There are three main divisions of living organisms: prokaryotes, eukaryotes and archaea. This essay will describe the division between prokaryotic and eukaryotic organisms and explore the reasoning behind these differences with respect to general structure, deoxyribonucleic acid storage and replication, metabolic processes, protein synthesis, and protein processing. ribonucleic acid. The cell is the most fundamental unit. of life, defined as “the fundamental structural and functional unit of all living organisms” (Oed.com, 2013). The prokaryotic cell is usually composed of a plasma membrane and a cell wall containing the cytosol and a structure known as a nucleoid. It is a single piece of circular or linear DNA that floats freely in the cytosol of the cell (Thanbichler et al., 2005, pp. 507). In contrast, eukaryotic organisms typically include (but are not limited to) membrane-bound organelles. such as the nucleus, mitochondria, endoplasmic reticulum (ER), Golgi body, lysosome and peroxisome. The main difference between a eukaryote and a prokaryote is that the latter does not contain a nucleus or such organelles. Such a definition, however, can be considered a poor discriminator between Eukarya and Prokarya organisms, because it describes only what prokaryotes lack, not what they fundamentally are. This essay aims to detail a more complete definition of why these two realms are so different from each other. A key example of this thinking is that while prokaryotes are often solely responsible for metabolic processes, cell reproduction and repair, eukaryotes are often highly specialized to perform certain functions and rely on other cells to perform different functions. For example...... middle of paper ......from double-stranded RNA. This would constitute a major disadvantage, because its mechanism does not constitute a form of immunity for the organism, if there were not another system specific to prokaryotic cells (and archaea) which uses "clusters of DNA chromosomal repetitive” (Van Der Oost and Brouns, 2009, pp. 863--865), which allow bacteria to store information from past infections with foreign DNA and thus build a future immune response. Prokaryotes and eukaryotes are organisms divided by their basic biological structure – the presence or lack of membrane-bound organelles. However, they can be defined and discriminated from each other based on certain key cellular functions and their respective differences: how their DNA is stored and replicated, how they breathe or photosynthesize, process their RNA transcripts, or respond to acids. foreign nucleic acids..