Prokaryotes and Endosymbiosis Flashcards
What are the two prokaryotic domains?
Bacteria and Archaea
How many cells does a prokaryote typically have?
One
What important structure of eukaryotic cells do prokaryotic cells lack?
A membrane bound nucleus
Characteristic of prokaryotic organelles
Not membrane bound
Characteristic of prokaryotic DNA
Have a single circular strand plus plasmids
Reproduction method of prokaryotes
Binary fission
What do all prokaryotes have that only some eukaryotes have?
Cell wall
What is a gram stain?
A dyeing system used to examine bacterial cell walls
What is a gram positive cell?
A cell that looks purple under a microscope
Characteristics of gram positive cells
Their cell wall has extensive peptidoglycan (sugars + amino acid) and they lack an outer membrane
What is a gram negative cell?
A cell that looks pink under a microscope
Characteristics of gram negative cells
Cell wall has a thin layer of peptidoglycan and has an outher phospholipid bilayer
What is peptidoglycan?
A polymer consisting of sugars and amino acids
What do antibiotics do?
Inhibit bacteria-specific metabolism, which prevents them from making a cell wall
How do antibiotics work?
Inhibit protein synthesis by binding to the 30S ribosomal subunit, which inhibits the proteins needed for the cell to survive
What are the functions of capsule-polysaccharide secretion?
Adhesion, secretion, and movement
What is the type of bacterial movement called and what does it do?
Taxis
Orients to the stimulus
How do prokaryotes move?
Flagella or gliding (secreting a sticky substance)
What type of reproduction do prokaryotes use?
Binary Fission
What are characteristics of binary fission?
Asexual, short generation times
What is an endospore?
A resistant stage that is dehydrated and dormant for centuries
What is conjugation?
When genetic information is transferred by direct cell-to-cell contact
What is transformation?
When bacteria or archaea naturally take up DNA from the environment that has been secreted or released by cell lysis
What is transduction?
When virsues pick up DNA from one prokaryotic cell and transfer it to another cell via injection
What is the benefit of conjugation?
It’s a way to transmit a plasmid with antibiotic genes between organisms
What is horizontal gene transfer?
When DNA is transferred between two different species
What are phototrophs?
Organisms that use light to excite electrons
How is ATP made in phototrophs?
Photophosphorylation
What are chemoorganotrophs?
Organisms that oxidize organic molecules with high potential energy, like carbohydrates and lipids, to gain their energy
How is ATP made in chemoorganotrophs?
Cellular respiration or fermentation pathways
What are chemolithotrophs?
Organisms that oxidize inorganic molecules with high potential energy, like H+, CO2, Fe2+, NH4+, with O2 as an electron acceptor to gain their energy
How is ATP made in chemolithotrophs?
Cellular respiration
What are autotrophs?
Organisms that synthesize building-block compounds from simple starting materials
What are heterotrophs?
Organisms that absorb building-block compounds from their environment
What are the two major impacts of prokaryotes?
1.) Nutrient cycling- the movement and exchange of inorganic and organic matter back into the production of matter (N, C, O)
2.) Ecological interactions- symbiosis, mutualism, commensalism, parasitism, pathogens
What is symbiosis?
When individuals of two different species live in physical contact
Interaction of two organisms living in close physical association, typically to the advantage of both
What is mutualism?
When both organisms benefit from an interaction
What is commensalism?
When one species benefits from an interaction and the other is unharmed
What is parasitism?
When one species obtains nutrition from the host but doesn’t kill it
What are pathogens?
Disease causing organisms
How do bacteria relate to mitochondria?
They are the probable ancestors of mitochondria
What are stromatolites?
The oldest known fossils- rocks formed by the biological accretion of sedimentary layers on prokaryotic cyanobacterial mats
What is microcystin?
An algal toxin consisting of protein and haptotoxins
The Gulf of Mexico is considered a what?
Dead Zone
Why is the Gulf of Mexico considered a dead zone?
Excess nutrients are released from the Mississippi River into the Gulf of Mexico, which causes algal blooms. The bacterial degradation of dead algae rapidly depletes the oxygen in the area- this phenomenon is known as hypoxia
What do rhizonium nodules do?
Fix atmospheric N2 to convert it to ammonium (NH4+)
How do bacteria relate to humans?
Majority are non-pathogenic to humans
What do bacteria do in the human microbiome?
Digest food, synthesize vitamins, and protect against disease causing bacteria
What are exotoxins?
Toxins secreted by pathogenic bacteria
What are endotoxins?
Toxins released when pathogenic bacteria die
How is antibiotic resistance developed so quickly?
Horizontal gene transfer
What products can be developed with bacteria?
Bioremediation, biofeuls, and pharmaceuticals
How can archaea be described?
Extremophiles
What are methanogens?
Organisms that use H2 to reduce CO2 to CH4 under anaerobic conditions
What are halophiles?
Photoheterotrophs found in hypersaline areas
What are thermo-acidophiles?
Organisms found in hot springs and thermal vents whose optimal conditions are pH 2-3 and temperature > 80 degrees C
What is bioprospecting?
Finding unique chemicals or metabolic pathways in microbes
What are targets of bioprospecting?
Archaea
What is the first step of how a virus works?
Glycoproteins on the virus envelope bind to specific receptors on the host cell membrane
What is the second step of how a virus works?
The virus enters the cell and the viral genome duplicates and directs the host cell’s protein synthesis machinery to synthesize virus components
What is the third step of how a virus works?
Many viruses are repackaged and bud from the host cell to infect other cells
Do viruses kill the host cell?
Not always
What are the 5 main functions of bacteria in the environment?
1.) They are the ultimate decomposers
2.) Perform mineralization- which is reducing organic molecules to soluble forms that are bioavailable to plants
3.) Release nutrients into the soil (P, S, NH3)
4.) Promote plant growth
5.) Help perform the nitrogen cycle
What is the endosymbiont theory?
Mitochondria and plastids (chloroplasts and related organelles) are derived from ancestral prokaryotes that were engulfed by another cell and after being engulfed this relationship became symbiotic
What is an endosymbiont?
An organism that lives within a host cell or body
What is endosymbiosis?
The engulfing and ‘enslaving’ of free-living cells to become organelles
What is the hypothesis of the origin of the nucleus?
It was formed by infoldings of the plasma membrane
This process also formed the endoplasmic reticulum
What is the explanation for the origin of mitochondria?
Endosymbiosis
Host cell engulfs aerobic bacterium -> host cell fails to digest it -> bacterium lives and reproduces in host cell -> eventually become dependent on each other
Where did endosymbiosis leading to photosynthesis first occur?
In the common ancestor of Plantae
What is the endosymbiotic event leading to the formation of chloroplasts in plants called?
Primary endosymbiosis of cyanobacterium
How often do chloroplasts appear in protists?
4 different lineages
What is different about the chloroplasts in protists?
They are surrounded by more than 2 membranes
What is the endosymbiotic event leading to the formation of chloroplasts in archae?
Secondary endosymbiosis- when a protist engulfs another protist with organelles in it
