CAIE A Level Biology 9700 · Energy and respiration
A researcher adds a small amount of glucose radioactively labelled with carbon-14 at the first carbon (C1) to a suspension of isolated mitochondria and cytosolic extract (containing all enzymes of glycolysis) from rat liver cells. After a short incubation, the researcher detects radioactive pyruvate.
Explain how the carbon atoms from the labelled glucose are converted into pyruvate and where this process occurs.
5 marks, so the mark scheme is looking for about 5 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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