Plant cell structureEdexcel International A Level Biology: Flashcards
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What is the cell wall made of and what is its function?
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- What is the cell wall made of and what is its function?
- Cellulose microfibrils; it supports the cell and resists expansion so the cell does not burst.
- What is the middle lamella?
- A pectin layer between the walls of adjacent cells that cements them together.
- What are plasmodesmata?
- Narrow channels of cytoplasm, lined by plasma membrane, that pass through cell walls and link adjacent cells.
- What are pits?
- Thin regions of the cell wall where plasmodesmata are concentrated.
- What is a chloroplast and what is its structure?
- The site of photosynthesis; it has a double membrane, thylakoids stacked in grana, and stroma.
- What is an amyloplast?
- A double-membrane organelle that stores starch; it has no thylakoids.
- Why is starch a good storage molecule?
- It is insoluble, so it does not affect water potential, and it is too large to diffuse out of the cell.
- What is the tonoplast?
- The membrane surrounding the vacuole, which controls movement of substances into and out of it.
- What is the function of the permanent vacuole?
- It stores cell sap and gives turgor pressure, which supports the cell.
- Name two features of plant cells that animal cells lack.
- A cellulose cell wall and a large permanent vacuole (also chloroplasts and plasmodesmata).
- How can you recognise a chloroplast in an electron micrograph?
- An oval organelle with a double membrane and stacks of thylakoids.
- How can you recognise an amyloplast in an electron micrograph?
- A double-membrane organelle containing large pale starch grains and no thylakoid stacks.
Exam questions on Plant cell structure
- A student examines an electron micrograph of a palisade mesophyll cell from a leaf. The cell has a thick layer outside its plasma membrane, a very large sac occupying most of the cell interior, and several oval organelles containing stacks of flattened membranes.The cell is placed in distilled water. Explain why it does not burst.2 marks
- A potato tuber stores energy over the winter. Cells from inside a tuber were stained with iodine solution and viewed under a light microscope. Many organelles in the cells contained dark blue-black granules.Explain why the tuber stores energy as starch in amyloplasts rather than as glucose in the cytoplasm.2 marks
- A researcher injects a fluorescent dye into one parenchyma cell in the stem of a plant. Within minutes the dye is detected in the neighbouring cells, even though the dye cannot cross the plasma membrane. Microscopy shows that where the dye passes between the cells, the cell wall is thin.Explain how the dye could move from the injected cell into its neighbours.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).