MYP Biology Diffusion Notes

How Does Diffusion Actually Move Substances Without Energy?

Definition

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration, down a concentration gradient, as a result of random movement.

Diffusion is a passive process, it doesn't require energy input from the cell (no ATP needed).

It works because of the concentration gradient:

More particles on one side = more random movement on that side.
More movement = more particles moving outward.
Fewer particles on the other side = fewer particles moving back.
Net movement is therefore from high to low concentration.

This will continue until equilibrium is reached (equal concentration everywhere).

Once equilibrium is reached, the concentration gradient will no longer exist.

Tip

Diffusion doesn't mean all particles move in one direction.
Individual particles will still move randomly in all directions.
It's just the case that more will move from high to low than the reverse.

Analogy

Imagine two rooms connected by a door.
Room A has 100 people, Room B has 10 people.
People walk randomly through the door in both directions, but because Room A is more crowded, more people happen to walk from A to B than from B to A.
Eventually, both rooms have 55 people.
No one forced anyone to move - it just happened through random movement.

Common Mistake

"Passive" doesn't mean slow.
Diffusion can be very fast over short distances - oxygen diffuses from your lungs to your blood in less than a second.

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Note

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Tip

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Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

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Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

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Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
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MYP Biology Diffusion Notes

MYP Biology Diffusion Notes

How Does Diffusion Actually Move Substances Without Energy?

Why Is Diffusion Fast in Some Places and Slow in Others?

Concentration gradient

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Unlock the rest of this chapter with a free account

How Does Diffusion Actually Move Substances Without Energy?

Why Is Diffusion Fast in Some Places and Slow in Others?

Concentration gradient

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MYP Biology Diffusion Notes

Cells7 subtopics

Organisms7 subtopics

Processes10 subtopics

Metabolism4 subtopics

Evolution7 subtopics

Interactions with environment6 subtopics

Interactions between organisms5 subtopics

Human interactions with environments3 subtopics

Biotechnology3 subtopics

MYP Biology Diffusion Notes

Cells7 subtopics

Organisms7 subtopics

Processes10 subtopics

Metabolism4 subtopics

Evolution7 subtopics

Interactions with environment6 subtopics

Interactions between organisms5 subtopics

Human interactions with environments3 subtopics

Biotechnology3 subtopics

How Does Diffusion Actually Move Substances Without Energy?

Why Is Diffusion Fast in Some Places and Slow in Others?

Concentration gradient

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

How Does Diffusion Actually Move Substances Without Energy?

Why Is Diffusion Fast in Some Places and Slow in Others?

Concentration gradient

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account