Primary Active Membrane Transport: Videos & Practice Problems

Primary active transport is an energy-driven process that moves molecules against their concentration gradient, utilizing ATP hydrolysis. There are five main types of primary active transport ATPases: P-type ATPases transport cations like sodium and potassium; V-type ATPases acidify vesicles; F-type ATPases synthesize ATP in mitochondria; A-type ATPases transport anions in archaea; and ABC transporters move various solutes, including drugs. Understanding these ATPases is crucial for grasping cellular transport mechanisms and their roles in maintaining homeostasis.

Primary Active Membrane Transport

In this video, we're going to begin talking about primary active membrane transport. Now, recall from our previous lesson videos that active transport is an active or an energy-driven process that transports molecules against their concentration gradient from areas of low concentration to areas of high concentration. And really, there are 2 main types of active membrane transport that you guys should know. The first type is primary active transport, and the second type is secondary active transport. Now, for now and in our next couple of videos, we're going to focus mainly on primary active transport. But later in our course, we'll talk more about secondary active transport.

Primary active transport is usually what people refer to when they just say the words "active transport." And so primary active transport is going to be directly driven by an energy source, such as the ATP hydrolysis. Now secondary active transport, which we'll talk more about later in our course, is not directly driven by ATP hydrolysis. Instead, secondary active transport is directly driven by an electrochemical ion gradient that is built up over time.

Down below in our image, what you'll notice is we have our map of the lesson on membrane transport. We've already talked about passive transport here, and we're now starting to focus more on active transport. We're specifically going to talk more about primary active transport moving forward when we talk about the 5 types of ATPases and then specific types of these ATPases. Later, we will focus more on secondary active transport.

Here in these two boxes, what you'll notice in the left one, you can see ATP hydrolysis is directly involved in this process of pumping a molecule from low concentration to high concentration. On the right-hand side, notice that there is no ATP molecule anywhere to be found over here, and so, we do have the transport of a molecule, the green one over here, from low concentration to high concentration. This green arrow represents a type of active transport. But because there is no ATP involved directly, this is going to be secondary active transport. And again, we'll talk a lot more about this later in our course, but it's going to be driven by the flow of another chemical down its electrochemical gradient.

For now, this here concludes our introduction to primary active transport. Moving forward in our lesson, we're going to talk about the 5 types of ATPases, which are all driving primary active transport. And so I'll see you guys in our next video.

Primary Active Membrane Transport

In this video, we're going to talk about the types of primary active transport ATPases. Now ATPase ends in the letters "ase," which we know indicates that it is an enzyme, and so ATPases are enzymes that utilize or hydrolyze ATP. And so primary active transport ATPases are ATPases that perform primary active transport and transport molecules across a membrane against their concentration gradient. And again, these primary active transport ATPases, they're defined as transporters that hydrolyze, to no surprise, ATP, in order to pump molecules against their concentration gradients from areas of low concentration to areas of high concentration across the membrane. Now really there are 5 main types of primary active transport ATPases that you guys should know. And notice down below in our table, we were going to discuss each of those 5 different types. Notice in the first column what we have is the ATPase type, and in the second column what we have is the function of that ATPase. And notice that in each of the functions, we have a letter that is bolded to help remind you guys of what exactly the type of ATPase it is. And so, for example, if we take a look at this first type of ATPase here, what you'll notice is that its function is to transport cations such as sodium and potassium cations, and specifically, what defines them is that they are reversibly phosphorylated by ATP. And so, because these guys are reversibly phosphorylated, the phosphorylated part reminds you that this is the P-type ATPase. And over here, what we have is an image of a transporter of an ATPase, and one thing to note is that it is specifically phosphorylated itself, and it creates a phosphorylated intermediate. And so really, this is what defines the P-type ATPase. Now moving forward in our course, we're going to talk about 2 specific types of P-type ATPases, and those are the sodium-potassium pump or the sodium-potassium ATPase and the sarco/endoplasmic reticulum calcium transport ATPase or the calcium ion pump. And again, we'll talk about those 2 types of P-type ATPases later in our course. But moving on here to the second type of ATPase, what we have is their function is to transport hydrogen ions to acidify intracellular regions of vesicles. And really, the "V" here in vesicles reminds us that this is going to be the V-type ATPase. And so lysosomes are, recall, vesicles that are found in animal cells that are responsible for recycling materials within the cell. And so V-type ATPases play a big role in forming lysosomes and the acidic environment within lysosomes. Now moving on to our third type of ATPase, their function is to transport free hydrogen ions across mitochondrial membranes producing ATP. And so, these guys actually function in the reverse way where, instead of hydrolyzing ATP, they actually function to produce ATP, and so they're also known as ATP synthases. And again, these guys are important in mitochondrial membranes, and so we have the mitochondria over here saying, "You're free," just to remind you that these are the F-type ATPases. And so, we'll talk more about F-type ATPases much later in our course when we talk about mitochondrial function. But for now, let's move on to our 4th type of ATPase, which is the A-type ATPase, and that's because its function is to transport anions across archaeal cell membranes. And over here, what we have is an image of an archaeal cell. And, again, you can see these anions that are on the outside, reminding us that this transports anions across archaeal cell membranes. Now last but not least, our 5th type of ATPase is actually the ABC (ATP Binding Cassette) transporters. And that's because this ATPase, its function is to transport many types of solutes, including drugs and toxins, and it does that by utilizing an ATP binding cassette, which we'll talk more about exactly what this is later in our course as well. But for now, what you can see is over here what we have is some kind of drug or toxin, and you can see that it's being canceled out because these ABC transporters will pump these drugs so that they do not have an effect within cells. And again, we'll talk more about this idea later in our course. And then, of course, we have this ABC ATP mixtape over here to remind you of the ATP binding cassette. And so, this here concludes our introduction to the types of primary active transport ATPases, and we'll be able to get some practice applying these concepts as we move forward in our course. So, I'll see you guys in our next video.

What initial effect would the loss of ATP production have on a cell's ability to transport substances?

• A. The cell would only be able to transport substances using active transport.
• B. The cell would be able to transport substances using active and passive transport.
• C. The cell would only be able to transport substances using passive diffusion.
• D. The transport of all substances across the membrane would stop.

Answer: (C)

What is the main difference between active transport and facilitated transport?

• A. Facilitated transport uses proteins, but active transport does not.
• B. Active transport uses ATP to power transport, but facilitated transport does not.
• C. Active transport occurs across the plasma membrane, but facilitated transport does not.
• D. Active transport moves a substance from higher concentration low concentration, while facilitated transport moves a substance from low concentration to high concentration.
• E. All of the above are differences between active and facilitated transport.

Answer: (B)

P-type ATPases ________.

• A. Transport phosphate against its concentration gradient.
• B. Undergo reversible phosphorylation by ATP hydrolysis.
• C. Transport anions only.
• D. Transports phosphate with its concentration gradient.
• E. Phosphorylates cations so they can be transported into the cell.

Answer: (B)

Here’s what students ask on this topic:

What is primary active transport and how does it differ from secondary active transport?

Primary active transport is an energy-driven process that moves molecules against their concentration gradient, utilizing ATP hydrolysis. This means it directly uses energy from ATP to transport molecules from areas of low concentration to high concentration. In contrast, secondary active transport does not directly use ATP. Instead, it relies on the electrochemical gradient created by primary active transport. This gradient drives the movement of other molecules against their concentration gradient. Essentially, primary active transport sets up the conditions that secondary active transport exploits.

What are the five main types of primary active transport ATPases?

The five main types of primary active transport ATPases are:

• P-type ATPases: Transport cations like sodium (Na⁺) and potassium (K⁺), and are reversibly phosphorylated by ATP.
• V-type ATPases: Acidify intracellular vesicles, such as lysosomes, by transporting hydrogen ions (H⁺).
• F-type ATPases: Synthesize ATP in mitochondria by transporting hydrogen ions (H⁺).
• A-type ATPases: Transport anions across archaeal cell membranes.
• ABC transporters: Move various solutes, including drugs and toxins, using an ATP-binding cassette.

How does the sodium-potassium pump (Na⁺/K⁺ ATPase) function in primary active transport?

The sodium-potassium pump (Na⁺/K⁺ ATPase) is a P-type ATPase that maintains cellular homeostasis by transporting sodium (Na⁺) and potassium (K⁺) ions across the cell membrane. It uses ATP to pump three Na⁺ ions out of the cell and two K⁺ ions into the cell, against their respective concentration gradients. This process is crucial for maintaining the electrochemical gradient, which is essential for various cellular functions, including nerve impulse transmission and muscle contraction.

What role do V-type ATPases play in cellular function?

V-type ATPases are responsible for acidifying intracellular vesicles, such as lysosomes, by transporting hydrogen ions (H⁺) into these vesicles. This acidification is crucial for the proper functioning of lysosomes, which are involved in recycling cellular materials and breaking down waste products. By maintaining an acidic environment, V-type ATPases ensure that lysosomal enzymes are active and can effectively degrade macromolecules.

What is the function of ABC transporters in primary active transport?

ABC transporters (ATP-binding cassette transporters) are a type of primary active transport ATPase that move a wide variety of solutes, including drugs, toxins, and lipids, across cellular membranes. They utilize the energy from ATP hydrolysis to transport these molecules against their concentration gradients. ABC transporters play a critical role in processes such as drug resistance, lipid transport, and the removal of toxic substances from cells.