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Fig. 1.11

Fig. 1.11. Nucleus: structure and function. Heterochromatin = too compacted, transcriptionally inactive. nuclear envelope. Nucleolus. Nucleoplasm. Euchromatin = can be transcriptionally active. Nuclear envelope and lamina. cytoplasm. N. lamina. Nuclear pore. heterochromatin.

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Fig. 1.11

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  1. Fig. 1.11

  2. Nucleus: structure and function Heterochromatin = too compacted, transcriptionally inactive nuclear envelope Nucleolus Nucleoplasm Euchromatin = can be transcriptionally active

  3. Nuclear envelope and lamina cytoplasm N. lamina Nuclear pore heterochromatin

  4. Nuclear lamina

  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. Nuclear pore • nuclear localization signals (nuclear import signals) • nuclear export signals • highly regulated

  7. Mitochondria(on) outer membrane DNA inner membrane matrix cristae ribosomes ATP synthase

  8. hi [H+] ATP synthase FADH2 NADH Krebs cycle ATP4- Antiporter ADP3- pyruvate Inner Membrane and matrix electron transport system symporter H+ P04-2

  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. Lysosomes: membranous organelles filled with digestive enzymes • Breakdown endocytosed materials • Thru’ phagocytosis or receptor mediated endocytosis • Breakdown old organelles (residual body) • Acidic pH

  11. Phagocytosis vs. Autophagy Phagocytosis lysosomes Autophagy

  12. Membrane trafficking • RER to cis Golgi • Modified in Golgi (glycosylation, phosphorylation) • Sorted at trans Golgi network into • Lysosomal • Regulated • constitutive

  13. Ribosomes Synthesis of secreted and membrane proteins Rough endoplasmic reticulum

  14. Rough Endoplasmic reticulum

  15. Signal hypothesis: signal peptide, SRP, SRP-receptor, translocon SRP = signal recognition particle

  16. Smooth ER, lipid synthesis, detox, Ca2+ sequestration

  17. Golgi

  18. Transport thru’ Golgi cisternae is vectorial Cis Trans Medial

  19. CIS & CGN RER retrieval, PO4 on mannose, mannose removal mannose removal N-acetylglucosamine addition MEDIAL TRANS fucose and glucose addition TGN sialic acid addition, sorting Protein modifications occur in steps in the Golgi. The extent of changes varies.

  20. Glycosylation Karp, Fig. 8.20

  21. Sorting at the TGN constitutive secretion lysosomal pathway regulated secretion trans Golgi network

  22. Receptor Mediated endocytosis

  23. Plasma membrane & Fluid mosaic model

  24. Phospholipids are most common in membranes Polar Head Fatty acid tails

  25. phospholipids, glycolipids, and cholesterol

  26. Thermodynamics drives membranes to form sealed compartments Cut open liposome H2O

  27. Fluidity means that lipids (& proteins) can “float” in the membrane via diffusion Time

  28. Three classes of membrane proteins: Transmembrane proteins (a type of IMP) Oligosaccharides - always face out Extracellular domain (ECD) OUT Transmembrane domain Intracellular domain (ICD) IN

  29. Three classes of membrane proteins: Lipid-anchored membrane proteins (IMPs) Covalently linked to a glycophospholipid. E.G.: Normal cellular scrapie protein & alkaline phosphatase OUT Covalently linked to fatty acid E.G.: ras IN

  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. IMPs as a-helix or b-barrel

  32. Selective permeability

  33. Osmosis causing cell lysis.

  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. 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. Passive transport by channel proteins: don’t bind solute & can be ligand-, voltage-, or stress-gated

  37. Passive Transport by Facilitated diffusion • Solute binds transporter protein • So, transport is saturable

  38. Kinetics of carrier-mediated transport

  39. Active transport by the Na/K pump or ATPase

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