microorganisms and microbiology Flashcards
microorganisms
organisms too small to be clearly seen by the unaided eye
prokaryotic cells
bacteria and archaea
their contents are not divided into compartments by membranes - open
eukaryotic cells
plants, animals, fungi
have a nucleus and other membrane-bound organelles that separate some cellular materials and processes from others
three domain system for microorganisms
bacteria
archaea
eukarya
bacteria
- usually single-celled
- most have cell wall with peptidoglycan
- most lack a membrane-bound nucleus
- live in extreme environments (including our bodies)
- both disease causing and non-disease causing exist
archaea
- distinguished from bacteria by unique rRNA sequences
- have unique membrane lipids
- many live in extreme environments
- some have unusual metabolic characteristics
- do not directly cause disease in humans
two classifications of eukarya
protists
fungi
protists
- unicellular, but generally larger than bacteria and archaea
- protozoa - animal like metabolism
- algae - photosynthetic
fungi
- unicellular or multicellular
viruses
acellular entities that must invade a host cell to multiply
viroids
infectious agents composed only of ribonucleic acid
satellites
composed of a nucleic acid enclosed in a protein shell
must coinfect a host cell with a virus, called a helper virus, to complete their life cycle
prions
infectious agents composed only of protein, responsible for causing neurological diseases such as scrapie and mad cow disease
ribozymes
catalytic RNA molecules
RNA molecules that form peptide bonds
RNA world
describes the precellular stage in the evolution of life
- must of had lipid membrane formed around RNA