Questions & Answers

Muramic acid is present in the cell wall of
(a)Bacteria/ Blue-green algae
(b)Green algae

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Hint: Muramic acid i.e N-acetyl muramic acid constitutes peptidoglycan. It is a typical cell wall component of the smallest and most successful prokaryotic organisms. In the five-kingdom classification, they were placed under the kingdom Monera.

Complete answer:
Muramic acid is the component of the bacterial cell wall. Bacterial cell walls are often multilayered and its chemical composition is different from that of fungal and plant cell walls. It contains neither cellulose or chitin but is formed of a network of murein. Murein is a heteropolymer, unique to bacteria. It is not found elsewhere in the living world. It is polypeptide or mucopeptide, formed of the alternating units of N-acetylglucosamine and N-acetyl Muramic acid which are joined by $\beta$-1, 4 linkages. They are cross-linked with each other by peptide chains. Attached to the carboxyl end of acetyl Muramic acid are the amino acids alanine, lysine, glutamic acid, etc. which impart structural rigidity and stability to the cell wall.

Additional information:
In some bacteria, the cell wall is surrounded by a capsule, formed of polysaccharides. The cell wall of Gram-positive bacteria differs from Gram-negative bacteria in chemical composition.
It is thick, relatively simple, almost homogeneous and non-layered, and contains up to 80%of peptidoglycan. In addition to peptidoglycan, it may also contain some amount of proteins and teichoic acid.
The cell wall of Gram be negative bacteria is relatively thin, three-layered, and complex, and it contains only 10-20% peptidoglycan.
So, the correct answer is option (a) 'Bacteria/ Blue-green algae'.

Note: Teichoic acid is a long heteropolymer of glucose, N-acetyl glucosamine, amino acid, and ribitol or glycerol phosphate.
It has three main roles; it binds peptidoglycan layer with the underlying plasma membrane, regulates the action of autolysins.
Autolysins are enzymes responsible for the loosening of bonds of the peptidoglycan layer. Teichoic acid also controls cell division.