Question

Murein does not occur in the wall of
(a) Diatoms
(b) Nostoc
(c) Eubacteria
(d) Blue-green algae

Answer 1

Hint: Bacteria's cell wall consists of peptidoglycan also known as Murein which is a polymer made up of sugars and amino acids. Murein consists of oligoglycan strands cross-linking by short peptides and thereby forming a net-like polymeric structure surrounding the cytoplasmic membrane.
Complete answer:
Murein does not occur in the wall of diatoms. Diatoms are a group of algae that have a silica cell wall. The prokaryotic species are eubacteria, Nostoc, and Blue-Green Algae. Nostoc is a genus that belongs to the cyanobacteria family (Blue-green algae). They lack true organelles in the cell. Rather than a true nucleus, they possess nucleoid. Nucleoid is a substance of genetic origin without a nuclear shell. The cell wall is composed of peptidoglycan.
Bacteria are categorized as either Gram-positive or Gram-negative, based on variations in their peptidoglycan cell wall composition.
Functions of Peptidoglycan:
Cross-linking between amino acids in the peptidoglycan layer forms a strong mesh-like structure that provides the cell with structure. It also has binary fission involvement which is how bacteria reproduce. The peptidoglycan develops in the cell wall as the bacterium elongates during asexual reproduction, before dividing. Then when the bacterium has split into two, the cell wall needs to reform to enclose the two new bacterial cells.
So, the correct answer is 'Diatoms’.

Note:
- Two alternating amino sugars make up peptidoglycan's crystal lattice structure; they are N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
- Amino sugars are sugar molecules with an amine group (-NH2) substituting for one of their hydroxyl groups. Each NAM molecule has four or five amino acid chains attached to it. The crosslinking between these amino acids gives its strong structure to peptidoglycan.