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Facilitated Diffusion

Facilitated Diffusion

Description:

This lesson will describe how transport proteins in the cell membrane allow solutes to cross the cell membrane without the use of ATP.

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Tutorial

What's Covered

Hello, I hope you are excited to learn about facilitated diffusion today. Specifically, you are going to learn about

  1. Facilitated Diffusion Process
  2. Active Transport
  3. Sodium Potassium Pumps
  4. Endocytosis & Exocytosis

1. Facilitated Diffusion Process

So to start off, facilitated diffusion is a type of passive transport.

Terms to Know

Facilitated Diffusion

Diffusion that uses transport proteins proteins to move molecules across a membrane

Passive Transport

A form of cell transport that does not require energy in the form of ATP

If you think back to osmosis and diffusion, passive transport is just a way to transport molecules across a cell membrane that does not require the use of ATP or cellular energy; so facilitated diffusion does not require cellular energy.

Facilitated diffusion uses transport proteins to transport molecules across a cell membrane.

Term to Know

Transport Proteins

Proteins in the cell membrane that move molecules across the membrane from low to high concentration by using energy in the form of ATP

In regular diffusion you would have molecules that would just be able to pass through the cell membrane. However, in facilitated diffusion the difference is you still have molecules passing through the membrane but they're passing through transporter proteins to get through the membrane. They need help to get through the membrane, so it's called facilitated diffusion because these transporter proteins are facilitating the way that these molecules are getting through the cell membrane.

Big Idea

That's facilitated diffusion, the use of transport proteins to move molecules across the cell membrane without the use of ATP.


2. Active Transport

Another way that molecules can get across a cell membrane include active transport. Active transport is when a molecule is moving across a cell membrane but requires the use of ATP. Unlike facilitated diffusion, diffusion, and osmosis active transport is using ATP to move molecules across a cell membrane.

Term to Know

Active Transport

Cell transport that uses energy in the form of ATP


3. Sodium Potassium Pumps

A good example of this are sodium potassium pumps. Sodium potassium pumps are moving sodium and potassium ions against their concentration gradient. Think back again to facilitated diffusion, diffusion, and osmosis. You’re moving from an area of high concentration to an area of low concentration, so where there's a lot to where there are fewer; so ATP isn't needed.

In active transport, you’re moving against the concentration gradient which means you're moving from an area where there's a low concentration to where there is a high concentration. Since it's moving against what is natural, it's going to require energy from the cell to push it in that direction.

The reason for this is because by moving against their gradient it's producing an electrochemical gradient that allows action potentials for neurons or muscle cells to be produced, which is necessary.


4. Endocytosis & Exocytosis

Another type of active transport besides sodium potassium pumps is endocytosis and exocytosis; this is another way to move molecules across the plasma membrane. Endocytosis and exocytosis are used to move larger particles that wouldn't be able to move through on their own.

Hint

Endocytosis means moving molecules into the cell, whereas exocytosis is moving them out. Those prefixes should help you remember what each process is responsible for. Endo- is moving in. Exo- is moving out or exiting out of the cell.

Basically what happens in endocytosis is you have the particles on the outside of the cell. The cell membrane will start to form this little vesicle and then that vesicle will pinch off and move those particles into the cell. Whereas in exocytosis, you have a vesicle that's moving towards the plasma membrane, attaches to it, and then expels whatever the contents are out of the cell; so it's a means of moving larger particles either into or out of the cell.


Summary

So this lesson has been a brief overview on the process of facilitated diffusion, as well as active transport. Specifically, you learned about two types of active transport processes: sodium potassium pumps and endocytosis & exocytosis.

Keep up the learning and have a great day!

Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Facilitated Diffusion

    Diffusion that uses transport proteins proteins to move molecules across a membrane

  • Passive Transport

    A form of cell transport that does not require energy in the form of ATP

  • Transport Proteins

    Proteins in the cell membrane that move molecules across the membrane from low to high concentration by using energy in the form of ATP

  • Active Transport

    Cell transport that uses energy in the form of ATP