aqa a level biology specimen paper 3 question help Watch

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Report Thread starter 2 months ago
Hi, on q2.2 on this paper, the ms gives z as the nucleus, yet I dont understand how you can distinguish between the nlucleus and vacuole? Also for 4.4, I understand from the ms that the th cell binds directly to the tumour cell which in this case is the antigen presenting cell. But if this is the case, what is the point in phagocytosis - surely the th cell can then bind directly to the bacteria or virus instead of to the phagocyte that acts as the apc ? many thanks
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Report 2 months ago
2.2. In black-and-white microscope images, the vacuole tends to turn up white, so there's your first telltale sign. The more obvious one to focus on is that there are multiple W organelles, whereas there's only Z organelle. As there is only one nucleus in a plant cell, it must be Z.

4.4. You're missing a more fundamental, mechanical reason why phagocytosis doesn't occur in this situation. Metastasising tumours are a large group of aggregated cells, acting like a single entity. Phagocytes can only digest individual, isolated pathogens, so will not be able to do much against a tumour.

I hope this helped!

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