AIPMT 2001 question paper with solutions

1. Recall that the Gram stain technique, developed by Christian Gram, classifies bacteria into two groups based on whether they retain or lose a violet dye after treatment with alcohol.

2. Recall that in Gram-positive bacteria, the cell wall has both horizontal and vertical peptide linkages forming a dense mesh (with an outer layer of teichoic acid), which traps the stain inside, so it is retained.

3. Recall that in Gram-negative bacteria, the cell wall has a looser mesh (with an outer layer of lipopolysaccharides), allowing the stain to be washed out by alcohol.

4. Since this staining difference arises directly from structural and compositional variations in the bacterial cell wall, this is the underlying cause of the Gram-positive/Gram-negative distinction.

Hence, the correct answer is Option A, cell wall.

1. Recall the general category of drugs called hallucinogens — these are substances that alter thoughts, feelings, and perceptions, causing hallucinations.

2. Recall the specific effects of LSD (Lysergic acid diethylamide) — it is a classic hallucinogen known to cause vivid/horrible dream-like experiences, chronic psychosis, and severe damage to the central nervous system with prolonged use.

3. Eliminate the other options — stimulants increase alertness and wakefulness, sedatives cause calmness and drowsiness, and tranquillisers reduce anxiety without inducing sleep — none of which describe LSD's defining hallucinogenic effect.

4. Hence, the answer is Hallucinogenic (Option C).

1. Recall what happens to the Graafian follicle after ovulation.

Since after an egg is released, the remaining follicular cells collapse and transform:

2. Recall the details of this transformation.

Given that the follicular cells fill with a yellow pigment called lutein, forming the corpus luteum from the same original structure:

3. Rule out the other option pairs by checking whether they represent a true "before-and-after" or equivalent relationship.

Therefore, sebum and sweat are different secretions from different glands, the bundle of His and pacemaker (SA node) are distinct cardiac conduction structures, and vitamin $B_7$ (biotin) and niacin are different, unrelated vitamins — none of these show the same direct transformation relationship.

Hence, the similar set is corpus luteum and Graafian follicles, so the answer is option A.