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57 Cards in this Set
- Front
- Back
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1. List the major phosphoglycerides (aka glycerophospholipids) and describe their structural features
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- Like triglyceride, but instead of 3rd fatty acid, you have a phospholipid group.
- Phosphatidyl ethanolamine: PO4-CH2-CH2-NH3+ - Phosphatidyl choline (lecithin): PO4 + instead of NH3+, H’s are replaced by CH3s. Methyls from SAM! Derivative of phosphatidyl ethanolamine - Phosphatidyl serine: phosphate + serine - Phosphatidyl inositol: ring structure |
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What is the name and structure of the core phospholipid from which all the others are derived
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Phosphatidic acid
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Which of the phospholipids is deficient in ARDS (acute respiratory distress syndrome)? What is its common name?
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Late onset in production of specialized dipalmitoyl lecithin. Without surfactant, alveoli collapse
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Why are phospholipids amphipathic
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Hydrophobic tails: fatty acid tails
- Hydrophilic head: phosphotidyl head group |
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What is cephalin
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Phosphatidylethanolamine;a phospholipid found particularly in the cells of nervous tissue; it is also the primary phospholipid in bacteria
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Which phospholipid has a role in intracellular signaling?
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Phosphatidyl inositol
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What structural feature distinguishes plasmalogens from the other phospholipids?
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Unsaturated fatty acid at carbon 1. Ether linkage at carbon 1 (vs. ester)
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What fundamental structure is joined in a dimer to form cardiolipins?
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phosphatidylglycerol
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2. Explain how the two major pathways for the synthesis of phosphoglycerides differ and how they are alike
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Phosphatidic (de novo) pathway: activate phosphatidic acid
Salvage pathway: activating molecule being salvaged Both use CTP to activate Both create phosphodiglycerides |
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Outline the steps in the formation of phosphatidylinositol from CTP and phosphatidic acid.
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> Synthesis of phosphatidic acid from glycerol-3-phosphate
> Reaction of phosphatidic acid with CTP to form activated intermediate (CDP-diacylglycerol) > Reaction of CDP-DAG to attach inositol (inositol synthesized from glucose 6P) |
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What is phosphatidic acid?
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An intermediate in phosphoglyceride synthesis
- Like triglyceride but instead of one FA there’s a phosphate group. - Can either make phosphoglyceride or triglyceride |
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What is phosphatidylinositol?
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Phospholipid involved in cellular signaling
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Outline the steps in the formation of phosphatidylcholine from free choline and CTP
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> Phosphatidate loses the Pi
> Choline is activated by phosphorylation (ATP ADP), then reacts with CTP to form CDP-choline (vs. phosphatidic acid being activated in de novo) > DAG and CDP-choline joined to form lecithin |
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How is choline activated?
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CTP to make CDP-choline
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What type of linkage do CDP-diglyceride and CDP-choline share in common?
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phosphoanhydride
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Describe the role of phospholipases in the process of remodeling of phospholipids
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Cleave off fatty acids or phospholipids
Phospholipase A1: cleaves fatty acid off C1 Phospholipase A2: cleaves fatty acid off C2 Phospholipase C: cleaves off entire phospho group of C3; cellular signaling Phospholipase D: cleaves everything but PO4 group on C3 |
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What type of fatty acid usually winds up on position 1? On position 2?
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C1: saturated. C2: unsaturated
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What is attached to the carbon at position 3?
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phospholipid
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Describe the steps in the remodeling of phosphatidyl serine to form phosphatidyl choline.
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- In liver mitochondria, CO2 leaves phosphatidylserine to become phosphoethanolamine
- In liver microsomes, 3 SAM donate 3 CH3 to phosphoethanolamine to make phosphatidylcholine Phosphatidylserine -->sphoethanolamine -->phatidylcholine |
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Compare and contrast the structures of platelet activating factor and ethanolamine plasmalogen.
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Plasmalogens: in brain and muscle membranes
- Unsaturated body at carbon 1 with no ester linkage (ether linkage) PAF: has ether linkage at C1 - Saturated FA at carbon 1 |
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What type of linkage joins the acyl group to position 1?
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ether
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What is the main difference between the acyl groups attached to position 2?
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R on ethanolamine plasmalogen vs. CH3 on PAF
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How is the ethanolamine added to the plasmalogen?
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CDP-ethanolamine
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Do both of these molecules have a structural function?
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No, only plasmalogens
Plasmalogens: major components of membranes in brain and muscle Platelet-activating factor: vasodilation (can make you faint, lightheaded), platelet adhesion (blood clotting enhanced), chemotaxis (fighting infection) |
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What are some of the structural features of sphingosine?
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18 carbons
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What substitutes for glycerol in sphingolipids?
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Sphingosine
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What role does ceramide play and just what is it anyway?
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Sphingosine with amide linkage with acyl on C2. Like diglyceride. Derivative for a lot of different sphingolipids. Different things attach at C1.
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What is sphingomyelin?
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Phosphosphingolipid. Similar to lecithin (because of phosphocholine attachment). Found in nerve cell membranes.
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Describe the synthesis of gangliosides from ceramides.
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Ceramide with side chain attachment. Need specialized enzymes to break that down
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What is the nature of the precursors that are added to the ceramides? Phospholipid or carbohydrate. What is a glycosphingolipid?
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Carbohydrate attached to a ceramide.
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Where are they added to the ceramide?
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C1
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Describe the synthesis of the A and B substances that determine the ABO blood groups.
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Both come frome a common H substance, difference is the terminal sugar of their oligosaccharide.
A-substance requires GalNAc transferase, adds N-acetyl-galactosamide B-substance requires a Gal transferase, sugar added: Galactose. |
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What is H substance? How are the A and B substance related to the H substance?
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Blood group substances are genetically polymorphic antigens on surface of RBC membranes.
H substance is non-antigenic, found in type O blood. A substance is made by adding Gal to H substance via Gal transferase B substance is made by adding GalNAc to H substance via GalNAc transferase |
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Are there different genes for the enzymes that produce the blood types, or are they just different alleles? So, what are alleles anyway?
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Different alleles. Alleles = variants of the same gene
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How do you get an O type? Can you get it in the heterozygous state?
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No
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How do you get the type A or type B phenotype? Can you get them in the heterozygous state?
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AA, AO, BB, or BO
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Is an AB type heterozygous? It's nice to have an easy one now and then isn't it.
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Yes
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List some of the major diseases caused by defects in lysosomal enzymes that degrade sphingolipids.
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Tay-sachs: AR, affects breakdown of oligosaccharides from gangliosides, fatal by age 3.
Fabray disease: X-Recessive, Fatal. A deficiency of any of the lysosomal enzyme leads to an accumulation of its substrate. Symptoms are mostly neurological due to role of sphingolipids in nerve cell membranes. |
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How long is the side chain on cholesterol? How many total carbons does it have?
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8 carbons, 27?
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What modifications are made to the CPPP ring in cholesterol structure
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- Hydroxyl group (on C3)
- 2 methyl groups (on C10 and C13) - Branched hydrocarbon chain (on C17) |
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How is the side chain on cholic acid different from that of cholesterol?
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Cholic acid side chain only has 5 carbons, one of which is a COO- group
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How is deoxycholic acid different from cholic acid?
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Missing an OH group from C12
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What makes the bile acids amphipathic and how does this affect their biological function?
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The direction their side chains are pointing. Can attach hydrophobic side to fat droplets and emulsify.
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What is HMG-CoA and how is it related to mevalonic acid? From what precursor is it derived?
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- Precursor of HMG-CoA: acetyl-CoA (transformed by HMG-CoA synthase)
- HMG-CoA is the direct precursor of mevalonic acid (changed by HMG-CoA reductase with NADPH NADP+) |
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Does squalene have the intact CPPP (cyclopentanoperhydrophenanthrene) nucleus? How many carbons in squalene?
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C30
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How does lanosterol fit in to the process?
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Direct precursor to cholesterol.
Squalene --> lanosterol --> cholesterol |
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Explain the significance of the HMG-CoA reductase reaction
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- Produces mevalonate
- Uses 2 NADPH |
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How is the activity of HMG-CoA reductase regulated?
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- Stimulated by insulin
- Inhibited by free cholesterol |
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Why is HMG-CoA reductase regulated?
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It is the rate-limiting, committed step of cholesterol synthesis
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Give the site of action of cholesterol lowering drugs (e.g. the statins: lovastatin, mevastatin).
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HMG-CoA reductase inhibitors
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Outline the conversion of cholesterol to bile acids.
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Primary bile acids: made by us in our liver
Secondary bile acids: when exposed to intestinal flora, made by bacteria Secondary bile acids Cholic acid --> deoxycholic acid Chenodeoxycholic acid --> lithocholic acid (via intestinal bacteria) |
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What are bile acids needed for?
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Emulsifying fats, lipid absorption
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What are the two major bile acids produced from cholesterol?
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Cholic and and chenodeoxycholic acid
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How does the quantity of bile acid production compare to other uses of cholesterol?
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Approximately 1/2
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What is the rate limiting step in the conversion of cholesterol into bile acids?
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Cholesterol --> 7α-hydroxycholesterol (via 7α-hydroxylase, using O2 molecular oxygen, H+, and NADPH). Mediated by cytochrome P-450. Adds hydroxyl group to cholesterol.
- Bile acids reduce level of 7α-hydroxylase - Cholesterol and thyroid hormones induce α-hydroxylase synthesis |
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What is a conjugated bile acid?
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Bile acids conjugated with glycine or taurine
Chenodeoxycholyl-CoA --> Glycochenodeoxycholic acid and taurochenodeoxycholic acid Cholyl-CoA --> Glycocholic acid and taurocholic acid Liver secretes bile acids in conjugated form |
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How does the enterohepatic system affect bile acid synthesis?
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Bile acids are recycled back to liver thru portal vein and inhibit its synthesis.
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