1. Identify the parts of the cell labelled A-G in the figure below.
Answer
2. How does a prokaryotic cell wall structure differ from a plant cell wall ?
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It contains murein (peptidoglycan) instead of cellulose.
3. Cell fractionation is the process by which different components of a cell are able to be separated due to their differing densities. Name and explain the three conditions necessary for successful cell fractionation.
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Cell fractionation requires three conditions: a buffer to maintain a constant pH and prevent enzymes from denaturing, a cold environment to slow down or stop enzyme activity, and a solution with the same water potential as the cells to prevent osmosis, which could cause organelles to burst or shrivel.
4. Give some features that make prokaryotic cells different from eukaryotic cells.
Answer
Prokaryotic cells have no membrane‑bound organelles, contain smaller 70S ribosomes, and possess a circular DNA molecule free in the cytoplasm. Their DNA is not associated with proteins, their cell wall is made of murein (peptidoglycan), and they lack a nuclear membrane. Some also have a double membrane.
5. Complete the table below.
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6. The figure below shows shows a single-celled protoctist called Euglena, which lives in fresh water. Give some features that enable you to identify this as a eukaryotic cell.
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This cell contains chloroplasts, mitochondria, a Golgi apparatus, and a nucleus.
7. The contractile vacuole collects excess water from inside the cell and releases it outside the cell. Explain why this is necessary.
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The water potential inside the cell is lower than outside (or vice versa), so water enters the cell by osmosis down a water potential gradient. Without the contractile vacuole, the cell would take in too much water and eventually burst (lyse).
8. The eyespot enables the Euglena to swim towards light. Explain the advantage of this to Euglena.
Answer
Enables Euglena to obtain more light for photosynthesis.
9. The flagellum allows the Euglena to swim forward, with the cell rotating all the time. Suggest how the position of the eyespot enables the Euglena to detect the direction of light as it swims.
Answer
If Euglena is swimming directly towards the light, the light intensity detected by eyespot will be uniform (or maximum). If Euglena is swimming in a different direction the light intensity will vary as the cell rotates.
10. The figure below shows a goblet cell from the lining of the intestine. The cytoplasm contains amino acids. These amino acids are used to make mucus, which is secreted from the cell. Place the appropriate letters in the correct order to show the path taken by an amino acid as it is secreted from the cell in mucus.
Answer
The order is A, C, E, F, G.
11. A technician prepared a suspension of chloroplasts for an investigation. The flow chart in the figure below shows the method he used. The mixture was filtered in Stage 3. Explain why.
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To get rid of cell debris, lumps of tissue or cell walls.
12. The mixture was spun in a high speed centrifuge in Stage 4. Explain why.
Answer
It separates organelles, with denser organelles settling at the bottom to form a pellet.