Diffusion

The cytoplasm consists many different substances dissolved in water. These particles move from areas of high concentration to areas of low concentration.

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This is called diffusion.​

Module 3B: Cell Transport & Processes

Passive Transport

Diffusion

Molecules will move across the cell membrane until equilibrium is reached. Equilibrium is where concentrations are equal on both sides.

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Diffusion is the movement of random molecular movements and does not require the use of energy (ATP).

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Molecule movement that does not require energy is called passive transport.​

Module 3B: Cell Transport & Processes

Passive Transport

Facilitated Diffusion

Some molecules (such as charged ions & large molecules like glucose) cannot cross the cell membrane. Instead they use channels (proteins inside of the cell membrane) to let them pass.

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The movement of these molecules using special protein channels is known as facilitated diffusion. Although it is fast & specific, facilitated diffusion is still passive transport.

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No energy (ATP) is required for this process.​

Module 3B: Cell Transport & Processes

Passive Transport