if there were 10,000 calcium ions inside the cell and 2,000 calcium ions outside the cell in which direction will these ions naturally flow

Question

the choices are

A.they flow from outside the cell in

B.they flow from inside the cell out

C.they flow from the inside of one cell into the next cell

D.Calcium ions cant fow in or out of the cell

Answer 1

Hi N.S.,

Cannot be determined.

Ions are stated as numbers, but it is the concentrations which are important (well, technically, the activities, but that's for a future course for you!). Since the volumes in which each reservoir of Ca2+ ions resides isn't given, you can't say.

But, if the problem were restated as ions/mm^3, let's say, then you'd say B, with the objection that Ca2+ levels outside the cell are normally 10,000 times higher than those inside. So where is a cell going to get the opposite imbalance? Even if the Ca2+ pump mechanism were disabled, levels would only possibly approach equal (there are other transport systems than the specific Ca2+ pump).

-- Cheers, -- Mr. d.