Which organisms have cell walls that can be affected by penicillin?
- bacteria
- protoctists
- viruses
▶️ Answer/Explanation
Ans: C
Penicillin targets peptidoglycan in bacterial cell walls (1). Protocists (2) have varied cell walls (e.g., cellulose), and viruses (3) lack cell walls entirely. Thus, the correct answer is C (1 only).
Which structures or compounds are present in a typical cell that can be killed by penicillin?
1. circular DNA
2. cytoplasmic DNA
3. 70S ribosomes
4. peptidoglycan
▶️ Answer/Explanation
Ans: A
Penicillin targets bacterial cells, affecting their circular DNA (1), cytoplasmic DNA (2), 70S ribosomes (3), and peptidoglycan cell walls (4). It inhibits cell wall synthesis (peptidoglycan) and disrupts bacterial protein synthesis (70S ribosomes), while bacterial DNA (circular/cytoplasmic) is also affected during cell death.
Which facts relate to the disease TB or its pathogen?
1. Viruses change their antigens to a limited extent.
2. TB is caused by only one species of pathogen.
3. HIV/AIDS makes the bacterial infection worse.
4. The pathogen may be transmitted by ingestion.
5. The pathogen may be transmitted from animals.
6. Multi-drug resistance occurs.
(A) 1, 4, 5 and 6
(B) 1, 2 and 6
(C) 2, 3 and 5
(D) 3, 4, 5 and 6
▶️ Answer/Explanation
Ans: D
To determine the correct answer, let’s analyze each statement in relation to TB (Mycobacterium tuberculosis):
- False: TB is caused by bacteria, not viruses.
- False: While M. tuberculosis is the main cause, other mycobacteria (e.g., M. bovis) can also cause TB.
- True: HIV weakens the immune system, exacerbating TB infections.
- True: TB can spread via contaminated food/drink (e.g., unpasteurized milk).
- True: Zoonotic transmission occurs (e.g., M. bovis from cattle).
- True: Multi-drug-resistant TB (MDR-TB) is a significant issue.
Only statements 3, 4, 5, and 6 are correct, making D the right choice.
Which disease does Mycobacterium bovis cause?
▶️ Answer/Explanation
Ans: D
Mycobacterium bovis is a pathogenic bacterium that primarily causes tuberculosis (TB) in cattle and can be transmitted to humans. While M. tuberculosis is the main cause of human TB, M. bovis is zoonotic and accounts for a small percentage of TB cases. The other options are caused by different pathogens: cholera by Vibrio cholerae, HIV/AIDS by a virus, and malaria by Plasmodium parasites.