Question

q2. an artificial membrane separates two sides of a beaker. the left side contains 50 glucose molecules and the right side contains 100 fructose molecules. if you add channels to the membrane for glucose molecules but do not add any for fructose molecules and then wait for a while, which will more likely be true?
the 50 glucose molecules will have moved from the left side to the right side of the beaker, because the channels allowed them to cross the membrane.
the 50 glucose molecules will not have moved to the right side of the beaker, because there are already 100 fructose molecules on the right side of the beaker.
about 25 glucose molecules will be on the right side of the beaker, and 25 will be on the left side of the beaker.
both sides of the beaker will contain approximately equal numbers of glucose and fructose molecules.

Explanation:

This question is about the movement of molecules across a membrane, related to diffusion (passive transport) through channels. Glucose channels allow glucose to move down its concentration gradient (from left, 50 glucose, to right, 0 initially for glucose). Fructose can't move as no channels. So glucose will diffuse until equilibrium (approx equal on both sides for glucose). The third option says about 25 on each side (since 50 total, equilibrium is 25 each). The first is wrong as it doesn't reach equilibrium. The second is wrong (fructose doesn't affect glucose's gradient). The fourth is wrong (fructose can't move, so sides won't have equal glucose and fructose, just equal glucose).

Answer:

About 25 glucose molecules will be on the right side of the beaker, and 25 will be on the left side of the beaker.