Aim: What is Diffusion?

1
Aim What is Diffusion?

• Do Now Predict what will happen with the
  diffusion demonstration.
• Tuesday 10/21 background information for Science
  Project due
• Wednesday 10/22 Read pages 184-189 answer
  questions 189 s 1-5
• Thursday 10/23 Exam
• Project 1 due on 11/12.

2
Diffusion Physical Demonstration

• In diffusion all substances move from a higher
  concentration to a lower concentration
• Once the concentrations are equal on both ends we
  have reached Dynamic Equilibrium
• DynamicRunning all the time
• EquilibriumBalance

3
Sketch the beaker contents.
Before
After

• Beaker contains water and iodine.
• Dialysis bag contains a starch solution.

4
Conclusions

• Why did the iodine move freely across the
  membrane while the starch did not?
• What process was demonstrated in this experiment?

5
Aim What are some factors that affect the rate
of diffusion?

• Do Now What is facilitated diffusion?
• Background Information due tomorrow via
  turnitin.com. Worth 3 HWs. NO LATE PAPERS WILL
  BE ACCEPTED! Include bibliography!
• Wednesday 10/22 Read pages 184-189 answer
  questions 189 s 1-5
• Thursday 10/23 Exam
• Project 1 due on 11/12.

6
How does Glucose enter a cell membrane?

• Glucose is a big molecule
• It emits a charge
• Cannot readily permeate lipid bilayer
• Uses Facilitated Diffusion to enter membrane
• DOES NOT USE ENERGY

7
Group Activity

• In pairs please read Analyzing Data page 188.
• Answer questions 1-4 on a sheet of loose leaf
  paper to be collected at the end of the period.
• Do Not copy questions
• Hand in one paper for each pair of students

8
Aim What is Active Transport and Osmosis?

• Do Now What are some factors that affect the
  rate of diffusion?
• Background Information due today via turnitin.com
  by 1159pm! Worth 3 HWs. NO LATE PAPERS WILL
  BE ACCEPTED! Include bibliography!
• Tomorrow 10/22 Read pages 184-189 answer
  questions 189 s 1-5
• Thursday 10/23 Exam
• Project 1 due on 11/12.

9
How do substances move across a cell membrane?

• Diffusion and facilitated diffusion
• Osmosis (water)
• Active Transport Requires ENERGY

10
Permeability of Lipid Bilayer

• Hydrophobic molecules cross with ease
• Why?
• They are all nonpolar
• Examples Hydrocarbons
• Carbon Dioxide
• Oxygen

• Hydrophillic Molecules and Ions cannot pass with
  ease
• Why?
• They are have charges
• Examples Glucose
• Water
• Na
• K

Main Question How will Ions and hydrophillic
molecules permeate the membrane if the
phospholipids wont allow them to?
11
Active Transport Up Close and Personal

• Na -- K Pump
• Moving Against the concentration gradient
• Movement from low to high concentrations
• Requires ENERGY!

12
Osmosis is

• The diffusion of water
• Water moves from an area of high water
  concentration (low solute concentration) to an
  area of low water concentration (high solute
  concentration).
• Remember Water always wants to move to a place
  where it can dissolve something

13
Osmosis Demonstration

• Goal To predict what will happen when eggs are
  placed in the following solutions
• Syrup
• Tap Water
• Procedure
• Egg placed in white vinegar overnight to remove
  shell. Membrane exposed
• Tonight they will each be placed in the above
  solutions.
• What measurement of the eggs will we need to take
  in order determine if osmosis occurred?

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Aim How can we demonstrate Osmosis?

• Do Now What is Osmosis and how does it differ
  from diffusion?
• Have out HW questions pg 189 s 1-5
• Test tomorrow 10/23!!!
• Project 1 due on 11/12.

15
Predictions

• In pairs discuss the answers to the following
  questions
• Place the answers in your notebook
• What do you predict will happen to the egg in the
  syrup? Why? How will you know?
• What do you predict will happen to the egg in the
  tap water? Why? How will you know?

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Data Table Period 3
Substance egg submerged in Eggs mass (g) before placed in substance Eggs mass (g) after removed from substance
Syrup 56.45g
Tap Water 62.00g
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Definitions

• Solute
• Solvent
• Hypertonic
• Hypotonic
• Isotonic

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Qualitative Data How do the eggs look?

• Egg immersed in Syrup (Hypertonic Solution)
• Egg immersed in Distilled Water (Hypotonic
  Solution)
• Egg immersed in Tap Water (Isotonic Solution?)

Egg immersed in Syrup (Hypertonic Solution)
Egg immersed in Tap Water (Hypotonic
Solution)
Isotonic Solution ?
19
Compare the following solutions to each other,
using the terminology we just discussed

• 10 salt solution vs. distilled water
• 20 salt solution vs. 10 salt solution
• 20 salt solution vs. 20 salt solution
• Distilled water vs. 20 salt solution

20
Describe the solutions in terms of concentration.
In which direction will the water move? Why?

Selectively Permeable Membrane
21
Onion Cell Plasmolysis
Onion Cell Wet Mount
Onion Cell in 10 salt solution
22
Summary

• What is osmosis?
• Where does water always want to travel?
• Why doesnt osmosis require energy?
• What happens to a cell when it is placed in a
  hypertonic solution? Hypotonic solution?
  Isotonic solution?

23
REVIEW QUESTIONS

• What are two ways in which substances can move
  across a membrane? Which requires energy?
• How do these two ways differ from each other?
• What types of substances rely on active transport
  for admission into the cell? Why?