Micro test 2
Which of the following is an example of phase variation?
E. coli producing pili for attachment to epithelial cells.
Which of the following is NOT common to aerobic respiration, anaerobic respiration, AND fermentation?
Electron transport chain
Glutaraldehyde
Environmental Protection Agency (EPA)-registered high-level disinfectant. AND is very good for use on heat-sensitive medical items.
Which of the following is (are) considered when selecting a germicidal chemical?
Environmental impact, toxicity, compatibility with the material being treated, AND cost
In Gram-negative bacteria, the electron transport chain involved in respiration is located in the lipopolysaccharide layer.
FALSE
the change in free energy of reaction varies
FALSE
Double-stranded DNA enters the recipient cell during transformation.
False
The Ames test determines antibiotic sensitivity of a bacterium.
False
A codon consists of two nucleotides.
False; three
Fermentation is sometimes used as a means of slowing food spoilage. Why would fermentation lead to this outcome?
Fermentation will lead to production of acidic by-products, dropping the pH of the food below a level that bacteria can tolerate.
Which may be or is an RNA molecule?
GGGCCCA AND GCCCUUA
Why is it a good idea for a bacterial cell to be able to use glucose FIRST as an energy source (until it is depleted), THEN switch to lactose?
Glucose is an easier compound to break down and obtain energy from than lactose AND for conservation of energy: why use the energy to make the enzymes for breaking down lactose when glucose doesn't need any extra enzymes for breakdown?
Does the presence of introns/exons in eukaryotic cells provide more potential diversity in gene products (proteins) than is possible in prokaryotic cells?
It does. Exons/introns can be spliced together in different ways post-transcription to yield different mRNAs (and therefore, different proteins). Bacteria lack this system.
To maximize the number of thymine dimer mutations following UV exposure, should you keep human cells in tissue culture in the dark, in the light, or does it matter at all?
It doesn't matter—human cells don't have the enzymes needed for photorepair of thymine dimers.
Why is the position of the first AUG after the ribosome binding site critical?
It establishes the reading frame
Select the FALSE statement regarding hydrogen peroxide. It is a sterilant for inanimate objects and is quickly inactivated on living tissue. It leaves no toxic residue and is safe on materials such as glass and plastic. It is broken down by catalase into water and oxygen. It is even more effective when used in combination with peracetic acid. It immediately kills all bacteria when applied to a wound.
It immediately kills all bacteria when applied to a wound. (the rest are true)
Which is true about DNA replication?
It is semiconservative. It starts at an origin of replication. It is bi-directional. It requires RNA primers.
Which is true about prokaryotic (bacterial) RNA polymerase?
It is used during transcription
Anoxygenic photosynthetic bacteria
May obtain electrons from H2S
NAD in its reduced form is abbreviated as
NADH
In the electron transport system
NADH donates electrons "upstream" of where FADH2 donates electrons.
Lister developed his ideas on prevention of infection during medical procedures after studying the work of
Pasteur
If you were carrying out a penicillin enrichment culture and you forgot to add penicillinase before plating the sample onto nutrient agar, what would happen?
Prototrophs and auxotrophs would both be killed by the penicillin; only PenR mutants would grow and you would not enrich for auxotrophs.
Both glycolysis and the pentose phosphate pathway oxidize glucose to pyruvate.
TRUE
The TCA cycle must "turn twice" in order to complete the oxidation of one glucose molecule.
TRUE
Why would a cell ferment rather than respire?
There is no oxygen present and it cannot use anaerobic respiration OR it lacks the ability to
Which is (are) true of coenzymes?
They are organic molecules. They transfer atoms from one molecule to another. They may bind to a number of different enzymes. They are synthesized from vitamins.
Some bacteria have a higher incidence rate of thymine dimer mutations following exposure to UV light than others. What might be going on here to lead to this outcome?
They may simply have a higher proportion of T nucleotides next to each other in their DNA than other bacteria, leading to more possible dimers being formed AND they may have a weaker expression of photoreactivation enzymes, leading to formation of more thymine dimers.
F plasmids and oftentimes R plasmids are both able to code for production of a pilus
True
True/False: Boiling is an effective way to removing most common waterborne pathogens
True
A mutation in E. coli results in the loss of both restriction endonucleases and modification enzymes. Would you expect any difference in the frequency of gene transfer via transduction FROM Salmonella INTO this E. coli strain?
Yes—the loss of the restriction endonucleases would leave the recipient E. coli unable to break down "invading" viral DNA from the transducing phage, AND the loss of the modification enzymes would leave the recipient E. coli unable to tag its own DNA as "self," leaving the viral DNA untagged and recognizable as "foreign," and targeted for destruction. Together, these would lead to higher rates of successful transduction
non-competitive inhibition
a molecule that binds to an enzyme at a location outside the active site (maybe allosteric) and inhibits the enzyme's function.
A regulatory protein binds to the operator in a strand of DNA, blocking transcription. The protein is
a repressor
Intercalating agents
act during DNA synthesis AND often result in frameshift mutations.
Which change in a gene's DNA sequence would have the least effect on the eventual amino acid sequence produced from it?
addition/deletion or 3 consecutive nucleotides
The largest group of chemical mutagens consists of
alkylating agents
Competent cells
are able to take up naked DNA, occur naturally, AND can be created in the laboratory.
Ribozymes
are self-catalytic RNA AND suggest that nucleic acids evolved before proteins.
The sugar component of RNA and DNA nucleotides is synthesized
as ribose and then changed to deoxyribose.
Chemical mutagens that mimic the naturally occurring bases are called
base analogs
Repressors
bind or do not bind to the operator depending on their shape (conformation) AND are involved in negative control.
X-rays
cause single and double strand breaks in DNA molecules.
The small, non-protein molecules that can be readily separated from an enzyme and are responsible for transfer of atoms from one molecule to another are referred to as
coenzymes
Gene transfer that requires cell-to-cell contact is
conjugation
The transfer of vancomycin resistance from Enterococcus faecalis to Staphylococcus aureus is thought to have involved
conjugation and transposons
Ultraviolet radiation at the bactericidal wavelength destroys bacteria by
damaging nucleic acids
Which are essentially equivalent treatments?
dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes
the suffix "-ase" indicates
enzyme
Pyruvate can be metabolized along two major routes. They are
fermentation and respiration
Post-translational modification may include
folding of the protein, often with the aid of chaperones AND removal of the signal sequence.
Bacteria that have properties of both the donor and recipient cells are the result of
genetic recombination
the simultaneous regulation of many bacterial genes is
global control
the most common starting point for the breakdown of glucose is
glycolysis
which of the following produce the most precursor molecules
glycolysis
To increase the chance of detecting carcinogens in the Ames test, the test substance is treated with
ground up rat liver
Allosteric enzymes
have both an active site for substrate binding and an allosteric site for regulation (activator, inhibitor)
Boiling is not reliable for sterilization because
heat resistant endospores are unaffected
Your brother has a bacterial infection. He tells you he going to the gym where he plans to sit in the sauna for an hour. He thinks that this will cure his infection, because the heat in the sauna will denature the enzymes of the bacteria making him ill. You are a nursing student who is currently studying microbiology. You tell him that
his plan won't work; homeostasis will keep his body temperature constant even in the sauna, so the bacteria (and his normal microbiota and body cells) will not be impacted.
The two strands of DNA are bonded to one another by
hydrogen bonds
The most important function of nitrites in processed foods is to
inhibit the germination of clostridium botulism endospores
Planar molecules used as chemical mutagens are called
intercalating agents
Among the easiest of the mutations to isolate are those which
involve haploid chromosomes AND involve antibiotic resistance.
Moist heat kills microorganisms by
irreversible denaturation of proteins
Chlorhexidine
is extensively used in antiseptics
Signal transduction
is the relay of information about conditions outside a cell to inside the cell.
Ethylene oxide is gas that
is very useful for sterilizing heat or moisture sensitive items AND is potentially carcinogenic.
enzymes speed up reactions by
lowering activation energy
The regulatory protein
may inhibit or enhance transcription.
Chemical germicides
may react irreversibly with proteins/enzymes, may react with cytoplasmic membranes or viral envelopes, may be disinfecting or even sterilizing. are sensitive to dilution factor, time of contact, and temperature of use.
An atom that has a lower affinity for electrons than another is ______ than the other.
more electronegativity
The ribosomes
move along the mRNA in a 5'-3' direction AND provide a platform that brings the amino acids into a favorable position for joining
DNA polymerases
move in a 3' to 5' direction on the template DNA.
Exergonic reactions
occur when there is more free energy in the reactants than the products.
The set of genes in bacteria that are linked together and transcribed as a single unit is referred to as a(n)
operon
OILRIG stands for
oxidation is losing, reduction is gaining
The P-site
peptidyl site on the ribosome
Bacteria that can absorb light energy and convert it into ATP are commonly called
phototrophs
Gamma rays cause biological damage in living systems by
producing reactive molecules such as superoxide and hydroxyl-free radicals.
The specific sequence of nucleotides in the DNA to which the RNA polymerase binds is the
promotor region
The 3' end of DNA
refers to the end that has a hydroxyl group attached to the number 3 carbon of deoxyribose
The transcription terminator
results in a hairpin loop structure in RNA AND results in the polymerase falling off the DNA template.
The F plasmid carries the information for
sex pilus
competitive inhibition
substance that resembles the normal substrate competes with the substrate for the active site
energy is defined as
the capacity to do work
Compounds of tin, mercury, arsenic, and copper are no longer used to prevent microbial growth in cooling water primarily because
their use contributes to serious pollution of natural waters.
Mutations are likely to persist after SOS repair, but not after light-induced or excision repair.
true
One end of a strand of DNA is different from the other end.
true
Plasmids often carry the information for antibiotic resistance.
true
The minus strand of DNA serves as the template for RNA production.
true
the genetic code is nearly universal
true ?
A drug that inhibits the activity of bacterial DNA gyrase ______ be a good antibiotic because ______
would; it would selectively inhibit bacterial DNA synthesis due to differences between bacterial/human gyrase
In a one D process, how many D values would it take to reduce a population of 1010 cells to one survivor?
10
INCORRECT statement regarding mutation:
A missense mutation is also called a synonymous mutation, meaning no change in the amino acid encoded.
On which of the following DNA strands would UV radiation have the most effect?
AATTAGTTC
A graduate student is trying to isolate bacterial mRNA for an enzyme that will degrade trinitrotoluene (TNT). She's frustrated to find that the enzyme isn't produced when the bacterium in question is grown on nutrient agar. What might she do to solve the problem and obtain the mRNA?
Add TNT to the agar—this will drive synthesis of the enzyme to degrade it, leading to production of the mRNA the student is looking for.
______ generated the most amount of energy
Aerobic respiration
A worker in a cheese-making facility argued that whey, a nutrient-rich by-product of the process, should be dumped into a nearby pond to serve as fish food. Is this a good idea or a bad one, and why?
Bad idea—bacteria would thrive on this rich nutrient source and multiply, using the oxygen in the water to harvest the energy from the whey. Without the oxygen, the fish will die
Please select the TRUE statement regarding metabolic processes.
Catabolic processes harvest the energy released during breakdown of compounds to synthesize ATP.
Which tasks must a bacterial cell accomplish in order to multiply?
DNA duplication, RNA synthesis, protein synthesis