Cycle 6: Endosymbiosis and Antibiotic Resistance Flashcards
(39 cards)
What is endosymbiosis?
A symbiotic association in which one symbiont or partner lives inside the other
How does endosymbiosis relate to mitochondria and chloroplasts?
Endosymbiotic model suggests that prokaryotic ancestors of modern mitochondria and chloroplasts were ENGULFED by larger prokaryotic cells and evolved to become inseparable parts of the same single-called organism
What was the Early mitochondrion?
Aerobic prokaryote that lived as an endosymbiont with anaerobic prokaryote causing anaerobic host to now need oxygen
What was the early chloroplast?
photosynthetic prokaryote that became an endosymbiont with an AEROBIC CELL that already had mitochondria
What are the six lines of evidence supporting endosymbiosis?
- Morphology: shape + size of mito & chloroplasts are similar to prokaryotes
- Reproduction: mito and chloro are NOT created in cell - pre-existing mito and chloroplasts undergo cell division for new cell - BINARY FISSION
- Genetic Info - mito and chloroplasts contains heir own DNA and DNA is circular
- Transcription and Translation: have own ribosomes and tRNA
- Electron transport: have own ETC and ATP synthase on plasma membrane for chemical energy
- Sequence analysis: chloroplasts genes match cyanobacteria closely and rRNA of mito to heterotrophic bacteria
why prokaryotes lack the complexity seen in eukaryotes?
need to copy entire genome so genome must remain small for efficiency so no introns
eukaryotes has no adv or disadvantage for having small/large genome bc so much energy is made by mito genome that nuclear genome can be any size
How does the c-value paradox compare?
holds only for eukaryotes
What does Epulopiscium do that allows it to be so much bigger than E. coli?
more volume = more energy/proteins/ATP synthesis/e- trasnsport/OXPHOS
What is the importance of proximity?
genome is found on periphery of cell bc DNA contains OxPhos genes and surrounds cells nearby OxPhos units
** more energetically costly
What is the difference between genome size (haploid genome size) and the amount of DNA in a cell?
haploid = 1 copy of circular genome
genome size = amt of DNA in 1 copy (amt DNA - genome size x number of copies)
What is genome asymmetry? What is the prokaryotic disadvantage?
mito (OxPhos) and chloro (photosynthesis) has smaller genome that in nucleus so energyica deals are low
while prokaryotes. has to copy the entire genome each time for periphery - polyploid
why prokaryotes need to keep genomes as small as possible (gene density is high)?
must remain small for efficiency so no introns
What is the origin of endomembrane system, nuclear membrane, ER etc.?
plasma membrane infolding
Why have the genomes shrunk compared to ancestors?
redundancy (ex. cytokinesis) and horizontal gene transfer to nucleus.
What is horizontal gene transfer and why do we think it occurs…two reasons?
- control and regulate easily
- safer that harsh mito/chloro conditions that might damage DNA - less reactive in nucleus
What is the role of the signal peptide in trafficking nuclear-encoded proteins that end up in the mitochondria or chloroplasts?
precursor protein has signal sequence which is detected by receptor protein of chloroplasts or mito, protein diffuses across organelle membrane, signal sequence cleaved and mature protein is in correct organelle
How is horizontal gene transfer using DNA hybridization detected?
labeled and see if DNA (ss) probe complementary base pairs to see where the copy of genome is located
if dark band in mtDNA, no transfer
if dark band in nDNA yes trasnfer
if dark band in both, copy made but hasn’t been degraded so it both genomes
Do all eukaryotes have mitochondria?
no!
What is the gene CPN60 and the significance of its presence in organisms that lack of mitochondria?
CPN60 is a chaperone protein that helps proteins imported into mito fold correctly
–> found in nucleus and organism without mito
–> gene found in organism without mito, so it did have mito HGT to nucleus, but lost mito bc there is no adv to having them
Of the genes that remain in the mito/chloro…in general, what is their function?
mito: genes encode for OxPhos
chloroplasts: genes for photosynthesis, Rubisco, thylakoid
What’s an antibiotic
organic compound that can kill or inhibit bacterial growth
Major aspects of bacterial cell structure?
cell wall and presence of plasmid, circular DNA, flagellum
What is the plasmid?
non-chromosomal DNA that is imprint for spreading antibiotic resistance
What is Gram + bacteria?
only one membrane that takes in purple stain bc it can easily pass through cell wall/membrane
