Biochemistry - Prokaryotes

Biochemistry - Prokaryotes
The most abundant and widespread organisms on Earth are prokaryotes, which are so named because they lack a distinct, membrane-bound nucleus. The bacteria (or eubacteria) and the archaea are two distinct but related groups that make up the prokaryotes (or archaebacteria). Early in Earth's history, these two different prokaryotic groupings split apart.

Prokaryotic cell makeup
Prokaryotes typically have one of three basic shapes: spherical (cocci), rod-like (bacilli), or helically coiled, and range in size from 0.1 to 10 mm (spirilla). A prokaryotic cell, like all cells, is surrounded by a plasma membrane that completely encloses the cytoplasm and keeps the cell isolated from its surroundings. A lipid bilayer with proteins makes up the plasma membrane, which is 8 nm thick. The membrane subcellular organelles that distinguish eukaryotes from prokaryotes are absent. The macromolecules [enzymes, messenger ribonucleic acid (mRNA), transfer RNA (tRNA), and ribosomes], chemical substances, and ions required for cellular metabolism are found in the aqueous cytosol. The prokaryotic "chromosome," which consists of a single circular DNA molecule condensed into a substance known as the nucleoid, is also found in the cytosol.