Download 1827: ROBERT BROWN DISCOVERED THAT POLLEN

Objective: 1)
Explain
Brownian
Motion as it
relates to
diffusion 2)
Define the 3
different types of
osmosis.
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1827: ROBERT BROWN DISCOVERED THAT
POLLEN GRAINS MOVED ON THEIR OWN
WHEN PLACED IN WATER
THIS RANDOM MOVEMENT OF PARTICLES
IS CALLED BROWNIAN MOTION.
BROWN’S EXPERIMENT WAS THE FIRST
EVIDENCE OF THE RANDOM MOTION OF
MOLECULES.
DIFFUSION: THE MOVEMENT OF
PARTICLES FROM AN AREA OF HIGHER
CONCENTRATION TO AN AREA OF LOWER
CONCENTRATION.
EXAMPLE: STINK BOMB SMELL SPREADING
TO COVER ENTIRE ROOM.
DYNAMIC EQUILIBRIUM: OCCURS
WHENTHE CONCENTRATION OF
PARTICLES ARE EVENLY DISTRIBUTED IN
AN AREA. EXAMPLE: EVERYBODY IN THE
ROOM SMELLS THE STINK!
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OSMOSIS: DIFFUSION OF WATER
THROUGH A SELECTIVELY
PERMEABLE MEMBRANE. SO WATER
MOVES FROM A HIGHER
CONCENTRATION TO A LOWER
CONCENTRATION.
MORE
WATER
LESS
WATER
MORE WATER
LESS WATER
EQUAL
CONCENTRATION
OF WATER
EQUAL
CONCENTRATION
OF WATER
HYPERTONIC
HYPOTONIC
ISOTONIC
SOLUTION
SOLUTION
SOLUTION
Objective: 1) Create a
graphic organizer that
illustrates the different
methods by which
substances cross the
cell membrane.
http://www.slimfilms.com/graphics/8cell.jpeg
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Crossing the Membrane
Many ions have difficulty passing through the cell
membrane because the inside of the membrane is nonpolar.
Why?
How to solve the ions’ problem: Go through the channel
protein doors called ion channels.
Ion Channels
1)All ion channels allow only one type of ion to pass.
2)Some ion channels resemble a tunnel that goes through
the cell membrane. It is open all of the time
3)Some ion channels resemble a tunnel with a “gate” on one
end that will only allow ions to pass when open.
Note: The inside of a cell has a slight negative
charge whereas the outside of the cell has a slight
positive charge.
How does this affect the rate of diffusion for the
following ions?
+ charge ions diffusing into the cell:
– charge ions diffusing into the cell:
+ charge ions diffusing out of the cell:
– charge ions diffusing out of the cell
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Facilitated Diffusion
Some substances use carrier proteins to
transport substances across a concentration
gradient.
Here is how it works:
Molecule binds to the carrier protein.
Carrier protein changes it shape to allow the
molecule to pass into the carrier protein.
The carrier protein releases the molecule on
the opposite side of the cell membrane.
Different proteins found in the cell membrane:
1. Channel Proteins: Used by water soluble substances
2. Transport Proteins: Uses energy (ATP) to move
material across the membrane.
3. Recognition Proteins: Recognizes other cells. Usually
have a short polysacharide chain attached to it,
extending out of the cell.
4. Receptor Proteins: Chemicals called hormones land
here to trigger the cell to do something.
5. Electron Transfer proteins: Pass electrons to other
proteins ( kind of like hot potato).
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Active vs. Passive Transport
Passive Transport
1) Particles move from a high concentration to a
low concentration.
2) Diffusion through membrane, channel, or
carrier protein.
3) No energy required.
Active Transport
1) Particles move from an area of lower
concentration to an area of higher concentration
(opposite of diffusion).
2) Active transport uses only special carrier
proteins.
3) Energy is needed in the form of ATP.
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Sodium Potassium Pump
What does it do?
This pump can transport 3 sodium ions out of the cell
and 2 potassium ions to the inside of the cell.
Problem: there is usually a high concentration of sodium
ions (Na + outside of the cell and a high concentration of
potassium (K+) inside the cell.
What do you do?
Answer: Active Transport.
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Why is the sodium-potassium pump
important?
1) Gets rid of Na + build up inside the cell.
Na + is toxic to the cell.
2) Maintains the correct concentration on
both sides of the membrane.
Endocytosis and Exocytosis
Endocytosis: the movement of a substance
into the cell by forming a vesicle.
Phagocytosis: “cell eating”
Pinocytosis: “cell drinking”.
Exocytosis: the movement of a substance by
vesicle out of the cell.
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