BIOL108 Chapter Notes - Chapter 27: Gram Staining, Negative Stain, Gram-Negative Bacteria

• School: University of Alberta
• Department: Biology (Biological Sciences)
• Course: BIOL108
• Professor: Cynthia Friedman

Document Summary

The first organisms that showed up on earth 3. 5 billion years ago were the prokaryotes. Prokaryotes are unicellular, smaller than eukaryotic cells as their diameter is 0. 5 to 5 (cid:373)i(cid:272)ro(cid:373)eters (cid:272)o(cid:373)pared to eukar(cid:455)otes" (cid:1005)(cid:1004)-100 micrometer. Prokaryotes have cell walls that maintain cellular shape, protect the cell, and prevent it from bursting in a hypotonic environment. Prokaryotes plasmolyze in a hypertonic environment, as in they shrink. Salt can be used to preserve food, as the loss of water from prokaryotes inhibits cellular reproduction which then keeps the prokaryotic levels low. In eukaryotes, cell walls are made up of cellulose (plants) or chitin (fungi). In bacteria however, cell walls are made up of peptidoglycan, a polymer composed of modified sugars cross-linked by short polypeptides. Archaeal cell walls are made up of polysaccharides and proteins, but lack peptidoglycan. Gram staining is a technique used to classify bacteria into two types.