2. The Structure and Function of the Plasma Membrane
Lecture5
The Structure and Function of the Plasma Membrane

3. Plasma membrane Only 5 to 10 nm wide
The simplest bacteria have only a single membrane

4. MEMBRANE FUNCTIONS Compartmentalization
Scaffold for biochemical activities
Providing a selectively permeable barrier
Transporting solutes
Responding to external signals
Intercellular interaction
Energy transduction

5. Membrane Structure
The lipids in cell membranes combine two very different properties in a single molecule: each lipid has a hydrophilic (“water-loving”) head and one or two hydrophobic (“water-fearing”) hydrocarbon tails.

6. Different type of membrane lipids

9. Liposomes as Potential Drug Carrier Systems for Drug Delivery

10. Membrane fluidity and its roles in the perception of environmental signals
The fluidity of a cell membrane is important for membrane function and has to be maintained within certain limits.
hyperosmotic stress reduce membrane fluidity similarly to low-temperature stress.

11. Asymmetry in membranes
Cell membranes are generally asymmetrical
Phosphatidylcholine and sphingomyelin are located primarily in the outer leaflet, while phosphatidylserine (PtdSer) and phosphatidylethanolamine (PtdEtn) are restricted to the cytoplasmic side.
Scramblases non-specifically and bidirectionally transport phospholipids between the inner and outer leaflets in an ATP-independent manner, while flippases, also known as ATP-dependent aminophospholipid translocases, transport PtdSer and PtdEtn from the extracellular to the cytoplasmic side.

13. Membrane proteins

14. Membrane proteins associate with the lipid bilayer in Various Ways

15. Cell cortex

16. Membrane domains

17. Carbohydrate layer

18. Lipid Bilayers Are Impermeable to Solutes and Ions

20. Membrane Transport Proteins

21. Passive and Active Transport

22. Conformational change in a transporter

23. Electrochemical gradient

24. Active transport by three main ways

25. Na+/K+ pump

26. The Na+/K+ Pump Helps Maintain the Osmotic Balance of Animal Cells

27. Coupled transporters

29. Glucose–na+ symporters

30. Two types of glucose transporters in epithelial cell

31. H+ Gradients Are Used to Drive Membrane Transport in Plants, Fungi, and Bacteria

32. Aquaporins

33. Ion channels

34. Stress-gated ion channels allow us to hear