If a drug is found in the brain but does not possess the properties needed for passive diffusion through the blood-brain barrier then a researcher should conclude:
A) the drug entered the brain through active transport mechanisms.
B) the drug is synthesized and released from cells in the brain.
C) the properties of the substance were altered by brain glial cells.
D) nonspecific binding allowed the drug to pass through the blood-brain barrier.

Question

Quizplus · Accepted Answer

If a drug is found in the brain but does not possess the properties needed for passive diffusion through the blood-brain barrier, then it must have entered the brain through active transport mechanisms. Active transport mechanisms require energy and transporters that can move substances against their concentration gradient, allowing drugs to enter the brain even if they normally wouldn't be able to pass through the blood-brain barrier.

If a Drug Is Found in the Brain but Does