BIOL 1202 Chapter : Chapter 27
Document Summary
The organisms that make up the two prokaryotic domains (bacteria and archaea) were the first organisms to arise on earth (about 3. 5 billion years ago). Most prokaryotes range in size from 0. 2-5. 0 micrometers in diameter (see fig 27. 2). The thickness of a dime is about 1 millimeter (1000 micrometers). The two domains appear similar in many respects however they are different in some very basic ways. Based on arrangement of genes and structures of molecules that build these structures. One main distinction between the bacteria and the archaea is the type of a semi-rigid permeable cell wall. Don"t really present a barrier for material to have a problem flowing in and out of a cell. This bacterial cell wall is composed of peptidoglycan. Peptidoglycan is a type of polymer in bacterial cell walls consisting of modified sugars cross-linked by short polypeptides. While only about 5000 prokaryotic species have been described, there may be as many as 100-1000 times that number.
