CAIE A Level Biology 9700 · Energy and respiration
A muscle cell actively transports sodium and potassium ions across its plasma membrane using the Na+/K+ pump. This process requires energy in the form of ATP.
Explain why ATP is described as the universal energy currency in living organisms.
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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