1. Diffusion, hypertonic, hypotonic, isotonic
Biology
Cell Membrane:
Diffusion, hypertonic, hypotonic, isotonic
MT: Cell Processes
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7-3 Cell Boundaries
7-3 Cell Boundaries
Photo Credit: © Quest/Science Photo Library/Photo Researchers, Inc.
What surrounds a cell?
A cell membrane!
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Cell Membrane
All cells are surrounded by a thin, flexible barrier known as the cell membrane.
Outside of cell
Carbohydrate chains
Proteins
Cell membrane
The cell membrane regulates what enters and leaves the cell.
Inside of cell (cytoplasm)
Protein channel
Lipid bilayer
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Cell Membrane
What is the main function of the cell membrane?
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Cell Membrane
Cell Membrane
1. Regulates what enters and leaves the cell
2. Provides protection and support
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Cell Membrane
The composition of nearly all cell membranes is a double-layered sheet called a phospholipid bilayer.
The cell membrane regulates what enters and leaves the cell.
Phospholipid bilayer
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Cell Membrane
The cell membrane is:
*Semi-permeable: only certain substances are let into/out of the cell. Usually small substances.
Ex: Strainer: water is let through but the beans/noodles are not
Ex: Window Screen: air and small bugs are let in but big bugs are not
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8. Diffusion Through Cell Boundaries
- is the movement of substances across the cell membrane.
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9. Diffusion Through Cell Boundaries
What happens during diffusion?
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10. Diffusion Through Cell Boundaries
Particles move from an area of HIGH concentration to an area of LOW concentration.
When particles are balanced on both sides of the membrane, the system has reached equilibrium.
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11. Diffusion Through Cell Boundaries
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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12. Diffusion Through Cell Boundaries
There is a higher concentration of solute on one side of the membrane as compared to the other side of the membrane.
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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13. Diffusion Through Cell Boundaries
Particles move from the side of the membrane with a HIGH concentration of solute to the side of the membrane with a LOW concentration of solute until EQUILIBRIUM is reached.
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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14. Diffusion Through Cell Boundaries
When equilibrium is reached, solute particles continue to diffuse across the membrane in both directions but with a net movement of zero.
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.
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Osmosis
What is osmosis?
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Osmosis
Osmosis
Osmosis is the diffusion of water through a membrane.
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17. Selectively permeable membrane
Osmosis
How Osmosis Works
Dilute sugar solution (Water more concentrated)
Concentrated sugar solution (Water less concentrated)
Sugar molecules
Osmosis is the diffusion of water through a selectively permeable membrane. In the first beaker, water is more concentrated on the right side of the membrane. As a result, the water diffuses (as shown in the second beaker) to the area of lower concentration.
Movement of water
Selectively permeable membrane
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Osmosis
Water tends to diffuse from a HIGH concentration region to a LOW concentration region.
hypertonic (“above strength”): more particles than the other side
hypotonic (“below strength”): less particles than the other side
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Osmosis
When concentrations of solutions are the same on both sides of a membrane, the solutions are isotonic (”same strength”).
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