Sodium-Potassium Ion Pump: Study with Video Lessons, Practice Problems & Examples

The Sodium Potassium Ion pump is a p-type ATPase that actively transports 3 sodium ions (Na⁺) out of the cell and 2 potassium ions (K⁺) into the cell, establishing an electrochemical gradient. This antiport mechanism relies on ATP hydrolysis, which phosphorylates an aspartic acid residue, causing conformational changes that facilitate ion transport. The pump maintains a high sodium concentration outside and a high potassium concentration inside the cell, crucial for cellular functions and maintaining membrane potential.

Sodium-Potassium Ion Pump

In this video, we're going to begin talking about a very specific type of P-type ATPase called the Sodium Potassium Ion pump. Some of you may have already covered this pump in your previous biology courses, and so it might even be a review for some of you. Now, what I want you to recall from our previous lesson videos is that the inside of cells are generally more negative with respect to the outside of the cells. This is what dictates the electrical gradient for ions. If we take a look at our image down below on the left-hand side, notice that we're showing you guys this plasma membrane here for a particular cell. Within this green dotted box right here, notice that we're reminding you that on the inside of cells, they are generally more negative, and you can see the negative charges here within the inside of the cell to remind you of that. This is with respect to the outside of the cells which are generally going to be more positive with respect to the inside. This determines the electrical gradient for ions. Now, most cells are going to maintain an oppositely oriented chemical gradient of sodium and potassium ions. The symbol for sodium ions is Na⁺, and the symbol for potassium ions is K⁺. The way this oppositely oriented chemical gradient works is that on the inside of the cells, there's going to be a lower sodium concentration and a higher potassium concentration with respect to the outside of the cells. If we take a look at our image down below right here at this portion, notice that on the inside of our cell over here, we have a lower sodium concentration with respect to the outside of the cell, which has a much higher sodium concentration. We have a much higher potassium concentration on the inside of the cell and a much lower potassium concentration on the outside of the cell. You can see here that the sodium concentration is oppositely oriented with respect to the potassium concentration. That's exactly what we were trying to describe up above right here. What might help you remember this particular orientation of the sodium and potassium gradients is this image that we have over here on the right. I think of the cell as this really popping super hot club that everybody wants to get into, and it's called Club Intracellular. You can see the DJ in here is playing some sick music with these strobe lights. Again, everybody wants to get into the cell and get into the club. But the sodium potassium ion pumps are really the bouncers of the cell, and you can see that there could be several sodium potassium ion pumps in the membrane. Of course, when sodium tries to get its way into Club Intracellular, it's got to go through the bouncer here, and so the sodium ions here, three of them for that matter, are asking, "Brah, can we enter into Club Intracellular and party?" The sodium-potassium pump, because these are sodium ions with Na, they say, "Nah." They are not able to enter Club Intracellular, and so they stay on the outside, and that's why the concentration of sodium is so high on the outside of the cell. Whereas, when the potassium ions are trying to get into the club, notice they're saying, "Hey. We're back. Let us in." The sodium-potassium pump bouncer here, because again, the symbol of potassium is K, they just say, "K, come right on into Club Intracellular." That's why the sodium ion concentration on the inside of the cell is much, much higher on the inside than it is on the outside. We'll be able to talk about more details of the sodium potassium ion pump and how it functions and things like that in our next lesson video. So, I'll see you guys there.

Sodium-Potassium Ion Pump

In this video, we're going to talk more details about how exactly the sodium potassium ion pump works. And again, the sodium potassium ion pump is a classic example of a p-type ATPase, which means that we know that at some point, this sodium potassium ion pump is going to get phosphorylated, but that'll come a little bit later in this video. And so here what we're saying is that the sodium potassium ion pump is, again, a p-type ATPase that transports, as its name implies, sodium and potassium cations, but in opposite directions across the membrane. And because sodium and potassium are being pumped in opposite directions, this classifies the sodium potassium ion pump as an antiport.

Now the way that this sodium potassium ion pump works is that 3 sodium ions are going to be exported to the outside of the cell, while 2 potassium ions are being imported to the inside of the cell. And so what helps me remember that there are 3 sodium ions and 2 potassium ions is that the sodium symbol here, Na⁺ has 3 characters, and so 3 sodium ions are gonna be exported. And the Potassium symbol, K⁺ has 2 characters, and so 2 Potassium ions are going to be imported. And we know that potassium is going to get imported because you could also think of a pumpkin because pump K+N. And so we know that potassium is gonna get pumped to the inside of the cell, and that's why it's being imported into the cell.

Now again, the sodium potassium pump is an ATPase, so that means that it is an ATP-dependent process, and ATP hydrolysis is going to take place. And because it is a p-type ATPase, this means that the sodium potassium pump is going to get phosphorylated, and it specifically gets phosphorylated on an aspartic acid residue, on the pump itself. And that is what causes a conformational shift that allows the pump to actually transport these ions. And we'll be able to see that down below in our images.

And so over here on the left-hand side of our image, what we're showing is a summarized image of the sodium potassium pump. And so what you'll notice is the sodium potassium pump is this structure here that's embedded in the membrane. And, of course, we know that it is an ATPase, so it utilizes ATP and hydrolyzes ATP. And more specifically, it's a p-type ATPase, which means that it actually gets phosphorylated itself, during this process. And that's what we're showing here is the sodium potassium ion pump being phosphorylated. And so, what you can see here in this image is that there are 3 sodium ions that are going to get pumped to the outside of the cell. And again, on the inside of the cell, there's a low sodium concentration, that's again because the sodium ions are constantly getting pumped to the outside of the cell. And what you'll also notice is that there are 2 potassium ions getting pumped to the inside of the cell, and that's what creates a high concentration of potassium on the inside of the cell.

But how exactly does this sodium potassium pump work? Well, that's exactly what we're showing you guys over here on this right side of the image. And what you'll notice is that the sodium potassium pump really works in a cycle that starts here up at the top, makes its way all the way around, and then ends right back at the top where it started. And so the very first step here is that there are going to be 3 sodium ions that bind to the sodium potassium pump, and they bind from the inside of the cell. So they're binding, here to the inside of the sodium potassium pump.

Now the second step, as you can see, ATP hydrolysis is coming into play. And so ATP hydrolysis, the enzyme here, is going to hydrolyze ATP, and in the process of the ATP being hydrolyzed, an aspartic acid residue on the enzyme on the sodium potassium ion pump itself is going to get phosphorylated. And so here you can see there's an aspartic acid residue, you could even add that in here, that is being phosphorylated. Now in the third step, the phosphorylation is going to cause a conformational change that is going to export the 3 sodium ions that pumps. And so now the 3 sodium ions have been released to the outside.

And, again, that's what creates such a high concentration of sodium on the outside of the cell. And so, in the 4th step right here, what you'll notice is that the potassium ions, specifically 2 potassium ions, are going to bind to the extracellular side of the sodium potassium pump. And then in the 5th step here, the phosphate group that was attached is going to get removed, and so you can see that the phosphate group bond here is going to get hydrolyzed and removed from the sodium potassium pump. And so, the phosphate group is removed here. And in the, 6th step, the removal of this phosphate group causes another conformational change that imports the 2 potassium ions that originally bound. So you can see the 2 potassium ions that are released to the inside itself, and that is what creates such a high concentration of potassium on the inside of the cell.

And so, at this point, we have the sodium potassium pump return to its original position, and so it can continue to take 3 more sodium ions and repeat this entire process in a cycle. And the sodium potassium ion pump is a pump that is usually constantly working to establish this gradient of sodium high on the outside, low on the inside, and potassium high on the inside and low on the outside. And so this video here, concludes exactly how this sodium potassium ion pump works, and moving forward we'll be able to get some practice in our next couple of videos applying these concepts. So I'll see you guys in our next video.

Which of the following defines the type of transport by the sodium-potassium ATPase?

• A. Active transport through a symporter.
• B. Passive transport through a symporter.
• C. Active transport through an antiporter.
• D. Facilitated diffusion through a symporter.

Which of the following statements about the mechanism of the sodium-potassium ATPase is FALSE?

• A. It helps to create a transmembrane potential that is more negative on the inside and more positive on the outside.
• B. It pumps 3 Na+ ions out of the cell.
• C. It pumps 2 K+ ions into the cell.
• D. The ATPase is phosphorylated by ATP to transport of Na+ into the cell.
• E. All of the statements above are correct.

Which of the following shows the correct order of steps for the mechanism of the sodium-potassium ATPase?

I. 2 K+ Ions bind.
II. Phosphorylation of an Asp residue.
III. Conformational change releasing 3 Na+ ions outside the cell.
IV. 3 Na+ ions bind.
V. Release of the phosphate group.
VI. Conformational change releasing 2 K+ ions inside the cell.

• A. II, I, V, III, IV, VI.
• B. IV, II, III, I, V, VI.
• C. I, II, III, IV, V, VI.
• D. IV, II, I, III, V, VI.
• E. IV, III, I, II, VI, V.

Here’s what students ask on this topic:

What is the function of the Sodium-Potassium Ion Pump?

The Sodium-Potassium Ion Pump is a p-type ATPase that actively transports 3 sodium ions (Na⁺) out of the cell and 2 potassium ions (K⁺) into the cell. This process establishes an electrochemical gradient, which is crucial for maintaining the cell's membrane potential and various cellular functions. The pump relies on ATP hydrolysis, which phosphorylates an aspartic acid residue, causing conformational changes that facilitate the transport of these ions. By maintaining a high sodium concentration outside the cell and a high potassium concentration inside, the pump plays a vital role in processes such as nerve impulse transmission and muscle contraction.

How does the Sodium-Potassium Ion Pump work?

The Sodium-Potassium Ion Pump operates through a cycle involving several steps. First, 3 sodium ions bind to the pump from the inside of the cell. ATP is then hydrolyzed, phosphorylating an aspartic acid residue on the pump, causing a conformational change that exports the 3 sodium ions to the outside. Next, 2 potassium ions bind to the pump from the extracellular side. The phosphate group is then removed, causing another conformational change that imports the 2 potassium ions into the cell. This cycle continuously maintains high sodium concentration outside and high potassium concentration inside the cell.

Why is the Sodium-Potassium Ion Pump considered an antiport mechanism?

The Sodium-Potassium Ion Pump is considered an antiport mechanism because it transports sodium and potassium ions in opposite directions across the cell membrane. Specifically, it exports 3 sodium ions (Na⁺) out of the cell while importing 2 potassium ions (K⁺) into the cell. This bidirectional movement of ions is characteristic of antiporters, which move two or more different ions or molecules in opposite directions across a membrane.

What role does ATP play in the function of the Sodium-Potassium Ion Pump?

ATP plays a crucial role in the function of the Sodium-Potassium Ion Pump by providing the energy required for ion transport. During the pump's cycle, ATP is hydrolyzed, and the energy released from this reaction phosphorylates an aspartic acid residue on the pump. This phosphorylation induces a conformational change in the pump, allowing it to transport 3 sodium ions out of the cell and 2 potassium ions into the cell. Without ATP, the pump would not be able to perform these essential ion transport functions.

What is the significance of the electrochemical gradient established by the Sodium-Potassium Ion Pump?

The electrochemical gradient established by the Sodium-Potassium Ion Pump is vital for various cellular processes. This gradient, characterized by a high concentration of sodium ions outside the cell and a high concentration of potassium ions inside, is essential for maintaining the cell's membrane potential. This membrane potential is crucial for nerve impulse transmission, muscle contraction, and the regulation of cellular volume. Additionally, the gradient drives secondary active transport processes, where the movement of sodium ions back into the cell can be coupled with the transport of other molecules, such as glucose and amino acids.