Micro Exam 2
A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 108 cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 x 107 cells/ml?
3 h
A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria, with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?
320,000
The optimal temperature for most human pathogens might be expected to range from
35-40 celcius
Which enzyme drives ATP synthesis in respiration?
ATP synthase
Please select the TRUE statement regarding metabolic processes.
Catabolic processes harvest the energy released during breakdown of compounds to synthesize ATP.
The scientist that contributed most to the development of pure culture techniques was
Robert Koch.
What structure is indicated by: 10A, 15T, 3G, 7C?
Single-stranded DNA
MacConkey agar is
a selective and differential medium.
Oxygen serves as the terminal electron acceptor in
aerobic respiration
Mercury in mercurochrome inhibits growth
by oxidizing the sulfhydryl groups in cysteine AND by changing the shape of proteins.
Generally, membrane filters are not used to remove
enzymes from liquids.
The general term used to describe the anabolic and catabolic reactions in a cell is
metabolism
Alcohols are not reliably effective at destroying
non-enveloped viruses AND endospores.
Exergonic reactions
occur when there is more free energy in the reactants than the products.Correct
The DNA site to which the repressor protein binds is the
operator
Microbial death rates may be affected by
pH. temperature. the presence of organics. growth in a biofilm.
Bacteria that can absorb light energy and convert it into ATP are commonly called
phototrophs
Glycolysis, the Entner-Duodoroff pathway, and the pentose phosphate pathway all produce
pyruvate
In the growth curve of a bacteria population, the bacteria are rapidly increasing in number in the
exponential (log) phase.
The electron transport chain is a group of membrane-embedded carriers that pass electrons from one to the next, while simultaneously pumping ______ across the membrane, generating a(n) ______.
hydrogen ions; proton motive force
Degradation of fats as an energy source involves all of the following except
transamination
RNA
a chain of nucleotides, each made of a sugar, a phosphate group, and a nitrogen-containing base
promoter
a nucleotide sequence on a DNA molecule to which an RNA polymerase molecule binds to start transcription
codon
a series of three nucleotides that code for a specific amino acid
The critical site of an enzyme to which a substrate binds by weak forces is called the
active site
The light-independent reactions of photosynthesis occur _______ the light-dependent reactions, and function to _______.
after; synthesize organic compounds from CO2
The solidifying agent used most successfully in bacterial nutrient media is
agar
Which of the following chemical classes destroy microorganisms by forming chemical bonds that cross-link and inactivate proteins and nucleic acids?
aldehydes
A sterile item is free of
all viable microbes, endospores, AND viruses
Cells can quickly alter the activity of certain key enzymes, using other molecules that bind reversibly and distort them. This control of enzymes is called ________ regulation.
allosteric
Aldehydes typically kill microbes by ______.
altering nucleic acids altering proteins
The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or ______.
catabolism;anabolism
Enzymes are biological ______ that are typically _______.
catalysts; protein
Quaternary ammonium compounds (quats) are ______. Multiple choice question.
cationic detergents that help wash surfaces
Adding sorbic, propionic, and benzoic acid to foods affects ______ of microbes.
cell membranes
High pressure (130,000 psi) is thought to kill microbes by altering their ______.
cell membranes proteins
Some enzymes act with the assistance of a non-protein component. This component is called a ____, if that component is an organic molecule it can be called a _______
cofactor; coenzyme
sigma factor
component of rna polymerase that recognizes a promoter. A cell can have different types of sigma factors that recognize different promoters, allowing the cell to transcribe specialized sets of genes as needed.
A surgical scalpel is rated as a ______ instrument because it penetrates skin and mucous membranes and therefore must be sterile. Multiple choice question.
critical
Medical instruments are classified into three categories according to their risk for transmitting pathogens. These are:
critical, semicritical, noncritical
Examples of electron carriers are proteins that contain heme, a molecule that holds an iron in its center. These are called
cyotchromes
In prokaryotes, the electron transport chain is located in the ________ membrane, whereas in eukaryotic cells it is in the ______ membrane of mitochondria.
cytoplasmic; inner
Phenolics
denature proteins and destroy cytoplasmic membranes.
Commercial canning processes
destroy Clostridium botulinum spores, are especially needed on low acid foods, AND are 12D processes (designed to kill 1012 endospores).
Low-level disinfectant
destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses. also called general purpose, used for disinfecting furniture and floors in hospital.
intermediate level disinfectants
destroy vegetative bacteria, mycobacteria, fungi, and most viruses Disinfect non-critical instruments
Gregor Mendel
determined that traits are inherited as physical units, now called genes
Upon treatment with heat or chemicals, bacteria will
die at a constant proportion.
Cationic detergents typically work by _____
disrupting the cell membrane
origin of replication
distinct region of a DNA molecule at which replication is initiated
Radio waves, X-rays, microwaves, UV light and gamma rays are all examples of ______.
electromagnetic radiation
In oxidative phosphorylation, quinones, cytochromes, and flavoproteins are all ______ carriers.
electron
In addition to four protein complexes, the mitochondrial electron transport chain has two freely-moving ______, ubiquinone and cytochrome c, that serve to ______.
electron carriers; shuttle electrons between the complexes
The most highly resistant microbial structure is the bacterial
endospore
Hydrogen sulfide is produced as a result of certain types of anaerobic respiration. Some chemolithotrophs can then use this as a/an ______.
energy source
Chemolithoautotrophs
energy source: inorganic chemicals (H2, NH3, NO2-) carbon source: CO2
photoautotroph
energy source: light carbon source: CO2
Photoheterotrophs
energy source: light carbon source: organic compounds
Chemoorganoheterotrophs
energy source: organic compounds (sugars, amino acids, etc) carbon source: organic compounds
Consider how cells obtain energy to make ATP. The chemical that serves as the electron donor is the _______ source, and and the one that ultimately accepts those electrons is the ______ electron acceptor
energy; terminal
The use of the suffix "ase" on a word denotes a(n)
enzyme
dna ligase
enzyme that joins two DNA fragments together by forming a covalent bond between the sugar and phosphate residues of adjacent nucleotides
DNA polymerase
enzyme that synthesizes DNA, using an existing strand as a template to make a new complementary strand. nucleotides can be added only to the 3' end of an existing fragment, therefore, synthesis always occurs in the 5' to 3' direction
rna polymerase
enzyme that synthesizes RNA using one strand of DNA as a template
primase
enzyme that synthesizes small fragments of RNA to serve as primers for DNA synthesis
Proteins that function as biological catalysts are called
enzymes
All of the following accurately describe enzymes EXCEPT ______.
enzymes provide energy to help reactions proceed more rapidly
Cells constantly produce ATP during the ______ reactions of ______, and use it to power _______ reactions of _______
exergenic, catabolism, endergenic, anabolism
detecting cell products
-used to detect growth not routine for quantitation. pH indicator can be used to detect acid production. gases can be trapped in an inverted tube in the broth. more sensitive method uses a fluorescent sensor that detects slight dec in pH that accompanies carbon dioxide production
Which of the following are true statements about what happens to glucose inside a cell?
1. Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism. 2. Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis. 3. Some glucose might be oxidized to CO2, generating the maximum amount of ATP.
3 key central metabolic pathways and beneficial products
1.glycolysis, 2.pentose phosphate pathway, 3.TCA cycle Benefits: ATP, precursor metabolites, reducing power
George Beadle and Edward Tatum
1941, showed precise function of genes; revealed that genes direct the production of enzymes
Proteins are composed of various combinations of usually how many different amino acids?
20
If the theoretical maximum ATP yield in prokaryotes from oxidative phosphorylation is 34 ATP for a single glucose molecule, what is the total ATP gain when substrate-level phosphorylation is included?
38 ATP
Chlorine-releasing compounds such as sodium hypochlorite (bleach is a 5.25% solution) are used for all of the following EXCEPT 1. swimming pool treatments 2. food equipment sanitation 3. household cleaning 4. wound treatment and skin cleansing 5. sewage and waste water disinfection
4. Wound treatment/skin cleansing
Aqueous solutions of alcohol at a concentration of ______ are more effective than 100% alcohol.
60-80%
ribosome (prokaryotic)
70s: 50s and 30s subunits
High-level disinfection
Disinfectants that destroy all viruses and vegetative organisms but not endospores. Used for semi-critical instruments (endoscopes)
chocolate agar
Complex medium used to culture fastidious bacteria, particularly those found in clinical specimens. Not selective or differential.
MacConkey Agar
Complex medium used to isolate Gram-negative rods that typically reside in the intestine. Selective because bile salts and dyes inhibit Gram-positive organisms and Gram-negative cocci. Differential because the pH indicator turns pink-red when the sugar in the medium, lactose, is fermented.
Thayer-Martin agar
Complex medium used to isolate Neisseria species, which are fastidious. Selective because it contains antibiotics that inhibit most organisms except Neisseria species. Not differential.
cell counting instruments
Coulter counters and flow cytometers count total cells in dilute solutions. Flow cytometers can also be used to count organisms to which fluorescent dyes or tags have been attached.
Which of the following correctly describe cytochromes found in an electron transport chain?
Cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center. Several different cytochromes exist.
What happens to an organism if it lacks one or more enzymes in a given biosynthetic pathway?
It must have the end product provided from an external source.
In respiring bacteria, how does ATP synthase generate ATP?
It uses the energy released from allowing protons to flow back into the cell to add a phosphate group to ADP.
Why is it important to completely remove all traces of ethylene oxide from items used to grow bacteria?
Its persistent effect will not allow the microbes to grow.
True or false: The Calvin cycle is a two-step linear pathway that photosynthetic organisms use to fix carbon dioxide
false
True or false: There is a standard antimicrobial procedure available from the Centers for Disease Control and Prevention (CDC) that can be used for all different microorganisms under any condition. True false question.
false
Glucose catabolism encompasses two key processes: (1) oxidizing glucose molecules to generate ATP, reducing power, and precursor metabolites; and (2) transferring the electrons carried by NADH and FADH2 to the terminal electron acceptor. The second process, transfer of electrons, is accomplished as part of which of the following?
fermentation cellular respiration
Agar replaced gelatin as the gelling (solidifying) agent for media because
fewer bacteria can break down agar compared with gelatin.
In the case of plants, algae, and cyanobacteria, the two major products of photosynthesis are ______.
glucose and oxygen
glucose-salts broth (chemically defined medium)
glucose, dipotassium phosphate, monopotassium phosphate, magnesium sulfate, ammonium sulfate, calcium chloride, iron sulfate, water
Starch and cellulose are both polymers made up of the monosaccharide ______, which means that hydrolysis of the polymers releases subunits that can enter directly into the central metabolic pathway of ______ to be oxidized.
glucose; glycolysis
A 2% solution of ______ is used as a liquid chemical sterilant for treating heat-sensitive medical items. Multiple choice question.
glutaraldehyde
Fats, the most common simple lipids, are broken down by lipases into their component ______.
glycerol and fatty acids
Lipid synthesis generally requires the components _______ and ______ acids.
glycerol; fatty
Microorganisms that can grow on polysaccharides and disaccharides first break these down to glucose or precursor metabolites that can then enter into the pathway of ______ to be oxidized.
glycolysis
The primary pathway used by many organisms to convert glucose to pyruvate is
glycolysis
Quorum sensing
involves the production and monitoring of signaling molecules AND is used by bacteria to sense the density of cells within their population
Ozone ______.
is a strong oxidizing agent
Glucose
is preferentially used over lactose in E. coli as a result of catabolite repression AND glucose levels are the inverse of cAMP levels
Ethylene oxide is gaseous agent that ______.
is very useful for sterilizing heat- or moisture-sensitive items
All of the following are characteristics of bleach, a solution of sodium hypochlorite, EXCEPT
it is only effective against a limited range of microorganisms
Microorganisms that are free living are ______ to chemical disinfectants than microorganisms in a biofilm.
less resistant
The prefix photo- indicates that an organism will make use of ______ for energy purposes.
light
Metabolic pathways can be
linear, branched, cyclic
In addition to glucose, which of the following organic compounds can serve as energy sources for microbes?
lipids fatty acids disaccharides monosaccharides proteins polysaccharides
A solution of sodium hypochlorite is more effective against bacteria at _______ pH.
low
In nature, bacteria
may adhere to surfaces by means of pili and slime layers.
Anoxygenic photosynthetic bacteria
may obtain electrons from H2S.
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.
The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a _____ pathway
metabolic
The lag phase of the bacterial growth curve is marked by
metabolically active cells.
The sum total of all chemical reactions in a cell is called
metabolism
The enzymes of the tricarboxylic acid cycle are found in the ______ matrix in eukaryotes and in the _____ in prokaryotes.
mitochondrial; cytoplasm
Household bleach applied at 55C is ________ effective in killing bacteria than if it were applied at 50
more
Chlorhexidine solutions are commonly used for ______.
mouthwashes antisepsis of skin and skin wound care
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.
Which four of the following microbial groups are the most resistant to chemical control methods?
nonenveloped viruses bacterial endospores Mycobacterium species protozoan cysts and oocysts
okazaki fragment
nucleic acid fragment produced during discontinuous synthesis of the lagging strand of DNA
terminator
nucleotide sequence at which RNA synthesis stops; the RNA polymerase falls off the DNA template and releases the newly synthesized RNA
The TCA cycle completes the ______ of glucose.
oxidation
Halogens are highly reactive _______ agents that _______.
oxidizing; cause damage to proteins
Used as an alternative to chlorine for disinfecting water, ______ is a strong but unstable oxidizing agent that must be generated on-site, usually be passing air or O2 between two electrodes.
ozone
The central metabolic pathway that generates reducing power in the form of NADPH is the ____ ______ pathway.
pentose phosphate
Proteins are hydrolyzed by proteases, enzymes that break the _____ bonds between amino acid subunits.
peptide
nutrient broth (complex medium)
peptone, beef extract, water
When selecting an appropriate chemical disinfectant, it is important to realize that the death rate is significantly influenced by
ph temperature
The chemical ortho-_______ provides an alternative to glutaraldehyde because it is less irritating on the eyes. However, it does stain skin proteins gray.
phthalaldehyde
A high-solute environment damages microbial cells by causing ______. Multiple choice question.
plasmolysis
After a deamination reaction removes the amino group from amino acids, the remaining carbon skeletons are converted into the appropriate ______ metabolites for entry into central metabolic pathways.
precursor
Silver sulfadiazine, a combination of silver and a sulfa drug, is used to
prevent infection of second- and third-degree burns.
Gamma rays cause biological damage in living systems by
producing reactive molecules such as superoxide and hydroxyl-free radicals.
Some members of which of the following groups can use inorganic chemicals such as hydrogen sulfide and ammonia for energy?
prokaryotes only
When boiling or pasteurizing a sample, microorganisms are destroyed because their ______.
proteins are irreversibly denatured
Aqueous solutions of ethyl or isopropyl alcohol are commonly used as antiseptics and disinfectants because they ______.
quickly kill vegetative bacteria and fungi are relatively non-toxic do not leave a residue are relatively inexpensive
The term antiparallel
refers to the opposite orientation of the two strands in DNA.
The process of destroying or removing all microbes through physical or chemical processes is ______.
steralization
(+) strand of dna
strand of DNA complementary to the one that serves as the template for RNA synthesis; the nucleotide sequence of the RNA molecule is the same as this strand, except it has uracil rather than thymine
(-) strand of dna
strand of DNA that serves as the template for RNA synthesis; the resulting RNA molecule is complementary to this strand
ribosome
structure that facilitates the joining of amino acids during translation; composed of ribosomal RNA and protein
Enzymes function as biological catalysts, accelerating the conversion of one substance, the ______, into another, the ________
substrate; product
As part of cellular respiration, a membrane-bound enzyme called ATP ________ uses energy from a proton-motive force to add a phosphate group to ADP.
synthase
All of the following are true about DNA sequence analysis EXCEPT
the (−) strand of DNA is used.
genome
the complete set of genes or genetic material present in a cell or virus
dna replication
the duplication of a DNA molecule
Proton motive force is ______.
the form of energy that results from the electrochemical gradient established by the electron transport chain
translation
the process by which the information carried by mRNA is used to synthesize the encoded protein
transcription
the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA)
Gene regulation may entail
turning on genes only when needed.Incorrect turning off genes when not needed. turning on or off entire groups of genes. None of the answer choices is correct.
Choosing the correct antimicrobial procedure depends on many factors including ______.
type and number of microbes composition of item environmental conditions
transfer rna (tRNA)
type of RNA molecule involved in interpreting the genetic code; each tRNA molecule carries a specific amino acid
tRNA
type of RNA molecule present in ribosomes
ribosomal rna (rRNA)
type of RNA that makes up the major part of ribosomes
mRNA
type of rna molecule that contains the genetic information decoded during translation
membrane filtration
used to count microorganisms in liquid samples that contain relatively few cells
viable cell counts
used to determine the number of cells capable of growing in a given set of conditions.
direct cell counts
used to determine total number of cells; counts include living and dead cells
RNAi
uses short pieces of single-stranded RNA to direct the degradation of specific RNA transcripts
Germicidal chemicals ______.
usually react irreversibly with proteins, DNA, cytoplasmic membranes, or viral envelopes are often poorly understood with regards to mechanisms of action
turbidity
very rapid method; used routinely. one time correlation with plate counts is rquired for turbidity to be used in determining cell number.
As the pressure in an autoclave increases, the boiling point of ________ also increases, as does the temperature at which _________ forms.
water, steam
direct microscopic count
Rapid, but at least 10^7 cells/ml must be present to be effectively counted.
Typical conditions used for sterilization are
121°C at 15 psi for 15 minutes.
During which phase of the bacterial growth curve does a bacterial population become much more resistant to harmful conditions?
Late log phase
Which pairing is incorrect?
A:G
To reduce or eliminate disease-/spoilage-causing organisms, food is often subjected to
All of the answer choices are correct.
Please select the TRUE statement regarding preservation of perishable products
Bacterial resistance to some of the chemicals included to perishable products has been reported.
Chemolithotrophs near hydrothermal vents support a variety of life forms. Why is this analogous to photosynthetic microbes supporting life forms closer to the surface of the planet?
Because all life forms need some energy source, electron source, and carbon source. Chemolithotrophs fix inorganic carbon and, if consumed by other microbes, could serve as sources for all three requirements for life. This is very similar to the role that photosynthetic microbes play in the top levels of the oceans/lakes.
Heart muscle is damaged after a heart attack (MI) because blood flow to the heart is stopped. A researcher injected cyanobacteria into the damaged hearts of test animals that has been given MIs. The animals' conditions improved after the procedure, but not significantly. The researcher repeated the experiment, this time illuminating the cyanobacteria with high intensity light after injecting the cells into the damaged hearts. Now the animals did much better, recovering well from their heart attacks. Which of the following explains this outcome?
Cyanobacteria produce oxygen by photosynthesis. Illuminating the cells increases amount of O2 released that is then used by heart cells for aerobic respiration.
Which tasks must a bacterial cell accomplish in order to multiply?
DNA duplication, RNA synthesis, protein synthesis
Which are essentially equivalent treatments?
Dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes
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?
Which of the following produces the most precursor metabolites?
Glycolysis
The amino acid that is placed first during translation in bacteria, mitochondria, and chloroplasts is
N-formyl-methionine.
Lister developed his ideas on prevention of infection during medical procedures after studying the work of
Pasteur.
You are working in a clinical laboratory in a hospital setting. You're handed a throat swab from a patient. You are told specifically that the physician is only interested in the presence and type of Gram positive cells. Identification isn't the main goal here—just a first step to work towards determining what Gram positive cells might be there. What might you do first to go about working towards this goal?
Perform a Gram stain.
A common environmental organism that may even grow in certain chemical disinfectants is
Pseudomonas aeruginosa.
Which would be most effective against Pseudomonas?
Radiation
Which pair is INCORRECT?
Splicing—removal of introns from prokaryote mRNA following transcription.
Hexachlorophene has been particularly effective against
Staphylococcus aureus.
Which type of phosphorylation does not require a membrane?
Substrate-level phosphorylation
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.
If a DNA triplet is AGT, the mRNA codon would be ______ and the tRNA anticodon would be ______.
UCA; AGU
You are in charge of water quality for your city's water treatment plant. Of the methods at your disposal, which will be the most efficient and cheapest method of determining the number of viable bacteria in the water coming out of your plant?
Using membrane filtration followed by placing the membrane in a growth medium for colony counts after incubation.
5'AUG3'
codes for methionine AND determines the reading frame.
A stop codon
codes for no amino acid.
Trace elements
include zinc, copper, and manganese AND may be needed for enzyme function.
The molecules that bind to a repressor and cause it to no longer bind to the operator are called
inducers
Moist heat kills microorganisms by
irreversible denaturation of proteins.
Feedback inhibition
is a way of regulating the amount of product produced.
The P-site
is the peptidyl site on the ribosome.
Pasteurization
is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level.Correct
Proton motive force
is used to synthesize ATP.
The energy yield of any energy-transforming pathway
is variable depending on the amount of precursor metabolites removed for biosynthesis.Correct
Glutaraldehyde
is very good for use on heat-sensitive medical items.
Hand washing with plain soap is very effective in controlling spread of microorganisms because
it is very effective at the mechanical removal of microorganisms.
An atom that has a lower affinity for electrons than another is ______ than the other.
less electronegative
The electron transport system
requires a membrane AND generates a concentration gradient of protons.
Generally the proteins of thermophiles
resist denaturation.
The transcription terminator
results in a hairpin loop structure in RNA, AND results in the polymerase falling off the DNA template.
A medium that inhibits the growth of organisms other than the one being sought is called a(n)
selective medium.
Most enzymes function best at
slightly above pH 7 and low salt concentrations.
A common application of dry heat in the microbiology laboratory is to
sterilize the inoculating loop.
Organisms may derive energy from
sunlight AND metabolizing chemical compounds.
The enzymes that deal with toxic oxygen-containing molecules is/are
superoxide dismutase AND catalase.
Which molecule carries an anticodon?
tRNA
Microwaves do not kill organisms directly but kill by
the heat they generate in a product.
DNA
A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell's proteins.
Which of the following are reasons an organism might use fermentation?
A suitable inorganic terminal electron acceptor is not available. They lack an electron transport chain.
All of the following are essential for an electron transport chain to function EXCEPT ______.
ATP
The main energy currency of cells is the molecule called
ATP
blood agar
Complex medium used routinely in clinical labs. Differential because colonies of hemolytic organisms are surrounded by a zone of red blood cell clearing. Not selective.
measuring biomass
Biomass can be correlated to cell number
Which of the following use moist heat to destroy microbes?
Boiling Pasteurization Pressurized steam
With respect to their synthesis, how are amino acids typically grouped?
By structurally related families that share common biosynthesis pathways
Considering the general equation that describes photosynthesis, the rate of the process would be most influenced by the availability of _______ in the atmosphere.
CO2
glucose salts agar
Chemically defined medium. Used in laboratory experiments to study nutritional requirements of bacteria. Not selective or differential.
start codon
Codon at which translation is initiated; it is typically the first AUG after a ribosome-binding site.
stop codon
Codon that terminates translation, signaling the end of the protein; there are three stop codons.
nutrient agar
Complex medium used for routine laboratory work. Supports the growth of a variety of nonfastidious bacteria. Not selective or differential.
Which of the following is an example of phase variation?
E. coli producing pili for attachment to epithelial cells.
activation energy
Energy needed to get a reaction started
dna gyrase
Enzyme that temporarily breaks the strands of DNA, relieving the tension caused by unwinding the two strands of the DNA helix
helicases
Enzymes that unwind the DNA helix at the replication fork.
most probable number
Estimates the likely concentration; it does not provide a precise count.
______ oxide is an extremely useful gaseous sterilizing agent that destroys all microbes and is often used to sterilize fabric, equipment, and implantable devices.
Ethylene
The TCA cycle produces
FADH2, NADH, and precursor metabolites.
In order to form lipids, how are fatty acids and glycerol synthesized?
Fatty acid chains are assembled from 2-carbon acetyl groups from the transition step; the precursor to glycerol comes from glycolysis.
reading frame
Grouping of a stretch of nucleotides into sequential triplets that code for amino acids; an mRNA molecule has three potential reading frames, but only one is typically used in translation.
Autotrophs use carbon dioxide (CO2) to synthesize organic compounds. Which of the following descriptions of this process are true?
In photosynthetic organisms, the process is called the light-independent reactions. It is called carbon fixation. It often involves the Calvin cycle.
Which of the following are physical ways to remove or destroy microbes?
Incineration Ultraviolet radiation Autoclaving Filtration
What are the effects of increasing the pressure of water in an autoclave?
Increases the temperature at which steam forms Increases the boiling point of water
______ provides an alternative to heat for sterilization and disinfection, but the process damages some types of plastics.
Irradiation
What is the effect of poisons such as mercury in antimicrobial products? Recall that mercury oxidizes the S-H groups of the amino acid cysteine in proteins, converting it to cystine.
Irreversible non-competitive inhibition—the mercury binds to an allosteric site on the enzyme and permanently changes the shape of the active site, so that the enzyme becomes nonfunctional.
Which is not true of RNA?
It contains both uracil and thymine.
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.
Why is the position of the first AUG after the ribosome binding site critical?
It establishes the reading frame.
Clostridium paradoxum grows optimally at 55°C, pH 9.3; it will not grow in the presence of O2. Please select the TRUE statement about this organism.
It is an obligate anaerobe.
Which is FALSE about the RNA transcript?
It is made in short fragments that are then stitched together.
Which is true about prokaryotic (bacterial) RNA polymerase?
It is used during transcription.
Which is true of iodine?
It is usually found as tinctures or iodophors.
What would true about an organism called Bacillus fastidiosus?
It might be expected to be very strict in its growth requirements.
Phenolic compounds are effective against ______.
Most vegetative bacterial cells
The electron transport chain is a cluster of membrane-embedded electron carriers that accept electrons from the coenzymes _______ and _________ and then pass these electrons along the chain.
NADH and FADH2
Which of the following combinations of molecules is produced during the light-dependent reactions of photosynthesis and used in the light-independent reactions?
NADPH and ATP
When E. coli is placed in a medium containing both glucose and lactose, why does cell growth stop temporarily when the glucose is used up?
Once glucose is depleted, the cell must use the lactose; before it can do this, it must express the lac operon and synthesize the enzymes needed to use lactose, which takes time.Correct
ribosome binding site
Sequence of nucleotides in mRNA to which a ribosome binds; the first time the codon for methionine (AUG) appears after that site, translation generally begins.
total weight
Tedious and time-consuming; however, it is one of the best methods for measuring growth of filamentous microorganisms
How would cellulose-degrading bacteria in the rumen (stomachs) of a cow benefit the animal?
The bacteria would produce, secrete, and incorporate organic molecules as they obtain energy from the cellulose in grass and replicate. The cow could then digest both the secreted organic molecules AND the bacteria that synthesized them.
Consider the following linear metabolic pathway of a bacterial cell: Starting compound → Intermediate-a → Intermediate-b → End Product. The first two reactions are catalyzed by enzymes A and B, respectively. If a mutant cell arose that was unable to produce enzyme B, what would be the impact on the other components of the pathway?
The cell could still produce intermediate-a but would be unable to produce intermediate-b or the end product.
replisome
The complex of enzymes and other proteins that synthesize DNA
What is the active site of an enzyme?
The critical site to which a substrate binds by weak forces.
Oxidative phosphorylation, the mechanism by which cellular respiration uses the NADH and FADH2 generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP, involves what two steps?
The electron transport chain generates a proton motive force. ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP.
Which of the statements about catabolism and anabolism is TRUE?
The energy gathered during catabolism is used during anabolism.
Which of the following is an example of activation energy?
The energy of a small flame used to light the natural gas of a Bunsen burner.
In order for cells to obtain energy, they remove electrons from an energy source and ultimately donate them to the terminal electron acceptor. What does this tell us about the electron affinity of the energy source and the terminal electron acceptor? Multiple choice question.
The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons.
What is one disadvantage of using heat treatment to sterilize plastic items?
The items may melt.
Fats are hydrolyzed by lipases. The glycerol component is then converted to a precursor metabolite, and the fatty acids are degraded using a series of reactions called β-oxidation that remove successive 2-carbon units. Where do these components enter the central metabolic pathways for further oxidation?
The precursor metabolites from glycerol enter glycolysis; the 2-carbon units from fatty acids are added to coenzyme A and enter the TCA cycle.
anticodon
The sequence of three nucleotides in a tRNA molecule that is complementary to a particular codon in mRNA. the anticodon allows the tRNA to recognize and bind to the appropriate codon
Which is (are) true regarding organic acids?
They are weak acids. They are often involved in metabolic reactions. They often exist in the ionized form at the near-neutral pH found in a cell.Incorrect Pyruvate and pyruvic acid refer to different forms of the same substance.
Microorganisms can grow on a variety of organic compounds other than glucose, including polysaccharides, proteins, and lipids. How do they accomplish this?
They break these macromolecules down into appropriate precursor metabolites that are then introduced into central metabolism or used in biosynthesis.
In photosynthesis, what do the light reactions, or light-dependent reactions, accomplish?
They capture radiant energy and convert it to chemical energy in the form of ATP.
Which of the following are advantages of using alcohol solutions for disinfection?
They do not leave a residue.
plate count
Time-consuming but technically simple method that does not require sophisticated equipment. Generally used only if the sample has at least 10^2 cells/ml
For each six-carbon molecule of glucose that enters glycolysis, how many molecules of pyruvate are made, and how many carbon atoms does each pyruvate have?
Two molecules of pyruvate, each with three carbon atoms.
messenger rna (mRNA)
Type of RNA molecule translated during protein synthesis
The term "precursor metabolite" refers to molecules that
are used in biosynthesis.
High concentrations of salt and sugar in foods
are useful in preserving the food AND tend to draw water out of a cell.
It is often difficult to choose which germicide to use because often the most effective options ______.
aren't safe
Nucleotide subunits of DNA and RNA are composed of three units: a 5-carbon sugar, a phosphate group, and a nucleobase. They are initially synthesized ______. Multiple choice question.
as ribonucleotides that can be converted to deoxyribonucleotides by replacing the 2' hydroxyl group with a hydrogen atom
The sugar component of RNA and DNA nucleotides is synthesized
as ribose and then changed to deoxyribose.
In the cultivation of microaerophilic and anaerobic bacteria,
atmospheric oxygen in a(n) candle/anaerobe jar is converted to water.
The process by which chemolithoautotrophs and photoautotrophs incorporate CO2 into organic compounds is called
carbon fixation
Silver is used as an antimicrobial in which of the following products?
bandage pads burn creams
Bacteria on fish caught in the Arctic Ocean would
be psychrophiles AND would continue to grow while the fish is in the refrigerator.
Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to ______.
biosynthesis
How do aqueous solutions of alcohol usually affect microbes?
by damaging lipid membranes by denaturing proteins
The three main types of electron carriers in a typical electron transport chain are
flavoproteins, quinones, cytochromes
Formalin is 37% aqueous solution of ________ that is used as a potent chemical fixative and microbicide.
formaldehyde
_______ is used to kill bacteria and inactivate viruses in vaccines. It can also preserve biological specimens.
formaldehyde
The electron transport chain of mitochondria has ______ different protein complexes.
four
primer
fragment of nucleic acid to which DNA polymerase can add nucleotides
gene
functional unit that controls inherited trait expression that is passed on from one generation to another generation
The simultaneous regulation of many bacterial genes is
global control.
Small organic molecules that must be provided to bacteria in order for them to grow are called
growth factors.
Chlorine and iodine are common disinfectants that belong to a class of chemicals called
halogens
Atoms that are more electronegative than others ______.
have a higher affinity for electrons
Although generally less reliable than heat, germicidal chemicals are especially useful for treating ______. Multiple select question.
heat-sensitive items large surfaces
what is used to decrease the number of microbes in food while maintaining the color and flavor.
high pressure processing (HPP)
In terms of their metabolism, prokaryotes are _______ with respect to compounds they use for energy and _______ in their biosynthetic processes.
highly diverse; remarkably similar
Salting and drying decrease the availability of water in food, resulting in an environment that is ______ relative to microbes, thereby preventing their growth.
hypertonic
Purines and pyrimidines are synthesized ______.
in distinctively different manners
The Calvin cycle ______.
incorporates CO2 into organic compounds
Certain intermediates of catabolic pathways, called precursor metabolites, are important because _____
they serve as carbon skeletons from which subunits of macromolecules can be made
Alcohol-based solutions of certain antimicrobial chemicals like iodine are called
tincture
True or false: With respect to the location of the electron transport chain, the inner membrane of mitochondria is analogous to the cytoplasmic membrane of bacterial cells.
true
