Transcript Transport Through the Cell Membrane

NOTE SHEET 8 – Transport
Through The Cell Membrane
What is cell transport?
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Cell Transport – when substances move
into or out of cells
In order to get into or out of the cell,
substances must pass through the cell
membrane
What is cell transport?
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Substances in a living
thing naturally move
from areas of high
concentration (where
there is a lot of that
substance) to areas of
low concentration
(where there is less of
that substance)
What are the 2 types of cell transport?
1. Passive Transport –
When substances
move in or out of cells
from areas of high
concentration to areas
of low concentration
Passive Transport
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The cell uses NO ENERGY in this
process, it happens naturally
Osmosis – the movement of
water from high to low
concentration
Diffusion – the movement of
any substance besides water
from high to low concentration
Osmosis and diffusion happen in
opposite directions
Passive Transport
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EX. If there is a lot of sodium outside of a cell, the
sodium moves into the cell by diffusion and water
moves out of the cell by osmosis
The Rime of the Ancient Mariner
By Samuel Taylor Coleridge (written in 1797-98)
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Water, water, every where,
And all the boards did shrink;
Water, water, every where,
Nor any drop to drink.
Salt-Cured Meat
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Meat or fish preserved or cured with salt
The only widely available method of preserving
food until the 19th century
Salt prevents the growth of bacteria by drawing
water out of bacteria cells by osmosis
Salted meat was a staple of the mariner's diet in
the Age of Sail. It was stored in barrels, and
often had to last for months spent out of sight
of land.
What are the 2 types of cell transport?
2. Active Transport –
When the cell uses
energy to move
substances in or out
from an area of low
concentration to an
area of high
concentration
Active Transport
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The cell must USE ENERGY because
substances do not naturally move from
low concentration to high concentration
The cell must also use energy to move
very large particles into or out of the cell
(endocytosis and exocytosis)
Another way to look at it…
Two Solutions Are
Separated By A
Selectively Permeable
Membrane
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Solution A has a high
concentration of
solute compared to
solution B
Solution B has a high
concentration of
water compared to
Solution A
So what happens?
Two Solutions Are
Separated By A
Selectively Permeable
Membrane
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Solute moves through
the membrane from
Solution A to Solution
B (Diffusion)
Solution A becomes
less concentrated,
Solution B becomes
more concentrated
Two Solutions Are
Separated By A
Selectively Permeable
Membrane
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Water moves through
the membrane from
Solution B to Solution
A (Osmosis)
Solution B becomes
more concentrated,
Solution A becomes
less concentrated
Two Solutions Are
Separated By A
Selectively Permeable
Membrane
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Dynamic equilibrium
is reached
Solute and Water
move back and forth
equally
What are the effects of passive
transport on cells?
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As the cell’s external environment
changes, passive transport causes water
and other substances to continuously
move into and out of cells
Turgor Pressure – pressure in a cell
caused by water
 Plant cells need the correct amount of
turgor pressure to stay rigid
Elodea Cells Before and After
Placement in a Hypertonic Solution
1.
What happens if there is a lower
concentration of substances outside the
cell?
1.
What happens if there is a lower
concentration of substances outside the
cell?
1.
What happens if there is a lower
concentration of substances outside the
cell?
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Type of Solution
Hypotonic
Turgor Pressure
High
Cell Shape
Swollen
Plant Cell - Hypotonic
2.
What happens if the concentration of
substances outside of the cell is equal to the
cytoplasm
2.
What happens if the concentration of
substances outside of the cell is equal to the
cytoplasm
2.
What happens if the concentration of
substances outside of the cell is equal to the
cytoplasm
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Type of Solution
Isotonic
Turgor Pressure
Normal
Cell Shape
Normal
Plant Cell - Isotonic
3.
What happens if there is a higher
concentration of substances outside of the
cell?
3.
What happens if there is a higher
concentration of substances outside of the
cell?
3.
What happens if there is a higher
concentration of substances outside of the
cell?
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Type of Solution
Hypertonic
Turgor Pressure
Low
Cell Shape
Shriveled
Plant Cell - Hypertonic
Animal Cells in Different Solutions
How do I figure out the direction of
passive transport?
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Look at the solution outside of the cell.
Compared to the cytoplasm, is the
concentration of substances higher, lower, or
equal?
Diffusion – Which way will the substances
move? (into cell, out of cell, in or out equally)
Osmosis – Which way will water move? (into
cell, out of cell, in or out equally)
To sum up…
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If there is a lot of substance outside a cell,
substance moves in (diffusion), water
moves out (osmosis) and the cell shrivels
If there is a lot of substance inside a cell,
substance moves out (diffusion), water
moves in (osmosis) and the cell swells
These processes happen naturally (passive
transport), if the cell wants the opposite to
happen, it must use energy (active
transport)
Cells need a steady supply
of energy for active
transport otherwise they
would not be able to adjust
to their environment
Cell Transport Animations
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http://www.northland.cc.mn.us/biology/Bi
ology1111/animations/transport1.swf