Stephen Fish, Ph'D'

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Stephen Fish, Ph.D. Marshall University J. C. E.
School of Medicine Fish_at_Marshall.edu
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Note to instructors I use these PowerPoint
slides in cell biology lectures that I give to
first year medical students. Copy the slides, or
just the illustrations into your own teaching
media. We all know that teaching science often
requires compromises and simplification for
specific student populations, or the requirements
of a specific course. Please feel free to offer
suggestions for improvements, corrections, or
additional illustrations. I would be pleased to
hear from anyone who finds my work useful, and am
always willing to make it better. Also, the
images have been compressed to screen resolution
to keep PowerPoint file size down, and I can
provide them at any resolution. Stephen E.
Fish, Ph.D.
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Organelles Molecular Traffic Nucleus sER
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Nuclear pore complex
Cytoplasm side
Filaments
Outer nuclear membrane (also ER membrane)
Top view
Inner ring
ER lumen
Inner nuclear membrane
Outer ring (transmembrane anchors)
Basket assembly
Nucleoplasm side
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Nuclear Pores Communicate Between Cytoplasm
Nucleoplasm

• Diffusion of small molecules (9nmlt)
• Active transport in
• Proteins for RNA
• Transcription factors
• Active transport of RNA out

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Ran GaP GEF create a transport cycle Ran GDP
in, Ran GTP out
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Movement of Ran through the pore is due to GTP
GDP concentration gradients
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Nuclear protein import

• Importin binds an import protein signal patch
  with Ran-GDP bound
• It releases its cargo in the nucleus when GEF
  catalyzes GTP for GDP exchange on Ran

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Nuclear protein export

• Exportin binds an export protein signal patch
  with Ran-GTP bound
• It releases its cargo in the cytosol when GTP is
  hydrolyzed to GDP by Ran-GaP

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Following the Ran cycle, Importin Exportin
return to pick up more cargo
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Phosphorylation of lamins the nuclear pore
causes disassembly
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A C lamins nuclear pore components become
soluble, membrane breaks up into vesicles
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Near the end of mitosis

• Cyclin B ubiquitinated removed by proteosomes
• A phosphatase dephosphorylates lamins pore
  proteins they reassemble
• B binds A C bind chromosomes

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Membrane lipids are made on the ER outer leaflet
Scramblase equilibrates the leaflets
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Membrane lipids are delivered to all cytosol
facing leaflets by random exchange proteins
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Flippase provides for specific lipid asymmetry in
membranes
Equilibrates sets lipid asymmetry in organelle
cellular membrane after exchange protein
delivers lipids
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Delivery of new membrane by transport vesicles
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Chylomicrons make liquid fat soluble for
transmission in the blood- they are made by
reprocessed by the ER
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Enterocytes chylomicrons

• Lymph vessels (called lacteals in the GI tract)
  have gaps in their walls
• Flow of excess tissue fluid carries chylomicrons
  other nutrients into the vessels, carry them
  to the blood stream

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Fat cells use sER to store release fat
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