Passive Transport vs. Active Transport

First of all, do you understand the difference between active transport and passive transport?

Hmm. Both refer to methods of transportation.

Yes. Passive transport refers to transportation methods that do not require energy (ATP) and move from an area of higher concentration to lower concentration.

And active transport, on the other hand, is a transportation method that requires energy (ATP) and moves substances from an area of lower concentration to higher concentration.

Hmm. As a commonly used example, let's consider a hill.

Following the concentration gradient, moving from a higher concentration to a lower concentration requires no energy, and this is called passive transport.

Moving against the concentration gradient, from a lower concentration to a higher concentration, requires energy, and this is known as active transport, more or less.

Hmm. Let's start by explaining passive transport first.

Let's start by explaining passive transport.

So, here's the scenario: Cellnosuke's friend has a video they want to send. If it were up to you, would you send this video through "Isosta" or "Loin"?

Which one would you use?

(Young people these days...)

Alright then. What if "Isosta" could send the video without worrying about speed limits? What would you do in that case?

That's right.

What I want you to understand here is that in this example,

Isosta incurs no cost, or in other words, requires no energy (ATP) to send the video.

Similarly, in the human body, there are transportation methods that don't require energy (ATP).

We call that passive transport.

Specifically, diffusion, osmosis, and filtration fall under passive transport.

You don't have to think of it as too complicated.

Diffusion, for example, is the phenomenon where milk added to coffee spreads throughout over time.

Osmosis has been explained previously. For more details, tap here to refer to the previous lecture.

Very well. To sum it up, these are all considered passive transport.

Great. Now, let's move on to the explanation of active transport.

Active transport is a method of transporting substances that requires energy (ATP).

In the example of video transmission we discussed earlier, both "Loin" and "Twipper" require energy (ATP), making it active transport.

While passive transport moves from areas of higher concentration to lower concentration,

active transport involves moving from areas of lower concentration to higher concentration, just like climbing uphill.

One crucial concept to grasp in active transport is the sodium pump.

Although the terminology may sound complex, think of it as a gate embedded in the cell membrane.

Yes, it is. Have you ever been told to consume more salt, especially during hot weather?

Well, in both our bodies and the external environment, there are inorganic salts, or better known as minerals.

Rather than calling them inorganic salts, you can think of them as minerals.

Indeed. Consuming salt is a way to replenish minerals in your body.

That's a good question.

The answer is to keep our bodies moving.

Yes, it is. When cells first move, they generate electricity.

And to generate that electricity, a large amount of sodium rushes into the cell from the outside.

Indeed, it is. However, without this movement of sodium, cells cannot function.

In other words, it's crucial for life.

The problem arises afterward. After nerve cells have worked, they must return the sodium to its original location outside the cell.

However, sodium, being a mineral, won't move on its own.

So, if nothing is done, it will remain inside the cell.

What's not good here is that if this continues, there won't be enough sodium for the next cell movement.

In other words, not moving sodium out would impact life.

Indeed. And that's where the sodium pump embedded in the cell membrane comes into play.

The sodium pump works to move sodium from inside the cell to the outside.

So, sodium passes through this gate called the sodium pump and returns to the outside of the cell.

Strictly speaking, when sodium exits, it also brings potassium back into the cell, but you don't need to worry about that for now.

Now, let's get back to active transport.

When sodium is moved outside, it requires energy (ATP).

I know it's been a lengthy discussion, but all you need to understand here is that the sodium pump is an example of active transport.

That's right. I want you to remember the sodium pump as a transport mechanism, including for future study materials.

Finally, there's endocytosis, which we discussed in the previous lecture.

And there are two types of exocytosis that also fall under active transport.

You can tap on each speech bubble to access the lecture, so if you forget something, be sure to check them.

Today's lecture had more information than usual, so let's conclude today's lesson.

First, the difference between passive transport and active transport lies in whether or not they require energy (ATP).

Representative examples of passive transport include diffusion, osmosis, and filtration.

On the other hand, I listed sodium pumps, endocytosis, and exocytosis as representative examples of active transport.

That's right. However, just by remembering these examples, your understanding of physiology will deepen in the future.

So, make sure not to neglect reviewing them.

With that, let's conclude today's lecture.

Finally, let's solve a problem.