1. Transport, con't.

3. The Na/K ATPase

5. Consequences of Na/K ATPase Two ion gradients –Used as energy source –Electrical signaling Charge difference across membrane –Membrane potential difference –Negative on inside -60 to –90 mV in animal cells ~ -150 mV in bacteria -200 to –300 mV in plants –Not just due to these ions Phosphatidylserine on inside of PM Other ions

6. Indirect (secondary) AT Na/glucose symporter –Intestinal absorptive cells

9. Thermodynamics of Transport

10. Thermodynamics of Transport, charged

11. Intracellular compartments The Endomembrane System

13. Endoplasmic Reticulum Smooth ER Rough ER ER cisternae ER lumen

14. Smooth ER Lipid biosynthesis –Membrane phospholipids –Cholesterol –TAG Drug detoxification Glycogen metabolism (catabolism) Calcium storage

15. Rough ER "rough" with ribosomes Synthesis of –Membrane proteins for endomembrane system –Secreted proteins Initial glycosylation of many of these

16. Golgi body Camillo Golgi, 1898

17. Golgi Glycosylation of secretory and membrane proteins Sorting/trafficking

18. Secretory and membrane proteins Synthesis starts in cytoplasm on ribosomes Signal sequence determines where it goes –Nucleus –Mitochondria Post-translational import –RER (endomembrane system) Co-translational import

19. Pg. 679

21. Co-translational import—secreted protein SRP=signal recognition particle

23. Membrane bound proteins

24. Post-translational import (mitochondrial) TOM= translocase of outer membrane TIM=translocase of inner membrane

27. Post-translational modification Proteolytic cleavage Glycosylation Phosphorylation Addition of a lipid group (lipid anchored proteins) Adenylation Etc.

28. Glycosylation

31. The Big Picture

33. Bulk Transport Exocytosis Endocytosis –pinocytosis –Phagocytosis Autophagy –Receptor-mediated endocytosis

34. Exocytosis -constitutive secretion -regulated secretion

35. Endocytosis -pinocytosis

37. Receptor Mediated Endocytosis Bulk transport Specific

39. The Big Picture

40. Coated Vesicles Clathrin –Golgi to endosomes –Endocytosis COP I COP II –ER and Golgi –Within the Golgi

43. How do coated vesicles go to the right place and fuse with the right membrane? The “SNARE” hypothesis

44. SNARE Vesicle-SNAP-receptors (v-SNAREs) Target-SNAP-receptors (t-SNAREs) SNAP=soluble NSF attachment proteins NSF=N-ethylmaleimide-sensitive factor

46. Lysosomes Digestive enzymes Low pH (4-5) Develop from late endosomes/hydrolases from Golgi Activated by lowering the pH