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Fig. 1.11

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Nucleus: structure and function

Nucleolus Nucleoplasm

nuclear envelope

Heterochromatin =too compacted,

transcriptionally inactive

Euchromatin = can be transcriptionally active

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Nuclear envelope and lamina

Nuclearpore

N. lamina

cytoplasm

heterochromatin

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Nuclear lamina

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Lamins are filamentous proteins inthe intermediate filament family

Laminphosphorylationin prophasedisassembles thenuclear lamina &allows for nuc.envel. breakdown

Laminins areextracellularproteins,

unrelated

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Nuclear pore

nuclear localizationsignals (nuclear

import signals) nuclear export

signals

highly regulated

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Mitochondria(on)

outermembrane

innermembrane

DNAmatrix

cristaeribosomes ATP synthase

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Inner Membrane and matrix

electrontransportsystem

ADP 3-

ATP 4-

pyruvate

Krebscycle

NADH

ATPsynthaseFADH 2

hi [H +]

Antiporter

P0 4-2 H+

symporter

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Endosymbiotic theory: Mitochondriaare 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

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Lysosomes: membranous organellesfilled with digestive enzymes

Breakdownendocytosed materials Thru phagocytosis or

receptor mediatedendocytosis

Breakdown oldorganelles (residual

body) Acidic pH

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Phagocytosis vs. Autophagy

Phagocytosis

Autophagy

lysosomes

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Membranetrafficking

RER to cis Golgi Modified in Golgi(glycosylation,phosphorylation) Sorted at trans Golginetwork into

Lysosomal Regulated constitutive

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Ribosomes

Rough endoplasmic reticulum

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Rough Endoplasmic reticulum

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Signal hypothesis: signal peptide,SRP, SRP-receptor, translocon

SRP = signal recognition particle

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Smooth ER, lipid synthesis,detox, Ca 2+ sequestration

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Golgi

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Transport thru Golgi cisternae isvectorial

Cis Medial Trans

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mannose removalN-acetylglucosamine addition MEDIAL

RER retrieval, PO 4 on mannose,mannose removal

CIS &CGN

fucose and glucose addition TRANS

sialic acid addition, sorting TGN

Protein modifications occur in steps inthe Golgi. The extent of changes varies.

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Glycosylation

Karp, Fig. 8.20

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trans Golgi network

regulatedsecretion

lysosomalpathway

constitutivesecretion

Sorting at the TGN

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Receptor Mediated endocytosis

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Plasma membrane & Fluidmosaic model

Ph h li id

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Phospholipids are most commonin membranes

PolarHead

Fattyacidtails

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phospholipids, glycolipids, andcholesterol

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Thermodynamics drives membranes toform sealed compartments

H2O

Cut openliposome

l d h l d ( )

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Fluidity means that lipids (& proteins)can float in the membrane via

diffusion

Time

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Three classes of membrane proteins:Transmembrane proteins (a type of IMP)

OUT

IN

Extracellulardomain (ECD)

Intracellular

domain (ICD)

Transmembranedomain

Oligosaccharides- always face out

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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 acidE.G.: ras

Th l f b i

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Three classes of membrane proteins:Peripheral membrane proteins (PMPs)

OUT

IN Or, PMPs could

bind to specific

lipid heads.

Specific interaction

between IMP & PMP

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IMPs as a -helix or b-barrel

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Selective permeability

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Osmosis causing cell

lysis.

F h i b hi h l t

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Four mechanisms by which solutemolecules move ACROSS membranes

Simple diffusionacross bilayer

Simple diffusionthru channel

FacilitatedDiffusion

thru passivetransporters

Activetransport

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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

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Passive transport by channel proteins : dont bind solute & can

be ligand-, voltage-, or stress-gated

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Passive Transport by Facilitated diffusion

Solute bindstransporter protein So, transport issaturable

Kinetics of carrier mediated

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Kinetics of carrier-mediatedtransport

Active transport by the

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Active transport by the Na/K pump or ATPase