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3
1. Passive TransportA. Diffusion
B. Gradients
C. Osmosis
D. Hypotonic
E. Hypertonic
F. Isotonic
2. Active Transport (energy expenditure, direction)
A. Endocytosis (phagocytosis )
B. Exocytosis
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1. Define diffusion:
The movement of molecules from an
area in which they are highly
concentrated to an area in which they
are less concentrated.
2. Define gradient:
An increase or decrease in the amount
of a concentration observed in passing
from one point or moment to another.
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• Draw a diagram of an
example of diffusion we
saw in class.
Remember:
tea bag,
food coloring drops,
sugar cubes,
etc.
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• French botanist working with
plant cells between 1824 and
1830.
• He looked for cells in animals,
but was unable to find any.
• He also discovered and
named the phenomenon of
osmosis, which is the
passage of a liquid through a
semi-permeable membrane.
• First to carefully study
respiration and light sensitivity
in plants.
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• Surface area to volume ratio
• Concentration gradient
• Size of molecule(s)
• Same things effecting diffusion.
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• The surface of a cell (membrane) is where it exchanges
materials and its external environment.
• This surface must allow sufficient exchange to support the
contents of the cell.
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As an object increases in size its volume increases as the cube of its linear dimensions while surface area increases as the square.
This ratio limits how large cells can be.
These cubes illustrate the surface area to volume ratio of a small object is larger than that of a large object of similar shape.
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Cell Dimensions(cm)
Surface Area(cm2)
Volume(cm3)
RatioSurface area to Volume
1 2 x 2 x 2 (2x2x6) = 24 (23) = 8 24:8
2
3
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CellDimensions
(cm)Surface Area
(cm2)Volume(cm3)
RatioSurface area to
Volume
1 2 x 2 x 2(2x2x6) =
24(23) = 8
24:83
2 4 x 4 x 4(4 x 4 x6) =
96(43) = 64
96:641.5
3 8 x 8 x 8(8 x 8 x 6)
= 384(83) = 512
384:5120.75
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are
• Semi-permeable / Permeable (Selectively)
• Membranes regulate passage of material in and out of cell.
• Double layer of lipid with proteins scattered throughout
• Oxygen & Carbon Dioxide can dissolve in lipids
• Water cannot dissolve, must be passed through protein carrier
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• Some proteins actively use energy from the Adenosine Triphosphate (ATPs) in the cell.
• Proteins drag molecules from area of low concentration to areas of high concentration (work against diffusion).
• An example of this is the sodium/potassium pump.
Here the energy of a phosphate (shown in red) is used to exchange sodium atoms for potassium atoms.
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Diffusion of water through a semi-permeable membrane
• Water is 70-95% of living cells
• Cell has no control over osmosis, dependanton water concentration
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• This experiment demonstrates the process of osmosis.
• Water flows through a semi-permeable membrane into a sugar solution, diluting the solution.
• The sugar molecules cannot pass through the membrane, so the water outside remains pure.
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3 Solution Conditions• Isotonic — equal, the
same
• Hypotonic —under
• Hypertonic —above, over
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Solution
Typev
Concentration
Amount
Cell Results
Hypotonic
Water in cell is
high solution
surrounding cell
is low.
Cell will swell
Isotonic
Exactly the same
concentration of
water and
solution.
No change
Hypertoni
c
Water in cell less
than solution
surrounding cell.
Cell will shrivel
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Hypotonic Isotonic Hypertonic
"HYPO" means
less
"ISO" means the
same
"HYPER" means
more
There are less solute
(salt) molecules outside
the cell, since salt
sucks, water will move
into the cell.
The water will move
back in forth but it won't
have any result on the
overall amount of water
on either side.
There are more solute
(salt) molecules outside
the cell, which causes
the water to be sucked
in that direction.
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Two types of active transport
1. Endocytosis — endo means internal; within
— cyt means cell
2. Exocytosis — exo means external; from outside
— cyt means cell
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Involves moving material through the plasma
membrane and incorporation of the bulk
material into a vacuole.
a)Phagocytosis involves the
engulfing of solid materials.
b)Pinocytosis involves the engulfing
of liquid materials.
Endocytosis