Prokaryotic Cells

Prokaryotic flagellum is not surrounded by any membrane. It consists of a single thread. The thread is made of numerous identical spherical protein sub-units called, flagellin. Each subunit is about 40 A in diameter. The flagellin sub-units are arranged in helical spirals and form a hollow cylinder. Each flagellum is about 120-150 A thick.

Ribosomes may occur in rosettes or helical groups called polyribosomes or polysomes (Gk. Poly - many, soma - body). The different ribosomes of a polyribosome are connected with a 10 - 20 A thick strand of messenger or mRNA and its maintenance requires energy. Polyribosomes are formed during periods of active protein synthesis when a number of copies of the same polypeptide are required.

Answer (d) a layer surrounding the cell wall of bacteria

The correct option (C): Mesosomes.

The correct option is (D): Glycocalyx.

Nissl granules are present in the cyton and even extend into the dendrite but absent in axon and rest of the neuron.
Nissl granules are in fact composed of free ribosomes and RER. They are responsible for protein synthesis.

Answer (d)

The mesosome is a specialized membranous structure found in prokaryotic cells. It plays a crucial role in cell wall formation, DNA replication, and respiration. The mesosome is an invagination of the plasma membrane that increases the surface area for these processes. Thus, the correct answer is Mesosome.