IB Diploma · Biology A2.2
IB Biology A2.2: Cell Structure — Practice Questions & Answers
IB Biology A2.2 Cell structure notes: cell theory, microscopy, prokaryotic versus eukaryotic cells, organelles, and the surface area to volume ratio.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
What is the basic structural unit of all living organisms?
- Cells
- Tissues
- Organs
- Organ systems
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WhyThe cell is the basic structural and functional unit of all living organisms.
2
Multiple choice
What is used to measure the size of cells in microscopy?
- Eyepiece graticule
- Micrometer
- Ruler
- Vernier caliper
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WhyAn eyepiece graticule, calibrated with a stage micrometer, is used to measure cell size under the microscope.
3
Multiple choice
What type of adjustment is used for coarse focusing in microscopy?
- Coarse adjustment knob
- Fine adjustment knob
- Stage adjustment knob
- Condenser adjustment knob
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WhyThe coarse adjustment knob moves the stage for initial, rough focusing at low magnification.
4
Multiple choice
Which microscopy technique involves freezing and fracturing cells to study membrane structures?
- Freeze fracture
- Cryogenic electron microscopy
- Immunofluorescence
- Phase contrast microscopy
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WhyFreeze fracture freezes and splits cells along membrane planes to reveal internal membrane structures.
5
Multiple choice
What encloses the cytoplasm in all cells?
- Plasma membrane
- Cell wall
- Nuclear envelope
- Endoplasmic reticulum
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WhyThe plasma membrane encloses the cytoplasm in all cells, controlling exchange with the surroundings.
6
Multiple choice
What is the advantage of cryogenic electron microscopy?
- Preserves native structures
- Uses fluorescent stains
- Uses radioisotopes
- Uses antibodies
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WhyCryogenic electron microscopy preserves molecules in a near-native state by rapid freezing without staining.
7
Multiple choice
What is used to visualize specific proteins in light microscopy?
- Fluorescent stains
- Heavy metals
- Dyes
- Radioisotopes
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WhyFluorescent stains bind specific molecules and emit light, allowing particular proteins to be visualised.
8
Multiple choice
What is the main component of cytoplasm?
- Water
- Proteins
- Lipids
- Carbohydrates
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WhyCytoplasm is mostly water, providing the medium in which cellular reactions and structures are suspended.
9
Multiple choice
What type of genetic material is found in typical cells?
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WhyTypical cells store their genetic material as DNA.
10
Multiple choice
What structure is found in prokaryotic cells but not in eukaryotic cells?
- Naked DNA in a loop
- Mitochondria
- Nucleus
- Endoplasmic reticulum
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WhyProkaryotic cells contain naked DNA in a single circular loop, lacking a membrane-bound nucleus.
Key terms in Cell Structure
Cell theory: The principle that all organisms are made of cells, the cell is the smallest unit of life, and cells come only from existing cells.
Prokaryote: A cell without a membrane-bound nucleus or organelles, with DNA in a nucleoid; bacteria and archaea.
Eukaryote: A cell with a true membrane-bound nucleus and membrane-bound organelles; animals, plants, fungi and protists.
Organelle: A specialised structure within a cell that performs a particular function.
Compartmentalisation: The separation of cell functions into membrane-bound regions, allowing different conditions and reactions side by side.
Resolution: The ability of a microscope to distinguish two close points as separate; higher in electron microscopes.
Magnification: The number of times larger an image appears than the actual object; image size divided by actual size.
Surface-area-to-volume ratio: The ratio of a cell’s surface area to its volume; it falls as size increases, limiting exchange and cell size.
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