How Cells are Affected by and Interact with Their External Environment

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How Cells are Affected by and Interact with Their
External Environment
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Definition Solution

• A uniform mixture of 2 or more substances.
• Can be solids, liquids, or gases, or a
  combination of these
• Dissolved substance Solute
• Examples?
• Substance in which solute dissolves Solvent
• Examples?

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Examples of Solutions

• Chocolate milk
• Tea
• Milk
• Cytoplasm!
• Blood
• Lymph

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Types of Molecular Movement
This type doesnt

• Diffusion
• Passive Transport
• Simple diffusion
• Facilitated diffusion
• Osmosis
• Active Transport

These types involve some sort of membrane
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1. Diffusion

• The random movement of molecules (liquid or gas)
  until they are evenly dispersed
• Molecules will travel down their concentration
  gradient
• from areas of high concentration to low
  concentration
• Why? Molecules drift into a less ordered state
  unless some energy input keeps it orderly.

https//www.youtube.com/watch?vVY0mZUDvbH4
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2. Osmosis

• A special type of diffusion where water moves
  down its concentration gradient through a
  membrane (i.e., cell membrane)
• Osmosis accounts for most material exchange
  between internal and external environments of the
  cell

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Discuss with a neighbor

• Based entirely on the definition of osmosis, in
  what direction will the water (solvent) move?
• Hint Where is there more water? Where is there
  less water?

thin membrane
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Types of Solutions Sketch and Label
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In which direction do you think water will move?
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In which direction do you think water will move?
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In which direction do you think water will move?
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Your Task

• Discuss with neighbor Why does all of this
  matter for a cell? For an organism?

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Homework due Thursday WS, Diffusion, Osmosis,
Water Balance
Questions?