Cell structure and organisation
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Which pairing correctly describes a plant cell?
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Membrane: controls exchange; cell wall: provides support.
These are different structures with different functions. The membrane lies inside the wall.
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Which observation is the strongest evidence that a cell is a plant cell?
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It has a cellulose cell wall.
Typical animal cells do not have cellulose cell walls. A plant cell can lack chloroplasts and still have a wall.
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Which conclusion is justified when a nucleus becomes visible after staining?
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An existing nucleus is now easier to distinguish.
Contrast increased. Visibility before staining was insufficient to show the nucleus clearly.
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A drawing of a cell is 60 mm long. The real cell is 0.12 mm long. What is the magnification of the drawing?
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x500
Magnification = drawing size / real size = 60 / 0.12 = 500.
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A 30 mm drawing represents a cell 60 micrometres long. What is its magnification?
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x500
60 micrometres = 0.060 mm, and 30 / 0.060 = 500. The magnification is a ratio with no unit.
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Which statement correctly interprets an electron micrograph?
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An organelle with a folded inner membrane is consistent with a mitochondrion, a site of aerobic respiration.
The internal pattern supports the identification and is linked to the correct function.
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A gland cell makes and secretes large amounts of an enzyme. Which pair of structures would you expect to find in large numbers?
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Ribosomes and mitochondria
Ribosomes make the protein, and mitochondria release energy for making and secreting it.
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Why does a mature mammalian red blood cell lack a nucleus?
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To leave more space for haemoglobin to carry oxygen.
Connect the missing nucleus to additional space for haemoglobin, then to oxygen transport.
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Which feature of a root hair cell most directly increases the rate of water uptake?
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A long extension that gives a large surface area
A larger surface area in contact with soil water gives more water uptake per second.
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