Chapter 27 Flashcards
Chapter 27
Prokaryotes
are single-celled organisms that make up domains bacteria and archaea
Cell wall
-Maintains cell shape, cell protection, and prevents it from bursting in a hypotonic environment
-Contain peptidoglycan: a network of sugar polymers cross-linked by polypeptides
Gram-positive
Simpler walls with a large amount of peptidoglycan
Gram-negative
Less peptidoglycan and an outer membrane that can be toxic
Taxis:
Ability to move toward or away from a stimulus
Three factors contribute to the high levels of genetic diversity observed in prokaryote populations
-Rapid reproduction
-Mutation
-Genetic recombination
Cells produced by
binary fission are generally identical, but difference can arise through mutation
Transformation
Prokaryotic cell takes up and incorporate foreign DNA from the surrounding environment
Transduction
Movement of genes between bacteria by bacteriophages (Viruses that infect bacteria)
Conjugation
Genetic Material is transferred between prokaryotic cells
Phototrophs
obtain energy from light
Chemotrophs
obtain energy from chemicals
Autotrophs
require CO2 or related compounds as a carbon source
Heterotrophs
require an organic nutrient to make other organic compounds
Obligate aerobes
require O2 for cellular respiration
Obligate anaerobes
are poisoned by O2 and use fermentation or Anaerobic respiration
Facultative anaerobes
can survive with or without O2
Cells of one or more prokaryote species cooperate to form surface-coating colonies called
Biofilms
Nitrogen fixation is isolated in cells called
heterocysts that prevent oxygen penetration
Extremophiles
archaea that live in extreme environments
Halophiles
highly saline
Thermophiles
Very hot environments
Gram-positive bacteria include
-Actinomycetes, which decompose soil
-Bacillus anthracis, the cause of anthrax
-Clostridium botulinum, the cause of botulism
-Mycoplasms, the smallest known cells
Symbiosis
Two species live in close contact: a larger host and smaller symbiont
