Cell Wall
Also written as PBP.
Its cell wall is made of chitin and glucans, not peptidoglycan
What our notes say
- Its cell wall is made of chitin and glucans, not peptidoglycan (Medical Virology & Mycology Paper Two 2022/2023 — MKU MBMM 3300 Questions & Answ)
- Partly synthesized bacterial cell-wall structure is transported out of the cell by a lipid carrier protein (bchem EOY 2011 — Past Paper Questions & Answers)
- Bacterial cell-wall peptidoglycan is fully synthesized outside the cell (bchem EOY 2011 — Past Paper Questions & Answers)
- Galactomannan is a polysaccharide component of the Aspergillus cell wall. (Respiratory system pathology mcqs — Past Paper Questions & Answers)
- Viridans streptococci — alpha-hemolytic; NOT identified by Lancefield grouping (that's the wrong statement in the "except" question) — Lancefield grouping is based on the C-carbohydrate in the cell wall and applies to other groupable streptococci (Streptococcus Classification, S. pyogenes, Rheumatic Fever, AGN)
- Why penicillin doesn't work against Mycobacterium: the cell wall of these organisms is not affected by penicillin (high mycolic acid content makes the cell wall impermeable to many antibiotics) (Streptococcus Classification, S. pyogenes, Rheumatic Fever, AGN)
Study material on Cell Wall
- Bacteria
- 📚 MEDICAL VIROLOGY & MYCOLOGY — MCQ BANK
- Pharmco Notes
- Department Of Medical Microbiology & Parasit.. MCQs
- Streptococcus Classification, S. pyogenes, Rheumatic Fever, AGN
- Pharmacology CRASH Course
- Medical Microbiology III Exam: Viruses, Fungi & Diagnosis
- 💊 Weeks 6 & 7 Must-Know Notes
- Pharmacology Wk 1 & 2
- MBPL3822 Chemotherapy CAT 1 MCQs
- Medical Mycology Q&A: Fungal Pathogens, Drugs, & Diseases
- Bacteria — Practice Questions
- MICROBIOLOGY AND PARASITOLOGY MCQs
- Weekly Year 2: Microbiology Exam - June 12, 2026 (Section A: MCQs)
- MYCOLOGY MCQs — Complete Bank
- Weekly Year 2: Microbiology Exam - April 17, 2026 (Section A: MCQs)
Practice questions on Cell Wall
Penicillins interfere with bacterial cell wall synthesis by
- Inhibiting conjugation between N-acetyl muramic acid and N-acetyl
- Penicillins
- Counterfeiting for D-alanine in the bacterial cell wall
- Inhibiting synthesis of N-acetyl muramic acid pentapeptide
- Limited to a single tissue compartment
Answer: B. Penicillins are β-lactam antibiotics that inhibit bacterial transpeptidases (also called penicillin-binding proteins or PBPs), which are essential for cross-linking peptidoglycan chains in the bacterial cell wall. This weakens the cell wall and leads to bacterial cell lysis. ---
Protein A in S. aureus cell wall has affinity for
- Complement C3b
- Fc portion of IgG
- Fab portion of IgM
- C-reactive protein
- Limited to a single tissue compartment
Answer: B. Protein A binds to the Fc portion of IgG antibodies, which inhibits opsonization and phagocytosis. This is an important virulence mechanism that helps S. aureus evade the immune system. ---
The cell wall peptidoglycan layer of bacteria contains species-specific antigens, making it a likely source for serological identification. Flagellar (H) antigens and capsule (K) antigens are also common targets.
- A) Cytoplasmic membrane
- B) Peptidoglycan layer
- C) Flagellar antigens
- D) Capsular polysaccharides
Answer: A. While all bacterial components can potentially contain antigens, the cytoplasmic membrane is an internal structure and less accessible for antibody binding compared to surface structures like the cell wall, flagella, or capsule. These external components are typically rich in specific antigens used for serotyping.
Isoniazid is a primary antitubercular agent that inhibits the synthesis of mycolic acids, which are essential components of the mycobacterial cell wall.
- A) It inhibits the synthesis of mycolic acids
- B) It inhibits protein synthesis by binding to the 50S ribosomal subunit
- C) It disrupts folic acid synthesis
- D) It inhibits cell wall synthesis by blocking peptidoglycan cross-linking
Answer: A. Isoniazid is a prodrug that, after activation within Mycobacterium tuberculosis, inhibits the synthesis of mycolic acids. Mycolic acids are crucial for the integrity of the mycobacterial cell wall, and their inhibition leads to cell death. This is its primary mechanism of action.
Protein A is a surface protein found in the cell wall of Staphylococcus aureus. It has a high affinity for the Fc region of IgG antibodies, leading to the opsonization of bacteria in a way that prevents effective phagocytosis.
- A) The Fc region of IgG antibodies
- B) The Fab region of IgG antibodies
- C) Complement components
- D) Bacterial toxins
Answer: A. Protein A, a virulence factor of Staphylococcus aureus, binds to the Fc portion of immunoglobulin G (IgG) antibodies. This binding interferes with opsonization and phagocytosis by preventing the antibody's Fc region from interacting with phagocytic cells.
Protein A in S. aureus cell wall has affinity for:
- Antibody Fc regions
- Bacterial peptidoglycan
- Host cell receptors
- Complement components
Answer: A. Protein A is a surface protein found in Staphylococcus aureus that binds to the Fc region of IgG antibodies, preventing opsonization and phagocytosis, thus contributing to immune evasion.