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54 Cards in this Set
- Front
- Back
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In what tissue are the sphingolipids highest in concentration?
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Central nervous system
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What makes the backbone of sphingolipids?
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Sphingosine
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How is the numbering of the "3-carbon backbone" different between sphingolipids and phospholipids?
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It is reversed
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What is the name of the compound that results when a FA is added to C2 of sphingosine?
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Ceramide
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What is Ceramide in relation to sphingolipids?
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Analagous to Phosphatidic acid for phospholipids - the precursor to them all.
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What are the 3 types of sphingolipids?
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1. Sphingomyelin
2. Glycosphingolipids 4. Ganglioside |
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What does sphingomyelin contain? (one of 2 things)
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-Phosphocholine
or -Phosphoethanolamine Resembles the phosphomolecules |
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How do the Glycosphingolipids and Gangliosides differ from Sphingomyelin?
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They don't contain phosphate
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What structural feature makes Glycosphingolipids unique?
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Head group consists of one or more sugars directly attached to the C1 hydroxyl.
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What is a Glycosphingolipid w/:
-one sugar -more than one sugar |
One = Cerebroside
>1 = Globoside |
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What are glycosphingolipids sometimes called, and why?
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Neutral glycolipids - b/c they are mostly on outer plasma membrane surface and are uncharged at pH 7
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What are the most complex sphingolipids?
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Gangliosides
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What is the head group on Gangliosides composed of?
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Oligosaccharides with one/more N-acetylneuraminic acids at the termini
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2 other names for N-acetylneuraminic acid:
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Neu5Ac or NANA
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What is Neu5Ac?
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a Sialic acid
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What does the presence of Neu5Ac do to Gangliosides?
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Gives them a negative charge at pH 7
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Where are Gangliosides found in highest concentration?
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Gray matter of CNS
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What intestinal toxin is associated with a ganglioside on the lumen of intestinal mucosal cells?
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Cholera
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What 2 reactants are used to produce sphingosine? what kind of reaction?
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-Palmitoyl CoA + Serine
-Condensation |
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What does Ser contribute to sphingosine?
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Carbons 1/2 and NH3 group
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What does Palmitoyl CoA contribute?
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The rest of it :)
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What enzyme catalyzes condensation of Palmitoyl CoA and Serine?
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Serine Palmitoyltransferase
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What gives this condensation its driving force?
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Cleaving the high energy thiol boyd of Palmitoyl CoA, and release of CO2
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How is Ceramide produced?
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By acetylating C2 amino group of sphingocine w/ a long chain FA.
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Ceramide + Phosphocholine =
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Sphingomyelin
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Where does the phosphocholine for making Sphingomyelin come from?
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Phosphatidylcholine
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Ceramide + UDP-glucose/galactose makes:
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Glycosphingolipids
(cerebrosides + gangliosides) |
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What is required for synthesis of Gangliosides?
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Stepwise addition of sugar residues to ceramide.
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What sugars are required for making Gangliosides?
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-UDP-glucose/galactose
-UDP-N-Acetylglucosamine -CMP-NeuAc |
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What is CMP-NeuAc?
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N-acetylneuraminic acid - its CMP derivative
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In general terms how does Ganglioside synthesis proceed?
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-Begins with cerebroside
-Continues thru globosides -Ends when Sialic Acid is added |
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What DETERMINES Ganglioside structure?
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Glycosyltransferases - specific for the moieties that they add.
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How many gangliosides have been characterised?
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More than 60.
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Where does Sphingolipid degradation occur?
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In lysozymes
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What is Sphingolipidosis?
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Accumulation of the substrate for an enzyme in sphingolipid degradation that is deficient.
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What tissues are most affected by Sphingolipidoses?
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Phagocytic cells of RES in
-Liver/spleen/bone marrow -Brain (from gangliosides) |
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What are the 2 most common sphingolipidoses?
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1. Tay-Sach's disease
2. Niemann-Pick disease |
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What is the deficiency in Tay-Sach's? In what tissue does it primarily manifest?
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B-hexosaminidase
-In the brain |
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What population is associated with Tay-Sach's?
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Ashkenazi Jews
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What is the deficiency in Niemann-Pick disease?
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Sphingomyelinase
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What reaction is catalyzed by Sphingomyelinase?
In what tissues does it primarily manifest? |
Degradation of Sphingomyelin into Phosphocholine + ceramide
-In the liver and spleen |
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What is the main difference between Polyisoprenoids and the other complex lipids?
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Derived from 5-Carbon isoprene units vs. Fatty Acids
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How are isoprene units made?
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By the synthesis of Mevalonic acid (6-C) from AcCoA
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What are the important isoprenoids? (7)
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-Bile salts
-Cholesterol -Dolichol -Protein-membrane anchors (Farnesyl and Geranylgeranyl) -Steroid hormones -Ubiquinone -Vitamins DEAK |
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What is the basic structure of steroids, and what are they made from?
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-Mainly a 4-ring structure
-Made from Squalene |
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What does modification of Squalene make?
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cholesterol
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What important membrane-protein anchors are cholesterol biosynthetic intermediates?
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Farnesyl (c15)
and Geranylgeranyl (C20) |
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How many carbons are in Squalene?
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30 (6 5-carbon isoprene units)
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What does phosphorylation of farnesyl produce?
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Dolichol
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Cholesterol is the precursor for: (3 things)
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-Bile acids
-Steroid hormones -Vitamin D |
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Bile acids (2):
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-Cholic acid
-Deoxycholic acid |
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Steroid hormones (4):
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-Estradiol
-Testosterone -Progesterone -Corticosterone |
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Vitamin D
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Cholecalciferol
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Interesting other polyisoprenoids:
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-Warfarin (coumadin)
-Vitamins EAK -Ubiquinone -Dolichol |
