Parkinson's disease is caused by a lack of specific neurotransmitters. The graph shows the effect of age on the number of dopamine-producing cells in people who develop Parkinson's disease. The drug L-DOPA is used in tablet form to treat Parkinson's disease. This drug is converted to dopamine by an enzyme found in the digestive system and the brain. Carbidopa is an inhibitor of the enzyme found in the digestive system. Suggest why carbidopa is given to patients when they are treated using L-DOPA in tablet form. (2) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................. ................................................................................................................................................................................................................................................................................

Biology

IGCSE&ALevel

EDEXCEL

Exam No：WBI1501-que-20241024 Year：2024 Question No：4(b)

Answer:

An answer that includes two of the following points
- (carbidopa) prevents L-DOPA being broken down (in digestive system / before blood-brain barrier) (1)
- (because) L-Dopa can pass blood-brain barrier / dopamine can't pass blood-brain barrier (1)
- allowing a lower dose of L-DOPA to be given (1)

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