Peptidoglycan is stained purple by the chemical crystal violet.
Which cells would stain purple in the presence of crystal violet?
▶️ Answer/Explanation
Ans: B
Crystal violet stains peptidoglycan found in bacterial cell walls. Vibrio cholerae (B) is a bacterium, while the others are eukaryotic (plant, protozoan, animal). Thus, only bacterial cells would stain purple with crystal violet.
Which row is correct for the control or prevention methods for each disease?
▶️ Answer/Explanation
Ans: C
TB is controlled by contact tracing, malaria by targeting mosquitoes (vector), and cholera through water treatment. Option C correctly matches each disease with its primary control method, making it the right answer.
Which statements are correct for penicillin?
- It is harmful to prokaryotic cells.
- It disrupts cell wall synthesis.
- It becomes less effective with regular use.
▶️ Answer/Explanation
Ans: A
All statements are correct: Penicillin targets prokaryotic cell walls (1), inhibits peptidoglycan synthesis (2), and bacteria can develop resistance with overuse (3). This makes option A the correct choice as it includes all true statements.
A vaccine is used to give immunity to the virus that causes the disease influenza.
A new influenza vaccine is needed every year because the virus mutates regularly.
What is the reason for needing a new influenza vaccine every year?
▶️ Answer/Explanation
Ans: D
Influenza viruses undergo antigenic drift, changing their surface antigens (D). This makes existing memory cells ineffective against new strains, requiring updated vaccines. The other options (A/B/C) describe immune system limitations, not the primary reason for annual vaccine updates.