1. Unit 2.2 Check and Reflect Target Vocabulary Target Knowledge:
I can predict the movement of molecules across a gradient.
I know the difference between active and passive transport.
I can describe the cell membrane as a fluid mosaic model.
I can explain semi-permeability.
Explain the role of macromolecules (lipids and protein) in cell transport.
Target Vocabulary
cell membrane
lipid bilayer
diffusion
equilibrium
osmosis
facilitated diffusion
active transport
concentration
isotonic
hypotonic

2. Cell Membranes Osmosis and Diffusion

3. Functions of Membranes
Protect cell
Maintain homeostasis
3. Selectively permeable - allows some molecules in, others are kept out

4. Homeostasis Balanced internal condition of cells
Also called equilibrium
Maintained by cell membrane controlling what enters & leaves the cell

5. Phospholipid Bilayer Polar heads are hydrophilic “water loving”
Nonpolar tails are hydrophobic “water fearing”
Makes membrane “Selective” in what crosses

7. Fluid Mosaic Model:
“Proteins floating in a sea of lipids”

8. Proteins Are Critical to Membrane Function

9. Blood-Brain Barrier
Allows some substances into the brain, but screens out toxins and bacteria
Substances allowed to cross include:
water, CO2, Glucose, O2, Amino Acids, Alcohol, and antihistamines. HIV and bacterial meningitis can cross the barrier.

10. Solutions Solutions are made of solute and a solvent
Solvent – The liquid part. It does the dissolving.
Solute – The thing being dissolved. Salt and sugar are solutes.

11. Methods of Transport Across Membranes
1. Diffusion
2. Osmosis
3. Facilitated Diffusion
4. Active Transport

12. Methods of Transport Across Membranes
1. Diffusion -passive transport - no energy used
2. Osmosis - Passive transport of water across membrane
3. Facilitated Diffusion – Needs a helper to get things across
4. Active Transport- requires energy to transport molecules against a concentration gradient – energy is in the form of ATP

13. Diffusion
Movement of molecules from an area of high concentration to an area of low concentration.
Movement from one side of a membrane to another, without help.

14. Diffusion

15. Diffusion of Liquids

16. Diffusion through a Membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
Cell membrane

17. Facilitated Diffusion
Does NOT require energy
Uses transport proteins to move things from high to low concentration
Examples: Glucose or amino acids moving from blood into a cell.

18. Facilitated Diffusion
Molecules will randomly move through the pores in Channel Proteins.

19. Facilitated Diffusion
This is a helper.

20. Active Transport Requires energy (ATP)
Moves materials from LOW to HIGH concentration AGAINST the concentration gradient.

21. Diffusion across a membrane Semipermeable membrane
Osmosis
Diffusion of water across a membrane.
Moves from HIGH water amount (low solute) to LOW water amount (high solute).
Diffusion across a membrane
Semipermeable membrane

22. You could think of it this way…
In osmosis, water FOLLOWS salt!! This is sometimes an easier way to remember this concept.

23. Where is the water moving?
The water is moving out of the cell.
Why?
Remember wherever salt is water follows!
Salt
SALT
SALT

24. Light blue = Salt Dark blue = water

25. There is a lot of salt outside of the cell. What will happen? Why?

26. What will happen if there is a lot of salt inside of the cell?

27. Red Onion Cells Normal In Salt Water
What happened to the cytoplasm and cell membrane?

28. Diffusion of H2O Across A Membrane
High H2O potential (amount) and Low solute concentration
Low H2O potential (amount) and High solute concentration

29. Osmosis: Draw this

30. Three Forms of Transport Across the Membrane

31. Question Why does eating popcorn make you thirsty?
Popcorn is very salty and may cause water to leave the cells of your mouth and through due to diffusion. This makes a person thirsty.

32. When a sea urchin egg is removed from the ocean and placed in freshwater, the egg swells and bursts. Which of these causes water to enter the egg?
Coagulation
Sodium Pump
Active Transport
Osmosis D

33. The picture shows a cell model and the solutions associated with it
The picture shows a cell model and the solutions associated with it. In this situation the cell model will —
Gain mass
Shrink
Increase in solute content
Start to vibrate B

34. Which of these best explains why a freshwater aquarium would be a dangerous habitat for saltwater fish?
A The tissues of the saltwater fish would absorb too much acid.
B The cells of the saltwater fish would lose too much water.
C The organ systems of the saltwater fish would consume too much energy.
D The cells of the saltwater fish would gain too much water. D

36. On a hot summer day, a road-crew worker perspires and then feels thirsty as her body temperature increases. This response is an example of –
Releasing enzymes
Maintaining homeostasis
Decreasing respiration
Assimilating proteins B

37. Think/Pair/Share
Work with a partner to create different situations that can be classified as diffusion.
Do the same for osmosis.

38. Active Transport Video: http://www. iteachbio
Diffusion Video:
Another Video: