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Plant cells vs. Animal cells
Both types of cell have these: Only plant cells
have these:
Nucleus
Cytoplasm
Cell wall
Permanent
vacuole
1)
2)
3)
7)
6)
8)
Ribosomes
Chloroplasts
5) Mitochondria
4)
Cell
membrane
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How do substances enter
and leave cells?
(transport across boundaries)
• There are 3 processes:
Diffusion
Osmosis
Active transport
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Diffusion
• Diffusion is the movement of all particles
from a region of HIGH concentration TO
a region of LOW concentration…
…until the concentrations are equal – this is
called equilibrium
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Examples of Diffusion in
Biology
• Oxygen diffuses from the lungs into the blood.
•Oxygen diffuses out of the blood
into the cells for respiration.
•Carbon dioxide diffuses out of
blood capillaries into the lungs.
•Carbon dioxide diffuses into
leaves for photosynthesis.
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Question on diffusion.
• The drawing below shows four ways in which particles
may move in and out of an animal cell. The dots show the
concentration of particles (molecules)
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1. The cell is carrying out aerobic respiration (it
needs oxygen). Which arrow, A, B, C or D
represents:
• A) the movement of oxygen particles?
• B) the movement of carbon dioxide particles?
2. Name the process by which these gases move into
and out of the cell?
A
B
Diffusion
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Osmosis.
• OSMOSIS is a special kind of diffusion
• It refers to the diffusion of WATER.
• Water particles move from a region of HIGH water
concentration to a region of LOW water concentration.
• Through a partially permeable membrane.
• This membrane allows water particles to pass through
but stops large particles from passing through.
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Osmosis
• In animal and plant cells the cell membrane is a
partially permeable membrane
• Water will travel from a region of
HIGH water concentration to a
region of LOW water concentration
until the concentrations are equal.
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Osmosis is the diffusion of water across a
partially permeable membrane
Cell 1 Cell 2
Solute
Solute
Solute
Solute
Partially
permeable
membrane
water
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Two visking tubing ‘cells’ have been set up as shown below:
Experiment A has salt solution inside the Visking
tubing and water outside
Experiment B has water inside the Visking
tubing and salt solution outside.
WATER
SALT
SOLUTION
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• The Beakers will be examined after 30 minutes.
• Describe what you expect to see in each beaker at
the end of the experiment
• A
• B
The tubing will get bigger and firmer because
the water will enter the Visking tubing by
osmosis. The water concentration outside the
tubing is greater than that inside the tubing.
The tubing will get smaller and floppy
because the water will leave the Visking tubing
by osmosis. The water concentration inside
the tubing is greater than that outside the
tubing.
13. The effect of osmosis on animal
cells
• If there is a higher water concentration outside
the cell water will move in until the concentrations
are equal. If the concentration gradient is too
high the cell will expand and possibly burst.
• If there is a lower water concentration outside
the cell water will move out until the
concentrations are equal. If the concentration
gradient is too high the cell will shrivel and no
longer be able to carry out essential reactions.
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14. The effect of osmosis on plant
cells
• If there is a higher water concentration outside
the plant cell water will move in to the cell until
the concentrations are equal. The cell will not
burst as the cell wall protects it. The cell will
become turgid.
• If there is a lower water concentration outside
the plant cell water will move out of the cell until
the concentrations are equal. If the concentration
gradient is too high the cell membrane will move
away from the cell wall (plasmolysis), the cell will
become flaccid and the plant will wilt.
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15. The effects of osmosis on a red
blood cell and a plant cell
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Which way will the water go?
Pure Water Strong sugar
solution
Root hair cell Water in the soil
25% salt solution 50% salt solution
1% salt solution 0.1% salt solution
Strong sugar
solution
Distilled water
50% sugar solution 50% sugar solution
Partially
permeable
Membrane
17. Active Transport
• Active transport is a
little like downfall.
• Molecules are
‘grabbed’ and forced
through a membrane.
• Active transport
moves against the
concentration
gradient.
18. Active Transport
• Active Transport is
the movement of
particles from a low
concentration to a
high concentration.
• Active Transport
requires energy to
happen.
