1. Structure and Function
The Plasma Membrane
Structure and Function

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
The property of a membrane that allows some materials to pass through while keeping others out.

8. Structure of the Plasma Membrane

9. outside cell
cytoplasm

10. 1) Cholesterol
Stabilizes the membrane by preventing phospholipids from sticking together

11. 2) Transport Proteins
help move large molecules across the membrane

12. 3) Carbohydrates are used for cell recognition and attachment

13. 4) Phospholipids

14. Phospholipids Phosphate head 2 Fatty acid tails hydrophobic
Phosphate + glycerol
hydrophilic
“attracted to water”
2 Fatty acid tails
hydrophobic
“repelled by water”
“attracted to water”
Fatty acid
“repelled by water”

15. Phospholipids are arranged in a bilayer
Hydro_______
Hydro________
Hydro________

16. Phospholipids are arranged in a bilayer
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.

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

18. 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.

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

20. QUESTIONS???

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

22. What is the function of this structure?

23. What is the function of this structure?

24. What is the function of this structure?

25. Describe the 2 components of this structure

26. 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

27. 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

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

29. Cornell SummarY