1. Structure of Cell Membrane:
Aim: How does the Structure of the Cell Membrane Contribute to its Function?
HW #3.: Intro to the Cell Membrane
Video:
Structure of Cell Membrane:

2. Function of the Cell Membrane
Regulates what enters and exits the cell, maintaining homeostasis
Provides protection and support

3. Structure of the Cell Membrane
Insights into Cell Membranes Via Dish Detergent
Fluid Mosaic Model – flexible organization of a mixture of lipids & proteins

4. Lipid Bilayer Two layers of phospholipids
Allows the cell membrane to be flexible/fluid
“attracted to water”
inside cell
outside cell
phosphate
lipid
“repelled by water”

5. Cell Membrane Proteins
Transport Protein: provide a channel so molecules can enter and exit the cell.
Receptor Protein: specifically shaped proteins that aid in cell communication
Messenger molecule: hormone or neurotransmitter
Transport Protein
Protein Receptor

6. Cell to Cell Communication Humans
To maintain homeostasis, cells must communicate.
Cells communicate using two body systems:
Nervous System (Neurotransmitters)
Endocrine System (Hormones)
An Example of Cell Communication: The Flight or Fight Response

7. Aim: How do Cell Membranes Select what can Enter the Cell?
Do Now:
Regents
Review
Questions

8. Selectively Permeable
Cell membrane SELECTS which materials enter and exit the cell based on SIZE.
Harmful substances (viruses/bacteria) may enter the cell 8

9. Only SMALL molecules can DIFFUSE through a membrane.

10. Small Molecules Easily diffuse through the cell membrane Water
Carbon Dioxide
Oxygen
Glucose 10

11. Large Molecules
Large organic molecules cannot easily pass through the cell membrane
They need to be digested into their building blocks
Starch 
Proteins 
Lipids  Fatty Acids + Glycerol 11

13. What does the term selectively permeable mean?
What molecules are able to easily pass through the membrane?
Explain how large molecules are able to diffuse the cell membrane.
Explain how the selectively permeable cell membrane aids in the maintenance of homeostasis.
Selectively Permeable - Ability to select and choose which materials enter & exit the cell.
Small Molecules: Water, Simple Sugars (Glucose), Oxygen, Carbon Dioxide
They must be broken down. Ex: Starch (Sugar)
Regulates what comes in and out of the cell; helping to keep toxic substances out 13

14. Aim: How do Molecules Travel Across a Cell Membrane?
Do Now: Selectively Permeable
HW #3.5: Active Vs. Passive Transport 14

15. Why does the dye “spread out” to take up the entire beaker?
2. How does the original concentration of the dye compare with the final concentration of the dye? 15

16. Cellular Transport
The cell membrane controls the movement of materials into and out of the cell
Types of cell transport: Diffusion (Passive Transport), Facilitated Diffusion, Active Transport

17. Diffusion (Passive Transport)
Low
Movement of molecules from HIGH to LOW concentration
Does NOT require ATP
High 17

18. Real Life Examples of Diffusion
The above image represents a real life example of diffusion. Can you think of any other examples?
A balloon filled with helium will deflate a little bit every day, because helium atoms diffuse out of the balloon through its wall • When spaghetti is cooked, water molecules diffuse into the spaghetti strings, making them thicker and more flexible. • Carbon dioxide bubbles in soft drinks diffuse out of your soda, leaving your soda flat. • A smelly gas distributes itself over a room by diffusion (flower fragrance, garbage stink, body odor ) • A sugar cube in a glass of water that is not stirred will dissolve slowly and the sugar molecules will distribute over the water by diffusion • A wilted carrot or celery made firm again by soaking in water. • The smell of cookies diffuses through the house as they bake. • Perfume - perfume gas molecules diffuse into the air when put on so you can smell it. • Air freshener/deodorant - same concept as above. • Teabag diffusion - tea leaf pigments diffuse through teabag to give the water its color and taste of tea • Cigarette smoke - it diffuses into the air and spreads throughout the room 18

19. Why does Diffusion Occur?
Concentration Gradient!
Count the number of molecules on each side of the cell membrane to determine the concentration gradient.
What is the concentration gradient for Oxygen?
Will Oxygen move INTO or OUT of the cell?

20. What is the concentration gradient for molecule 1?

21. Facilitated Diffusion
Movement of molecules from HIGH to LOW concentration using a protein channel
Does NOT require ATP 21

22. Real Life Diffusion in Our Bodies!
According to the video, where in your body is diffusion occurring?
Do you think it is limited to that organ? Where else do you think diffusion is occurring?

23. Dynamic Equilibrium
Molecules continuously diffuse causing equal concentration of molecules on both sides of the membrane
High
Low

24. Active Transport Movement of molecules from LOW to HIGH concentration
Against the concentration gradient
Requires Energy (ATP)
High 24

25. Determine the concentration for molecule 3.
If molecule 3 moves OUT of the cell, is that active or passive transport? Explain your reasoning.

26. Active Vs. Passive Transport
HIGH
HIGH
Low
Low

28. Transport Summary
diffusion
facilitated diffusion
active transport
ATP

29. Aim: How is Osmosis a Form of Passive Transport?
Do Now: Cell Membrane Regents Questions
HW #3.6: Osmosis
Foldables 29

30. Osmosis
Water molecules DIFFUSE from HIGH water concentration to LOW water concentration
H2Osmosis
NO ENERGY (ATP) 30

31. Cells in DISTILLED Solution
Water moves INTO the cell from high to low concentration
Problem: Animal cells gain water, SWELL and burst
Plant cells do NOT burst – Why?
Rigid cell wall
Distilled Water
KABOOM!
No problem, here

32. Real Life Example of a Cell Living in a DISTILLED Environment
Paramecium are single-celled freshwater organisms
Water continually enters the cell due to osmosis
Cell has a contractile vacuole to pump out the excess water

33. I’m shrinking, I’m shrinking!
Cells in SALT Solution
Water moves OUT the cell from high to low concentration
Problem:
Animal cells shrink
Plant cells undergo plasmolysis
Cytoplasm pulls away from the cell wall
saltwater
I’m shrinking, I’m shrinking!
I will survive!

34. Real Life Example of a Cell Living in a SALT Environment
During the winter, salt on the road NEGATIVELY affects plants. This is because water diffuses out of their cells (highlow concentration).

36. Cells in BALANCED Solutions
Balanced conditions
The water concentration on both sides of the membrane is equal
Real-life example: blood
Problem: None
water flows across membrane equally, in both directions
That’s better!
balanced
I could be better…

37. Osmosis Review Salt Water -Water moves HL OUT of the cell
Distilled Water
-Water moves HL INTO the cell
Isotonic Water
-Equilibrium

38. Under What Conditions do Cells Gain or Lose Water?

39. Diffusion and Osmosis Activity

40. Wrap-up: Using what you have learned today about osmosis, explain what would happen to the slugs in the cartoon if they were covered with salt. 40