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Crossing Membranes Passive Processes
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Crossing Membranes 1  Passive Processes

Crossing Membranes 1 Passive Processes

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Diffusion

Diffusion

The After Shave Man

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Diffusion in Air

Diffusion in Air

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Diffusion in water

Diffusion in water

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What is diffusion? (definition)

What is diffusion? (definition)

Diffusion is the movement of molecules (or ions) from a region of high concentration to a region of lower concentration until they are spread out evenly

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Example 1:Diffusion in the Alveoli: O2 diffusing into the blood and CO2 diffusing out of the blood

Example 1:Diffusion in the Alveoli: O2 diffusing into the blood and CO2 diffusing out of the blood

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Example 2: Some digested food diffuses across the gut wall into the blood

Example 2: Some digested food diffuses across the gut wall into the blood

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What affects the rate of diffusion?

What affects the rate of diffusion?

Concentration gradient: The greater the difference in the concentration of a substance in two areas, the faster the rate of diffusion

The rate of diffusion is directly proportional to the concentration gradient

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What affects the rate of diffusion?

What affects the rate of diffusion?

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Small particles tend to diffuse faster than larger ones

Small particles tend to diffuse faster than larger ones

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Diffusion takes place more quickly through thin membranes (e.g. exchange of gases through the alveolar wall)

Diffusion takes place more quickly through thin membranes (e.g. exchange of gases through the alveolar wall)

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The larger the surface area the higher the rate of diffusion (e.g. in gases diffusing into/out of leaves)

The larger the surface area the higher the rate of diffusion (e.g. in gases diffusing into/out of leaves)

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The shorter the distance, the faster the rate of diffusion

The shorter the distance, the faster the rate of diffusion

An increase in temperature

increases the rate of diffusion

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Facilitated Diffusion

Facilitated Diffusion

Faster movement

Cell membrane proteins used

Channel proteins

Carrier proteins

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Channel Proteins facilitate the diffusion of Ions

Channel Proteins facilitate the diffusion of Ions

Na+

K+

Ca2+

Cl-

Why can ions not diffuse freely across the membrane?

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