Question 1

The structure shown in the first image is a triglyceride composed of three identical fatty acid chains. Which of the following best describes the chemical nature of this molecule?

Accepted Answer

It is a triacylglycerol (triglyceride), an ester formed from glycerol and three fatty acids.

Question 2

The second image shows the structure of ricinoleic acid, a major component of castor oil. Which functional groups are present in ricinoleic acid?

Accepted Answer

Carboxylic acid, alkene, and secondary alcohol

Question 3

Gamma-linolenic acid (GLA), shown in the third image, is classified as which type of fatty acid?

Accepted Answer

Polyunsaturated fatty acid

Question 4

The fourth image shows the structure of streptomycin, an aminoglycoside antibiotic. Which of the following statements about aminoglycosides is correct?

Accepted Answer

They disrupt bacterial protein synthesis by binding to the 30S ribosomal subunit.

Question 5

The fifth image compares cardenolide and bufadienolide skeletons. Which structural feature distinguishes bufadienolides from cardenolides?

Accepted Answer

Presence of a six-membered unsaturated lactone ring at C-17

Question 6

The sixth and seventh images show two related cardiac glycosides. What is the main difference between these two molecules?

Accepted Answer

The position of the hydroxyl group on the steroid nucleus

Question 7

Which of the following best describes the pharmacological action of cardiac glycosides such as digoxin and digitoxin?

Accepted Answer

They inhibit the Na+/K+-ATPase pump, increasing intracellular Ca$$^{2+} in $$cardiac muscle.

Question 8

Which chemical test is used to detect the presence of anthraquinone glycosides in plant extracts?

Accepted Answer

Borntrager's test

Question 9

Which of the following statements about glycosides is correct?

Accepted Answer

The sugar portion is called the glycone, and the non-sugar portion is called the aglycone.

Question 10

Which of the following is a correct statement regarding the isolation of glycosides from plant material?

Accepted Answer

Lead acetate is used to precipitate tannins and remove nonglycosidal impurities.

Question 11

Which of the following best describes the difference between fixed oils and volatile oils?

Accepted Answer

Fixed oils are saponifiable and leave a permanent grease spot, while volatile oils evaporate and do not saponify.

Question 12

Which of the following is a correct statement about the stereochemistry of drugs?

Accepted Answer

Only the S-enantiomer of ibuprofen is pharmacologically active.

Question 13

Which of the following is a correct description of the Hammett substituent constant ($$\sigma$$)?

Accepted Answer

It quantifies the electron-donating or electron-withdrawing effect of a substituent on an aromatic ring.

Question 14

Which of the following strategies is used to make drugs more resistant to hydrolysis?

Accepted Answer

Adding steric shields near labile functional groups

Question 15

Which of the following is a correct statement about the mechanism of action of sulphonamides?

Accepted Answer

They act as competitive inhibitors of dihydropteroate synthetase, blocking folate synthesis.

Question 16

Which of the following is a correct statement about the classification of terpenoids?

Accepted Answer

Monoterpenes contain 10 carbons and are formed from two isoprene units.

Question 17

Which of the following statements about tannins is correct?

Accepted Answer

Hydrolysable tannins are easily broken down by acids or enzymes to yield gallic or ellagic acid.

Question 18

Which of the following is a correct statement about the pharmacological classification of crude drugs?

Accepted Answer

It groups drugs based on their therapeutic action or effect.

Organic Chemistry Study Notes: Natural Products, Stereochemistry, and Structure-Activity Relationships

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