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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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nucleus structure and function
Nucleus: structure and function

Heterochromatin =

too compacted, transcriptionally inactive

nuclear envelope

Nucleolus

Nucleoplasm

Euchromatin = can be transcriptionally active

nuclear envelope and lamina
Nuclear envelope and lamina

cytoplasm

N. lamina

Nuclear

pore

heterochromatin

lamins are filamentous proteins in the intermediate filament family
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 pore
  • nuclear localization signals (nuclear import signals)
  • nuclear export signals
  • highly regulated
mitochondria on
Mitochondria(on)

outer

membrane

DNA

inner

membrane

matrix

cristae

ribosomes

ATP synthase

inner membrane and matrix

hi [H+]

ATP

synthase

FADH2

NADH

Krebs

cycle

ATP4-

Antiporter

ADP3-

pyruvate

Inner Membrane and matrix

electron

transport

system

symporter

H+

P04-2

endosymbiotic theory mitochondria are similar to prokaryotes
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
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
Phagocytosis vs. Autophagy

Phagocytosis

lysosomes

Autophagy

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

SRP = signal recognition particle

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

TRANS

fucose and glucose addition

TGN

sialic acid addition, sorting

Protein modifications occur in steps in the Golgi. The extent of changes varies.
glycosylation
Glycosylation

Karp, Fig. 8.20

sorting at the tgn
Sorting at the TGN

constitutive

secretion

lysosomal

pathway

regulated

secretion

trans Golgi network

three classes of membrane proteins transmembrane proteins a type of imp
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
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

three classes of membrane proteins peripheral membrane proteins pmps
Three classes of membrane proteins: Peripheral membrane proteins (PMPs)

OUT

IN

Or, PMPs could bind to specific lipid heads.

Specific interaction between IMP & PMP

four mechanisms by which solute molecules move across membranes
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
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 channel proteins: don’t bind solute & can be ligand-, voltage-, or stress-gated
passive transport by facilitated diffusion
Passive Transport by Facilitated diffusion
  • Solute binds transporter protein
  • So, transport is saturable