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DIFFUSION AND OSMOSIS
SECTION
3.4
Study Guide
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KEY CONCEPT
Materials move
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VOCABULARY
passive transport
across membranes
because of
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concentration gradíent
concentration
differences.
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facilitated diffusion
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MAIN IDEA: Diffusion and osmosis are types of passive transport.
1. What is a concentration gradient?
The difference in the concentration of a substance from one location to another
2.
What does it mean for a molecule to diffi.lse down a concentration gradient?
the molecule defuses from one area of a higher concentration into a area of lower concentration
Complete the concept map below about passive transport.
Passive transport
example
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7. energy from the cell
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the movement of molecules
down a concentration gradient
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6. the natural motion of
particles
the diffusion
of water
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The higher the concentration of dissolved particles in a solution, the
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Unit 2 Resource Book
McDougal Littell Biology
Study Guide 13
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STUDY GUIDE, CONTINUED
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Suppose you have three solutions with different concentrations of particles. Relative to the
concentration of particles in a cell, one solution is isotonic, one is hypertonic, and one is
hypotonic, Use this information to anslver the next two questions,
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Which solution has the highest concentration of particles?
hypertonic
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1O. Which solution has the highest concentration of water molecules?
hypotonic
MAIN IDEA:
Some molecules diffuse through transport proteins.
11. How does facilitated diffusion differ from simple diffusion?
It occurs through selective transport proteins, not simplv across the membrane
12. ln facilitated diffirsion, do molecules move down a concentration gradient or against
a
concentration gradient?
down a concentration gradient
Vocabulary Gheck
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3.
The difference in the concentration of a substance from one location to another is
a
concentration gradient
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14.
15.
People with excess energy are described as hyper. How does this relate to the meaning
of hypertonic?
Just as a hyper person has higher level of energy than most people, a hypertonic solution has a higher
level of solutes than the solution it is being compared to.
The wordfacilitale means "to make easier." How does this meaning apply to facilitated
diffusion?
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The transport protein makes it easier for a molecule that cannot directly cross the cell membrane
to enter or exit a cell.
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14
srudy Guide
Unit 2 Besource Book
McDougal Littell Biology