A-LevelBiologyEnzymes9700/12 · Oct/Nov 2015 · Q141 Mark
Tyrosinase is an enzyme that catalyses the conversion of the amino acid tyrosine into the black pigment melanin. It is responsible for the black fur colour of some rabbits. A group of rabbits kept at 30°C resulted in 90% of the rabbits with light fur colour. A second group of rabbits kept at 10°C resulted in 90% of the rabbits with black fur colour. Which hypothesis is supported by these results?
AAn inhibitor is present in rabbit skin cells that can bind strongly to tyrosinase when the external temperature is 30°C.
BAt 10°C external temperature there are fewer tyrosinase-tyrosine complexes formed and less melanin is produced.
CTyrosinase is an enzyme that is coded for by a gene that is switched off when the external temperature is 10°C.
DTyrosinase is a temperature-sensitive molecule that is only activated when the external temperature is 30°C.
✓ Correct answer
A: An inhibitor is present in rabbit skin cells that can bind strongly to tyrosinase when the external temperature is 30°C.
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