Cycle 6: Endosymbiosis and Antibiotic Resistance

Question 1

What is endosymbiosis?

Answer 1

A symbiotic association in which one symbiont or partner lives inside the other

Question 2

How does endosymbiosis relate to mitochondria and chloroplasts?

Answer 2

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

Question 3

What was the Early mitochondrion?

Answer 3

Aerobic prokaryote that lived as an endosymbiont with anaerobic prokaryote causing anaerobic host to now need oxygen

Question 4

What was the early chloroplast?

Answer 4

photosynthetic prokaryote that became an endosymbiont with an AEROBIC CELL that already had mitochondria

Question 5

What are the six lines of evidence supporting endosymbiosis?

Answer 5

1. Morphology: shape + size of mito & chloroplasts are similar to prokaryotes
2. Reproduction: mito and chloro are NOT created in cell - pre-existing mito and chloroplasts undergo cell division for new cell - BINARY FISSION
3. Genetic Info - mito and chloroplasts contains heir own DNA and DNA is circular
4. Transcription and Translation: have own ribosomes and tRNA
5. Electron transport: have own ETC and ATP synthase on plasma membrane for chemical energy
6. Sequence analysis: chloroplasts genes match cyanobacteria closely and rRNA of mito to heterotrophic bacteria

Question 6

why prokaryotes lack the complexity seen in eukaryotes?

Answer 6

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

Question 7

How does the c-value paradox compare?

Answer 7

holds only for eukaryotes

Question 8

What does Epulopiscium do that allows it to be so much bigger than E. coli?

Answer 8

more volume = more energy/proteins/ATP synthesis/e- trasnsport/OXPHOS

Question 9

What is the importance of proximity?

Answer 9

genome is found on periphery of cell bc DNA contains OxPhos genes and surrounds cells nearby OxPhos units

** more energetically costly

Question 10

What is the difference between genome size (haploid genome size) and the amount of DNA in a cell?

Answer 10

haploid = 1 copy of circular genome

genome size = amt of DNA in 1 copy (amt DNA - genome size x number of copies)

Question 11

What is genome asymmetry? What is the prokaryotic disadvantage?

Answer 11

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

Question 12

why prokaryotes need to keep genomes as small as possible (gene density is high)?

Answer 12

must remain small for efficiency so no introns

Question 13

What is the origin of endomembrane system, nuclear membrane, ER etc.?

Answer 13

plasma membrane infolding

Question 14

Why have the genomes shrunk compared to ancestors?

Answer 14

redundancy (ex. cytokinesis) and horizontal gene transfer to nucleus.

Question 15

What is horizontal gene transfer and why do we think it occurs…two reasons?

Answer 15

1. control and regulate easily
2. safer that harsh mito/chloro conditions that might damage DNA - less reactive in nucleus

Question 16

What is the role of the signal peptide in trafficking nuclear-encoded proteins that end up in the mitochondria or chloroplasts?

Answer 16

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

Question 17

How is horizontal gene transfer using DNA hybridization detected?

Answer 17

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

Question 18

Do all eukaryotes have mitochondria?

Answer 18

no!

Question 19

What is the gene CPN60 and the significance of its presence in organisms that lack of mitochondria?

Answer 19

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

Question 20

Of the genes that remain in the mito/chloro…in general, what is their function?

Answer 20

mito: genes encode for OxPhos

chloroplasts: genes for photosynthesis, Rubisco, thylakoid

Question 21

What’s an antibiotic

Answer 21

organic compound that can kill or inhibit bacterial growth

Question 22

Major aspects of bacterial cell structure?

Answer 22

cell wall and presence of plasmid, circular DNA, flagellum

Question 23

What is the plasmid?

Answer 23

non-chromosomal DNA that is imprint for spreading antibiotic resistance

Question 24

What is Gram + bacteria?

Answer 24

only one membrane that takes in purple stain bc it can easily pass through cell wall/membrane

Question 25

What is Gram - bacteria?

Answer 25

harder for things to pass through cell wall/membrane bc it has 2 membranes

has porin- nonspecific channel that allows things to enter

Question 26

How does antibiotics relate to gram + and gram - bacteria?

Answer 26

antobiotocs are hydrophobic so it is more difficult to pass through Gram - membranes

Question 27

What is peptidoglycan?

Answer 27

makes cell wall that is like “mesh” not a barrier that is larger in gram + than gram -

Question 28

What are the components of peptidoglycan?

Answer 28

two layers of polysaccharide and small peptides that are cross linked through transpeptidase causing cell wall to become more rigid

Question 29

How does penicilin acts to block cell wall biosynthesis?

Answer 29

inhibits transpeptidase as an irreversible competitive inhibitor linking peptidoglycan by mimicking normal substrate and blocking active site bt covent bond to AA in active site and never leaves

Question 30

What are 4 bacterial function that are inhibited by by antibiotics?

Answer 30

1. metabolic pathways
2. cell wall formation (penicillin)
3. DNA replication/trasncription
4. Protein synthesis (lincomycin)

Question 31

Why don’t antibiotics kill us?

Answer 31

only prokaryotes have DNA gyrase (enzyme for circular DNA rep) and antibiotics go after prokaryotic enzymes

Question 32

Issue with having too much antibiotics?

Answer 32

Mitochondria are prokaryotic!
- most eukaryotic have mito which have DNA gyrase

Question 33

What was the assay for antibiotic resistance?

Answer 33

plate with bacterial culture
- bacterial lawn grows of plate
- soak paper disks in different antibiotics and lay them on bacteria
- determine if bacteria is resistant to antibiotic

Question 34

Two ways antibiotic resistance is acquired?

Answer 34

1. random mutation
2. DNA from an already resistant cell (proximity-bacterial conjugation)

Question 35

What happens during bacterial conjugation?

Answer 35

donor bacterium replicates plasmid which has resistance gene

replicated plasma enter recipient

Question 36

Major mechanisms of resistance (there are 5)?

Answer 36

1. Downregulation of Porin - antibiotic has difficulty entering the cell when large proteins are not available
2. Upregulation of Active efflux - antibiotics gets in through porin , antibiotic is pumped back out immediately
3. Inactivation of antibiotic - change antibiotic structure with enzyme so it is unactivated and can’t bind to ribosome
4. Target site modification - change site antibiotic is supposed to bind to
5. Target Bypass - new protein with the same metabolic capacity as antibiotic target protein - new path around what the antibiotic would block

Question 37

What are efflux pumps? What are their role in antibiotic resistance and cancer treatments

Answer 37

efflux pumps are ABC transporters that can pump antibiotics out can can pump out cancer fighting drugs

Question 38

Antibiotics and the environment?

Answer 38

antibiotics thrown away = environment becomes antibiotic resistant

Question 39

Major steps needed to tackle resistance?

Answer 39

1. Public education
2. New antibiotic development
3. control antibiotics use