General Pathology Practice Questions

Q: Which amino acid is present in the active site of caspases?

Cysteine. **Explanation:** **Caspases** (Cysteine-aspartic proteases) are a family of protease enzymes that play an essential role in programmed cell death (apoptosis) [1]. The name "Caspase" is derived from its two primary functional characteristics: 1. **"C" (Cysteine):** The enzyme utilizes a **Cysteine** residue at its active site to perform the nucleophilic attack on the target protein. 2. **"Aspase" (Aspartic acid):** The enzyme cleaves its target proteins specifically at peptide bonds following an **Aspartic acid** residue. **Analysis of Options:** * **A. Cysteine (Correct):** As the catalytic nucleophile, the thiol (-SH) group of cysteine is indispensable for the proteolytic activity of all caspases. * **B. Cystine:** This is a dimeric amino acid formed by the oxidation of two cysteine residues (disulfide bond). It does not possess the free thiol group required for the catalytic mechanism. * **C. Methionine:** While it contains sulfur, it is non-polar and lacks the reactive thiol group necessary for the active site of these proteases. * **D. Taurine:** This is an amino sulfonic acid, not a proteinogenic amino acid, and is not involved in the catalytic site of caspases. **High-Yield Clinical Pearls for NEET-PG:** * **Initiator Caspases:** Caspase 8 and 9 (and 10) [1]. * **Executioner Caspases:** Caspase 3, 6, and 7 (Caspase 3 is the most common). * **Inflammatory Caspase:** Caspase 1 (involved in the formation of the inflammasome and processing of IL-1β). * **Marker of Apoptosis:** The presence of cleaved (active) caspase-3 is a definitive histological marker for cells undergoing apoptosis [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 64-71.

Q: Liquefaction foci are seen in which dental tissue?

Dentin. **Explanation:** The presence of **liquefaction foci** is a characteristic histopathological feature of **dentinal caries**. **Why Dentin is correct:** Dentin consists of organic collagen fibers and inorganic hydroxyapatite. When dental caries progress into the dentin, acidogenic bacteria first demineralize the inorganic component. Subsequently, proteolytic enzymes (produced by bacteria or derived from the host) degrade the organic collagen matrix. As the bacteria proliferate within the dentinal tubules, the pressure and enzymatic activity cause the tubules to distend and coalesce, forming ovoid areas of necrosis and disintegration known as **liquefaction foci**. These foci are filled with necrotic debris and bacteria, eventually leading to the total destruction of the dentin structure. **Why other options are incorrect:** * **Enamel:** Enamel is the most highly mineralized tissue in the body (96% inorganic). Caries in enamel involve demineralization and structural breakdown (micro-cavitation) but do not form liquefaction foci because it lacks the significant organic matrix and tubular structure required for such focal necrotic expansion. * **Cementum:** While cementum can undergo decay (root caries), the specific term "liquefaction foci" is classically described in the context of the tubular architecture of dentin. **High-Yield Clinical Pearls for NEET-PG:** * **Transverse Clefts:** These are cracks that run at right angles to the dentinal tubules, often connecting multiple liquefaction foci. * **Pioneer Bacteria:** These are the initial bacteria that penetrate deep into the dentinal tubules before the actual cavitation occurs. * **Beaded Appearance:** In the early stages of dentin caries, bacteria colonize the tubules, giving them a "beaded" histological appearance before they coalesce into liquefaction foci.

Question 1

A couple has two children affected with tuberous sclerosis. On detailed clinical and laboratory evaluation (including molecular studies), both parents are normal. Which one of the following explains the occurrence of two affected children in this family?

Accepted Answer

Germline mosaicism

Answer

Non-penetrance

Answer

Uniparental disomy

Answer

Genomic imprinting

Question 2

Which of the following diseases demonstrates monogenic inheritance?

Accepted Answer

Hereditary spherocytosis

Answer

Atherosclerosis

Answer

Hypertension

Answer

Coronary disorder

Question 3

How can a cyst be differentiated from a granuloma?

Accepted Answer

All of the above

Answer

Radiopaque dyes

Answer

Polyacrylamide gel electrophoresis

Answer

Biopsy

Question 4

All the following protein defects can cause hereditary spherocytosis EXCEPT?

Accepted Answer

Glycophorin C

Answer

Ankyrin

Answer

Alpha-Spectrin

Answer

Beta-Spectrin

Question 5

Raised alpha-fetoprotein (AFP) is typically seen in which of the following conditions?

Accepted Answer

Hepatocellular carcinoma (HCC)

Answer

Hepatitis

Answer

Seminoma

Answer

All of the above

Question 6

Which amino acid is present in the active site of caspases?

Accepted Answer

Cysteine

Answer

Cystine

Answer

Methionine

Answer

Taurine

Question 7

Which of the following is not a protein misfolding disorder?

Accepted Answer

Tuberculosis

Answer

Creutzfeldt Jakob disease

Answer

Alzheimer's disease

Answer

Cystic fibrosis

Question 8

Liquefaction foci are seen in which dental tissue?

Accepted Answer

Dentin

Answer

Enamel

Answer

Cementum

Answer

All of the above

Question 9

Apoptosis is associated with all the following features EXCEPT?

Accepted Answer

Inflammation

Answer

Cell shrinkage

Answer

Intact cellular contents

Answer

Nucleosome size fragmentation of nucleus

Question 10

In Marfan syndrome, the defect is in which of the following?

Accepted Answer

Fibrillin I

Answer

Fibrillin II

Answer

Collagen

Answer

Elastin

General Pathology — MCQs

General Pathology — MCQs

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