# How many potassium ions pass through if the ion channel opens for 1.0 {\rm ms}?

1. Oct 28, 2012

### deborahcurrie

1. The problem statement, all variables and given/known data
The biochemistry that takes place inside cells depends on various elements, such as sodium, potassium, and calcium, that are dissolved in water as ions. These ions enter cells through narrow pores in the cell membrane known as ion channels. Each ion channel, which is formed from a specialized protein molecule, is selective for one type of ion. Measurements with microelectrodes have shown that a 0.30-nm-diameter potassium ion ({\rm{{\rm K}}}^{\rm{ + }} ) channel carries a current of 1.8 {\rm pA}.

How many potassium ions pass through if the ion channel opens for 1.0 {\rm ms}?

2. Relevant equations

Delta charge (Q)=Current (I) * delta time
1 ion = 1.6E-19 C

3. The attempt at a solution
Delta Q=1.8E-12*1E-3=1.8E-15C

1.8E-15C/1.6E-19=11,250

Mastering physics wants 2 sig figs, so entered "11,000" which is wrong.

2. Oct 28, 2012

### aralbrec

It looks right to me. Is it possible to enter "1.1e4"?

3. Oct 28, 2012

### deborahcurrie

That did it. Thanks for thinking of the tip!