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MO31 Phase 2 Metabolism

Mer Scott 11 questions

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Questions in this quiz (11)

  1. 1Glucuronidation is [blank_start]conjugation[blank_end] with alpha-D-glucuronic acid provided by the co-factor UDP–glucuronic acid (UDPGA). It adds 3 [blank_start]-OH[blank_end] groups and 1 [blank_start]-COOH[blank_end] (negatively charged) group to a drug.
    UDP-glucuronosyl transferase (UGT) enzymes are microsomal, situated with CYPs on the [blank_start]ER[blank_end]. They are [blank_start]low[blank_end] affinity, [blank_start]high[blank_end] capacity enzymes
    1. Aconjugation
    2. B-OH
    3. C-COOH
    4. DER
    5. Elow
    6. Fhigh
  2. 2In glucuronidation, the added polar group of the drug acts as a nucleophile and attacks an electrophilic site on UDPGA.
    1. ATrue
    2. BFalse
  3. 3Glucuronides can be [blank_start]recycles[blank_end] through the liver. Glucuronides excreted into bile can be [blank_start]hydrolysed[blank_end] back to the parent drug or a metabolite by [blank_start]alpha-glucuronidases[blank_end] present in gut microflora. Drug or Phase 1 metabolite (aglycone – glucuronide has been removed) undergoes [blank_start]reabsorption[blank_end] into the portal circulation. Aglycone is then available for another cycle through the liver. The end result is an [blank_start]extension[blank_end] of the half life of elimination and (if
    active) the [blank_start]duration[blank_end] of action.
    1. Arecycled
    2. Bhydrolysed
    3. Calpha-glucuronidases
    4. Dreabsorption
    5. Eextension
    6. Fduration
  4. 4Sulfation is important in the transport and metabolism of catecholamines, steroids, [blank_start]bile[blank_end] acids, [blank_start]phenolic[blank_end] drugs and other xenobiotics. The total pool of inorganic sulfate is [blank_start]limited[blank_end] and at high doses of drug [blank_start]glucuronidation[blank_end] predominates. The enzyme of sulfation, [blank_start]sulfotransferase[blank_end] (SULT) is polymorphic with 2 major isoforms SULT1 and SULT 2. They are [blank_start]high[blank_end] affinity, [blank_start]low[blank_end] capacity enzymes.
    1. Aphenolic
    2. Bbile
    3. Climited
    4. Dglucuronidation
    5. Esulfotransferase
    6. Fhigh
    7. Glow
  5. 5Phenols are more reactive than alcohols because they are more acidic, which makes them a better nucleophile.
    1. ATrue
    2. BFalse
  6. 6Methylation occurs at [blank_start]O, N and S[blank_end] to form metabolites that are equally or more active than the parent compound, removing an [blank_start]H[blank_end] and replacing with a [blank_start]CH3[blank_end]. Mainly occurs with [blank_start]endogenous[blank_end] compounds rather than drugs. Uses the cofactor ([blank_start]SAM or SAMe[blank_end]) and enzymes called methyl transferases. Does not increase [blank_start]polarity[blank_end] of compound. Has several isozymes mostly [blank_start]specific[blank_end] for a specific substrate.
    1. AO, N and S
    2. BH
    3. CCH3
    4. Dendogenous
    5. ESAM or SAMe
    6. Fpolarity
    7. Gspecific
  7. 7Catechol O-Methyltransferase (COMT) transfers a methyl group to the para- and less frequently the meta- phenolic group of catecholamines.
    1. ATrue
    2. BFalse
  8. 8Acetylation is mediated by [blank_start]N-acetyltransferases[blank_end], NAT1 and NAT2. NAT2
    is expressed only in the [blank_start]liver[blank_end] whereas NAT1 is expressed throughout the [blank_start]body[blank_end]. [blank_start]Secondary[blank_end] amines are not acetylated.
    1. AN-acetyltransferases
    2. Bliver
    3. Cbody
    4. DSecondary
  9. 9Choose the incorrect statement about amino acid conjugation.
    1. ACatalysed by transacetylase
    2. BEnzymes reacts with amino group of amino acid, usually glycine
    3. CXenobiotic carboxylic acids are either glucuronidated or conjugated with glycine, glycine conjugation is preferred at high doses
  10. 10Glutathione Conjugation:
    • Some xenobiotics and highly reactive species are conjugated with glutathione (GSH) ([blank_start]Glu-Cys-Gly[blank_end]).
    – catalysed by [blank_start]glutathione-S-transferases[blank_end] (GSTs)
    • The reaction is “protective” – it [blank_start]inactivates[blank_end] potentially toxic electrophilic compounds preventing them from reacting with [blank_start]nucleophilic[blank_end] centres in macromolecules e.g. proteins & nucleic acids. Electrophiles include:
    – Aromatic / aliphatic [blank_start]halogens[blank_end]
    – nitro groups
    – Alkenes / [blank_start]Epoxides[blank_end]
    – Sulfonic acid [blank_start]esters[blank_end]
    – Reactive intermediates
    1. AGlu-Cys-Gly
    2. Bglutathione-S-transferases
    3. Cinactivates
    4. Dnucleophilic
    5. Ehalogens
    6. FEpoxides
    7. Gesters

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Description
PHCY211 (Molecules) Quiz on MO31 Phase 2 Metabolism, created by Mer Scott on 02/06/2018.
Author
Mer Scott
Language
English
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