(A) Prokaryotic cells are unicellular organisms that lack membrane-bound organelles.
The characteristics of prokaryotic cells are as follows:
$1$. Most of them are unicellular.
$2$. They are generally small in size,typically ranging from $0.5-5 \mu m$.
$3$. The nuclear region is poorly defined due to the absence of a nuclear membrane; hence,they lack a true nucleus.
$4$. The genetic material is naked,consisting of a single,circular chromosome. In addition to genomic $DNA$,they often contain small,circular plasmid $DNA$.
$5$. They possess specialized membranous structures called mesosomes,formed by the invagination of the cell membrane. These assist in cell wall synthesis,$DNA$ replication,and the distribution of chromosomes to daughter cells.
$6$. Membrane-bound organelles such as mitochondria,plastids,and the endoplasmic reticulum are absent.
$7$. Most prokaryotic cells have a three-layered cell envelope: the outermost glycocalyx,the middle cell wall,and the innermost plasma membrane,which acts as a protective unit.
$8$. Examples include bacteria and blue-green algae.