1. The Plasma Membrane
Essential Questions: How does the structure of the plasma membrane allow it to function as a regulatory organelle and protective barrier for a cell?

3. Function: Plasma Membrane
Maintains homeostasis by controlling substances entering & leaving the cell.

4. Think-pair-share What kinds of substances might need to enter or leave the cell?

5. A cell must take in and keep needed materials, such as glucose, while maintaining a balance with its surroundings.

6. A cell must remove wastes and keep harmful substances from entering.

7. Selective Permeability
inside cell
outside cell
The property of a membrane that allows some materials to pass through while keeping others out.

8. Selective permeability allows different cells to carry on different activities within the same organism.

9. Structure of the Plasma Membrane

10. outside cell
cytoplasm

11. Cholesterol
Stabilizes the membrane by preventing phospholipids from sticking together

12. Proteins Transport-help move large molecules across the membrane
Markers-helps chemicals recognize certain cells
Enzymes

13. Proteins
Transport Proteins
Marker Proteins
Enzymatic Proteins

14. Channel protein
Provide a “tunnel” or channel for molecules to pass through the membrane

15. Carrier protein
Protein that picks up a molecule and “carries” it across the membrane

16. Cell recognition protein
Carbohydrate chain at the end of a protein and is used for cell to cell recognition and attachment

17. Phospholipids
Phosphate head (glycerol +phosphate)
2 Fatty acid tails

18. Phospholipids Phosphate head polar hydrophilic “water-loving”
Fatty acid tails
nonpolar
hydrophobic
“water-fearing”
“attracted to water”
Fatty acid
“repelled by water”

19. Phospholipids are arranged in a bilayer
outside cell
Polar Heads
Non-polar tails
Because there is water inside and outside of a cell, the phospholipids line up with the tails on the inside of the layer (away from the water) and the heads are on the outside of the layer (near the water). The phosphate group is soluble in water because it is polar and therefore attracted to water molecules.
Fatty acid tails are not soluble in water because they are not polar and therefore not attracted to water molecules.
inside cell

20. Think - Pair - Share
Why do the phosphate heads point outward and the fatty acid tails point inward?
Phospholipid molecule
Polar head (includes phosphate group)
Nonpolar tails (fatty acids)
Section 2 Check

21. phospholipids move around
The phospholipids can move sideways through their layer, but not from one layer to the other.

22. Name given to this model of the plasma membrane.
Fluid because the phospholipids are free to move within the membrane.
Mosaic because of the pattern it produces when viewed from above.

23. Plasma Membrane
Talk to a Partner
Carbohydrates, transport proteins, cholesterol, phospholipids, bilayer, cytoplasm, outside cell

24. QUESTIONS???

25. What does it mean that a cell membrane has a lipid bilayer?

26. What is the function of this structure?

27. What is the function of this structure?

28. What is the function of this structure?

29. Describe the 2 components of this structure

30. Which of the following best describes the plasma membrane's mechanism in maintaining homeostasis?
A. protein synthesis
B. selective permeability
C. fluid composition
D. structural protein attachment
Section 2 Check

31. Explain why the model of the plasma membrane is called the fluid mosaic model.
Section 2 Check

32. Cornell SummarY