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54 Cards in this Set

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In what tissue are the sphingolipids highest in concentration?
Central nervous system
What makes the backbone of sphingolipids?
Sphingosine
How is the numbering of the "3-carbon backbone" different between sphingolipids and phospholipids?
It is reversed
What is the name of the compound that results when a FA is added to C2 of sphingosine?
Ceramide
What is Ceramide in relation to sphingolipids?
Analagous to Phosphatidic acid for phospholipids - the precursor to them all.
What are the 3 types of sphingolipids?
1. Sphingomyelin
2. Glycosphingolipids
4. Ganglioside
What does sphingomyelin contain? (one of 2 things)
-Phosphocholine
or
-Phosphoethanolamine
Resembles the phosphomolecules
How do the Glycosphingolipids and Gangliosides differ from Sphingomyelin?
They don't contain phosphate
What structural feature makes Glycosphingolipids unique?
Head group consists of one or more sugars directly attached to the C1 hydroxyl.
What is a Glycosphingolipid w/:
-one sugar
-more than one sugar
One = Cerebroside

>1 = Globoside
What are glycosphingolipids sometimes called, and why?
Neutral glycolipids - b/c they are mostly on outer plasma membrane surface and are uncharged at pH 7
What are the most complex sphingolipids?
Gangliosides
What is the head group on Gangliosides composed of?
Oligosaccharides with one/more N-acetylneuraminic acids at the termini
2 other names for N-acetylneuraminic acid:
Neu5Ac or NANA
What is Neu5Ac?
a Sialic acid
What does the presence of Neu5Ac do to Gangliosides?
Gives them a negative charge at pH 7
Where are Gangliosides found in highest concentration?
Gray matter of CNS
What intestinal toxin is associated with a ganglioside on the lumen of intestinal mucosal cells?
Cholera
What 2 reactants are used to produce sphingosine? what kind of reaction?
-Palmitoyl CoA + Serine
-Condensation
What does Ser contribute to sphingosine?
Carbons 1/2 and NH3 group
What does Palmitoyl CoA contribute?
The rest of it :)
What enzyme catalyzes condensation of Palmitoyl CoA and Serine?
Serine Palmitoyltransferase
What gives this condensation its driving force?
Cleaving the high energy thiol boyd of Palmitoyl CoA, and release of CO2
How is Ceramide produced?
By acetylating C2 amino group of sphingocine w/ a long chain FA.
Ceramide + Phosphocholine =
Sphingomyelin
Where does the phosphocholine for making Sphingomyelin come from?
Phosphatidylcholine
Ceramide + UDP-glucose/galactose makes:
Glycosphingolipids
(cerebrosides + gangliosides)
What is required for synthesis of Gangliosides?
Stepwise addition of sugar residues to ceramide.
What sugars are required for making Gangliosides?
-UDP-glucose/galactose
-UDP-N-Acetylglucosamine
-CMP-NeuAc
What is CMP-NeuAc?
N-acetylneuraminic acid - its CMP derivative
In general terms how does Ganglioside synthesis proceed?
-Begins with cerebroside
-Continues thru globosides
-Ends when Sialic Acid is added
What DETERMINES Ganglioside structure?
Glycosyltransferases - specific for the moieties that they add.
How many gangliosides have been characterised?
More than 60.
Where does Sphingolipid degradation occur?
In lysozymes
What is Sphingolipidosis?
Accumulation of the substrate for an enzyme in sphingolipid degradation that is deficient.
What tissues are most affected by Sphingolipidoses?
Phagocytic cells of RES in
-Liver/spleen/bone marrow
-Brain (from gangliosides)
What are the 2 most common sphingolipidoses?
1. Tay-Sach's disease
2. Niemann-Pick disease
What is the deficiency in Tay-Sach's? In what tissue does it primarily manifest?
B-hexosaminidase

-In the brain
What population is associated with Tay-Sach's?
Ashkenazi Jews
What is the deficiency in Niemann-Pick disease?
Sphingomyelinase
What reaction is catalyzed by Sphingomyelinase?
In what tissues does it primarily manifest?
Degradation of Sphingomyelin into Phosphocholine + ceramide
-In the liver and spleen
What is the main difference between Polyisoprenoids and the other complex lipids?
Derived from 5-Carbon isoprene units vs. Fatty Acids
How are isoprene units made?
By the synthesis of Mevalonic acid (6-C) from AcCoA
What are the important isoprenoids? (7)
-Bile salts
-Cholesterol
-Dolichol
-Protein-membrane anchors (Farnesyl and Geranylgeranyl)
-Steroid hormones
-Ubiquinone
-Vitamins DEAK
What is the basic structure of steroids, and what are they made from?
-Mainly a 4-ring structure
-Made from Squalene
What does modification of Squalene make?
cholesterol
What important membrane-protein anchors are cholesterol biosynthetic intermediates?
Farnesyl (c15)
and
Geranylgeranyl (C20)
How many carbons are in Squalene?
30 (6 5-carbon isoprene units)
What does phosphorylation of farnesyl produce?
Dolichol
Cholesterol is the precursor for: (3 things)
-Bile acids
-Steroid hormones
-Vitamin D
Bile acids (2):
-Cholic acid
-Deoxycholic acid
Steroid hormones (4):
-Estradiol
-Testosterone
-Progesterone
-Corticosterone
Vitamin D
Cholecalciferol
Interesting other polyisoprenoids:
-Warfarin (coumadin)
-Vitamins EAK
-Ubiquinone
-Dolichol