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Molecular phylogenetics has provided insight into the evolution and interrelationships of the three domains of life. The division between prokaryotes and eukaryotes reflects two very different levels of cellular organization; only eukaryotic cells have an enclosed nucleus that contains its DNA, and other membrane-bound organelles including ...
Organelles are parts of the cell that are adapted and/or specialized for carrying out one or more vital functions, analogous to the organs of the human body (such as the heart, lung, and kidney, with each organ performing a different function). [2] Both eukaryotic and prokaryotic cells have organelles, but prokaryotic organelles are generally ...
Prokaryotes have fewer organelles than eukaryotes. Both have plasma membranes and ribosomes (structures that synthesize proteins [ clarification needed ] and float free in cytoplasm ). Two unique characteristics of prokaryotes are fimbriae (finger-like projections on the surface of a cell) and flagella (threadlike structures that aid movement).
Eukaryotic cells contain membrane bound organelles. Some examples include mitochondria, a nucleus, or the Golgi apparatus. Prokaryotic cells probably transitioned into eukaryotic cells between 2.0 and 1.4 billion years ago. [31] This was an important step in evolution. In contrast to prokaryotes, eukaryotes reproduce by using mitosis and meiosis.
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
The outer nuclear membrane is continuous with the rough endoplasmic reticulum membrane, and like that structure, features ribosomes attached to the surface. The outer membrane is also continuous with the inner nuclear membrane since the two layers are fused together at numerous tiny holes called nuclear pores that perforate the nuclear envelope.
The endoplasmic reticulum is found in most eukaryotic cells and forms an interconnected network of flattened, membrane-enclosed sacs known as cisternae (in the RER), and tubular structures in the SER. The membranes of the ER are continuous with the outer nuclear membrane. The endoplasmic reticulum is not found in red blood cells, or spermatozoa.
Prokaryotes do not have a complex internal membrane network like eukaryotes, but they could produce extracellular vesicles from their outer membrane. [41] After the early prokaryote was consumed by a proto-eukaryote, the prokaryote would have continued to produce vesicles that accumulated within the cell. [41] Interaction of internal components ...