How does the sodium-potassium pump contribute to the net negative charge of the interior of the

How does the sodium-potassium pump contribute to the net...

Key Concepts

Sodium-Potassium Pump

The sodium-potassium pump is an active transport mechanism that uses ATP to move ions against their concentration gradients. Specifically, it pumps three sodium ions out of the cell and brings two potassium ions in, establishing and maintaining distinct ion concentrations on either side of the cell membrane.

Electrogenic Transport

Because the pump moves a different number of positive charges in each direction (three out versus two in), its activity results in a net export of positive charge. This electrogenic effect contributes to the generation of an electrical gradient, leading to a net negative charge inside the cell.

Membrane Potential

The membrane potential refers to the voltage difference across a cell's membrane, primarily arising from the unequal distribution of ions. The activity of the sodium-potassium pump, by establishing both ion concentration and charge gradients, is crucial for maintaining the resting membrane potential, which is essential for processes like nerve impulse transmission and muscle contraction.

Transcript

00:01 How does a cell become more negative on the inside versus the outside? the protein, the membrane protein that accomplishes this is the sodium potassium pump.

00:17 And what i've drawn here is a very simplistic diagram of that.

00:23 So on this side, we are inside the cell.

00:27 And on this side, we are outside of the cell.

00:29 And this is the membrane right here okay and the pump sits in the membrane and what the pump does is it pumps sodium and potassium right it's a sodium potassium pump so before sodium potassium pump does anything let's do a tally of our charges so we have three positive charges on the outside we have three k plus three potassium so we have three plus charges and we also have three sodiums on the inside so we have three plus how does a sodium potassium pump work a sodium potassium pump work uses atp it uses energy all pumps use energy so think of like a water pump right you have to plug it in to move the water so that's kind of where the name comes from a protein that is called a pump uses energy to move substrates across a membrane.

01:36 It doesn't do this in an equal way for sodium and potassium.

01:41 It puts out three sodium and it brings in two potassium.

01:55 So in this very simple example that we have here, if the potassium pump uses one atp to do one of its cycle, the scenario that we end up with so let me draw the pump here again this is my membrane and again this is out of the cell this is in so initially we had three sodiums on the inside but the pump puts out three sodiums on the outside so now on the inside we will have no sodiums that's the n8 plus and there would be three sodiums outside and it brings in two potassiums so it brings in two potassiums but we still have one of the potassiums left outside because it only brought in two so now let's do a tally of our charges again out here so on this side we have four plus charges on this side we have two plus charges and if you see now the difference between the outside and the inside is a minus two right two minus four is minus two whereas three minus three is zero so that is how the sodium potassium pump establishes a net negative charge inside the cell it uh puts more sodium more positive charges out and it brings positive charges in.

03:45 So think about it this way.

03:46 If you spend more money than you earn, your bank is going to be in the negative, right? if you put out more positives than you bring in, you are going to be in the net negative.

03:59 So choice a is the correct choice here...

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