The Plasma Membrane

1. The Plasma Membrane BIO 1113/1114 Oklahoma City Community College Dennis Anderson

2. Cystic Fibrosis • Danni is a college student • "I have a regime that I follow every day," she says. It involves taking antibiotics, a puffer, vitamins, pancreatic enzymes with food and three lots of nebulisation. On top of that she has one to two hours of chest percussion to clear her airways.

3. Plasma Membrane or Cell Membrane

4. (a) Phospholipid molecule Polar head – nonpolar tails

5. (a) Phospholipid molecule (b) Phospholipid bilayer watery extracellular fluid polar head – hydrophilic hydrophobic nonpolar tails hydrophilic watery cytosol hydrophobic molecules pass through freely hydrophilic molecules do not pass through freely

6. cholesterol proteins phospholipids glycocalyx cell exterior Figure 5.1The Plasma Membrane cell interior integral protein peripheral protein cytoskeleton Phospholipid bilayer: a double layer of phospholipid molecules whose hydrophilic “heads” face outward, and whose hydrophobic “tails” point inward, toward each other. Glycocalyx: sugar chains that attach to proteins and phospholipids, serving as protein binding sites and as cell lubrication and adhesion molecules. Cholesterol molecules that act as a patching substance and that help the cell maintain an optimal level of fluidity. Proteins, which are integral, meaning bound to the hydrophobic interior of the membrane, or peripheral, meaning not bound in this way.

7. (a) Structural support (b) Recognition (c) Communication (d) Transport Figure 5.3Roles of Membrane Proteins Membrane proteins can provide structural support, often when attached to parts of the cell’s scaffolding or “cytoskeleton.” Binding sites on some proteins can serve to identify the cell to other cells, such as those of the immune system. Receptor proteins, protruding out from the plasma membrane, can be the point of contact for signals sent to the cell via traveling molecules, such as hormones. Proteins can serve as channels through which materials can pass in and out of the cell.

9. Phospholipids • Prevents movement of water soluble molecules and ions

10. Cholesterol • Strengthens cell membrane

11. Transport Proteins • Form channels to allow molecules or ions to enter or leave the cell

12. Recognition Proteins • Carbohydrate • Identify the cell

13. Peripheral Protein • Enzymes

14. Receptor Proteins • React with molecular signals

15. (a) Dye is dropped in (b) Diffusion begins (c) Dye is evenly distributed Figure 5.4From Concentrated to Dispersed water molecules dye molecules

16. Diffusion High Concentration Low Concentration

17. Diffusion • Movement of molecules from a high concentration to a low concentration • Passive process

18. Lung Blood

19. Lipids • Oxygen • Carbon dioxide • Sodium • Chloride • Glucose Diffusion

20. Facilitated Diffusion • Movement of molecules across a membrane with the help of a carrier protein • Passive process

21. glucose outside cell plasma membrane inside cell 1. The transport pro- tein has a binding site for glucose that is open to the outside of the cell. 2. 3. 4. Glucose binds to the binding site. This binding causes the protein to change shape, exposing glucose to the inside of the cell. Glucose passes into the cell and the protein returns to its original shape.

22. solute (a) An aqueous solution divided by a semipermeable membrane has a solute —in this case, salt— poured into its right chamber. solvent semipermeable membrane (b) As a result, though water continues to flow in both directions through the membrane, there is a net movement of water toward the side with the greater concentration of solutes in it. osmosis (c) Why does this occur? Water molecules that are bonded to the sodium (Na+) and chloride (Cl–) ions that make up salt are not free to pass through the membrane to the left chamber of the container. pure water water bound to salt ions

23. Osmosis Semipermeable membrane High Solute Low Solute

24. Osmosis • The movement of water through a semipermeable membrane to the side with more solutes • Passive process

25. Salt • Salt • Salt No movement of water Cells • 300 • 300 • 300 Blood

26. Salt • Salt • Salt Which way will water move? Cells • 300 • 300 • 320 Blood

27. 1% NaCl 0.2% NaCl Hypertonic A solution with a higher concentration than another Hypertonic

28. 1% NaCl 0.2% NaCl Hypotonic A solution with a lower concentration than another Hypertonic Hypotonic

29. 0.9% NaCl Isotonic A solution with the same concentration as another 0.9% NaCl

30. (b) Isotonic surroundings (c) Hypotonic surroundings (a) Hypertonic surroundings H2O Animal cell: plasma membrane H2O H2O Plant cell: H2O plasma membrane H2O H2O cell wall wilted turgid Balanced water movement Net movement of water into cell Net movement of water out of cell

31. Isotonic IV Solution • Most IV solutions are isotonic • Prevents blood cells from swelling or shrinking

32. Low Concentration Active Transport High Concentration

33. Active Transport • Movement of molecules from a low concentration to a high concentration • Requires energy • Requires a transport protein

34. + + + + + + + + + + + + + + + + + + Active Transport in a Nerve Cell +

35. Passive transport Active transport simple diffusion facilitated diffusion ATP Materials move down their concentration gradient through the phospholipid bilayer. The passage of materials is aided both by a concentration gradient and by a transport protein. Molecules again move through a transport protein, but now energy must be expended to move them against their concentration gradient.

36. Phagocytosis

37. Phagocytosis

38. Pinocytosis

39. (a) Exocytosis extracellular fluid protein Figure 5.9aMovement Out of the Cell transport vesicle cytosol

40. The End