Transcript Cell Transport Notes

7-3 Cell Boundaries
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7-3 Cell Boundaries
All cells are surrounded by a thin, flexible
barrier known as the cell membrane.
Many cells also produce a strong supporting
layer around the membrane known as a cell
wall.
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7-3 Cell Boundaries
Cell Membrane
Cell Membrane
The cell membrane regulates what enters
and leaves the cell and also provides
protection and support.
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Cell Membrane
Cell Membrane
Outside of
cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside of cell
(cytoplasm)
Protein
channel
Lipid bilayer
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7-3 Cell Boundaries
Cell Walls
What is the main function of the cell wall?
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7-3 Cell Boundaries
Cell Walls
Cell Wall
Cell walls are found in plants, algae, fungi, and
many prokaryotes.
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
Measuring Concentration
A solution is a mixture of two or more substances.
The substances dissolved in the solution are called
solutes.
The concentration of a solution is the mass of
solute in a given volume of solution, or
mass/volume.
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
What happens during diffusion?
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
Diffusion
Particles in a solution tend to move from an area
where they are more concentrated to an area
where they are less concentrated.
This process is called diffusion.
When the concentration of the solute is the same
throughout a system, the system has reached
equilibrium.
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Diffusion Through Cell Boundaries
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7-3 Cell Boundaries
Osmosis
What is osmosis?
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Osmosis
Osmosis
Osmosis is the diffusion of water through a
selectively permeable membrane.
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Osmosis
How Osmosis Works
Dilute sugar
solution
(Water more
concentrated)
Concentrated
sugar solution
(Water less
concentrated)
Sugar
molecules
Selectively
permeable
membrane
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Movement of
water
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Water tends to diffuse from a highly concentrated
region to a less concentrated region.
If you compare two solutions, three terms can be
used to describe the concentrations:
Hypertonic– surrounding solution is MORE
concentrated than interior of cell – water moves out
of the cell.
• hypotonic - surrounding solution is LESS
concentrated than interior of cell – water moves
into of the cell
• isotonic - surrounding solution is EQUALLY
concentrated to the interior of cell – Water moves
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both in and out but no net gain or loss
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Osmosis
• Diffusion of water
across a
membrane
• Moves from HIGH
water potential
(low solute) to
LOW water
potential (high
solute)
Diffusion across a membrane
Semipermeable
membrane
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Osmosis
Osmotic Pressure
Osmosis exerts a pressure known as osmotic
pressure on the hypertonic side of a selectively
permeable membrane.
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7-3 Cell Boundaries
Cell in Isotonic Solution
10% NaCL
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
NO NET
MOVEMEN
T
What is the direction of water movement?
equilibrium
The cell is at _______________.
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Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
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Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
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7-3 Cell Boundaries
Cells in Solutions
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Isotonic Solution
NO NET
MOVEMENT OF
H2O (equal
amounts entering
& leaving)
Hypotonic
Solution
CYTOLYSIS
Hypertonic
Solution
PLASMOLYSIS
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Cytolysis & Plasmolysis
Cytolysis
Plasmolysis
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Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
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hypotonic
hypertonic
hypertonic
isotonic
isotonic
hypotonic
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Types of Transport Proteins
• Channel proteins are embedded
in the cell membrane & have a
pore for materials to cross
• Carrier proteins can change
shape to move material from
one side of the membrane to
the other
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Facilitated Diffusion
Molecules will randomly move through the
pores in Channel Proteins.
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Facilitated Diffusion
• Some Carrier
proteins do not
extend through
the membrane.
• They bond and
drag molecules
through the lipid
bilayer and
release them on
the opposite side.
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Carrier Proteins
• Other carrier
proteins
change shape
to move
materials
across the cell
membrane
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7-3 Cell Boundaries
Active Transport
Active Transport
Sometimes cells move materials in the opposite
direction from which the materials would normally
move—that is against a concentration difference.
This process is known as active transport.
Active transport requires energy.
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Active Transport
Molecular Transport
In active transport, small molecules and ions are
carried across membranes by proteins in the
membrane.
Energy use in these systems enables cells to
concentrate substances in a particular location,
even when diffusion might move them in the
opposite direction.
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Active Transport
Molecular Transport
Molecule to be carried
Active
Transport
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Active Transport
• Requires energy or ATP
• Moves materials from
LOW to HIGH
concentration
• AGAINST concentration
gradient
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Active transport
Examples: Pumping
Na+ (sodium ions)
out and K+
(potassium ions) in
against strong
concentration
gradients.
Called Na+-K+ Pump
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Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped
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out; creates a membrane potential
7-3 Cell Boundaries
Active Transport
Endocytosis and Exocytosis
Endocytosis is the process of taking material into
the cell.
Two examples of endocytosis are:
• phagocytosis
• pinocytosis
During exocytosis, materials are forced out of the
cell.
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Pinocytosis
• Cell forms an
invagination
• Materials
dissolve in
water to be
brought into cell
• Called “Cell
Drinking”
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Phagocytosis
- Capture
of a Yeast
Cell (yellow)
by
Membrane
Extensions
of an
Immune
System Cell
(blue)
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Exocytosis
The opposite of endocytosis is exocytosis.
Large molecules that are manufactured in
the cell are released through the cell
membrane.
Inside Cell
Cell environment
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7-3
Unlike a cell wall, a cell membrane
a. is composed of a lipid bilayer.
b. provides rigid support for the surrounding
cell.
c. allows most small molecules and ions to
pass through easily.
d. is found only in plants, fungi, algae, and
many prokaryotes.
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7-3
The concentration of a solution is defined as the
a. volume of solute in a given mass of solution.
b. mass of solute in a given volume of solution.
c. mass of solution in a given volume of solute.
d. volume of solution in a given mass of solute.
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7-3
If a substance is more highly concentrated
outside the cell than inside the cell and the
substance can move through the cell membrane,
the substance will
a. move by diffusion from inside the cell to
outside.
b. remain in high concentration outside the cell.
c. move by diffusion from outside to inside the
cell.
d. cause water to enter the cell by osmosis.
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7-3
The movement of materials in a cell against a
concentration difference is called
a. facilitated diffusion.
b. active transport.
c. osmosis.
d. diffusion.
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7-3
The process by which molecules diffuse across
a membrane through protein channels is called
a. active transport.
b. endocytosis.
c. facilitated diffusion.
d. osmosis.
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