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Movement In and Out of
Cells
Chapter 2
1. Diffusion
2. Osmosis
3. Active Transport
1. Diffusion
 The net movement of molecules from a region of their
higher concentration to a region of their lower
concentration along a concentration gradient, as a result
of their random movement.
 When they can move freely, particles tend to spread
themselves out as evenly as possible.
 Examples:
Plant cells: Gas exchange
Plant cells: Flowers
Animal cells: Gas exchange
Animal cells: Digestion
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Example: Plant Cell-Gas Exchange
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 Carbon dioxide diffuses into the leaves through the stomata
from a high concentration to a low concentration along the
concentration gradient.
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 Oxygen diffuses out of the leaves through the stomata from
a high concentration to a low concentration along the
concentration gradient.
Example: Plant Cell-Flowers
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 The scent from flowers diffuse from a high concentration to
a low concentration along the concentration gradient into
the air around them, which stimulate receptors in the bee’s
body.
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Example: Animal Cell-Gas Exchange
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 Oxygen diffuses into of the cell from a high concentration to
a low concentration along the concentration gradient.
 Carbon dioxide diffuses out of the cell from a high
concentration to a low concentration along the concentration
gradient.
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Example: Animal Cell-Digestion
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 Food diffuses out of the ileum (small intestine) during
digestion from a high concentration to a low concentration
along the concentration gradient.
1.
2. Osmosis
 The diffusion of water molecules from a region of their
higher concentration (dilute solution) to a region of their
lower concentration (concentrated solution), through a
partially permeable membrane.
 The diffusion of water molecules from a region of their
high water potential to a region of their low water
potential, along the water potential gradient.
 Dilute Solution: high water potential:
• More solvent (water)
• Less solute (sugar/salt)
 Concentrated Solution: low water potential:
• Less solvent (water)
• More solute (sugar/salt)
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Animal cell: Dilute solution
Plant cell: Dilute solution
Animal cell: Concentrated solution
Plant cell: Concentrated solution
Osmosis in
Animal Cells:
Dilute solution
 Dilute solution: pure water:
high concentration
 Concentrated solution:
cytoplasm: low concentration
 More concentrated solution
inside the cytoplasm
 Less concentrated solution in
the pure water
 Water diffuses into the cell
through the partially
permeable cell surface
membrane.
 Water diffuses from a high
concentration (dilute
solution: pure water) to a
low concentration
(concentrated solution:
cytoplasm) along the
concentration gradient
through the partially
permeable cell surface
membrane
2.
Osmosis in
Animal Cells:
Concentrated solution
 Dilute solution: cytoplasm:
high concentration
 Concentrated solution:
outside cytoplasm: low
concentration
 Water diffuses out of the cell
through the partially
permeable cell surface
membrane.
 Water diffuses from a high
concentration (dilute
solution: cytoplasm) to a low
concentration (concentrated
solution: outside cytoplasm)
along the concentration
gradient through the partially
permeable cell surface
membrane
2.
Osmosis in
Plant Cells:
Dilute solution
 Dilute solution: pure water:
high concentration
 Concentrated solution:
cytoplasm: low concentration
 More concentrated solution
inside the cytoplasm
 Less concentrated solution in
the pure water
 Water diffuses into the cell
through the partially
permeable cell surface
membrane.
 Water diffuses from a high
concentration (dilute
solution: pure water) to a
low concentration
(concentrated solution:
cytoplasm) along the
concentration gradient
through the partially
permeable cell surface
membrane
 The cell swells and becomes
turgid.
2.
Osmosis in
Plant Cells:
Concentrated solution
 Dilute solution: cytoplasm:
high concentration
 Concentrated solution:
outside cytoplasm: low
concentration
 Water diffuses into the cell
through the partially
permeable cell surface
membrane.
 Water diffuses from a high
concentration (dilute
solution: cytoplasm to a low
concentration (concentrated
solution: outside cytoplasm)
along the concentration
gradient through the partially
permeable cell surface
membrane
 The cell shrinks and becomes
flaccid.
2.
 The cell plasmolysis: the cell
membrane detaches from the
cell wall.
3. Active Transport
 The movement of ions in or out of a cell through a cell
membrane, from a region of their lower concentration o
a region of their lower concentration against their
concentration gradient, using energy released during
respiration.
 Cell membranes contain carrier proteins
Active Transport in Plants
Active Transport in Animals
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Active Transport: Root hair cells
Vacuole
soil particles
Cell membrane
with cell wall
Minerals and Water absorbed
 The movement of nitrate ions into a root hair cell through
the cell membrane, from a region of their lower
concentration to a region of their higher concentration
against their concentration gradient, using energy released
during respiration.
3.
Active Transport:
Small intestine
 The movement of
glucose into cells of villi
through the cell
membrane, from a
region of their lower
concentration to a region
of their higher
concentration against
their concentration
gradient, using energy
released during
respiration.
3.