Exam 4 Flashcards
(26 cards)
What does the term “selective toxicity” mean?
the drug is more likely to harm viral cells than human cells
What was Paul Ehrlich’s
contribution to antimicrobial drug discovery
he created the first antimicrobial drug (selversan- used to treat syphilis) that have selectively toxic
What was Alexander Fleming’s contribution to antimicrobial drug discovery?
he discovered that a certain mold had antimicrobial qualities, but he had trouble isolating that active compound
What were Howard Florey and Ernst Chain’s contribution to antimicrobial drug discovery?
they developed the method for isolating the active compound in penicillin
What’s a general definition for “antibiotic”?
it inhibits growth or kills bacteria
What’s the difference between antibiotics that are bacteriostatic vs. those that are bacteriocidal?
bacteriostatic antibiotics slow the growth of bacteria, while bacteriocidal antibiotics kill bacteria
What’s the difference between broad spectrum and narrow spectrum antibiotics?
broad spectrum antibiotics are effective against gram positive AND gram negative bacteria, while narrow spectrum antibiotics are effective against a certain group of bacteria
Briefly describe the four mechanisms of antibiotic action:.
prevention of cell wall synthesis, inhibition of protein synthesis, inhibition of nucleic acid synthesis, and growth factor analogs (molecules with a similar structure to a nutrient molecule).
Describe how penicillin harms bacteria.
Penicillin deactivates transpeptidases which breaks down the bonds between NAMS and therefore breaks down the bacterial cell wall
transpeptidases are…
…the enzyme that helps to form the linkage between NAMs in the NAM NAG sugar chain.
Explain why this antibiotic that inhibit protein synthesis do not generally cause harm to human cells.
these antibiotics are selectively toxic; they can tell the difference between bacteria and our own cells because bacterial ribosomes have a different structure than human ribosomes
Antibiotics that work to inhibit protein synthesis could cause harm to us, especially if used for
a long period of time. Explain two reasons why this harm could occur. !!!!!!!!!!!
Our normal flora could get wiped out and they can harm mitochondria within our cells because mitochondria have their own prokaryotic ribosomes
Explain why this antibiotics that inhibit nucleic acid synthesis do not generally cause harm to human cells.
because the enzymes involved in DNA replication differ between human cells and bacterial cells
Describe how sulfanilamides harm bacteria
bacterial enzymes convert paba, an essential nutrient that bacteria need to grow, into folic acid after binding. folic acid is important because it is directly used to make bacterial DNA and RNA (nucleotides).Sulfanilamides are able to bind to the bacterial enzymes, blocking paba from binding instead. This prevents the production of bacterial DNA and RNA.
Explain how sulfanilamides harm bacteria and not human cells.
paba is needed for bacterial cells because it can be converted into folic acid, but humans intake folic acid (vitamin B) through diet, and therefore do not require paba.
Describe four mechanisms of antibiotic resistance.
- Outer structure of bacterium prevents antibiotic from entering
- structure targeted by antibiotic cannot be bound by antibiotic
- antibiotic is pumped out of bacterial cell before it can do any damage
- bacterium releases enzymes that degrade antibiotic molecules
Explain why it is easier to develop antibacterial drugs vs. antiviral drugs.
viruses hijack our own cells and use them to replicate, and it’s hard to create a drug that can kill just the virus once it has taken over.
Give a general description of how a nucleoside analog might prevent the production of new viruses
once a nucleoside is inserted into a template strand, DNA polymerase comes through to read that strand, but it cannot attach any more nucleotides to the strand past the point of nucleoside insertion. That unfinished portion of the template strand becomes degraded, and the virus is not able to continue production.
As this nucleotides are brought into the “building area”, they must each contain how many phosphate groups?
3
Explain why incoming nucleotides must have 3 phosphate groups.
they need 3 phosphate groups because the energy released when two of those phosphate groups break off is used to form the covalent bond between the sugar and the phosphate.
What role does thymidine kinase play in the building of a new nucleic acid strand?
it adds an additional 2 phosphate groups to thyamidine (containing one phosphate) so that it can attach to the nucleic acid chain
What type of cell would contain more thymidine kinase: a normal human cell or a human cell that’s infected by a virus?
Human cell infected by a virus because the virus can produce more thymidine kinases once it has hijacked the healthy human cell, which helps to produce more viral nucleic acids at a higher rate.
How does acyclovir interfere with the process of DNA synthesis?
real thymines have an OH group at the 3’ carbon, but acyclovir does not. Thyamidine kinase attaches two phosphate groups to it so that it can be added to the nucleotide chain, but DNA/RNA replication stops there since the covalent bond between the sugar and phosphate group occur at the 3’ carbon.
Thymidine kinase _______
acyclovir.
activates
