Lipid Synthesis & Lipid Storage Diseases
What are the 4 stages in synthesis of sphingolipids?
1. synthesis of shinganine 2. attachment of FA via amide bond 3. desaturation of the alkane chain → makes ceramide 4. headgroup attachment
______ is the receptor for cholera toxin in our intesines.
Ganglioside GM1
In mammals, methylation of __ → __ only occurs in the _______________.
In mammals, methylation of PE → PC only occurs in the LIVER.
What glycerophospholipid is a major component in surfactant?
PC (most notably DPPC and unsaturated PC) however, PC biosynthesis does not start until late in gestation, which is why this can be problematic for premature infants
What is the most abundant glycerophospholipid in animal tissue?
PC = phosphatidylcholine
What are the 2 strategies for glycerophospholipid synthesis?
Strategy 1: activation of DAG Strategy 2: activation of head group
How is phosphatidylcholine synthesized outside of the liver?
Strategy 2: Activated headgroup
________________ are associated with blood type marking.
glycosphingolipids
sphingolipid synthesis following ceramine takes place in the...
golgi
How is PS (phosphatidylserine) synthesized in eukaryotes?
headgroup exhange with PE or PC
Tay-Sachs disease
hydrolase hexosaminidase A is defective; ganglioside GM2 accumulates in lysosome, yielding characteristic "onion" appearance of lysosome in histology
What happens to lipid synthesis rate in lipid storage diseases?
nothing - rate remains normal. the issue is with the hydrolases required for breakdown
plasmalogens and other ether linked glycerophospholipids are synthesized in...
peroxisomes
Where does glycerophospholipid synthesis occur in bacteria?
plasma membrane
What are the 2 glycerophospholipids with ether linkages?
plasmalogen + platelet activating factor
How is CL (cardiolipin) synthesized in prokaryotes versus eukaryotes?
prokaryotes: 2 x PG (phosphatidylglycerol) eukaryotes: CDP-DAG + PG cardiolipin synthase is used
Define cerebroside
simple, neutral glycosphingolipid with 1 sugar (physiologically, it is usually Gal → Galactocerebroside)
Where does glycerophospholipid synthesis occur in eukaryotes?
smooth ER
glycerophospholipid synthesis takes place in the...
smooth ER
sphingolipid synthesis pre-ceramide takes place in the...
smooth ER
What membrane lipid is not derived from glycerol?
sphingomyelin
The first steps of glycerophospholipid biosynthesis are shaerd with the pathway for the synthesis of _____. Starts with transition from ____ → universal precursor ______.
synthesis of TAGs DHAP → phosphatidic acid
Where does plasmalogen/ether-linked phospholipid synthesis take place? What is its precursor?
takes place in peroxisomes precursor: DHAP (distinct pathway, no phosphatidic acid/DAG/activation)
How is PC synthesized in prokaryotes?
using Strategy 1: activation of DAG
Define ganglioside. Where are these commonly found?
acidic glycosphongolipid, contains at least one sialic acid high concentration of gangliosides found in nervous tissue and commonly found on outer leaflet of the plasma membrane
How are the DAGs / headgroups "activated"?
addition of CDP
What uses Strategy 1: Activation of DAG?
bacteria → for all glycerophospholipid synthesis eukaryotes → for synthesis of anionic phopsholipids → GP, CL (cardiolipin), PI (phosphatidylinositol) eukaryotes can also synthesize PC in a manner similar to prokaryotes, but only in the liver (via methylation of PE)