Prokaryotic Cells are cells that do not have a true nucleus or membrane-bound organelles. These are single-celled microorganisms known to be the earliest on earth. Prokaryotes include Bacteria and Archaea. The photosynthetic prokaryotes include cyanobacteria that perform photosynthesis. A prokaryotic cell consists of a single membrane and therefore, all the reactions occur within the cytoplasm. They can be free-living or parasites. A prokaryotic cell does not have a nuclear membrane. However, the genetic material is present in a region in the cytoplasm known as the nucleoid.
Structure of Prokaryotic Cells
A prokaryotic cell structure is as follows:
- Capsule: It is an outer protective covering found in the bacterial cells, in addition to the cell wall. It helps in moisture retention, protects the cell when engulfed, and helps in the attachment of cells to nutrients and surfaces.
- Cell Wall: It is the outermost layer of the cell that gives shape to the cell.
- Cytoplasm: The cytoplasm is mainly composed of enzymes, salts, cell organelles, and is a gel-like component.
- Cell Membrane: This layer surrounds the cytoplasm and regulates the entry and exit of substances in the cells.
- Pili: These are hair-like outgrowths that attach to the surface of other bacterial cells.
- Flagella: These are long structures in the form of a whip, that help in the locomotion of a cell.
- Ribosomes: These are involved in protein synthesis.
- Plasmids: Plasmids are non-chromosomal DNA structures. These are not involved in reproduction.
- Nucleoid Region: It is the region in the cytoplasm where the genetic material is present.
Characteristics of Prokaryotic Cell
- They lack a nuclear membrane.
- Mitochondria, Golgi bodies, chloroplast, and lysosomes are absent.
- The genetic material is present on a single chromosome.
- The histone proteins, the important constituents of eukaryotic chromosomes, are lacking in them.
- The cell wall is made up of carbohydrates and amino acids.
- The plasma membrane acts as the mitochondrial membrane carrying respiratory enzymes.
- They divide asexually by binary fission. The sexual mode of reproduction involves conjugation.