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Name: ______________________
Date: _______________
Unit 3B Cell Membrane and Transport
NOTES
What is Cell Transport?
• Transport- the movement of materials between an organism and its _______________
• Cellular Transport- movement of materials into and out of a cell
• Materials move from the water based solution outside the cell (its environment) to the
water based solution inside the cell (the cytoplasm/cytosol), or vice versa
• Movement occurs across the __________ ______________________.
Solutions
• Solution- a type of mixture in which all components are evenly distributed
• Made of a
– Solvent- the substance that _________________________________________ (ex:
water is an excellent solvent)
– Solute- the substance that is ___________________
• Cells are surrounded by aqueous (_________________________) solutions and contain
an aqueous solution called cytoplasm
Cell Membranes
• Found surrounding all cells
• Made of a lipid bilayer
• Protects and supports the cell
• Regulates what comes in and out of the cell
Additional Notes/Summary:
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The Lipid Bilayer
• Has 2 layers of ___________________ (“Bi” means two)
• The layers are made up of molecules called __________________________
• Each phospholipid has a HYDROPHOBIC fatty acid tail region
• and a HYDROPHILIC head region
• HYDRO = means water
Hydrophilic head region
• PHOBIC = means afraid
• PHILIC = means loving
Hydrophobic tail region
• Because the fatty acid tails are “afraid” of water
(________________________), they turn towards each other so they won’t be exposed to
the cytoplasm, or the outside of the cell (both of which
contain water)
The Fluid Mosaic Model
• “Fluid” means moving
• “Mosaic” means many different things put together
– The Cell membrane contains different types of
molecules that can move around through the phospholipids
– Proteins in Membrane- allow for
_________________ of molecules
across the membrane
(ABUNDANT)
– Carbohydrates attached to proteins
and act as ___________ for
molecules to attach (NOT AS MANY)
Additional Notes/Summary:
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The Cell Membrane is Selectively Permeable (__________________________)
• Some substances can pass through the membrane and some cannot.
• The structure of the membrane and the proteins in it decide which molecules can enter
and which can leave.
How does a cell membrane help a cell maintain homeostasis?
– __________________________________________________________________
______________(the correct amount of each material inside and outside each cell)
2 Main Types of Transport
– passive -no energy needed from the cell
– active -energy from cell needed
1. Passive Transport
Diffusion- ___________________ move from an area of high concentration to an area of low
concentration to maintain equilibrium
– This is called movement “_____________ the concentration
gradient”
– A concentration gradient occurs where there are two
_________________ concentrations of a particle on either
side of the membrane
– Particles move straight through the lipid bilayer and no
energy is required. Ex: O2 and CO2
Additional Notes/Summary:
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Dynamic Equilibrium
Once diffusion has occurred and the cell has reached equilibrium, will the solutes stop moving
entirely?
• ________________________________________________________________________
________________________________________________________________________
• This is called dynamic equilibrium (dynamic means movement)
What happens if a molecule/solute is too large and/or not dissolvable in lipids?
Facilitated Diffusion
-the molecule/solute will go through a __________________ specific for that molecule.
-still goes from high to low concentration; so no energy needed.
Additional Notes/Summary:
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Water Can Use a Channel to get through the Cell Membrane
• Why does water have difficulty dissolving through the cell membrane by regular
diffusion?
• __________________________________________________
__________________________________________________
• Water needs the aquaporin protein channel to get through quickly!
• This is an example of facilitated diffusion
Osmosis
• The simple or facilitated diffusion of
__________________ molecules across a cell
membrane.
• From where there is more water (less solute) to where
there is less water (more solute)
• Depends upon the solvent/solute ratio
Solutions can be classified by the amount of solutes they contain compared to other solutions:
• HYPERTONIC: A solution with a _____________________ solute [concentration]
– (Ex: a solution with 20% sugar and 80% water is hypertonic to a solution of 10%
sugar and 90% water)
• HYPOTONIC: a solution with a _________________ solute concentration
– (Ex: a solution of 5% NaCl and 95% water is hypotonic to a solution of 20% NaCl
and 80% water)
• ISOTONIC: a solution with _______________ solute concentration with another solution
– (Ex: outside of a cell has 10% NaCl and the cytoplasm inside the cell also has 10%
NaCl)
Additional Notes/Summary:
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What happens to our cells if they are placed into a/an…
HypErtonic Solution• Since the [solute] is higher and the [water] is lower outside the cell, the cell attempts to
correct this by rushing water out (________________________________)
• Result= cell ___________________________
• E for water exiting the cell
HypOtonic Solution• Since the [solute] is lower and [water] is higher outside the cell, water rushes into the cell
(osmotic pressure)
• Result= _______________________________________________________
• O for the cell “opens the door” to let water in
Isotonic Solution• Since the solution has a similar [solute] and [water] as the cytoplasm, water moves in/out
at ____________________________
• Dynamic equilibrium
• In addition to osmosis, solutes can also be moving at the same time by diffusion or
facilitated diffusion
Osmosis in Plant and Animal Cells
What is different
about the plant and
animal cells during
the process of
osmosis?
________________
________________
________________
________________
Additional Notes/Summary:
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Practice
•
•
•
•
What is the solvent concentration of a solution with a 3% concentration of solute? ____
What is the solvent concentration of a solution with a 15% concentration of glucose? __
What is the solute concentration of a solution with 98% solvent? ________________
What is the solute concentration of a solution with 75% water? _________________
Fill in…
Conditions
Solute concentration in the
environment is equal to that in
the cell
Solute concentration in the
environment is greater than
the cell
Solute concentration in the
environment is less than the
cell
Additional Notes/Summary:
Water will…
Environment is…
(move in, out, or both?)
(Hypotonic, hypertonic, or isotonic?)
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Draw the following cells if placed in each type of environment:
(draw a shrunken cell, a swelled cell, or a cell of the same size)
2. Active Transport
• Cells move substances from ____________ concentrations to _________ concentrations
• This is also called moving substances “______ their concentration gradient”
• Energy is needed in the form of __________
Additional Notes/Summary:
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A. Molecular Active Transport
• Uses a _____________ in the cell membrane to carry the substance across
• Allows for a cell to purposely ________________ a molecule in a particular location
even when the forces of diffusion will want the molecule to move in the other direction
Example:
Sodium-Potassium
Pump
B. Bulk Transport (for large Molecules)
1. Some substances are too _______________ to pass through any of the pores, channels,
and pumps in the cell membrane
2. Or _____________________________ need to be transported into/out of the cell
3. Vesicles are produced by the membrane: pouches that are extensions of the cell
membrane that pinch off and surround
the substance
a. Endocytosis
• _________________________ large
particles (ingestion)
• 2 Types:
Pinocytosis- transports large amounts of ________________ solutes or liquids
Phagocytosis- transport of _________________ molecules or whole cells (ex. white blood cells
“eat” damaged cells)
Cell membrane surrounds the particles and _________________________ to bring the
materials into the cell using a ___________________.
Additional Notes/Summary:
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b. Exocytosis
• Reverse of endocytosis
• Materials to be ___________________ from the cell are taken into a vesicle
• The vesicle _________________ with the cell membrane and ___________________ the
materials from the cell (ex: releasing proteins)
• This is how wastes are removed from many cells
Additional Notes/Summary: