Question

A membrane has two sides, side A and side B. The net electrochemical potential is negative on side A compared to side B. There are 100 calcium ions on both sides of the bilayer. The free energy of moving a Calcium (+II) ion from side A to side B is:

	A.	It depends on the temperature, which is not given.
	B.	negative
	C.	zero
	D.	positive

Answer 1

The correct option is D, Positive

Because the side A of the membrane is already negatively charged, to balance this charge Ca+2 increase the the stability or decreases the free energy due to its positive charge. moreover, the concentration of Ca (II) is same on both sides, so calcium cannot move along the concentration gradient but only due to charge. when Calcium moves from more negative to less negative side enegy is used to do so. Thus free energy chane would be POSITIVE.

Other options are incorrect as:

A). Temperature will only increase the rate of movement but will not change free energy change.

B). Cannot be negative as mentioned above.

C). Cannot be ZERO because there is charge difference.