5: A microscope has an eyepiece lens of ×10 and an objective lens of ×40. What is the total magnification?
- ×50
- ×400 (Correct answer)
- ×4
- ×4000
Correct answer: ×400
Total magnification = eyepiece × objective = 10 × 40 = ×400.
The total magnification of a light microscope is found by multiplying the magnification of the eyepiece lens by the magnification of the objective lens. Here 10 × 40 = 400, so the image appears 400 times larger than the real object. Remember also that magnification = image size ÷ real size when calculating from measurements.
Question 6: Which process moves water across a partially permeable membrane from a dilute solution to a more concentrated solution?
- Active transport
- Diffusion
- Osmosis (Correct answer)
- Translocation
Correct answer: Osmosis
Osmosis is the diffusion of water through a partially permeable membrane.
Osmosis is the net movement of water molecules from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution) across a partially permeable membrane. It is passive, so no energy is required. Active transport, by contrast, moves substances against a concentration gradient using energy from respiration.
GCSE Biology Cell Biology
Which structure is found in plant cells but NOT in animal cells?