Download Intro to Diffusion - Biology Fall Semester

Intro to Diffusion
Drill:
Would you rather stand in a
very crowded room, which
made it hard to move
through, or in a room that
was less crowded, which
made it easy to move
through?
Briefly explain.
Outcome:
Explain how diffusion
works.
Discuss the purpose of
diffusion in the body.
Draw the movement of
water/salt due to diffusion.
Cell Membrane
The cell
membrane is
flexible and
allows a
unicellular
organism to
move
2
Structure of the Cell
Membrane
3
Slide 1
What is Diffusion?
• Diffusion: The movement of molecules from
an area of high concentration to an area of
low concentration.
Slide 2
Diffusion
• The molecules will pass in or out of a cell
membrane.
• Always from high to low concentration
– Way to abbreviate: High Concentration  [High]
– Way to abbreviate: Low Concentration  [Low]
Slide 3
Diffusion: Salt Movement
• Ex: Which way would the
salt molecules move?
• Explain.
(use arrow to show movement)
– H2O =
– Salt =
Slide 4
Diffusion: Salt Movement
• Ex: Which way would the
salt molecules move?
• Explain.
(use arrow to show movement)
– H2O =
– Salt =
Slide 5
Diffusion: Equilibrium
• When molecules are equal they are considered to
be at equilibrium.
4 of each
– H2O =
– Salt =
4 of each
1
1
1
2
1
2
2
2
3
3
3
3
4
4
4
4
Slide 6
Diffusion Movement
• Kinetic E: The movement of molecules being
diffused across a membrane.
• The rate (speed) of this movement is
determined by the temperature and the size
of molecules.
Slide 7
Diffusion Movement
• Temperature
– Increasing the temp.
• Molecules diffuse faster
– Decreasing the temp.
• Molecules diffuse slower
Slide 8
Diffusion Movement
• Size of molecules
- Smaller molecules
•
Molecules diffuse faster
- Bigger molecules
•
Molecules diffuse slower
Slide 9
Recap Diffusion
• Molecules move from [high] to [low]
• Equilibrium is when all particles on both sides are
equal in number
• Kinetic E causes them to move randomly
• Temperature and Size changes rate of movement
Slide 10
Osmosis
• Osmosis: The movement of water across a
semipermeable membrane.
• The most important thing here is that:
– We are ONLY talking about the movement of WATER
Slide 11
Osmosis: Water Movement
• Diffusion occurs from an area of high [water]
(less solute) to an area of lower [water] (more
solute)
• Explain which way the
water molecules will move.
– H2O:
– Salt:
Slide 12
Direction of Osmosis
• Hypertonic
– Smaller amount of water outside the cell (more
solute outside)
– Water moves out of the cell
– Cell shrinks
Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
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16
Slide 13
Direction of Osmosis
• Hypotonic
– Less water inside the cell (solute is higher)
– Water moves in of the cell
– Cell grows and can burst
Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
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18
Slide 14
Direction of Osmosis
• Isotonic
– Water inside and outside the cell is equal
– Water moves in and out of the cell equally
– Cell stays the same
Cell in Isotonic Solution
10% NaCL
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
NO NET
MOVEMENT
What is the direction of water movement?
equilibrium
The cell is at _______________.
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20
Moves in
Moves out
Moves Out
Moves in/out
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Moves in/out
Moves in
21
Slide 15
Recap Osmosis
• Water molecules move from [high] to [low]
• Hypertonic:
• Hypotonic:
• Isotonic: