Botany - B.E. Yakubenko 2017

Part One. Plant Anatomy and Morphology
Chapter I. Cytology
1.5. Structure of the Prokaryotic Cell

Prokaryotic Cells have a relatively simple Structure. They lack a true Nucleus; its function is instead performed by the nucleoid, which is devoid of a nuclear membrane and consists of a single circular DNA molecule associated with a minimal amount of protein. Extrachromosomal DNA segments known as Plasmids are found in the Cytoplasm. By migrating from Cell to Cell, they drive prokaryotic Variability, compensating to some extent for the absence of sexual reproduction.

Prokaryotic cells lack internal membranes, with the exception of the Plasmalemma. They have no Mitochondria, Endoplasmic reticulum, Plastids, Lysosomes, or Golgi apparatus. Vacuoles are also absent; the only Organelles present are small Ribosomes.

Prokaryotic cells are enclosed by a rigid Cell wall and frequently by a mucous capsule. The Cell wall contains murein. Its molecule consists of parallel polysaccharide chains cross-linked by short peptide chains.

The Plasma Membrane can fold inward into the cytoplasm (invagination), forming structures known as mesosomes. Redox Enzymes are located on the mesosomal membranes, along with relevant pigments in phototrophic prokaryotes (bacteriochlorophyll in Bacteria, and chlorophyll a and phycobilins in cyanobacteria). Consequently, these membranes are capable of performing the Functions of mitochondria, METABOLISM/14.html">Chloroplasts, and other organelles.

Asexual reproduction in prokaryotes occurs through binary fission, and occasionally by budding. Lipids and Glycogen are stored within prokaryotic cells as reserve nutrients.