Biochem Block 4

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pszurnicki
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Biochem Block 4
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2011-04-10 22:34:54
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Biochem Block 4
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  1. What enzyme catalyzes the formation of cAMP?
    Adenylate cyclase
  2. cAMP pathway uses what type of receptor?
    G protein--7 transmembrane domains
  3. When a hormone binds a G protein, GDP is exchanged for what?
    GTP
  4. What are the 3 subunits of G protein?
    • Alpha
    • Beta
    • Gama
  5. Upon binding of a hormone, what subunit dissociates and binds the enzyme?
    alpha
  6. GTPase activity is present on what subunit?
    alpha S
  7. cAMP activates what kinase?
    protein kinase A
  8. Phosphorylation is usually on what a.a residue?
    • serine
    • threonine
  9. O glycosidic bonds are formed from what a.a?
    • serine
    • threonine
  10. What effect does Cholera have on the G protein activity?
    activation of alpha s subunit which constitutively activates protein kinase A
  11. Cholera uses what receptor?
    GM1--ganglioside
  12. ADP ribosylation of alpha s subunit of Gprotein is caused by what toxin?
    Cholera
  13. What causes constitutive activatio of alpha s Subunit of G protein?
    Cholera
  14. What inhibits GTPase activity of alpha s subunit?
    Cholera
  15. What is the sourse of ADP ribosylation?
    NAD
  16. What hormones act thru Gi receptor?
    • ach
    • angiotensin II
    • somatostatin
  17. What is the difference between Gs and Gi receptor proteins?
    • upon activation of Gs--cAMP is activated
    • Upon activation of Gi--cAMP is deactivated
  18. What hormone stimulates phosphodiestarase?
    Insulin
  19. Methyl Xanthine has what effect on phosphodiesterase?
    it inhibits it----possible hyperglycemia
  20. What are the two types of Guanylyl cyclase?
    • membrane
    • cytosolic
  21. What are the hormones that act thru cGMP?
    • vasodilators:
    • ANF
    • NO
  22. ANF acts thru what type of cGMP receptor, membrane or cytosolic?
    membrane
  23. NO acts thru what type of cGMP receptor, membrane or cytosolic?
    cytosolic (soluble)
  24. cGMP stimulates what protein kinase?
    protein kinase G
  25. What is the action of Silenafil?
    • inhibits phophodiesterase
    • prevents breakdown of
  26. Insulin is needed for entry of glucose into what cells?
    What receptor?
    • adipocytes
    • skeletal muscle
    • GLUT-4
  27. Mutation of RAS gene causes what?
    • decreased hydrolysis of GTP to GDP
    • G protein is constitutively active
  28. Source of ADP ribosylation?
    NAD
  29. What two toxins do ADP ribosylation?
    • Cholera
    • E.coli
  30. Cholera and E.coli cause what by constitutively activating alpha s subunit?
    diarhea bc of increased Cl secretion which takes water out
  31. What effect does Pertussis toxin have?
    whooping cough
  32. Mode of action of pertussis toxin?
    ADP ribosylation of Gi receptor protein
  33. Insulin is made up of how many a.a?
    51
  34. Insulin has what kind of chains?
    • intra chain disulfide bonds
    • inter chain disulfide bonds
  35. Initially insulin is synthesized as what?
    Proinsulin
  36. Where is the one polypeptide proinsulin is cut into two peptides?
    Golgi Apparatus
  37. Glucagon is made up of how many a.a?
    29
  38. Glucagon acts on what organ?
    Liver
  39. Glucagon stimulates glycogen metabolism in what organ?
    Liver
  40. What happens to acetone that is produced?
    it is exhaled
  41. What are the 2 organs that undergo gluconeogenesis?
    • kidney
    • liver
  42. How does the kidney compensate for the ketoacidosis?
    it uses ammonia to neutralize H+
  43. What kind of obesity has worse health consequence
    Android
  44. What is the mode of action of Orlistat?
    Inhibits pancreatic lipases and gastric lipases
  45. How does sibutramine work?
    Serotonin or norepinephrine reuptake inhibitor
  46. "Metabolic Syndrome" is associated with what?
    insulin resistance
  47. Why do men loose fat more easily because?
    Has access to portal circulation
  48. Lipoprotein lipase digests TAG found where?
    • Chylomicrons
    • VLDL
  49. Class III obesity is what BMI?
    over 40
  50. Class II obesity is what BMI?
    35-40
  51. Class I obesity is what BMI?
    over 30
  52. Numbering of purine rings is done in what direction?
    Counterclockwise direction
  53. Numbering of carbon and nitrogen atoms in a pyrimidine is in what direction?
    clockwise
  54. What is the difference between ribose and deoxyribose?
    • ribose--OH on 2'
    • deoxyribose--H on 2'
  55. Methylation of uracil produces what?
    thymine
  56. What is the rate determining step of De novo purine synthesis?
    Glutamine PRPP amidotransferase
  57. Sulfonamides like Trimethropin inhibits what enzyme?
    formyltransferase
  58. Methotrexate inhibits what enzyme?
    dihydrofolate reductase
  59. What is the only enzyme that uses thiamine only?
    trans ketolase
  60. 6-Mercaptopurine is an inhibitor of what 2 enzymes?
    • adenylosuccinase
    • IMP dehydrogenase
  61. 6-Mercaptopurine blocks synthesis of what 2 nucleotides?
    • AMP
    • GMP
  62. Why is GTP used in the synthesis of AMP and ATP used in the synthesis of GMP?
    To balance the use of nucleotides
  63. Lesch-Nyhan syndrome is caused by a deficiency of what enzyme?
    HGPRT (hypoxanthine-guanine
  64. What enzyme is involved in the making of uric acid?
    Xanthine Oxidas
  65. What amino acidpathy mimics the symptoms of Uric acid?
    Alkaptonuria
  66. Gout is caused by deposition of what?
    uric acid
  67. Allopurinol action?
    Inhibitor of xanthine oxidase
  68. What is a competitive inhibitor of Aspartate transcarbamoylase?
    Glycine
  69. 5 Fluorouracil does what?
    inhibits thymidylate synthesis
  70. Trimethropin does what?
    inhibits bacterial dihydrofolate reductase
  71. Methotrexate does what?
    inhibits bacterial dihydrofolate reductase
  72. Ribonucleotide reductase is inhibited by what?
    Hydroxy urea
  73. What enzyme is used to reduce the 4 ribonucleotides?
    ribonucleotide reductase
  74. What reducing agent is used to reduce ribonucleotides?
    NADPH
  75. What is used along with ribonucleotide reductase to reduce ribonucleotide
    Thioredoxin
  76. What is the result of dATP binding to ribonucleotide reductase activity site?
    • decreased catalytic activity
    • prevents DNA synthesis
  77. Adenosine deaminase deficiency primarily affects what kinds of cells?
    Lymphocytes
  78. High levels of dATP have what effect?
    decreased ribonucleotide reductase activity
  79. What chemical prolongs the half life of adenosine deaminase?
    PEG --polyethylene glycol
  80. What are the enzymes that require vit b 1?
    • Transketolase
    • pyruvate dehydrogenase
    • alpha keto acid dehydrogenase
    • branched chain AA dehydrogenase
  81. Beri Beri results from a deficiency of what?
    Vit b 1
  82. BeriBeri results in what?
    • Cardiomegaly
    • Peripheral neuropathy
    • Foot-Drop
    • Wrist Drop
  83. In alcoholics with vit b1 deficiency you get what?
    Wernicke-Korsakoff syndrome
  84. Vit B1 and 2 are found where?
    Animal Products
  85. Deficiency of Vit b2?
    2 C's
    • Chelosis
    • Corneal Vascularization
  86. What does Folate carry/Transfer?
    methyl
  87. What is checked at end of G1 phase?
    pre-replicative damage
  88. Is the pentose sugar or the nitrogenous base labeled with the " prime" symbol?
    pentose sugar
  89. What kind of bond connects the phosphate in a nucleotide?
    ester bond
  90. What are the precursors of purine?
    glycine, CO2, N-10 tetrahydrofolate, glutamine, aspartate
  91. What is the rate limiting step in de novo purine synthesis?
    glutamine PRPP amidotransferase
  92. What activates Glutamine PRPP amidotransferase?
    Pi
  93. What inhibits Glutamine PRPP amidotransferase
    purine nucleotides
  94. Sulfanamides inhibit what?
    synthesis of Folate
  95. What is the mode of action of Sulfanamides?
    • PABA analog
    • blocks Dihydropteroate synthase
  96. Trimethropin inbihits what?
    dihydrofolate reductase
  97. Methotrexate inhibits what?
    Human dihydrofolate reductase
  98. Conversion of IMP to AMP requires what type of high energy molecule?
    GTP
  99. Conversion of IMP to GMP requires what type of high energy molecule?
    ATP
  100. Mycophenolic acid blocks what enzyme?
    IMP dehydrogenase
  101. What drug is used in preventing graft rejection?
    Mycophenolic acid
  102. Degradation of nucleic acids produces what?
    Uric acid
  103. Hypoxanthine-guanine phosphoribosyltransferase uses what two precursorse to produce IMP and GMP?
    • Hypoxanthine + PRPP--->IMP
    • Guanine + PRPP----> GMP
  104. How are dietary sources of vitamin A absorbed?
    • esters are broken down into retinol
    • retinol is absorbed
    • retinol is esterified into esters
  105. Lipid soluble vitamins are carried how from the intestinal cell?
    in the chylomicron
  106. Too much retinoic acid causes what?
    tumor
  107. Are teratogens mutagens?
    no
  108. Examination of what PTH derivative establishes its presence?
    PTH (35-84)
  109. How does calcium exist in plasma?
    • 50 % free (ionized)
    • 50% protein bound
  110. How does a malignant myeloma cause hypercalcemia?
    causes PTHrp
  111. What are the 2 signs of Hypocalcemia?
    • Trusseau's sign
    • Chvostek's sign
  112. Hypocalcemia in kids?
    Rickets
  113. Hypocalcemia in adults?
    osteomalacia
  114. What is the abreviation of dicarboxylic glutamate?
    GLA
  115. What is the rate determining step in purine synthesis?
    Glutamine-PRPP amidotransferase
  116. What inhibits xanthine oxidase?
    allopurinol
  117. What prevents reabsorption of uric acid in the PCT?
    probenecid
  118. Glutamine-PRPP amidotransferase is inhibited by?
    IMP, GMP, AMP
  119. IMP dehydrogenase is inhibited by?
    GMP
  120. Adenylosuccinate is inhibited by?
    AMP
  121. What deoxyribonucleotide inhibits Ribonucleotide reductase?
    dATP
  122. What stimulates the activity of Ribonucleotide Reductase?
    ATP
  123. Hydroxyurea blocks what enzyme?
    ribonucleotide reductase
  124. Severe combined Immunodeficiency diseases is caused by a deficiency of what enzyme?
    adenosine deaminase
  125. What accumulates in Adenosine Deaminase deficiency?
    dATP from adenosine

    fyi..adenosine + PRPP-->AMP-->ADP-->dADP--dATP
  126. What is the consequence of accumulated dATP on Nucleotide synthesis?
    • dATP inhibits Ribonucleotide Reductase--> no nt
    • no nt--> low division of cell especially..lymphocytes
    • -->immuno-suppressed
  127. What extends the life of AD?
    PEG
  128. What is the rate limiting enzyme pyrimidine synthesis?
    carbamoyl phosphate synthase II
  129. What two sources give rise to a pyrimidine ?
    • Aspartate
    • carbamoyl Phosphate
  130. What enzyme converts dUMP to dTMP?
    Thymidylate synthase
  131. What drug binds to thymidylate synthase and thus preventing the conversion of dUMP to dTMP?
    5 Fluoro Uracil (5FU)
  132. What is the methyl donor in the conversion of dUMP to dTMP?
    N5N10 methylene tetrahydrofolate
  133. CTP synthase is inhibited by what?
    activated by what?
    • CTP
    • GTP
  134. What drugs allows for suicide inhibition?
    5-FU
  135. Methotrexate and Trimethropin are what type of inhibitors?
    competitive
  136. What are the degradation products of Pyrimidines?
    • Thymine--->methylmalonyl coA-->succinyl coA
    • Uracil---->acetyl coA
  137. Receptors for steroid hormones, thyroid and retinoic acid have what 2 domains on the intracellular receptors?
    • ligand binding domain for the hormone
    • DNA binding domain
  138. Gs protein is also called what?
    Gprotein
  139. Which subunit of a Gs protein has GTPase activity?
    alpha
  140. What subunit of the G protein detaches with the GTP and binds to AC?
    alpha
  141. Phosphorylation takes place on what a.a residue?
    serine or threonine
  142. What toxin causes ribosylation of the alpha subunit?
    cholera toxin
  143. What hormones act thru the Gi proten?
    • acetylcholine
    • ATII
    • somatostatin
  144. What calcium binding protein is used intracellularly?
    calmodulin
  145. Receptor for what hormone has intrinsic kinase activity?
    • Insulin
    • GF
    • GH
    • PDGF
    • VEGF
    • Prolactin
  146. How does mutated ras gene cause uncontrolled proliferation?
    alpha s subunit is constitutively active
  147. What 2 toxins cause ribosylation of alpha s subunit?
    By what mechanism is the cholera brought on?
    • cholera
    • E.coli----no degradatation of GTP to GDP
    • phosphorylation of CFTR channel--loss of Cl
    • water follows--->diarhea
  148. Proinsulin to insulin cleavage occurs where?
    in the Golgi Apparatus
  149. Which 2 G.I hormones stimulate the release of Insulin?
    • cholecystikinin
    • Gastric Inhibitory Protein
  150. What is the mechanism of insulin secretion after glucose uptake?
    • glucose metabolized--> high ATP
    • High ATP---> prevents efflux of K+
    • high Intracellular K+---> depolarization
    • depolarization-->Ca influx
    • Ca influx---> fusion of vesicle with PM
  151. What effect does insulin have on HMP shunt?
    it promotes it b/c in fed state you can allow urself to maintain upkeep..which HMP shunt does by producing NADPH and Ribulose-5-phosphate
  152. What is the a.a chain length of insulin?
    Glucagonn
    • insulin--55
    • Glucagon--29
  153. Branched chain a.a are primarily metabolized where?
    skeletal muscle
  154. What are two symptoms of Hypoglycemia?
    • Adrenergic---due to epi
    • Neuroglycopenia---low glucose in brain
  155. What are the 2 regulatory systems that respond to hypoglycemia?
    • alpha cells of islets of langerhans--glucagon
    • hypothalamus---acth---cortisol
    • epinephrine
  156. What BMI is overweight?
    • overweight-- >25
    • Obese class I--- >30
    • Obese Class II--- >35
    • Obese Class III --- >40
  157. Men's obesity is classified as what?
    Android
  158. Woman's obesity is classified as what?
    Gynecoid
  159. What type of obesity, Android or Gynecoid has worse health consequences?
    Android
  160. Why do men tend to loose faster?
    • because the abdominal fat(android) has a
    • - higher turnover rate
    • - more hormone sensitive
  161. Leptin is produced by what cells?
    Adipocytes
  162. What action does leptin have on the hypothalamus?
    leptin inhibits hunger center in the brain
  163. Nutritional hormones relay to what part of the brain?
    Hypothalamus
  164. What 2 nuclei in the hypothalamus control fuel intake and metabolism?
    • orexigenic
    • anorexigenic
  165. What hypothalamic nucleus stimulates eating?
    orexigenic
  166. Orexigenic nucleus secretes what peptide to stimulate eating?
    neuropeptide Y
  167. Anorexigenic nucleus produces what signal that prevent eating?
    alpha-MSH
  168. Is Leptin appetite stimulating or inhibiting?
    leptin is appetite inhibitng
  169. Is ghrelin appetite stimulating stimulating or inhibitng?
    appetite stimulating
  170. Which neurons, orexigenic or anorexigenic are inhibited by leptin?
    orexigenic---neuropeptide Y
  171. TNF-alpha has what effect on insulin resistance?
    increases insulin resistance
  172. What effect does PYY-36 have on the appetite?
    in inhibits it
  173. What 3 hormones inhibit the orexigenic neurons from releasing neuropeptide Y?
    • insulin
    • PYY-36
    • leptin
  174. What are the 3 components of metabolic syndrome?
    • Dyslipidemia
    • glucose intolerance
    • insulin resistance
  175. How does insulin resistance lead to dyslipidemia?
    • hormone senstitive lipase is not inhibited by insulin
    • HSP breaks down TAGs
    • increases of FA and cholesterol
  176. What does orlistat do?
    prevents release of pancreatic and gastric lipase
  177. What does subatramine do?
    serotonin and norepinephrine reuptake inhibitor
  178. Prothrombin Time (PT) tests which clotting pathway?
    Extrinsic
  179. PTT tests which clotting pathway?
    Instrinsic
  180. What receptor does Insulin and Growth hormone use?
    associated tyrosine kinase
  181. What receptor do growth factors like PDGF, Insulin?
    Intrinsic tyrosine kinase
  182. What receptor uses JAK/STAT?
    associated tyrosine kinase
  183. 15-17 translocation produces what condition?
    Acute Meylegenous Leukemia
  184. 11-22 translocation produces what cancer?
    Ewing's sarcoma
  185. 11-14 translocation produces what cancer?
    Mantle cell Lymphoma
  186. Koilychia and dysphagia are caused by what?
    iron deficiency anemia
  187. What effect do nitrates have on hemoglobin?
    nitrates oxidize ferrous iron to ferric
  188. What is responsible for the polymerization of HbS?
    hydrophobic interactions between the globin genes because of the valine instead of the glutamate
  189. What is the antidote for cyanide poisoning?
    administration of nitrites b/c nitrites oxidize hemoglobin to methemoglobin which binds CN- with high affinity sequestering it from the mitochondria
  190. Radiation has what 2 effects on cells?
    • introduces double strand breaks
    • produces free radicals
  191. The most abundant amino acid in collagen?
    glycine
  192. During exercise what metabolite stimulates the breakdown of glycogen?
    Ca
  193. Disulfide bond is an example of what type of protein structure?
    super-secondary
  194. Where does CO2 bind on a hemoglobin molecule?
    amino terminal of
  195. Which hemoglobin form T or R has higher oxygen affinity?
    R
  196. Alport's syndrom is due to what?
    abnormal type IV collagen
  197. What are the 3 symptoms of Alport's syndrome?
    • nephritis
    • deafness
    • ocular disturbances
  198. What is an example of super-secondary structure?
    • Leucine-zipper
    • Zinc-finger
    • Helix-turn-helix
  199. Proteins with super-secondary protein structures usually perform what function?
    Transcription factors
  200. Proteins with sequences are degraded ubiquitously without selection?
    PEST sequences
  201. Digestion of what is mostly affected in cystic fibrosis?
    fat---steatorhea
  202. Which monosaccharide is not dependent on sodium- monosaccharide synport?
    Fructose
  203. What activates trypsin?
    enterokinase/enteropeptidase
  204. What is the mode of action of orlistat?
    blocks gastric and pancreatic lipases
  205. Gamma glutamyl transferase is used for what?
    amino acid transport across the cell membrane of the intestinal cell
  206. What traps the glucose in the cell?
    phosphorylation via glucokinase
  207. What effect does HPV have on p53?
    E6 protein degrades p53

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