1. Cell Membrane & The Cellular Processes
Osmosis & Diffusion

2. The Plasma Membrane - Gateway to the Cell The Plasma Membrane
6/11/2018
The Plasma Membrane -
Gateway to the Cell
G. Podgorski, Biol. 1010

3. Research Question Find some functions of the plasma membrane
You have 2 minutes to Google your responses…
Begin NOW!!

4. Functions of Plasma Membrane
The Plasma Membrane
6/11/2018
Functions of Plasma Membrane
Protective barrier
Regulate transport in & out of cell (selectively permeable)
Allow cell recognition
Provide anchoring sites for filaments of cytoskeleton
G. Podgorski, Biol. 1010

5. Functions of Plasma Membrane
The Plasma Membrane
6/11/2018
Functions of Plasma Membrane
Provide a binding site for enzymes
Interlocking surfaces bind cells together (junctions)
Contains the cytoplasm (fluid in cell)
G. Podgorski, Biol. 1010

6. Structure of the Cell Membrane
The Plasma Membrane
6/11/2018
Structure of the Cell Membrane
G. Podgorski, Biol. 1010

7. What is Homeostasis???

8. Homeostasis Balanced internal condition of cells
The Plasma Membrane
6/11/2018
Homeostasis
Balanced internal condition of cells
Also called equilibrium
Maintained by plasma membrane controlling what enters & leaves the cell
G. Podgorski, Biol. 1010

9. Research Question Draw and label what a Phospholipid looks like
You have 2 minutes
Begin NOW!!

10. Phospholipids Contains 2 fatty acid chains that are nonpolar
The Plasma Membrane
6/11/2018
Phospholipids
Contains 2 fatty acid chains that are nonpolar
Make up the cell membrane
Polar Head
water loving
Head is polar & contains a –PO4 group & glycerol
Non-polar tail
Water fearing
G. Podgorski, Biol. 1010

11. Cell Membrane Polar heads are hydrophilic “water loving”
The Plasma Membrane
Cell Membrane
6/11/2018
Polar heads are hydrophilic “water loving”
Nonpolar tails are hydrophobic “water fearing”
Makes membrane “Selective” in what crosses
G. Podgorski, Biol. 1010

12. Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT
The Plasma Membrane
Cell Membrane
6/11/2018
The cell membrane is made of 2 layers of phospholipids called the lipid bilayer
Hydrophobic molecules pass easily; hydrophilic DO NOT
G. Podgorski, Biol. 1010

13. The Plasma Membrane
6/11/2018
Solubility
Materials that are soluble in lipids can pass through the cell membrane easily.
G. Podgorski, Biol. 1010

14. Semipermeable Membrane
The Plasma Membrane
Semipermeable Membrane
6/11/2018
Small molecules and larger hydrophobic molecules move through easily.
e.g. O2, CO2, H2O
G. Podgorski, Biol. 1010

15. Types of Transport Across Cell Membranes
The Plasma Membrane
6/11/2018
Types of Transport Across Cell Membranes
G. Podgorski, Biol. 1010

16. Transport across the Membrane
There are 2 main types of transport across the cell membrane
Passive Transport – requires NO energy
Active Transport – requires Energy (ATP) to move particles across the cell membrane

17. Passive Transport
Passive Transport requires NO energy in order to move particles across the cell membrane
Like going down a slide

18. Diffusion
Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

19. Diffusion of Liquids The Plasma Membrane 6/11/2018
G. Podgorski, Biol. 1010

20. Diffusion
Solute molecules moving from an area of high concentration to an area of low concentration
Random motion drives diffusion
Equilibrium is reached when there is an even distribution of solute molecules
(water) 2 3 1 4

21. Osmosis = Diffusion of H2O Across A Membrane
The Plasma Membrane
6/11/2018
Osmosis = Diffusion of H2O Across A Membrane
Draw this picture 
High H2O potential Low solute concentration
Low H2O potential High solute concentration
G. Podgorski, Biol. 1010

22. Osmosis Diffusion of water through a semi-permeable membrane
Semi-permeable: permeable to solvents (WATER), but not to large molecules
High [water] to low [water]
Dissolved molecules (i.e. glucose, starch) are called solutes
REMEMBER:
Water = solvent
Glucose, Starch = solutes

23. Salt Sucks Salt draws water to where it is.
Water wants to equal everything out.
A simple rule to remember is: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

24. 3 Key Terms
Hypo = below
Hyper = above
Iso = equal

25. Isotonic Solution
The solution the cell is in is equal to the inside of the cell.
"ISO" means the same

26. Hypotonic The word "HYPO" means less
There are less solute (salt) molecules outside the cell then inside the cell
since salt sucks, water will move into the cell
Animal cell could burst
Plant cell wall keeps it from bursting

27. Hypertonic The word "HYPER" means more
There are more solute (salt) molecules outside the cell.
Water goes in the direction of the salt
Cell may die if too much water is lost.

28. Osmosis in Living Cells
Cellulose in cell wall
Plasmolysis = cell membrane detaching from the cell wall (shrinking)

29. Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
Iso: Normal blood cells
Hypertonic solution: the cells shrink
Cell may die if too much water is lost.
Crenation
Hypotonic solution: In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

30. Effect of Water on Cells
Hypertonic Environment
High [solute], low [water]
Cell shrinks
Hypotonic Environment
High [water], low [solute]
Cell fills with water, too much water can cause the cell to lyse
Isotonic Environment
[water] = [solute]
Normal cell: everything is equal
Hypertonic
Hypotonic
Isotonic

31. Osmosis in Plant Cells
Hypertonic
Plasmolysis
Hypertonic: In plant cells, the central vacuole loses water and the cells shrink, causing wilting.
Hypotonic
Hypotonic: In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting

32. Review Passive Transport = _____ Energy used Diffusion is defined as:
What occurs in osmosis?
Identify the 3 types of solutions.