Question

why is facilitated diffusion necessary?
a) to transport gasses between vessels
b) to pass large insoluble molecules
c) to break up large insoluble molecules
d) to move liquids from one capsule to another

question 20 (5 points)
listen
as the protons move down their concentration gradient in the electron transport chain, whats happening with the electrons in the chain?
a) they split apart from oxygen.
b) they combine with oxygen to form water.
c) they take a phosphate group off atp.

Explanation:

First Question (Why is facilitated diffusion necessary?):

Facilitated diffusion uses transport proteins to move substances across cell membranes. Small, non - polar molecules can diffuse freely, but large or insoluble (polar) molecules (like glucose) can't cross the lipid - bilayer of the membrane on their own. So facilitated diffusion is needed to pass these large insoluble molecules. Option A is wrong because gas transport (like $O_2$ and $CO_2$) is simple diffusion. Option C is wrong as facilitated diffusion doesn't break molecules. Option D is wrong as it's not about moving liquids between capsules.

Second Question (As the protons move down their concentration gradient in the electron transport chain, what's happening with the electrons in the chain?):

In the electron transport chain, electrons move through protein complexes and finally combine with oxygen and protons ($H^+$) to form water. Option A is wrong as electrons don't split from oxygen here. Option C is wrong because electrons don't take a phosphate group off ATP; instead, the proton gradient is used to make ATP (by adding a phosphate to ADP).

Answer:

B) To pass large insoluble molecules