CAIE A Level Biology 9700 · Energy and respiration
A muscle cell is actively transporting sodium ions out of the cell against their concentration gradient using a sodium-potassium pump. Explain why ATP is described as the universal energy currency, and describe how ATP is regenerated in the cell to support this process.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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