Question

Cell wall is absent in which of the following organisms?
(a) Nostoc
(b) Aspergillus
(c) Funaria
(d) Mycoplasma

Answer 1

Hint: The hard protective coating of all plants, fungal and some bacterial cells is the cell wall. In animal cells, the cell wall is missing. It is lacking in an organism that is often referred to as mollicutes. They are the simplest prokaryotes that are free-living and the smallest.

Complete answer:
Mycoplasma is a bacterial genus that lacks a cell wall and is surrounded only by its cell membrane. Mycoplasma is a class of bacteria lacking a cell wall around their cell membranes. This attribute makes them naturally resistant (like the beta-lactam antibiotics) to antibiotics that target cell wall synthesis. They may be saprotrophic or parasitic.
Mycoplasmataceae can contort into a wide variety of shapes, from round to oblong, due to the lack of a rigid cell wall. Therefore, they cannot be categorized as rods, cocci, spirochetes.
Nostoc is a blue-green alga or cyano-bacterial genus. Every cell has a thick peptidoglycan-composed cell wall.
Aspergillus belongs to the fungal group. A complex and versatile structure consisting essentially of chitin, alpha- and beta-linked glucans, glycoproteins, and pigments is the fungal cell wall.
Funaria is classified under a kingdom of plants. Their cell wall consists of cellulose.

So, the correct answer is, ‘Mycoplasma’.

Note:
A cell wall, just beyond the cell membrane, is a structural layer covering certain cell types. It can be rugged, versatile, and, at times, rigid. It provides both structural support and protection to the cell and also serves as a mechanism for filtering. A major task is to function as pressure vessels, avoiding the cell's over-expansion when water enters.