1. The Plasma Membrane - Gateway to the Cell
11/19/2018
The Plasma Membrane -
Gateway to the Cell
G. Podgorski, Biol. 1010

2. Cell Membrane Helps Maintain Homeostasis
The Plasma Membrane
11/19/2018
Cell Membrane Helps Maintain Homeostasis
Balanced internal condition of cells
Also called equilibrium
Maintained by cell membrane controlling what enters & leaves the cell
G. Podgorski, Biol. 1010

3. Semipermeable Membrane
The Plasma Membrane
Semipermeable Membrane
11/19/2018
Ions, molecules larger than water like glucose, and large molecules such as proteins do not move through the membrane on their own.
Small molecules (O2, CO2, H2O) move through easily (diffusion/osmosis)
G. Podgorski, Biol. 1010

4. Functions of Plasma Membrane
The Plasma Membrane
11/19/2018
Functions of Plasma Membrane
Protective barrier
Regulate transport in & out of cell (selectively permeable)
Allow cell recognition
Receptor proteins function in cell communication
Contains the cytoplasm (fluid in cell)
Provide a binding site for enzymes
G. Podgorski, Biol. 1010

5. Structure of the Cell Membrane
The Plasma Membrane
11/19/2018
Structure of the Cell Membrane
G. Podgorski, Biol. 1010

6. Phospholipids Make up the cell membrane
The Plasma Membrane
11/19/2018
Phospholipids
Make up the cell membrane
2 lipid chains are nonpolar hydrophobic
Phosphate Head is polar
hydrophilic
G. Podgorski, Biol. 1010

7. The Plasma Membrane
11/19/2018
FLUID MOSAIC MODEL
FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.
G. Podgorski, Biol. 1010

8. Types of Transport Across Cell Membranes
The Plasma Membrane
11/19/2018
Types of Transport Across Cell Membranes
G. Podgorski, Biol. 1010

9. Experiment
Put cornstarch & water baggie into large beaker containing water and iodine
NOTE: When Iodine mixes with starch it turns purple
Measure life saver. Width and height
write measurement on note sheet
Place lifesaver into small beaker of water

10. Simple Diffusion Molecules move from area of HIGH to LOW concentration
The Plasma Membrane
11/19/2018
Simple Diffusion
Molecules move from area of HIGH to LOW concentration
Fill a plastic baggie with 1 teaspoon of corn starch and 30 ml water.
Fill a 200 ml beaker halfway with water ad add 40 drops of iodine
G. Podgorski, Biol. 1010

11. DIFFUSION Diffusion is a PASSIVE process Trying to reach EQUILIBRIUM
The Plasma Membrane
11/19/2018
DIFFUSION
Diffusion is a PASSIVE process
no energy is used to make the molecules move.
Trying to reach EQUILIBRIUM
Same amount of particles inside as outside
G. Podgorski, Biol. 1010

12. Diffusion through a Membrane
The Plasma Membrane
11/19/2018
Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
G. Podgorski, Biol. 1010

13. Two types of diffusion Facilitated Diffusion Simple Diffusion
The Plasma Membrane
11/19/2018
Two types of diffusion
Facilitated
Diffusion
Simple
Diffusion
G. Podgorski, Biol. 1010

14. Doesn’t require energy Moves high to low concentration
The Plasma Membrane
11/19/2018
Simple Diffusion
Doesn’t require energy
Moves high to low concentration
Example: Oxygen diffusing into a cell and carbon dioxide diffusing out.
G. Podgorski, Biol. 1010

15. Facilitated diffusion
The Plasma Membrane
11/19/2018
Facilitated diffusion
Doesn’t require energy
Uses channel proteins to move high to low concentration
Examples: Glucose or amino acids moving from blood into a cell.
G. Podgorski, Biol. 1010

16. Write a Hypothesis Create a data table
Starting color
Ending color
Beaker
Baggie
Based on your observation which substance moved?
How did you determine this?
Did this process require energy?

17. Diffusion across a membrane Semipermeable membrane
Osmosis
The Plasma Membrane
11/19/2018
Diffusion across a membrane
Diffusion of water across a membrane
Moves from HIGH water potential (low solute) to LOW water potential (high solute)
Semipermeable membrane
Measure the diameter and the height of the gummy lifesaver.
Fill a 100ml beaker half filled with water and place the gummy lifesaver in the beaker.
G. Podgorski, Biol. 1010

18. Osmosis H2O Across A Membrane
The Plasma Membrane
11/19/2018
Osmosis H2O Across A Membrane
High H2O potential Low solute concentration
Low H2O potential High solute concentration
G. Podgorski, Biol. 1010

19. Cell in Isotonic Solution Equal salt inside and outside the cell
The Plasma Membrane
11/19/2018
Cell in Isotonic Solution Equal salt inside and outside the cell
10% NaCL 90% H2O
ENVIRONMENT
CELL
NO NET MOVEMENT
10% NaCL
90% H2O
What is the direction of water movement?
equilibrium
The cell is at _______________.
G. Podgorski, Biol. 1010

20. The Plasma Membrane
11/19/2018
Cell in Hypotonic Solution Less salt outside the cell than inside the cell
10% NaCL 90% H2O
CELL
60% NaCL
40% H2O
What is the direction of water movement?
G. Podgorski, Biol. 1010

21. The Plasma Membrane
11/19/2018
Cell in Hypertonic Solution more salt outside the cell than inside the cell
20% NaCL 80% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
G. Podgorski, Biol. 1010

22. NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
The Plasma Membrane
11/19/2018
Isotonic Solution
Hypotonic Solution
Hypertonic Solution
NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
CYTOLYSIS
PLASMOLYSIS
G. Podgorski, Biol. 1010

23. Osmosis in Red Blood Cells
The Plasma Membrane
11/19/2018
Osmosis in Red Blood Cells
Hypotonic
Cytolysis
Hypertonic
Plasmolysis
Isotonic
Equilibrium
G. Podgorski, Biol. 1010

24. Write a Hypothesis Create a data table
Before water
After water
Diameter
Describe what happened to the diameter of your lifesaver?
Describe what happened to the texture of the life saver after soaking?
Is the water in the beaker hypertonic, hypotonic, or isotonic?

25. ACTIVE TRANSPORT The Plasma Membrane 11/19/2018
G. Podgorski, Biol. 1010

26. Active Transport Requires energy or ATP
The Plasma Membrane
11/19/2018
Active Transport
Requires energy or ATP
Moves materials from Low to High concentration
EXAMPLE: Sodium/Potassium pump Pumping Na+ out & K+ in against strong concentration gradients.
G. Podgorski, Biol. 1010

27. The Plasma Membrane
11/19/2018
Transport Proteins
Some carrier proteins change shape to move materials across the cell membrane
G. Podgorski, Biol. 1010

28. Materials:
Plastic grocery bag, a piece of string, a pair of scissors and two small pieces of candy.
The grocery bag represents the cell membrane. Pretend the membrane is completely sealed.
Problem:
Get the candy into the bag without using the opening of the bag

29. Moving the “Big Stuff” Exocytosis - moving things out.
The Plasma Membrane
11/19/2018
Moving the “Big Stuff”
Exocytosis - moving things out.
Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.
This is how many hormones are secreted.
G. Podgorski, Biol. 1010

30. The Plasma Membrane
11/19/2018
Exocytosis Large molecules that are manufactured in the cell are released through the cell membrane.
Inside Cell
Outside the Cell
G. Podgorski, Biol. 1010

31. Intake particles suspended in water
The Plasma Membrane
11/19/2018
Moving the “Big Stuff”
Large molecules move materials into the cell by one of two forms of endocytosis.
Phagocytosis
Pinocytosis
Intake particles suspended in water
Intake solid material
G. Podgorski, Biol. 1010

32. The Plasma Membrane
11/19/2018
G. Podgorski, Biol. 1010