Chemistry and properties of endotoxins MCQs With Answer

Chemistry and properties of endotoxins MCQs With Answer

Introduction: Endotoxins (lipopolysaccharides, LPS) are critical molecules in the study of biological evaluation of drug therapy because they profoundly influence safety, pyrogenicity and immune responses to pharmaceutical products. For M.Pharm students, mastering LPS chemistry — including lipid A structure, core sugars such as KDO, and O-antigen variability — is essential to understanding detection methods, removal strategies and clinical consequences like sepsis and cytokine release. This quiz focuses on detailed aspects of endotoxin chemistry, biological properties, assays (LAL, MAT, rFC), depyrogenation techniques and neutralization approaches, reinforcing the conceptual and practical knowledge required in drug development and quality control.

Q1. What is the principal chemical entity responsible for Gram-negative bacterial endotoxic activity?

• Lipopolysaccharide (LPS)
• Peptidoglycan
• Teichoic acid
• Capsular polysaccharide

Correct Answer: Lipopolysaccharide (LPS)

Q2. Which three structural domains make up a typical lipopolysaccharide molecule?

• Lipid A, core oligosaccharide, O-antigen
• Peptidoglycan, teichoic acid, capsule
• Lipid A, teichoic acid, flagellin
• Core polysaccharide, peptidoglycan, lipoteichoic acid

Correct Answer: Lipid A, core oligosaccharide, O-antigen

Q3. Which sugar is a characteristic component of the inner core region of many bacterial LPS?

• 3-deoxy-D-manno-octulosonic acid (KDO)
• Glucosamine
• Mannose-6-phosphate
• Galacturonic acid

Correct Answer: 3-deoxy-D-manno-octulosonic acid (KDO)

Q4. Which portion of LPS is primarily responsible for its pyrogenic and endotoxic activity?

• Lipid A
• Core oligosaccharide
• O-antigen polysaccharide
• Flagellar protein

Correct Answer: Lipid A

Q5. Innate immune recognition of LPS is mediated principally by which receptor complex?

• TLR4–MD-2 complex
• TLR2–TLR1 heterodimer
• NOD2 receptor
• C5a receptor (C5aR)

Correct Answer: TLR4–MD-2 complex

Q6. Which depyrogenation method is considered reliably effective for eliminating LPS on glassware and stainless steel?

• Dry heat depyrogenation at 250°C for 30 minutes
• Standard autoclaving at 121°C for 20 minutes
• Soaking in distilled water at 60°C
• Gamma irradiation at low dose

Correct Answer: Dry heat depyrogenation at 250°C for 30 minutes

Q7. The classical Limulus amebocyte lysate (LAL) assay detects endotoxin using materials derived from which organism?

• Horseshoe crab (Limulus) amebocytes
• Rabbit serous cells
• Mouse macrophages
• Yeast cell wall extract

Correct Answer: Horseshoe crab (Limulus) amebocytes

Q8. Which in vivo test has historically been used for assessing pyrogenic contamination of parenteral products?

• Rabbit pyrogen test
• Guinea pig skin test
• Mouse LD50 test
• Chick embryo assay

Correct Answer: Rabbit pyrogen test

Q9. The Monocyte Activation Test (MAT) commonly measures which cytokine as an indicator of pyrogenic activity?

• Interleukin-6 (IL-6)
• Interferon-gamma (IFN-γ)
• Transforming growth factor-beta (TGF-β)
• Interleukin-10 (IL-10)

Correct Answer: Interleukin-6 (IL-6)

Q10. Which antibiotic is known to bind lipid A and can neutralize endotoxin activity in vitro?

• Polymyxin B
• Vancomycin
• Penicillin G
• Tetracycline

Correct Answer: Polymyxin B

Q11. Approximately how many nanograms of E. coli LPS are equivalent to 1 Endotoxin Unit (EU)?

• About 0.1 ng
• About 10 ng
• About 1 µg
• About 100 ng

Correct Answer: About 0.1 ng

Q12. What distinguishes “smooth” LPS from “rough” LPS?

• Presence of O-antigen in smooth LPS and its absence or truncation in rough LPS
• Smooth LPS lacks lipid A while rough LPS contains lipid A
• Smooth LPS is only found in Gram-positive bacteria
• Rough LPS contains additional protein anchors absent in smooth LPS

Correct Answer: Presence of O-antigen in smooth LPS and its absence or truncation in rough LPS

Q13. The highly endotoxic form of E. coli lipid A is typically characterized by how many acyl chains?

• Six (hexa-acylated)
• Two (di-acylated)
• Four (tetra-acylated)
• Eight (octa-acylated)

Correct Answer: Six (hexa-acylated)

Q14. Endotoxin-induced septic shock is mainly driven by excessive release of which mediators?

• Tumor necrosis factor-alpha (TNF-α) and interleukin-1 (IL-1)
• Insulin and glucagon
• Antibodies IgG and IgM only
• Histamine exclusively

Correct Answer: Tumor necrosis factor-alpha (TNF-α) and interleukin-1 (IL-1)

Q15. The LAL assay detects endotoxin through activation of which initial component in the cascade?

• Factor C (a serine protease zymogen)
• Thrombin directly
• Complement C3
• Monocyte-derived IL-6

Correct Answer: Factor C (a serine protease zymogen)

Q16. Which modern in vitro assay is an animal-free alternative that uses recombinant protein to detect endotoxin?

• Recombinant Factor C (rFC) assay
• Rabbit pyrogen test
• Guinea pig wheel test
• Heat coagulation assay

Correct Answer: Recombinant Factor C (rFC) assay

Q17. Which physical-chemical property best describes LPS molecules in aqueous environments?

• Amphipathic, tending to form aggregates or micelles
• Highly hydrophilic and monomeric only
• Completely insoluble and crystalline
• Only volatile at room temperature

Correct Answer: Amphipathic, tending to form aggregates or micelles

Q18. Which of the following is least effective for reliable depyrogenation of endotoxin-contaminated glassware?

• Standard moist-heat autoclaving at 121°C for 15 minutes
• Dry heat at 250°C for 30 minutes
• Alkali treatment with NaOH followed by rinsing
• Using validated endotoxin-adsorbing materials and washing

Correct Answer: Standard moist-heat autoclaving at 121°C for 15 minutes

Q19. Apart from cytokine induction, LPS can directly activate which humoral system contributing to inflammation?

• Complement cascade leading to anaphylatoxins (C3a/C5a)
• Insulin signaling pathway
• Vitamin D synthesis pathway
• Renin–angiotensin system exclusively

Correct Answer: Complement cascade leading to anaphylatoxins (C3a/C5a)

Q20. High-quality LAL reagents can often detect endotoxin down to approximately what sensitivity?

• 0.01 EU/mL
• 1 EU/mL
• 10 EU/mL
• 100 EU/mL

Correct Answer: 0.01 EU/mL

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