Osmosis is based upon:?

Question

a. All of these choices.
b. Tonicity.
c. Differential pressure.
d. Concentration.

Answer 1

a.

Answer 2

A bit tricky question, since you can find different definitions for tonicity.

Osmosis is the net movement of water across a selectively permeable membrane. Differential pressure is certainly not the principle driving force but will affect in isolated cases like the famous experiment with the u-shape tube, where hydrostatic pressure also influences the final outcome. Thus (c) and (a) are rejected.

In general osmosis will depend on the difference in concentration of solutes.Thus (d), although it is not exactly correct since it is the difference in solute concentration and not concentration itself, seems to be the more suitable answer.

However, when defining tonicity as "the effective osmolality and equal to the sum of the concentrations of the solutes which have the capacity to exert an osmotic force across the membrane" , then (b) is the correct one. (consider that solutes which can pass through the membrane do not contribute to osmosis unless there is a mechanism that affects their distribution on the two sides of the membrane, like in the case of the Donnan effect).
Also when you consider tonicity as the difference in osmolality it is again more correct than concentration. Furthermore, tonicity according to the first definition above depends on the selectivity of the membrane and it is true that e.g. if you have a solution of glucose on one side of a membrane and pure water on the other you will have osmosis only if the membrane doesn't allow glucose to pass-otherwise the two simply mix.

Things get even more complicated when dealing with charged macromolecules and small ions (Donnan effect and Bjerrum ion pairs)

I'd say that this question looks like one from a course or text-book so your answer [(b) or (d)] depends on the exact definition of tonicity that was given to you. The most general/basic and probable answer I think is (d).

Answer 3

A. Yes
B. Tonicity is what creates the concentration gradient for osmosis
C. This is the same as tonicity
D. Concentration of solute directs osmosis

Answer 4

Im not quite sure, this question is so simple its almost complicated. D is def one. However if we are talking about osmosis in a cell i would have to say A.

Answer 5

a. All of these choices.

Answer 6

its d. concentration

Answer 7

d.