Transcript 7-3 Cell Boundaries - Eastern Wayne High

7-3 Cell Boundaries
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7-3 Cell Boundaries
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
• Provides protection and support.
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7-3 Cell Boundaries
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? It
supports and protects the cell.
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Diffusion through Cell
Boundaries:
Every living cell exists in a
liquid environment. For
example, cactus plants
scorpions all have liquid
within them.
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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.
4 g/L is more concentrated than 2 g/L.
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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
Is when particles (or solutes) in a solution tend to
move from an area where they are more
concentrated (4 g/L) to an area where they are
less concentrated (2 g/L).
When the concentration of the solute is the same
throughout a system, the system has reached
equilibrium.
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What does diffusion and
equilibrium have to do with
cell membranes?
Suppose a substance is present in unequal
concentrations on either side of a cell membrane. If
the substance can cross the cell membrane, it’s
particles will tend to move toward the area where it is
less concentrated until equilibrium is reached. At that
point, the concentration of the substance on both sides
of the cell membrane will be the same.
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7-3 Cell Boundaries
Diffusion Through Cell Boundaries
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7-3 Cell Boundaries
Osmosis
What is osmosis?
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7-3 Cell Boundaries
Osmosis
Osmosis
Osmosis is the diffusion of water through a
selectively permeable membrane.
Remember our EGG lab?
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7-3 Cell Boundaries
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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7-3 Cell Boundaries
Osmosis
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:
Hypotonic solution (Example: Water). Water
enters the cell.
Hypertonic solution (Example: Corn Syrup). Water
leaves cell.
isotonic (”same strength”) Solutes are the same
inside and outside of a cell
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7-3 Cell Boundaries
Facilitated Diffusion
Facilitated Diffusion: Where sugar glucose
can pass through the membrane
Glucose
with the help of a protein
molecules
channel.
Protein
channel
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7-3 Cell Boundaries
Active Transport
Active Transport (3 Types: Molecular,
Endocytosis, and Exocytosis)
In active transport, cells move materials in the
opposite direction from which the materials would
normally move—that is against a concentration
difference.
Active transport requires energy.
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7-3 Cell Boundaries
Active Transport
Molecular Transport
In active transport, small molecules and ions are
carried across membranes by proteins in the
membrane.
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7-3 Cell Boundaries
Active Transport
Molecular Transport
Molecule to be carried
Active
Transport
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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: “Cell eating.”
• Pinocytosis: Cells taking up fluid from the
surrounding environment.
During exocytosis, materials exit the cell.
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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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