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121 Cards in this Set
- Front
- Back
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Do prokaryotes endocytose molecules?
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No they are incapable of ingesting particles or liquid droplets
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What is the ploidy of a prokaryote?
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haploid, one chromosome but do have extrachromosomal plasmids
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What is occurring in a dental plaque?
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It is a build up of polysaccharides that create a biofilm
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Do both eukaryotes and prokaryotes have cytoplasmic DNA?
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In a way yes. Prokaryotes lack a nucleus and eukaryotes have mitochondria which reside in the cytoplasm and have DNA in them
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What type of genes do prokaryotes have? Eukaryotes?
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Prokaryotes have Operon-polycistronic mRNA and eukaryotes have single genes
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Does post-transcriptional mRNA processing occur in prokaryotes?
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No they do not have introns
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Are transcription and translation coupled in eukaryotes?
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No but it is in prokaryotes
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If a drug were targeted at the poly A tail or 5' cap of an mRNA how effective would it be against E. coli?
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Not effective. Only eukaryotes have 5' cap and poly A tail
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The first amino acid translated in bacterial protein synthesis is? In eukaryotes?
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Prokaryotes have formylated methionine and eukaryotes have methionine
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What is the main difference of the start signal for translation between bacteria and yeast?
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Bacterial ribosomes recognize the AUG sequence; however, yeast ribosomes recognize the 5' cap
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How many initiation factors for translation exist in bacteria? In Yeast?
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bacteria have 3 and yeast more than 6
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If a urine sample is visibly turbid it can be assumed that the density of bacterial growth exceeds___?
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1-10 million bacteria per milliliter
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How many bacteria on average are estimated to be in the large intestine alone?
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10-100 trillion
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What property about microbes allows them to have high metabolic rates?
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The fact that they have a large surface to volume ratio. The trend is surface to volume increases as the cell size decreases
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Gram (-) bacteria have what feature that allows them to transport hydrophillic molecules into the periplasm?
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porin trimers p.21
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List the steps of the gram stain!
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1) Begin with crystal violet
2) Modify with KI 3) Decolorize with ethanol (Note gram + remain purple) 4)Counterstain with safarin (Note gram (-) are pink) |
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List the steps of the acid fast stain!
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1) Stain with hot carbol-fuchsin (red)
2) Decolorize with acid alcohol (Note only the acid fast bacteria remain red) 3) Counterstain with methylene blue (Note other bacteria become blue) |
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What two sugars are unique to the bacterial cell wall? Which sugar is involved the protein crosslinking?
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N-acetylmuramic acid and N-acetylglucosamine. N-acetylmuramic acid Links the murein chains via peptide bonds.
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What shape are spirilla?
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helical
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What does the cell wall do for bacteria in regards to osmotic pressure?
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The cell wall allows bacteria to resist low pressure environments.
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If a Streptoccocus culture is prepared and lysozyme is added to the culture and then placed in a isoosmotic media what will result?
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The cells will not lyse or shrivel however they will become spherical. The cell wall is what give the bacteria their unique shapes, cocci, bacilli, etc.... S
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What is the name of the bacteria without a cell wall?
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Spheroplasts
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Is it easier for a lipophillic drug or a hydrophillic drug to cross the murein layer? What property of murein explains this?
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It would be easier for hydrophillic drugs to cross the cell wall because murien is composed of polar and charged molecules like amino acids.
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What unique polymers do Gram+ cell walls have and what are the molecules that compose them?
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Gram+ bacteria have teichoic acid which is composed of glycerol or ribitol linked by phosphodiester bonds
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What component is unique to the outer leaflet of the gram- bacterial membrane?
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LPS
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What is the function of lipid A? What are its characteristic features?
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Lipid A anchors LPS to the outer leaflet of the membrane. It is composed of sugars linked to fatty acids and phospate groups
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What is the middle portion of the LPS molecule called and what are the main two characteristic molecules?
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The central portion is called the core. It has two sugars ketodeoxyctanoic acid and heptose. These are nearly the same in all gram- bacteria
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What part of the LPS molecule repels lipophillic molecules such as drugs and bile?
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The O antigen. It is composed of up to 40 linearly linked sugars.
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In gram+ bacteria what is the characteristic feature that links chains of murein? What about gram-?
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Links occur between the free amino group of lysine and the terminal carboxyl group of D-alanine in gram+ murein. In gram- the cross-link is between diaminopimelic acid and D-alanine.
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Which component of LPS varies or changes resulting in different antigentic specificities?
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The O antigen
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What are the name of the channels that allow molecules to enter the periplasmic space from the extracellular space? If researchers were designing an antibiotic that would use these channels to enter the bacteria how large could it be?
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porins. The drug could be no larger than 700 daltons
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How are large molecules like vit B12, iron chelates, and trisaccarhides taken up?
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Via unique protein permeation mechanisms
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Name some of the components found in the periplasm! Do gram+ bacteria have these molecules if so where are they located?
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proteases, nucleases, phosphatases, binding proteins to soak up amino acids and sugars, B-lactamases. Gram+ bacteria release these molecules into the extracellular space
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Generally speaking are gram- or + bacteria more resistant to antibiotics?
In nature are gram- or gram+ bacteria in higher number? |
gram-, in particular penicillin. The gram- are more abundant in nature
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Which component of LPS elicits fever? What is another name for this component? In large concentrations what happens?
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Lipid A, endotoxin, shock and death
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What is unique about the cell wall of acid-fast bacteria? Do they have murein? Are they slow or fast dividing organisms?
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It is composed of hydrocarbon chains that produce waxes. Murein is interlaced with the hydrocarbons. They slowly divide
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Are carbapenems bacterialcidal? What about penicillins? Cephaloporins?
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They are all bacterialcidal and inhibit murein synthesis
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What molecule is linked to a Nag/Nam subunit to transport it outside the cytosol?
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uridine diphosphate (UDP)
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Disaccharides of NAG/NAM are linked to a chain murien chain. What antibiotic inhibits this step?
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vancomycin
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In order for a NAG/NAM subunit to move from the inner leaflet to the outer leaflet a lipid carrier is needed. What drug inhibits the lipid carriers regeneration?
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bacitracin
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What is the final step of murein synthesis? What drugs block this step?
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Transpeptidation is the last step and B-lactams inhibit it.
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What component of murein do the B-lactams resemble and as a result impede murein synthesis?
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They resemble the D-alanine-D-alanine linkage and therefore bind and inactivate the transpeptidase that forms this linkage
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In what cell condition would all the B-lactams be ineffective?
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They would not work if the bacteria were not actively dividing
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What is the action of fosfomycin?
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It inhibits cell wall synthesis early by acting as an analog of phosphoenolpyrovate (PEP) and thus prevents the enzyme enolpyruvate transferease from adding PEP to UDP-NAG. It is the earliest inhibitor!
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What is the action of cycloserine? Does it inhibit gram- or gram+?
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It is an analog of D-alanine and inhibits D-alanine incorporation which is needed for murein linkage. It inhibits both gram- and +
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How can organism be tolerant to B-lactams?
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If the bacteria are lacking the enzyme autolysin which breaks down peptidogylcan they are not actively synthesizing murein.
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What group of bacteria are innately resistant to B-lactams, vancomycin and other cell wall inhibitors? What do they have in their cell wall?
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Mycoplasmas have sterols which is a unique feature of prokaryotes
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What bacteria has a special protein layer cover called the S layer?
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Bacillus anthracis
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What structures are found in the cytoplasmic membrane of bacteria that allows them to take up metabolites?
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permeases
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In facilitated diffusion what determines how quickly the molecules are taken up?
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Intracellular use.
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Is group translocation energy dependent or independent? What types of molecules does it take up?
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Energy depenedent, up take of certain sugars
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What processes are used in bacterial active transport? How is lactose concentrated in the cell?
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proton motive force and ATP hydrolysis. Lactose is concentrated via symport of H+ and lactose into a relatively alkaline cell
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What are siderophores used for?
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They are chelating agents released by bacteria to trap iron
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Where are the cytochromes located in bacteria for oxidative metabolism?
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plasma membrane
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How good of a target is the cytoplasmic membrane?
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It's not good possibly because of its resemblance to eukaryotic cell membranes
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What is the DNA structure called in bacteria?
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nucleiod
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What is the function of DNA gyrase? Topoisomerase I?
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To introduce supercoils into circular DNA. To unwind supercoils with single stranded nicks
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What is directionality of DNA replication in bacteria?
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Bidirectional from point of origin
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What is the relationship of growth rate to DNA polymerase activity? What variable needs to be fixed for this to occur?
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DNA polymerase movement is nearly independent from growth rate. The temperature needs to be relatively constant and optimal for growth
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Anearobic bacteria have the capacity to partially reduce a certain drug that can bind DNA. This reduction rarely occurs in humans what is the drug and it's mechanism?
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metronidazole is inert until it is reduced to its active form. Full reduction completely inactivates. partially reduced metronidazole is incorporated into the DNA of bacteria
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Besides anaerobic bacteria what other organism will metronidazole work on?
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amebas that grow anaerobically
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Metronidazole action is an example of what?
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lethal synthesis
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What drug inhibits DNA gyrase? Is the drug bacteriostatic or bacteriocidal?
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nalidixic acid is bacteriocidal
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What is the more stable derivative of nalidixic acid? What do they interfere with?
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fluoroquinolones interfere with DNA gyrase or topoisomerase causing double stranded breaks
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What is the chief biosynthetic pathway bacteria in the log phase of bacterial growth?
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protein synthesis
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Is the polymerization of protein and RNA molecules greater during rapid or slow growth? The synthesis of macromolecules regulated mainly by what?
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It is constant in both. Macromolecule synthesis is regulated mainly by the frequency with which each chain is initiated and so much by speed elongation
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Some antibiotics act selectively at initiation or elongation of macromolecular synthesis. Name a drug that acts at the initiation step! What is its mechanism?
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rifampin binds strongly to molecules of RNA polymerase that are free floating in the cytoplasm but binds less strongly to DNA polymerase
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What two bacteria is rifampin particularly effective against?
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tuberculosis and leprosy
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Which drugs act specifically at the tRNA binding site on the large ribosomal subunit?
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chloramphenicol and macrolides
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After treatment with erythromycin the patients infection returned. Mechanistically what is occurring in the bacteria?
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macrolides do not permanently inactivate the 50S ribosome therefore the drug is bacteriostatic. Thus there is a pool of active ribosomes present in the cytosol. Once the drug is discontinued the bacteria resume growth in full force.
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What is the result of aminoglycosides? Are they bacteriostatic or cidal?
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They permanently inactivate the 30S subunit and cause the accumulation of 70S ribosomes which cannot function properly. The 70S complex binds RNA strands and block their translation. They are thus bacterialcidal. Aminoglycosides cannot be removed from the cell also
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List the B-lactams and their mechanism of action!
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Penicillins, cephaloporins, carbapenems, and monobactams. They interfere with cell wall cross-linking through interaction with penicillin-binding transpeptidases. Cause autolysis
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List examples of glycopeptides and mechanism of action!
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Vancomycin, interferes with incorporation of new subunits into growing murein chains
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Fluconazole is an example of what type of drug and what are other examples of drugs in this class? What is the MOA?
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Imidazoles: itraconazole, voriconazole, posaconazole. They block synthesis of ergosterol required for fungal cell wall integrity
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Caspofungin and mycofungin are examples of what type of drug?
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Echinocandins block B-glucan synthesis a fungal cell wall component
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Daptomycin is an example of what type of drug? What is the MOA?
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Lipopeptide antibiotics. They form channels in the cell membranes of gram-positive bacteria resulting in K+ leakage and metabolic death
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Amphotericin B is an example of what type of drug? what is the MOA?
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It is a polyene. It binds to sterols in eukaryotic cell membranes, leading to membrane leakiness and, at high levels, lysis
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Sulfamethaxole and sulfadiazine are examples of what type of drug? what is the MOA?
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They are sulfonamides. They are competitive inhibitors of dihydropteroate synthesis; blocks synthesis of tetrahydrofolate and cell-linked metabolic pathways
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What is the MOA of trimethoprim?
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inhibition of bacterial dihydrofolate reducatase
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Gentamicin is an example of what type of drug? What is the MOA?
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It is an aminoglycoside. Its MOA is to bind to the 30s subunit of bacterial ribosomes; cause translational misreading and inhibit elongation of protein chain; kills by blocking initiation of protein synthesis.
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What are examples of aminoglycosides?
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gentamicin, tobramycin, streptomycin, amikacin, neomycin
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What is the MOA of macrolides? What are examples of macrolides?
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bind to ribosome 50s subunit; inhibit protein synthesis at chain elongation step. Examples include erythromycin, azithromycin, clarithromycin, clindamycin
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What type of drug is telithromycin?
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Ketolides
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What type of drugs are dalfopristin and quinupristin?
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Streptogramins
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What is the MOA of rifampin?
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binds to bacterial RNA polymerase and blocks transcription (synthesis of RNA) at initiation step
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What is the MOA of metronidazole and nitofurans?
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partially reduced nitro groups give addition products on DNA that lead to cidal strand breakage
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What are ciprofloxacin, levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin?
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Fluroquinolones
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What is the MOA of fluroquinolones?
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interfere with DNA replication by inhibiting the action of DNA gyrase or topoisomerase
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What is the MOA of chloramphenicol?
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protein synthesis inhibitor
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Which drug blocks the assembly of the initiation complex?
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linezolid
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What is the MOA of tetracycline?
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inhibits aminoacyl transfer RNA binding
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What does a bacteria have to have inorder to pass along an F plasmid?
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F pillus
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What structures attach bacteria to surfaces such as teeth?
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fimbriae
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If the bacterial flagellum rotates counterclockwise what happens?
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The bacteria move straight toward a stimulus
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If the bacterial flagella spin clockwise what results?
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They are stationary "tumbling" occurs
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In the absence of attractants or repellents what do bacteria do?
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Combination of tumbling and swimming
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What is needed for conjugation to occur?
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a sex pili
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The protein pilin makes up the pili structure. What organism has several pilin genes that give it many antigenic properties?
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Gonococci
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How many constant and variable regions does pilin have? Which is antigenic?
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1 constant region and 1 variable region. The variable region is recognized by the immune system
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Which organism rapidly changes the expression of different flagellar proteins? What is this called?
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Salmonella. Phase variation is the control of a gene for flagellar protein
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How are bacteria classified based on nutritional requirements? Which group do all pathogenic bacteria fall into?
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photosynthetic or chemosynthetic and all other organisms that need preformed nutrients. Organisms requiring preformed nutrients
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Based on oxygen requirements how is the tubercle bacillus classified?
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strict aerobe
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What type of organisms are clostridium an example of in relation to the environment they grow?
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strict anearobes
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What are facultative anearobes?
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Organisms like E. coli can grow in both the absence and presence of oxygen. This group comprises the largest group of medically important bacteria
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What are examples of electron acceptors in the fermentation process?
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pyruvate goes to lactate and acetyl CoA is reduced to alcohol
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Which two organisms can effectively grow on media lacking preformed nutrients?
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E. coli and psuedomonas
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What are nutritionally fastidious organisms? Give examples
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They need nutrient rich environments such as the human body. These include staphylococci and streptococci
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List examples of organisms that have never been cultivated and explain why?
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Chlamydia can only grow intracellularly, treponema pallidum or mycobacterium leprae
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What is generation time?
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the doubling time or the time it takes an organism to divide
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What is the equation for law of growth?
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Nt=No ekt
where k is the growth constant |
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In what stage do bacteria stop growing?
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stationary phase
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If an organism is exposed to UV what occurs?
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The SOS response to try and repair the damage incurred
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how can an organism cause damage in the process of sporulating?
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During sporulation many of the cytoplasmic contents are released and these can be cytotoxic. Occurs in tetanus, gas gangrene
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An organism is taken from minimal media and placed in nutrient dense media. What occurs?
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metabolic parsimony in which the bacteria stop making constituents they can simply obtain from environment
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What is a DNA sequence containing multiple genes strung together called?
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an operon
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A bacterium that suddenly stops synthesizing certain amino acids becuase it is importing them from the environment is using what process?
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attenuation
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Use leucine and describe how attenuation works?
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A small stretch of RNA is synthesized from the beginning of the coding sequence of the leucine operon, regardless of the presence or absence of leucine. The RNA polymerase encounters the attentuator sequence which if leucine is present transcription is terminated. If leucine is absent transcription occurs.
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When lactose is the only nutrient present what enzyme is needs to made?
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beta-galactosidase to convert lactose into glucose and galactose
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What is downstream of the promoter that regulates whether the beta-galactosidase gene is transcribed or not?
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The operator where the repressor protein binds when lactose is present
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Is beta-galactosidase an example of an inducible or constitutive enzyme?
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Inducible. Constitutive enzymes are made all the time like RNA polymerase
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What is lactose called in relation to its activity with a repressor protein?
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an inducer
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