Question

Fill in the blank with a suitable option:
According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with the ______________.

• A. Amount of protein present in a meal
• B. Concentration of serotonin in the brain before a meal
• C. Concentration of leucine in the blood rather than with the concentration of tyrosine in the blood after a meal
• D. Concentration of tryptophan in the brain before a meal
• E. Number of serotonin-containing neurons

Answer 1

Answer: (A)

Amount of protein present in a meal

Option A is the right answer because it is clearly mentioned in the last paragraph of the passage that - 'The more protein is in a meal, the lower is the ratio of the resulting blood-tryptophan concentration to the concentration of competing for amino acids, and the more slowly is tryptophan provided to the brain.'

There is no evidence in the passage to suggest that Options B, C, D, and E are the right answers.

Hence, these are incorrect.