Membrane synthesis Flashcards
How do cells produce new membranes
by expansion of existing membranes
what happens to membrane lipids once formed
- delivered to the correct leaflet of the bilayer
- distributed to membranes of organelles
- distributed to the plasma membrane
where are cell membranes primarily synthesised
at the smooth endoplasmic reticulum
what do early steps of synthesis take place and produce
in the cytoplasm and produce water soluble intermediates
what does membrane synthesis start with
fatty acid synthesis
do saturated or non-saturated fatty acids have higher melting points
saturated
what gives unsaturated fatty acids kinks
presence of C=C double bonds
are unsaturated fatty acids liquid at room temperature
yes
two types of fatty acids
cis and trans
how long can sphinoglipids be
up to 26 carbon atoms
what is converted to fatty acids during their synthesis
acetyl-CoA
what two enzymes make saturated fatty acids
actetyl-CoA carboxylase and fatty acid synthase
where are fatty acids incorporated into phospholipids
on the SER membrane
what anchors the molecule to the membrane
long hydrocarbon chains
what enzyme catalyses the movement of phospholipids from the cytosolic to the cytoplasmic leaflet
Flippases
what has to converted in the SER to begin the cholesterol synthesis process
conversion of acetyl-CoA to HMG-CoA
what is HMG-CoA converted to in cholesterol synthesis
mevalonate
what do 5 of the 8 transmembrane helices compose
the sterol-sensing domain
what happens when membrane cholesterol is high
HMG-CoA reductase degradation by the proteasome which in turn stops mevalonate production
what is melvalonate converted to
IPP
what is IPP condensed into
six units into squalene
three mechanisms of lipid transport
vesicular transport, transfer mediated by small, soluble lipid- transfer proteins and lipid transfer mediated by direct contact between membranes
