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Facilitated Diffusion

Facilitated Diffusion

Author: Sophia Tutorial
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

In this lesson, you're going to learn about facilitated diffusion. Specifically, you will look at:

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

1. Facilitated Diffusion Process

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 without the use of ATP or cellular energy. Facilitated diffusion also 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 have molecules that would just be able to pass through the cell membrane. However, in facilitated diffusion, the molecules are passing through transporter proteins to get through the membrane. We use the term facilitated diffusion because the molecules need help getting through the membrane; the transporter proteins are facilitating the way that these molecules are getting through the cell membrane.

Big Idea

Facilitated diffusion is 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 is through 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 is 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 - from 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 an where there's 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 the 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 is through 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 means 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 the cell.

In endocytosis, the particles are 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. In exocytosis, you have a vesicle that's moving towards the plasma membrane, attaching to it, and then expelling whatever the contents are out of the cell; it's a means of moving larger particles either into or out of the cell.


Summary

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
Active Transport

Cell transport that uses energy in the form of ATP

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