Q.59 Which of the following statements are hue regarding the nature of cell wall of different microorganisms?
A. Cell wall of bacteria is composed of true peptidoglycan a complex having muramic acid and cross links
of L-amino acids.
B. Membrane lipids of Archaea contains branched chains attached to glycerol by ether linkage.
C. Cell wall of fungi are majorly made up of chitin.
D. Vitus and viroids lack cell wall.
E. Cell wall is absent in mycoplasma.
Choose the conect answer from the options given below:
1. B, C, D, E only
2. A. B. C, D, E only
3. D. E, Aonly
4. C, D. E only
All statements A, B, C, D, E are true. The correct answer is 2. A, B, C, D, E only.
Detailed Statement Analysis
A. True: Bacterial cell walls contain peptidoglycan (murein)—alternating N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (muramic acid) sugars, cross-linked by L-amino acid peptide bridges (e.g., L-lysine, L-alanine). Gram+ have thick peptidoglycan; Gram- have thin layer + outer membrane.
B. True: Archaea membrane lipids feature branched isoprenoid chains (phytanyl, C20) linked to glycerol by ether bonds (vs. ester bonds in Bacteria/Eukarya). This provides stability in extreme environments.
C. True: Fungal cell walls are primarily chitin (β-1,4-N-acetylglucosamine polymer) + β-glucans + mannoproteins. Chitin forms microfibrils for rigidity.
D. True: Viruses (nucleoprotein complexes) and viroids (naked circular ssRNA) lack cell walls, membranes, or organelles—they’re acellular.
E. True: Mycoplasma (Mollicutes) are wall-less bacteria bounded only by plasma membrane, causing pleomorphic shapes and antibiotic resistance (no β-lactam target).
Incorrect Options Explained
1. B,C,D,E only: Wrong—A is definitively true (peptidoglycan hallmark).
2. A,B,C,D,E only: Correct—All five statements accurate.
3. D,E,A only: Wrong—B and C also correct.
4. C,D,E only: Wrong—A and B omitted.
Introduction
The nature of cell wall of different microorganisms reveals distinct biochemical identities: bacteria (peptidoglycan with muramic acid), archaea (ether-linked branched lipids), fungi (chitin), while viruses/viroids and mycoplasma lack walls entirely. All five statements accurately reflect microbial cell wall diversity.
Cell Wall Composition Table
| Microorganism | Cell Wall Composition | Key Feature |
|---|---|---|
| Bacteria | Peptidoglycan | Muramic acid + L-amino cross-links |
| Archaea | No peptidoglycan | Ether-linked branched chains |
| Fungi | Chitin + glucans | β-1,4-GlcNAc polymer |
| Viruses/Viroids | Absent | Acellular |
| Mycoplasma | Absent | Wall-less bacteria |
Statement Verification
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A: Confirmed—peptidoglycan = GlcNAc-MurNAc + peptide bridges
-
B: Archaea signature—ether vs bacterial ester lipids
-
C: Chitin universal in fungal kingdom
-
D: Definitional—viruses lack cellular structure
-
E: Mycoplasma classification criterion
Exam Key Points
All five true tests comprehensive microbiology knowledge. Peptidoglycan = Bacteria only distinguishes from archaeal pseudomurein. Ether linkage = Archaea hallmark.
