MGY377 EXAM
Aminoglycosides are antibiotics containing _____-modified _____
Aminoglycosides are antibodies containing amino-modified sugars
Streptomycin, Kanamycin and gentamycin are all examples of
_____
Aminoglycosides
What is the broad category of inhibiton that aminoglycosides
have?
-What are two specific mechanisms of this?
-Overall, aminoglycoside mechanisms (are/are not) well
understood?
Aminoglycosides are involved in protein synthesis inhibition
-One way is that they interfere with tRNA translocation from the A
site to the P site.
-Another way they interfere is via protein proofreading-> causes the
wrong amino acids to be substituted in.
-Overall the mechanisms are not well understood
Tetracyclins:
1. Originally isolated from which genus?
2. Tetracyclins bind to _____
3. What is the mechanism of being bacteriostatic?
4. Why are tetracyclines not given to children/pregnant mothers?
1. They are isolated from streptomycin genus bacteria
2. They bind to the 30S subunit of ribosome
3. They block docking of tRNAs, preventing protein synthesis
4. They are readily absorbed into developing/growing bone, which are
present in children/pregant women.
,Macrolides:
1. Defining structural characteristic?
2. Macrolides bind to _____
1. It has a 14,15 or 16 membered ring
2. It binds to the 23S rRNA of the 50S subunit
3. It binds to the ribosome, preventing it from shifting tRNAs from
the A site to the P-site and also fails to transfer amino acids from
tRNAs to the growing peptide chain
Erythromycin is an example of what class of antibiotic?
-What genus is it isolated from?
A macrolide
-Isolated from streptomyces erythraea.
Fluoroquinolones
1. Bind to what?
2. Inhibit what?
1. Bind to DNA gyrase
2. Inhibit DNA replication
Rifampin
1. Binds to what?
2. Inhibits what?
3. What is the mechanism for this?
4. Is this considered bacteriostatic or cidal?
1. Binds to RNA polymerase
2. Inhibits RNA synthesis
3. The mechanism it uses it that it blocks the channel on RNA
polymerase that new RNA is supposed to come out of, must bind
before transcription begins.
4. Considered bacteriocidal
What does DNA gyrase do?
,It releases tension in supercoiled DNA, it is required for both DNA
replication and RNA synthesis
What differentiated different quinones?
The element at position 6. E.g. a fluoroquinone has a fluorine at
position 6
Polymyxin is an example of a _____
Cell membrane disruptor
Cell membrane disruptors
1. Are evolutionarily suited to kill bacteria but don't harm
humans (most of the time) why?
2. What is the mechanism they use?
3. Why do they not affect human/animal membranes?
1. Don't harm humans because they are generally produced in other
animals, and thus humans cells are sufficiently similar to the animal
cells to not be affected.
2. They put holes in the membrane
3. They have a positive charged end and a hydrophobic end. THe
positive end is attracted to bacterial membranes because they tend to
have negative charges on the exterior, but this is not the case in
human membrane
Over ___% of streptococcus pneumoniae strains are resistant to
penicillin
80%
Prevalence of antibitoic resistance correlates strongly with ____
Degree of usage
, What are 4 mechanisms of "natural"/inherent resistance to
antibitoics?
1. Lack of a target --> e.g. if a cell doesn't have a cell wall, will be
immune to beta-lactams
2. Membrane permeability barrier --> gram negative bacteria have
OM
3. Efflux pumps that are able to flush the drug from the cell before it
can do its function
4. Metabolic shutdown --> "persister" can remain dormant, rendering
them immune to drugs that inhibit metabolism steps
What are 3 mechannisms of acquired resistance?
1. Alteration of the target
2. Efflux
3. Alterations or inactivation of the drug itseld. E.g. via beta lactamase
production
How does streptomycin resistance arise?
Mutations in the 23, 16 or 5S of the ribosome or its associated
proteins
True or false: MRSA kills more people than AIDS in USA and
Canada?
True
What adaptation does MRSA have that makes it resistant to
methicillin?
-Where is the MRSA "resistance gene" coded?
It has a different transpeptidase (PBP) called MecA that has low
affinity for beta lactams but still functions to cross link cell wall
proteins
-The mecA gene is coded on a genomic island which appears to have
Aminoglycosides are antibiotics containing _____-modified _____
Aminoglycosides are antibodies containing amino-modified sugars
Streptomycin, Kanamycin and gentamycin are all examples of
_____
Aminoglycosides
What is the broad category of inhibiton that aminoglycosides
have?
-What are two specific mechanisms of this?
-Overall, aminoglycoside mechanisms (are/are not) well
understood?
Aminoglycosides are involved in protein synthesis inhibition
-One way is that they interfere with tRNA translocation from the A
site to the P site.
-Another way they interfere is via protein proofreading-> causes the
wrong amino acids to be substituted in.
-Overall the mechanisms are not well understood
Tetracyclins:
1. Originally isolated from which genus?
2. Tetracyclins bind to _____
3. What is the mechanism of being bacteriostatic?
4. Why are tetracyclines not given to children/pregnant mothers?
1. They are isolated from streptomycin genus bacteria
2. They bind to the 30S subunit of ribosome
3. They block docking of tRNAs, preventing protein synthesis
4. They are readily absorbed into developing/growing bone, which are
present in children/pregant women.
,Macrolides:
1. Defining structural characteristic?
2. Macrolides bind to _____
1. It has a 14,15 or 16 membered ring
2. It binds to the 23S rRNA of the 50S subunit
3. It binds to the ribosome, preventing it from shifting tRNAs from
the A site to the P-site and also fails to transfer amino acids from
tRNAs to the growing peptide chain
Erythromycin is an example of what class of antibiotic?
-What genus is it isolated from?
A macrolide
-Isolated from streptomyces erythraea.
Fluoroquinolones
1. Bind to what?
2. Inhibit what?
1. Bind to DNA gyrase
2. Inhibit DNA replication
Rifampin
1. Binds to what?
2. Inhibits what?
3. What is the mechanism for this?
4. Is this considered bacteriostatic or cidal?
1. Binds to RNA polymerase
2. Inhibits RNA synthesis
3. The mechanism it uses it that it blocks the channel on RNA
polymerase that new RNA is supposed to come out of, must bind
before transcription begins.
4. Considered bacteriocidal
What does DNA gyrase do?
,It releases tension in supercoiled DNA, it is required for both DNA
replication and RNA synthesis
What differentiated different quinones?
The element at position 6. E.g. a fluoroquinone has a fluorine at
position 6
Polymyxin is an example of a _____
Cell membrane disruptor
Cell membrane disruptors
1. Are evolutionarily suited to kill bacteria but don't harm
humans (most of the time) why?
2. What is the mechanism they use?
3. Why do they not affect human/animal membranes?
1. Don't harm humans because they are generally produced in other
animals, and thus humans cells are sufficiently similar to the animal
cells to not be affected.
2. They put holes in the membrane
3. They have a positive charged end and a hydrophobic end. THe
positive end is attracted to bacterial membranes because they tend to
have negative charges on the exterior, but this is not the case in
human membrane
Over ___% of streptococcus pneumoniae strains are resistant to
penicillin
80%
Prevalence of antibitoic resistance correlates strongly with ____
Degree of usage
, What are 4 mechanisms of "natural"/inherent resistance to
antibitoics?
1. Lack of a target --> e.g. if a cell doesn't have a cell wall, will be
immune to beta-lactams
2. Membrane permeability barrier --> gram negative bacteria have
OM
3. Efflux pumps that are able to flush the drug from the cell before it
can do its function
4. Metabolic shutdown --> "persister" can remain dormant, rendering
them immune to drugs that inhibit metabolism steps
What are 3 mechannisms of acquired resistance?
1. Alteration of the target
2. Efflux
3. Alterations or inactivation of the drug itseld. E.g. via beta lactamase
production
How does streptomycin resistance arise?
Mutations in the 23, 16 or 5S of the ribosome or its associated
proteins
True or false: MRSA kills more people than AIDS in USA and
Canada?
True
What adaptation does MRSA have that makes it resistant to
methicillin?
-Where is the MRSA "resistance gene" coded?
It has a different transpeptidase (PBP) called MecA that has low
affinity for beta lactams but still functions to cross link cell wall
proteins
-The mecA gene is coded on a genomic island which appears to have
