Question

q10. if you were to watch an individual neurotransmitter molecule just after it was released, what would happen to it? the molecule would rapidly collide with a large number other molecules at first, and the collision rate would remain just as high over time. the molecule would rapidly collide with a small number of other molecules at first, and then the collision rate would increase as the molecule diffuses into the middle of the fluid pocket. the molecule would rapidly collide with lots of other molecules at first, and then the collision rate would decrease over time as the molecule diffuses away from the axon.

Explanation:

To determine the fate of a neurotransmitter molecule after release, we analyze the diffusion and collision principles:

1. When a neurotransmitter is released near the axon, the local concentration of molecules (including other neurotransmitters, ions, and fluid molecules) is high initially. So, the molecule will rapidly collide with many other molecules at first due to the high density of particles in the immediate vicinity.
2. As the molecule diffuses away from the axon (where it was released), it moves into regions with a lower concentration of molecules. With a lower density of surrounding molecules, the number of collisions per unit time (collision rate) will decrease over time.

Now let's analyze the options:

• Option 1: States the collision rate remains high over time. This is incorrect because as the molecule diffuses away, the concentration of surrounding molecules decreases, so collision rate should decrease, not stay the same.
• Option 2: Claims the molecule collides with a small number initially and collision rate increases. This is wrong. Initially, near the axon, the concentration is high, so collisions should be frequent initially, and as it diffuses (away from high - concentration area), collision rate should decrease, not increase.
• Option 3: Correctly states that the molecule rapidly collides with lots of other molecules at first (due to high local concentration near axon) and then the collision rate decreases over time as the molecule diffuses away from the axon (into areas of lower molecule concentration).

Answer:

The molecule would rapidly collide with lots of other molecules at first, and then the collision rate would decrease over time as the molecule diffuses away from the axon.