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Lecture

Notes taken during lecture


Department
Biology
Course Code
BIO120H1
Professor
Jean Jiang Nash

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LECTURE 7 Feb. 1. 2010
Intracellular vesicular transport part 1 and Molecular mechanisms
Each cisternae has different [enzymes]
Remove or add sugars
Proteins today all synthesize into ER lumen or
Golgi has series of membrane stacks/pancakes there are resident proteins in each stack
Vesicle tracking
Synthesis of membrane lipids
In the smooth ER
Ceramide more minor component made in ER transported to other
compartments in vesicles
oSynthesized in ER, transported into golgi, where it is modified to produce
Sphingomyelin
Glycolipids sugars attached to fat happens in Golgi
Found in luminal leaflet
Likely to find in extraplasmic leaflet ?
Do not need to memorize the chemical pathway
Enzymes labelled in green in cytosol or are transmembrane membranes with
acive sites in cytosol
OCCURS IN CYTOSOL *** cytosolic leaflet will grow,
Made by ER expansion
oPlasma membrane expands lipids from ER
oNew lipids in cytosolic leaflet of ER
Newly synthesized lipids inserted into cytosolic leaflet luminal leaflet a bit smaller not
stable so some lipids in cytsolic leaflet flipped into other leaflet
Rapidly flipped to other leaflet
Scramblase
oSo random distribution in ER membrane
By vesicular transport
Asymmetry of lipid bilayer from LEC1
Synthesized on luminal face of Golgi
Signalling
These for lec1
Negatively charge on outside surface of cell cell is dying so important to maintain
asymmetry
Intracellular vesicle that fuse and deliver these lipids
Delivery of randomly distributed lipids flippase at plasma membrane that grabs
onto lipids like phsoptidyserine and flips them from outside to inside
Flippase (ABC transport)
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Energy from ATP hydrolysis
Know the phsoptidyserine example *****
oScavenger cells survey body looking for dead or dying cells to digest
oWhen cell dies, exposes phosophidylserine recognized by scavenger cells
oCannot maintain asymmetric membrane so sick cell must be killed
2. formation and fusion of vesicles (part a)
Vesicular transport
Budding with cargo
oBuds from donor membrane, containing cargo
Fusion to target
Release cargo as it fuses thus deliver cargo
Vesicle ball with lipid bilayer, studded with transmembrane proteins and
proteins that stick out, and contains cargo
Know overview of intracellular vesicular transport know the arrows, come from, go to,
details…etc
***********
- blue is a retrieval pathway
Transport vesicles
Vesicles in process of buding, eventually buds off, moves to target, fuses, and
delivers cargo
Transmemebrane proteins
Soluble proteins bound by transmembrane cargo receptors
Imagine target compartment is the plasma membrane, donor is Golgi
oThe transmembrane proteins now on cytosolic
oN-terminal luminal now outside
oCargo now outside cell
Vesicle formation depends on protein coats
Repeated subunits of protein that stick together, curve membrane and cause
vesicle to form
Select cargo for vesicle
Give curvature to vesicle
Promote vesicle budding
COPI-coated vesicles
Cop one is how it is pronounced
From Golgi to ER
Light blue ones in the diagram
Between different Golgi cisternae
COP2
From ER to Golgi
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