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Exam questions · Biology · Cell Structure

Eukaryotic and Prokaryotic Cells

  • 7 exam questions
  • 20 marks
  • 8 quick checks
  1. 1 Name [1 mark]

    Name the type of cell that has no nucleus.

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    Model answer

    A prokaryotic cell, for example a bacterial cell.

    Mark scheme

    • Prokaryotic (cell) — 1 mark
  2. 2 Describe [2 marks]

    Describe two differences between a bacterial cell and an animal cell.

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    Model answer

    Any two from: a bacterial cell has a cell wall but an animal cell does not; the DNA of a bacterial cell is a single loop in the cytoplasm but in an animal cell it is enclosed in a nucleus; a bacterial cell may have plasmids but an animal cell does not; a bacterial cell is much smaller than an animal cell.

    Mark scheme

    • Cell wall present in bacteria but not in animal cells — 1 mark
    • DNA is a single loop (no nucleus) in bacteria, but enclosed in a nucleus in animal cells — 1 mark
    • Plasmids in bacteria only — 1 mark
    • Bacterial cell is smaller — 1 mark
  3. 3 Name [3 marks]

    Figure 1 shows a bacterial cell. Name the structures labelled A, B and C.

    A bacterial cell with three structures marked A, B and C.
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    Model answer

    A is the cell wall. B is the (single loop of) DNA. C is a plasmid.

    Mark scheme

    • A: cell wall — 1 mark
    • B: DNA / single loop of DNA / genetic material — 1 mark
    • C: plasmid — 1 mark
  4. 4 Calculate [2 marks]

    A bacterial cell is 2 µm long. Calculate how many of these cells, laid end to end, would stretch 1 mm.

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    Model answer

    1 mm = 1000 µm. 1000 ÷ 2 = 500 cells.

    Mark scheme

    • Converts 1 mm to 1000 µm — 1 mark
    • 1000 ÷ 2 = 500 — 1 mark
  5. 5 Calculate [2 marks]

    The width of an animal cell is \(2 \times 10^{-5}\text{ m}\). The width of a bacterial cell is \(2 \times 10^{-6}\text{ m}\). Calculate how many times wider the animal cell is, and give the difference as an order of magnitude.

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    Model answer

    \(\dfrac{2 \times 10^{-5}}{2 \times 10^{-6}} = 10\). The animal cell is 10 times wider, which is one order of magnitude bigger.

    Mark scheme

    • Divides the two widths to give 10 — 1 mark
    • One order of magnitude — 1 mark
  6. 6 Describe [4 marks]

    Describe the structure of a bacterial cell.

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    Model answer

    A bacterial cell is a prokaryotic cell with no nucleus. Its genetic material is a single loop of DNA lying free in the cytoplasm, and it may also contain small rings of DNA called plasmids. The cytoplasm is surrounded by a cell membrane, and outside the membrane there is a cell wall.

    Mark scheme

    • Cytoplasm and cell membrane — 1 mark
    • Cell wall (outside the membrane) — 1 mark
    • Single loop of DNA, not in a nucleus — 1 mark
    • Plasmids — 1 mark
  7. 7 Compare [6 marks]

    Compare the structure of a bacterial cell with the structure of a plant cell.

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    Model answer

    Both cells have a cell membrane, cytoplasm, ribosomes and a cell wall. In a plant cell the wall is made of cellulose, but a bacterial wall is not. A plant cell has its DNA enclosed in a nucleus, whereas a bacterial cell has no nucleus and its DNA is a single loop in the cytoplasm. A plant cell has chloroplasts and a permanent vacuole, which a bacterial cell does not. A bacterial cell may have plasmids and a flagellum, which a plant cell does not. A bacterial cell is much smaller.

    Mark scheme

    • Both have a cell membrane, cytoplasm and a cell wall — 1 mark
    • Plant cell DNA is in a nucleus; bacterial DNA is a loop in the cytoplasm — 1 mark
    • Plant cells have chloroplasts — 1 mark
    • Plant cells have a permanent vacuole — 1 mark
    • Bacterial cells may have plasmids (and a flagellum) — 1 mark
    • Bacterial cell is smaller / plant cell wall is cellulose — 1 mark

Quick check

  1. 1

    Which type of cell has no nucleus?

    1. AAnimal cell
    2. BPlant cell
    3. CBacterial cell
    4. DYeast cell
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    C: Bacterial cell

    A prokaryotic cell, such as a bacterium, has no nucleus. Its DNA lies free in the cytoplasm.

  2. 2

    What is a plasmid?

    1. AThe part of a cell that makes energy
    2. BA small ring of DNA in a bacterial cell
    3. CA layer around the outside of a plant cell
    4. DThe jelly-like part of a cell
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    B: A small ring of DNA in a bacterial cell

    A plasmid is a small extra ring of DNA found in bacteria, separate from the main loop of DNA.

  3. 3

    Which structure is found in both bacterial cells and plant cells?

    1. ANucleus
    2. BChloroplast
    3. CCell wall
    4. DMitochondrion
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    C: Cell wall

    Both have a cell wall, although a plant cell wall is made of cellulose and a bacterial one is not. Neither the nucleus nor chloroplasts nor mitochondria are found in bacteria.

  4. 4

    How is the genetic material arranged in a bacterial cell?

    1. AAs a single loop in the cytoplasm
    2. BInside a nucleus
    3. CInside a chloroplast
    4. DIt has no genetic material
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    A: As a single loop in the cytoplasm

    Bacteria have a single loop of DNA in the cytoplasm, and sometimes plasmids too.

  5. 5

    What is the value of 1 µm in metres?

    1. A\(1 \times 10^{-3}\text{ m}\)
    2. B\(1 \times 10^{-9}\text{ m}\)
    3. C\(1 \times 10^{6}\text{ m}\)
    4. D\(1 \times 10^{-6}\text{ m}\)
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    D: \(1 \times 10^{-6}\text{ m}\)

    Micro means one millionth, so 1 µm is one millionth of a metre.

  6. 6

    One cell is 1000 times wider than another. How many orders of magnitude bigger is it?

    1. A1
    2. B2
    3. C3
    4. D1000
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    C: 3

    Each order of magnitude is a factor of 10, and \(1000 = 10^{3}\), so the difference is 3 orders of magnitude.

  7. 7

    Which of these is the smallest?

    1. AA bacterium
    2. BA virus
    3. CAn animal cell
    4. DA plant cell
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    B: A virus

    A virus is about 100 nm across, much smaller than a bacterium (about 2 µm), an animal cell or a plant cell.

  8. 8

    Which organisms are made of prokaryotic cells?

    1. ABacteria
    2. BFungi
    3. CPlants
    4. DAnimals
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    A: Bacteria

    Bacteria are prokaryotes. Fungi, plants and animals are all made of eukaryotic cells.