cell membranes, diffusion, and transport ms. klinkhachorn december 7, 2010
TRANSCRIPT
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Cell Membranes, Diffusion, and Transport
Ms. KlinkhachornDecember 7, 2010
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Homework
• Finish Concept Check 6.3 p 122 – #1-5
• Complete Chapter 6 Review p 132– #s 1, 3, 4, 11, 12, 13, 20, 21– Answers must be written in complete sentences
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Cell Membrane Function
• How does the cell membrane act as a protective barrier?– It is selectively permeable. It selects what is going
to go in and out of the cell.• Oxygen, Carbon Dioxide, Waste, Nutrients
• Why is it important that the membrane is selectively permeable?
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Cell Membrane: Analogy
• The cell membrane is like a window screen.• How?
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How do different materials get into and out of the cell?
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Background Information
• Concentration: the number of molecules of a substance in a given area/volume– Examples:
• The concentration of 5th period is 29 students/classroom
• There are 40 grams of sugar per 1 liter bottle of Coke• Chicago has 100,000 people living in it per square mile
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Practice
Period Number of Students
1 29
2 28
5 29
7 22
8 26
• Which period has the highest concentration of students in the classroom?
• Which period has the lowest?
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Where are the areas of high and low concentration?
This is an example of a concentration gradient.
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Concentration Gradient
• A concentration gradient is established when, in a given area/volume, there is a difference in concentration
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Diffusion
• Diffusion is the movement of molecules from a high concentration to a low concentration– Does NOT require energy– Molecules stop moving when they hit equilibrium
• No concentration gradient exists anymore
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Examples of Diffusion
1. Food coloring in water2. Baking cookies3. Spraying air freshener
• What are other examples of diffusion that you encounter regularly? Explain your answer using the terms concentration and concentration gradient.
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What is the role of diffusion in cells?
• Diffusion across a cell membrane is known as passive transport.
• Can use a protein but doesn’t always.
Outside of CellOutside of Cell
Inside of CellInside of Cell
Cell MembraneCell Membrane
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Passive Transport
Cell MembraneCell Membrane
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Passive Transport
Cell MembraneCell Membrane
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• What do you notice about this picture? Look carefully.
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Active Transport
• Active Transport is the movement of molecules from low to high concentration– Since it is going up concentration gradient, it
requires energy (ATP)– Always needs a protein to help with this
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Compare and Contrast Passive and Active Transport