Chapter 20.2 Prokaryotes Flashcards
What is a prokaryote?
smallest and most abundant microorganisms that are unicellular and lack a nucleus
Where is prokaryote DNA located?
in the cytoplasm
Where is eukaryote DNA located?
in a membrane-bound nuclear envelope
Domain Bacteria
(Kingdom Eubacteria)
- the larger of the two domains
- surrounded by a cell wall that protects from injury and determines its shape
- cell walls contain peptidoglycan
- some bacteria (ie. E. coli) have a second membrane outside the peptidoglycan wall that makes the cell especially resistant to damage
- live in wide range of environments
What is peptidoglycan?
a polymer of sugars and amino acids
Domain Archaea
(Kingdom Archaebacteria)
- cell walls lack peptidoglycan
- membranes contain different lipids
- archaea and eukaryotes are more closely related to each other than bacteria
- live in harsh/extreme environments
- methanogens
- halophiles
- thermoacidphiles
What are methanogens?
bacteria that can live in swamps, lake sediment, animals’ guts and produce methane gas (greenhouse gas)
- live in places with little or no oxygen
What are halophiles?
bacteria that live in very salty habitats like the Dead Sea, seawater-evaporating ponds for salt production
What are thermoacidphiles?
bacteria that live in acid, hot conditions, like hot springs, deep-sea volcanic vents
How do prokaryotes vary in their structure and function?
prokaryotes vary in their size and shape, in the way they move, and in the way they obtain and release energy
Describe the size of prokaryotes.
range in size from 1 to 5 micrometers (smaller than most eukaryotic cells)
What are the three different shapes of prokaryotes?
- bacilli: rod-shaped
- cocci: spherical
- spirilla: spriral and corkscrew-shaped
Describe the movement of prokaryotes.
some do not move at all, some are propelled by a flagella, some glide slowly along a layer of slimelike material they secrete
Describe the nutrition and metabolism of prokaryotes.
store chemical energy in the form of fuel molecules (sugars), this energy is released during cellular respiration, fermentation, or both
What is a photoautotroph?
organism that carries out photosynthesis in a manner similar to that of plants
What is a chemoautotroph?
organism that makes food from chemical reactions such as ammonia
What is a decomposer?
organism that takes in organic molecules and then breaks them down
What is a photoheterotroph?
organism that uses light energy in addition to processing organic molecules
What is binary fission?
a type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells
What is an endospore?
a thick internal wall that encloses the DNA and a portion of the cytoplasm
What is conjugation?
a process in which paramecia and some prokaryotes exchange genetic info
hollow bridge forms between two bacterial cells, and genetic material, usually in the form of a plasmid
2 bacteria joined by pili and a small piece of DNA (plasmid) moves from one bacterium to the other
AKA LATERAL GENE TRANSFER: increases genetic diversity
How do decomposers help the ecosystem recycle nutrients when a tree dies?
They feed and digest dead tissue, breaking it down into its raw materials which are released back into the environment.
What would happen to plants and animals if decomposers did not recycle nutrients?
Plants would drain the soil of minerals and die, and animals that depend on plants as food would starve.
Why do all organisms need nitrogen?
to make proteins and other molecules
Why is the process of nitrogen fixation important?
the process converts nitrogen gas into ammonia which can then be converted to nitrates that plants use or can be attached to amino acids that all organisms use
What kind of relationship do many plants have with nitrogen-fixing bacteria?
symbiotic relationship
Where does conjugation happen?
in harsh environments, plasmids may contain genes to survive in new environments or to resist antibiotics
What are the 6 important things about prokaryotes?
- decomposers
- producers
- nitrogen fixers
- human uses
- human body
- diseases
How are prokaryotes classified?
prokaryotes are classified as Bacteria or Archaea (two of the three domains of life)
DECOMPOSERS: importance of prokaryotes (3)
- assist in breaking down dead organisms
- supply raw materials (recycles) and help to maintain equilibrium in the environment
- sewage treatment, purify water
PRODUCERS: importance of prokaryotes (2)
- photosynthesizers: produce oxygen in the open ocean
- basis of many food chains: depended on for food and biomass production
NITROGEN FIXERS: importance of prokaryotes (2)
- nitrogen fixation
- some plants have symbiotic relationships with nitrogen-fixing prokaryotes
HUMAN USES: importance of prokaryotes
- food production
- mining
- synthesizing drugs and chemicals
- remove wastes
- etc.
HUMAN BODY: importance of prokaryotes
- 9/10 cells are bacterial
- each cm squared of skin has 100,000 bacteria
- helps digestion
- helps immunity
DISEASES: importance of prokaryotes
- some bacteria are disease causing
What are the most abundant photosynthetic organisms in the world?
cyanobacterium “Prochlorococcus”
- may account for more than half of the primary
production in the open ocean
What roles do prokaryotes play in the living world?
Prokaryotes are essential in maintaining every aspect of the ecological balance of the living world. In addition, some species have specific uses in human industry.
What do plasmids carry?
genes that enable bacteria to survive in new environments or to resist antibiotics that might otherwise prove fatal
What are mutations?
random changes in DNA that occur in all organisms
How are mutations inherited in prokaryotes?
by daughter cells produced by binary fission
Mode of Metabolism: OBLIGATE AEROBE
- meaning
- how energy is released
- habitat
- example
meaning: “requiring oxygen”
how energy is released: cellular respiration (must have ready supply of oxygen to release fuel energy)
habitat: oxygen-rich environments (ie. near water, in animal lungs)
example: mycobacterium tuerculosis (sometimes in human lungs)
Mode of Metabolism: OBLIGATE ANAEROBE
- meaning
- how energy is released
- habitat
- example
meaning: “requiring a lack of oxygen”
how energy is released: fermentation; die in presence of oxygen
habitat: oxygen-deficient environments (ie. deep soil, airtight containers, intestines)
example: clostridium botulinum (found in improperly sterilized food: food poisoning)
Mode of Metabolism: FACULTATIVE ANAEROBE
- meaning
- how energy is released
- habitat
- example
meaning: “surviving without oxygen when necessary”
how energy is released: can use either cellular respiration or fermentation as necessary
habitat: oxygen-rich or oxygen-deficient environments
example: E. coli (aerobically in sewage and human large intestines)
Mode of Nutrition: HETEROTROPH
- meaning
- how energy is released
- habitat
- example
meaning: “other feeder”
how energy is released: take in organic molecules from environment or other organisms to use as both energy and carbon supply
habitat: wide range of environments
example: clostridium
Mode of Nutrition: PHOTOHETEROTROPH
- meaning
- how energy is released
- habitat
- example
meaning: “light and other feeder”
how energy is released: like basic heterotrophs, but also use light energy
habitat: where light is plentiful
example: rhodobacter, chloroflexus
Mode of Nutrition: PHOTOAUTOTROPH
- meaning
- how energy is released
- habitat
- example
meaning: “light self-feeder”
how energy is released: use light energy to convert carbon dioxide into carbon compounds
habitat: where light is plentiful
example: anabaena
Mode of Nutrition: CHEMOAUTOTROPH
- meaning
- how energy is released
- habitat
- example
meaning: “chemical self-feeder”
how energy is released: use energy released by chemical reactions involving ammonia, hydrogen sulfide, etc.
habitat: in chemically harsh and/or dark environments (ie. deep in the ocean, thick mud, digestive tracts of animals, boiling hot springs)
example: nitrobacter
