1. At the end of this unit you should be able to explain why the following occurs…

2. Questions of the day… What keeps cells from exploding?
Why do they “mist” or spray water at the grocery store?
How does your body get the nutrients it needs in and the waste nutrients out of each cell?

3. Which cells have Cell Membranes?

4. Cell Membranes vs. Cell Walls
Cell Membranes regulate what
comes into and
out of cells
Cell Walls
provide
protection and
support for
the cell

5. Electron micrograph of cell membrane

6. Phospholipids make up cell membranes
Polar “head” that is attracted to water
Non-polar “tails” that are not attracted to water but are attracted to other phospholipid tails

7. Phospholipids make up cell membranes

8. Water molecules
Polar head faces out towards water because of the attraction
Nonpolar tails face inward so they are protected from water
Water

9. Membranes are picky!!!
Membranes are semi-permeable because they only let certain molecules through
Small and non-polar molecules can pass through easily
Large and polar molecules cannot pass through without help

10. Both water and nutrients can move in and out of cells.

11. Diffusion discusses the movement of particles
Diffusion- The movement of particles from a region of higher concentration to a region of lower concentration, caused by the random motion of particles.
Ex: Body Spray
Food Coloring/Water

12. Osmosis- The diffusion of water across a semi-permeable membrane towards the side with higher solute concentration.

13. Draw a picture where molecules would diffuse out of a membrane

14. Draw a picture where molecules would diffuse into a membrane

15. Osmosis discusses water movement:
If there is more water outside(less particles)…
Water will move into the cell
If there is more water inside (more particles)
Water will move out of the cell

16. Draw a picture where water would move into the cell

17. Draw a picture where water would move out of a cell

18. Visual Examples Water will move into cell Water will move out of cell.
Water will stay put.

19. Where will particles diffuse?

21. Lets set up a Lab
Purpose: To determine if glucose and starch are permeable through a model cell membrane.
Hypothesis:

22. Glucose bonds have some areas of charge (somewhat polar)

23. Starch
Few areas of Charged bonds
Picture

24. How could we check for the presence of starch?
Starch turns black in the presence of Iodine

25. How could we check for the presence of sugar?
Glucose test strips tell presence of sugar

26. How could we set up an experiment to see if starch and sugar will move through a membrane?

28. Procedure: 3-150 mL beaker 1-10 mL graduated cylinder 10% IKI solution
MATERIALS
3-150 mL beaker
1-10 mL graduated cylinder
10% IKI solution
2 Glucose Test Strips
2 pieces of string (10-20 cm)

29. Materials Continued 1-20 cm piece of dialysis tubing
1-100 mL graduated cylinder
1-Scissors
Starch/Glucose Solution

30. 1. Record color of Initial Solutions
2. Record Glucose presence of Starch/Glucose Solution (Done by Miss H)
3.Obtain one piece of Moist Dialysis tubing
4. Seal one end of the tube by folding the end over and tying with thread to form an open bag

31. 5. Obtain 10 mL of Starch/Glucose Solution in your graduated cylinder
Fill your bag with Starch/Glucose solution (about 10 mL)
Leave about 2 cm of room at the top of bag.
Squeeze excess air of of bag
Place your bag in the 150 mL beaker and completely cover with 10% Iodine Solution

32. Procedure Continued.. Tie up bag as shown by Miss H
Wait 10 minutes and remove your cell from the iodine.
Use scissors to empty contents of your cell into a clean beaker
Observe color and contents of the cell
Test contents for glucose
Test the iodine solution for glucose

33. What Data should we take?

34. Observations inside and outside of cell membrane
Initial Cell Contents
Initial Beaker
Final Cell Contents
Final Beaker
Color
Glucose Test Strip