Nucleus

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Nucleus

  1. 1. Fig. 1.11
  2. 2. Nucleus: structure and function Nucleolus Nucleoplasm nuclear envelope Heterochromatin = too compacted, transcriptionally inactive Euchromatin = can be transcriptionally active
  3. 3. Nuclear envelope and lamina Nuclear pore N. lamina cytoplasm heterochromatin
  4. 4. Nuclear laminaNuclear lamina
  5. 5. Lamins are filamentous proteins in the intermediate filament family Lamin phosphorylation in prophase disassembles the nuclear lamina & allows for nuc. envel. breakdown Laminins are extracellular proteins, unrelated
  6. 6. Nuclear pore • nuclear localization signals (nuclear import signals) • nuclear export signals • highly regulated
  7. 7. Mitochondria(on) outer membrane inner membrane DNA matrix cristae ribosomes ATP synthase
  8. 8. Inner Membrane and matrix electron transport system ADP3- ATP4- pyruvate Krebs cycle NADH ATP synthaseFADH2 hi [H+ ] Antiporter P04 -2 H+ symporter
  9. 9. Endosymbiotic theory: Mitochondria are similar to prokaryotes • Own circular, naked DNA • Own ribosomes - similar to prokaryotic – e.g. sensitive to same inhibitors • Divide by fission • Double membrane suggests endocytosis
  10. 10. Lysosomes: membranous organelles filled with digestive enzymes • Breakdown endocytosed materials – Thru’ phagocytosis or receptor mediated endocytosis • Breakdown old organelles (residual body) • Acidic pH
  11. 11. Phagocytosis vs. Autophagy Phagocytosis Autophagy lysosomes
  12. 12. Membrane trafficking •RER to cis Golgi •Modified in Golgi (glycosylation, phosphorylation) •Sorted at trans Golgi network into •Lysosomal •Regulated •constitutive
  13. 13. Synthesis of secreted and membrane proteins Ribosomes Rough endoplasmic reticulum
  14. 14. Rough Endoplasmic reticulum
  15. 15. Signal hypothesis: signal peptide, SRP, SRP-receptor, translocon SRP = signal recognition particle
  16. 16. Smooth ER, lipid synthesis, detox, Ca2+ sequestration
  17. 17. Golgi
  18. 18. Transport thru’ Golgi cisternae is vectorial Cis Medial Trans
  19. 19. mannose removal N-acetylglucosamine addition MEDIAL RER retrieval, PO4 on mannose, mannose removal CIS & CGN fucose and glucose addition TRANS sialic acid addition, sorting TGN Protein modifications occur in steps in the Golgi. The extent of changes varies.
  20. 20. Glycosylation Karp, Fig. 8.20
  21. 21. trans Golgi network regulated secretion lysosomal pathway constitutive secretion Sorting at the TGN
  22. 22. Receptor Mediated endocytosis
  23. 23. Plasma membrane & Fluid mosaic model
  24. 24. Phospholipids are most common in membranes Polar Head Fatty acid tails
  25. 25. phospholipids, glycolipids, and cholesterol
  26. 26. Thermodynamics drives membranes to form sealed compartments H2O Cut open liposome
  27. 27. Fluidity means that lipids (& proteins) can “float” in the membrane via diffusion Time
  28. 28. Three classes of membrane proteins: Transmembrane proteins (a type of IMP) OUT IN Extracellular domain (ECD) Intracellular domain (ICD) Transmembrane domain Oligosaccharides - always face out
  29. 29. Three classes of membrane proteins: Lipid- anchored membrane proteins (IMPs) OUT IN Covalently linked to a glycophospholipid. E.G.: Normal cellular scrapie protein & alkaline phosphatase Covalently linked to fatty acid E.G.: ras
  30. 30. Three classes of membrane proteins: Peripheral membrane proteins (PMPs) OUT IN Or, PMPs could bind to specific lipid heads. Specific interaction between IMP & PMP
  31. 31. IMPs as α-helix or β-barrel
  32. 32. Selective permeability
  33. 33. Osmosis causing cell lysis.
  34. 34. Four mechanisms by which solute molecules move ACROSS membranes Simple diffusion across bilayer Simple diffusion thru channel Facilitated Diffusion thru’ passive transporters Active transport
  35. 35. Membrane Potential Affects Molecular Movement A. neutral No effect on inward transport No effect on outward transport B. cation Favors inward transport Opposes outward transport C. anion Opposes inward transport Favors outward transport
  36. 36. Passive transport by channel proteins: don’t bind solute & can be ligand-, voltage-, or stress-gated
  37. 37. Passive Transport by Facilitated diffusion •Solute binds transporter protein •So, transport is saturable
  38. 38. Kinetics of carrier-mediated transport
  39. 39. Active transport by the Na/K pump or ATPase

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