CLEP CLEP Biology Microbiology and Immunology 1 — Questions and Answers
Question 1: Which bacteria lack a cell wall, making them naturally resistant to penicillin?
- Gram-positive bacteria
- Mycoplasma (Correct answer)
- Gram-negative bacteria
- Cyanobacteria
Correct answer: Mycoplasma
Mycoplasma are bacteria that lack a cell wall, making them resistant to antibiotics like penicillin that target cell wall synthesis.
Question 2: What is the genetic material found in a retrovirus like HIV?
- Double-stranded DNA
- Single-stranded DNA
- Single-stranded RNA (Correct answer)
- Double-stranded RNA
Correct answer: Single-stranded RNA
Retroviruses contain single-stranded RNA that is reverse-transcribed into DNA by the enzyme reverse transcriptase inside the host cell.
Question 3: Which bacterial structure allows genetic material to be transferred between cells through direct contact (conjugation)?
- Flagella
- Sex pili (Correct answer)
- Capsule
- Endospore
Correct answer: Sex pili
Sex pili form a direct cytoplasmic bridge between bacterial cells, enabling the transfer of plasmid DNA during conjugation.
Question 4: The lytic cycle of a bacteriophage ends with which event?
- Integration of viral DNA into the host chromosome
- Dormancy of the viral genome as a prophage
- Lysis of the host cell and release of new phages (Correct answer)
- Formation of a lysogenic bacterium
Correct answer: Lysis of the host cell and release of new phages
In the lytic cycle, viral replication culminates in the destruction of the host bacterial cell and release of newly assembled bacteriophages.
Question 5: Which type of immunity involves T cells and B cells responding specifically to pathogens?
- Innate immunity
- Passive immunity
- Adaptive immunity (Correct answer)
- Non-specific immunity
Correct answer: Adaptive immunity
Adaptive immunity involves lymphocytes — T cells for cell-mediated responses and B cells for antibody-mediated responses — providing specific and long-lasting protection.
Question 6: The outer membrane component of gram-negative bacteria that acts as an endotoxin is called:
- Peptidoglycan
- Teichoic acid
- Lipopolysaccharide (LPS) (Correct answer)
- Protein A
Correct answer: Lipopolysaccharide (LPS)
Lipopolysaccharide (LPS) in the outer membrane of gram-negative bacteria triggers severe immune responses and acts as a potent endotoxin.
CLEP CLEP Biology Microbiology and Immunology 1
Which bacteria lack a cell wall, making them naturally resistant to penicillin?