Diffusion

Diffusion

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Vocabulary: Diffusion

Diffusion: molecules move from an area of high concentration to an area of low concentration.

Diffusion

Did you ever notice that that when a person farts, the person next to them notices first?

Diffusion doesn't just happen in liquids.

Molecules that cause odors diffuse through the air...whether the odor is your sibling's fart, or something delicious being cooked in the kitchen.

Diffusion is passive transport; it requires no energy.

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​Passive Transport

Video Segments

You will next watch two videos, answering questions about what you see and hear. The first video is the Amoeba Sisters' Diffusion. The second video shows you red blood cells under a microscope.

Multiple Choice

The movement of molecules traveling down its concentration gradient is

• diffusion

• active transport

• exocytosis

Multiple Choice

What happened to the methylene blue used to treat the fish?

• It stayed in the corner of the tank.

• Molecules spread from an area of high concentration to low concentration.

Multiple Choice

Once molecules have diffused, they stop moving.

• True

• False

Molecules are always in motion.

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They continue to move after they have reached equilibrium.

Note: In this case, equilibrium is a balance of molecules on either side of the membrane.

Factors that affect the speed of diffusion

• Type of solvent

• Type of molecules

• Temperature (diffusion speeds up in heat)

• Distance

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​Duplicate this text as many times as you would like.

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​Small molecules that can diffuse through a cell membrane

​Water - H₂O

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Oxygen - O₂

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Carbon Dioxide - CO₂

​Small molecules that can diffuse through a cell membrane

Multiple Choice

The process of diffusion uses no energy, so it is an example of

• active transport

• passive transport

Multiple Choice

In facilitated diffusion, a molecule passes through a

• carbohydrate membrane

• lipid channel

• protein channel

Multiple Select

Factors that are most likely to affect diffusion include (choose 3)

• characteristics of the solvent

• characteristics of the molecules

• latitude

• distance

• day of week

Multiple Choice

When temperature increases, the rate of diffusion generally

• speeds up

• slows down

Multiple Select

Molecules small enough to diffuse across a cell membrane include (choose 3)

• DNA

• water

• oxygen

• proteins

• carbon dioxide

​Solutions can be hypertonic, isotonic, or hypotonic to a cell.

Concentrations of solutions

Hypotonic solutions have a high concentration of water compared to the cell.

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In a hypotonic solution, cells can burst (explode).

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Hypotonic

Isotonic solutions have a concentration the same as the cell.

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In an isotonic solution, cells stay healthy.

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Isotonic

Hypertonic solutions have a high concentration of solute (salt, sugar) compared to the cell.

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In a hypotonic solution, cells can shrink.

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Hypertonic

Multiple Choice

The picture that best represents the blood cells in an hypertonic solution is

Multiple Choice

Which picture represents the blood cells of a healthy person, who is able to maintain homeostasis?

Human blood: salt concentration of 0.9%

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Seawater: salt concentration of about 3.5%

Fun Fact