A-LevelBiologyEnzymes9700/12 · May/June 2023 · Q131 Mark
CYP3A4 is an important enzyme in the human digestive system where it is needed to break down a range of different toxins. The activity of CYP3A4 has been shown to be reduced by substances called furanocoumarins. Furanocoumarins are found in some fruits and so dangerous concentrations of toxins may develop in the human digestive system when fruits containing furanocoumarins are eaten. From the information provided, what can be concluded about molecules of the enzyme CYP3A4?
AThey lower the activation energy of the toxin breakdown reactions.
BThey bind specifically through the active site to a substrate found in some fruits.
CThey change permanently when acted upon by furanocoumarin molecules.
DThey resume normal activity when concentrations of furanocoumarins decrease.
✓ Correct answer
A: They lower the activation energy of the toxin breakdown reactions.
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