Question

Are prokaryotes bacteria?

Answer 1

Prokaryotes are unicellular organisms lacking organelles or other internal membrane-bound structures. Therefore, they do not have a nucleus, but instead generally have a single chromosome: a piece of circular, double-stranded DNA located in a cell area called the nucleoid.

Complete answer:
Most prokaryotes have a cell wall outside of the plasma membrane. The composition of the cell wall varies considerably between the domains Bacteria and Archaea, the two domains of life in which prokaryotes are divided. The composition of their cell walls is also different from the eukaryotic cell walls found in plants (cellulose) or fungi and insects (chitin).

The cell wall functions as a protective layer and is responsible for the shape of the body. Some bacteria have a capsule outside of the cell wall. Other structures are present in some prokaryotic species, but not others. For example, the capsule found in some species enables the body to attach to surfaces, protects it from dehydration and attack by phagocytic cells, and increases its resistance to our immune responses.

Only single-celled organisms of the Bacteria and Archaea domains are classified as prokaryotes—pro means pre-and kary means nucleus. Animals, plants, fungi and protists are all eukaryotic—eu means true—and they are made up of eukaryotic cells. Some species also have flagella used for locomotives and pili used for surface attachment. Plasmids, which consist of extra-chromosome DNA, are also present in many species of bacteria and archaea.

Note: Bacteria and Archaea are both prokaryotes, but they differ enough to be placed in separate domains. The ancestor of modern Archaea is believed to have given rise to Eukarya, the third realm of life. Archaeal and bacterial phylae are shown; the evolutionary relationship between these phylae is still open to debate.