Q: Which of the following is the correct sequence of steps in the glycine conjugation of benzoic acid?

$$\text{benzoic acid} + \text{ATP} \rightarrow \text{benzoyl-AMP} + \text{PP}_i$$; \text{benzoyl-AMP} + \text{CoA} \rightarrow \text{benzoyl-CoA} + \text{AMP}; \text{benzoyl-CoA} + \text{glycine} \rightarrow \text{hippuric acid} + \text{CoA-SH}$

Question 1

Which of the following statements best describes the main purpose of Phase II (conjugation) reactions in drug metabolism?

Accepted Answer

To convert drugs into more hydrophilic compounds for easier excretion.

Question 2

Which cofactor is required for the glucuronidation reaction catalyzed by UDP-glucuronosyltransferase?

Accepted Answer

UDP-glucuronic acid (UDPGA)

Question 3

Which of the following drugs is most likely to undergo sulfate conjugation as a major metabolic pathway?

Accepted Answer

Paracetamol

Question 4

What is the main enzyme responsible for the transfer of a methyl group to catechols during methylation reactions?

Accepted Answer

Catechol O-methyltransferase

Question 5

Which of the following is a key difference between glucuronidation and amino acid conjugation reactions?

Accepted Answer

Amino acid conjugation activates the drug, while glucuronidation activates the cofactor.

Question 6

Which phase II reaction is most important for the detoxification of electrophilic compounds such as epoxides and haloalkanes?

Accepted Answer

Glutathione conjugation

Question 7

Which of the following is the correct sequence of steps in the glycine conjugation of benzoic acid?

Accepted Answer

$$	ext{benzoic acid} + 	ext{ATP} ightarrow 	ext{benzoyl-AMP} + 	ext{PP}_i$$; 	ext{benzoyl-AMP} + 	ext{CoA} ightarrow 	ext{benzoyl-CoA} + 	ext{AMP}; 	ext{benzoyl-CoA} + 	ext{glycine} ightarrow 	ext{hippuric acid} + 	ext{CoA-SH}$

Question 8

Which of the following statements about acetylation is TRUE?

Accepted Answer

Acetylation uses acetyl-CoA as a cofactor and is common for aromatic amines and sulfonamides.

Question 9

Which of the following is NOT a typical end product of glutathione conjugation?

Accepted Answer

UDP-glucuronide conjugates

Question 10

Which high-energy molecule is required for the synthesis of S-adenosylmethionine (SAM) used in methylation reactions?

Accepted Answer

ATP

Question 11

A patient is prescribed isoniazid for tuberculosis. Which phase II reaction is primarily responsible for its metabolism?

Accepted Answer

Acetylation

Question 12

Which of the following statements about the role of UDP-glucuronic acid in glucuronidation is correct?

Accepted Answer

It is the activated conjugating agent that donates the glucuronic acid moiety.

Question 13

Which of the following is a major consequence of enterohepatic circulation of drug glucuronides?

Accepted Answer

Prolongation of drug action due to recycling of the parent drug.

Question 14

Which enzyme is responsible for the removal of glutamate from glutathione conjugates during mercapturic acid formation?

Accepted Answer

Glutamyltranspeptidase

Question 15

Which of the following is TRUE regarding the methylation of noradrenaline?

Accepted Answer

It is catalyzed by catechol O-methyltransferase using SAM as a methyl donor.

Question 16

Which of the following amino acids is NOT typically involved in amino acid conjugation reactions?

Accepted Answer

Methionine

Question 17

Which of the following statements about the energy requirements of Phase II reactions is correct?

Accepted Answer

Phase II reactions require a source of free energy, often in the form of phosphoanhydride ester bonds.

Question 18

Which of the following is a common substrate for sulfation reactions?

Accepted Answer

Phenols

Question 19

Which of the following is the correct order of enzymes involved in the formation of mercapturic acid from a glutathione conjugate?

Accepted Answer

Glutamyltranspeptidase → peptidase → N-acetyltransferase

Question 20

Which of the following is a real-world example of a drug that undergoes glucuronidation and is subject to enterohepatic circulation, potentially prolonging its half-life?

Accepted Answer

Morphine

Biotransformation: Phase II (Conjugation) Reactions in Organic Chemistry

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