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USMLE

New FA Biochem 9

QuestionAnswer
"Where do GLUT1 receptors predominate over other GLUT receptors?" "RBCs"
"Where do GLUT4 receptors predominate over other GLUT receptors?" "Adipose tissue and skeletal muscle"
"Which tissues have cotransport of glucose?" "Epithelial cells of the intestine, renal tubular cells, and choroid plexus"
"Which tissues (7) need glucose as fuel?" "Brain, RBCs, Renal medulla, lens, cornea, testes, exercising muscle"
"Where is pyruvate carboxylase found and not found?" "Found in mitochondria of liver and kidney cells, not found in mitochondria of muscle"
"Where is Fructose 1-6 bisphosphatase found?" "Liver and kidney"
"What is the Cori cycle?" "Lactate in muscle is shuttled to liver where it is turned into glucose."
"How does glucagon stimulate gluconeogenesis?" "Regulation of F2,6-BP and inactivation of Pyruvate Kinase via elevation of cAMP-dependent protein kinase A."
"This oxidation accounts for about two thirds of the total oxygen consumption and ATP production in most animals, including humans." "Oxidation of acetyl coA to CO2 and H2O."
"What inhibits pyruvate dehydrogenase?" "Acetyl CoA and NADH (no need for more of either). These activate PD kinase (Phosphorylates enzyme with ATP, which must be in abundance, so no more is needed)"
"What stimulates pyruvate dehydrogenase?" "ADP (need more ATP. Inhibits PD kinase and stimulates PD phosphatase.)"
"Which is active?: Phosphorylated or dephosphorylated pyruvate dehydrogenase" "Dephosphorylated."
"What inhibits citrate synthase?" "ATP and NADH (no need for more of either), Succinyl CoA (""Slow down partner, the guys ahead of you are trying to do their job!""), Acyl CoA fatty acid derivatives (Citrate provides acetyl CoA to synthesize fatty acids and activates acetyl CoA carboxylas
"Where in glycolysis and TCA does CO2 come off?" "3 places: Pyruvate to Acetyl CoA, Isocitrate to alpha-ketoglutarate, and alpha-ketoglutarate to Succinyl CoA"
"What is the rate-limiting step of the TCA?" "Isocitrate to alpha-ketoglutarate by isocitrate dehydrogenase"
"What activates isocitrate dehydrogenase?" "ADP"
"What inhibits isocitrate dehydrogenase?" "ATP and NADH"
"Sources of Succinyl CoA" "TCA intermediate, and from odd chained fatty acids, and from propionyl coA from metabolism of branched-chain amino acids."
"Uses of Succinyl CoA" "TCA intermediate, and biosynthesis of heme"
"Where in the TCA does NADH come from?" "Pyruvate to Acetyl CoA, Isocitrate to alpha-ketoglutarate, alpha-ketoglutarate to succinyl coA, Malate to Oxaloacetate"
"Where in the TCA does FADH2 come from my dear?" "Succinate to fumarate my sweet."
"Why is FAD used to oxidize succinate?" "Succinate is not powerful enough to reduce NAD."
"What are the important products of the HMP pathway?" "2 NADPH, Ribose, and glyceraldehyde-3-Phosphate and Fructose-6-phosphate"
"Which major metabolic reactions require Thiamine as a cofactor?" "TCA: Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, HMP shunt: Transketolase"
"What is NADPH used for?" "1. Reductive biosynthesis (eg fatty acids and steroids) 2. Reduction of oxygen directly (myeloperoxidase system's famed respiratory burst) and hydrogen peroxide indirectly (through reduction of glutathione) 3. Cytochrome P-450 mono-oxygenase system"
"What is the famed respiratory burst?" "The rapid conversion of O2 to superoxide using NADPH."
"What disease process is due to a missing respiratory burst?" "Chronic granulomatous disease"
"Where is the mutation for G6PD?" "Point mutation in coding region of the G6PD gene (X-linked)"
"What is the relation of polyols to sugars?" "Polyols are monosaccharides where the carbonyl group is reduced to an alcohol."
"What is a glycoside?" "Carbohydrate attached to non-carbohydrate structures."
"What is a reducing sugar?" "A monosaccharide where the anomeric carbon (Carbon 1) is free."
"What is the result of lack of disaccharidase activity of intestinal mucosa?" "Osmotically active disaccharides suck water out of mucosa causing osmotic diarrhea."
"Where is fructokinase found?" "Liver (processes most dietary fructose), kidney, small intestine"
"Why is fructose metabolism faster than glucose metabolism?" "Bypasses PFK, major regulatory step of glycolysis."
"What enzyme is missing in hereditary fructose intolerance?" "Aldolase B"
"What does aldose reductase do?" "Reduces glucose to sorbitol"
"Where is aldose reductase found?" "Lens, retina, Schwann cells, kidney, placenta, RBCs, and gonads"
"What does sorbitol dehydrogenase do?" "Oxidizes sorbitol to fructose."
"Where is sorbitol dehydrogenase found?" "Liver and gonads (ovaries, seminal vesicles, sperm)"
"Mechanism of sorbitol toxicity" "Extra glucose freely enters cells containing aldose reductase which converts it to sorbitol. Sorbitol may not pass through, and low or absent sorbitol dehydrogenase prevents it from being changed to fructose. Strong osmotic effects lead to swelling and
"Chondroitin Sulfate: Where found?/Distinguishing characteristic from other GAGs" "Cartilage, tendons, ligaments, aorta. Most abundant GAG in body."
"Chondroitin Sulfate: Use/Mechanism" "Form proteoglycan aggregates. Cartilage: Bind collagen and hold fibers in a tight, strong network"
"Dermatan Sulfate: Where found?/Distinguishing characteristic from other GAGs" "Found in skin, blood vessels, and heart valves"
"Keratan Sulfate: Where found?/Distinguishing characteristic from other GAGs" "Found in cartilage proteoglycan aggregates with chondroitin sulfate, and in cornea. Most heterogeneous GAG."
"Heparin: Where found?/Distinguishing characteristic from other GAGs" "Intracellular compound (unlike other GAGs). Found in mast cells of artery walls, especially in lungs, liver, and skin"
"Heparin: Use/Mechanism" "Anticoagulant"
"Heparan Sulfate: Where found?/Distinguishing characteristic from other GAGs" "Extracellular, unlike heparin. Found in basement membrane and as a ubiquitous component of cell surfaces."
"Hyaluronic Acid: Where found?/Distinguishing characteristic from other GAGs" "Found in synovial fluid of joints, vitreous humor f eye, umbilical cord, and loose connective tissue. Unlike other GAGs: Unsulfated, not covalently attached to protein, and only GAG not limited to animal tissue, but also found in bacteria."
"Hyaluronic Acid: Use/Mechanism" "Lubricant and shock absorber"
"Hunter's Syndrome vs Hurler's Syndrome: Enzyme deficiency" "Hunter's: Iduronate sulfatase, Hurler's: alpha-L-iduronidase"
"Hunter's Syndrome vs Hurler's Syndrome: Corneal clouding?" "Hunter's: No, Hurler's: Yes"
"Hunter's Syndrome vs Hurler's Syndrome: Mental retardation?" "Both (Hunter's ranges from mild to severe)"
"Hunter's Syndrome vs Hurler's Syndrome: Physical deformity?" "Hunter's: Mild to severe, Hurler's: Dwarfing, coarse facial features, (gargoylism)"
"Hunter's Syndrome vs Hurler's Syndrome: Which GAGs' degradation is affected?" "Both: Dermatan sulfate and Heparan sulfate"
"Hunter's Syndrome vs Hurler's Syndrome: Severity?" "Hunter's: Less Hurler's: More"
"Hunter's Syndrome vs Hurler's Syndrome: Inheritance?" "Hunter's: X-linked Recessive, Hurler's (and all other mucopolysaccharidoses): Autosomal recessive"
"Hunter's Syndrome vs Hurler's Syndrome: Aggressive behavior?" "Hunter's: Yes, Hurler's: No"
"Mnemonic for Hurler's syndrome: HURLERS. What does it stand for?" "H: Hepatosplenomegaly/Heparan and Dermatan sulfate, U:Ugly facies, R: aRteries filled with GAGs, L: L-iduronidase, E: Eyes clouded, early death, R: Retardation/Respiratory obstruction, S: Short/stubby fingers"
"I-Cell disease: Pathophysiology" "Inability of cell to phosphorylate mannose residues on glycoproteins indicating that they are lysosome bound."
"I-Cell disease: Presentation" "Skeletal abnormalities, restricted joint movement, coarse facial features, severe psychomotor impairment, death by 8 years"
"Refsum Disease: Pathophysiology" "Inability to degrade phytanic acid, resulting in accumulation in plasma and tissues"
Created by: Asclepius