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

Nuclear lamina

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

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

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

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

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

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

Phagocytosis vs. Autophagy lysosomes Autophagy

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

Rough endoplasmic reticulum Ribosomes Synthesis of secreted and membrane proteins

Rough Endoplasmic reticulum

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

Smooth ER, lipid synthesis, detox, Ca2+ sequestration

Golgi

Transport thru’ Golgi cisternae is vectorial Medial Trans

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

Glycosylation Karp, Fig. 8.20

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

Receptor Mediated endocytosis

Plasma membrane & Fluid mosaic model

Phospholipids are most common in membranes Polar Head Fatty acid tails

phospholipids, glycolipids, and cholesterol

Thermodynamics drives membranes to form sealed compartments Cut open liposome H2O

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

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

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 IN E.G.: ras

Three classes of membrane proteins: Peripheral membrane proteins (PMPs) OUT IN Or, PMPs could bind to specific lipid heads. Specific interaction between IMP & PMP

IMPs as -helix or -barrel

Selective permeability

Osmosis causing cell lysis.

Four mechanisms by which solute molecules move ACROSS membranes Simple diffusion across bilayer Simple diffusion thru channel Facilitated Diffusion thru’ passive transporters Active transport

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

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

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

Kinetics of carrier-mediated transport

Active transport by the Na/K pump or ATPase