chapter 22 Flashcards
What are prokaryotes?
The oldest, structurally simplest, and most abundant forms of life.
How long before eukaryotes did prokaryotes evolve?
Over a billion years.
What percentage of prokaryotes are unknown and undescribed?
90–99%.
What percentage of prokaryotes cause disease?
Less than 1%.
Into how many domains are prokaryotes divided?
Two domains.
Name the two domains of prokaryotes.
- Bacteria
- Archaea
What are extremophiles?
Prokaryotes that thrive in extreme environments.
Give an example of an extremophile.
Halobacteria thrive in high-salt environments.
What are biofilms?
Microbial communities held together by polysaccharides, proteins, and nucleic acids.
What are two roles of biofilms?
- Harmful (infections, plaque)
- Beneficial (environmental cleanup)
Are prokaryotes unicellular or multicellular?
Always single-celled.
What is the typical size range of prokaryotic cells?
0.1–5 μm.
What type of genetic material do prokaryotes have?
Single, circular double-stranded DNA.
What is binary fission?
Asexual reproduction in prokaryotes.
What is horizontal gene transfer?
The transfer of genetic material between organisms without reproduction.
Name the three methods of horizontal gene transfer.
- Conjugation (plasmid transfer)
- Transduction (via viruses)
- Transformation (uptake of foreign DNA)
Do prokaryotes have membrane-bound organelles?
No.
What is the cell wall composition of bacteria?
Peptidoglycan.
What distinguishes Gram-positive bacteria from Gram-negative bacteria?
Gram-positive has a thick peptidoglycan layer; Gram-negative has a thin peptidoglycan layer plus outer membrane.
What are the two types of photosynthesis exhibited by prokaryotes?
- Oxygenic photosynthesis
- Anoxygenic photosynthesis
What is a photoautotroph?
An organism that uses light as an energy source.
What is a chemoautotroph?
An organism that uses inorganic chemicals as an energy source.
What is mutualism in symbiotic relationships?
Both organisms benefit.
Give an example of a mutualistic bacterial relationship in humans.
Escherichia coli in human gut.
