MCB Exam 3 HW Questions
How many polypeptide chains and antigen-binding sites does the basic structure of an antibody molecule contain? a) 2 and 1, respectively b) 4 and 2, respectively c) 2 and 2 d) 4 and 4
B
In which of the following processes of the nitrogen cycle does ammonium ion serve as an electron donor and nitrite serve as an electron acceptor?Choose one: A. denitrification B. anammox reaction C. nitrification D. nitrogen fixation
B
Interferons are cytokines produced by host cells in response to intracellular infection. There are two types of interferons, type I and type II. Which of the following is a difference between these two types?Choose one: A. Type I is part of innate, nonspecific immunity, while type II is part of adaptive, specific immunity. B. Type I interferes with viral replication, while type II activates white blood cells. C. Type I includes interferon-alpha and interferon-beta, while type II includes interferon-omega. D. Type I binds to extracellular pathogens, while type II binds to intracellular pathogens.
B
The bacterium Listeria monocytogenes enters a new host by: Choose one: A. inhalation of droplets. B. ingestion of contaminated food. C. puncture wounds. D. tick bites .E. sexual contact.
B
Because the reduction potential of the CO2/glucose redox pair is more negative than the Fe3+/Fe2+ redox pair, energy is released as electrons flow Choose one: A. from glucose (the donor) to Fe3+ (the acceptor). B. from glucose (the donor) to Fe2+ (the acceptor). C. from Fe2+ (the donor) to CO2 (the acceptor). D. from CO2 (the donor) to Fe3+ (the acceptor). E. from Fe2+ (the donor) to glucose (the acceptor).
A
On a phylogenetic tree, an organism that has undergone genetic reduction would be positioned where? Choose one: A. at the end of a long branch B. in an outgroup C. at the end of short or "broken" branch D. at the root
A
The ATP synthase can be thought of as a type of molecule motor that is powered by the flow of ____________ through the subunits and __________ their concentration gradient. Choose one: A. H+ / down B. e- / down C. e- / up D. H+ / up
A
The enormous productivity and species diversity of wetlands is due primarily to the presence of soils that: Choose one: A. are only flooded at certain times of the year. B. contain virtually unlimited amounts of oxidized minerals for anaerobic respiration. C. remain well oxygenated even when flooded. D. are never aerobic because of the high biological oxygen demand (BOD) of resident microbiota. E. become dry on sunny days but remain water saturated on cloudy ones.
A
Microbes carry out many unique forms of metabolism that are essential for uptake and recycling of nutrients in ecosystems. In fact, of the processes listed here, the only one also performed by animals is: Choose one: A. anaerobic respiration. B. anoxygenic photosynthesis. C. lignin degradation. D. nitrogen fixation. E. protein degradation.
E
The cell type associated with the cell-mediated immune response A) B-cells B) Macrophage C) B-memory cells D) Plasma cells E) T-cells
E
Which of the following conditions would most strongly favor adaptive evolution in bacteria? Choose one: A. nonobligatory commensal relationships B. growth in a nutrient-rich broth C. growth at moderate temperatures and pH D. absence of predators or viruses E. continuous exposure to antibiotics
E
List from least oxidized to most oxidized: NH3 NO3- NO2- N2
NH3 N2 NO2- NO3-
Paralogs can evolve from random ___ of genes during DNA replication.
duplication
The pyruvate dehydrogenase complex plays an important role in cellular metabolism by connecting __ to __. .
glycolysis; the TCA cycle
Certain archaea can also generate a small amount of energy by using the hydrogen released by E. coli to produce ___
methane
A position in a phylogenetic tree where two clades diverge is referred to as a ____ .
node
Carl Woese used ____ RNA gene sequences as a "molecular clock" to develop his three domains of classification.
ribosomal
The mitochondria in eukaryotic cells is most closely related to modern day .
rickettsias
What are characteristics of respiration, fermentation, and both?
- Respiration: high ATP yield (mostly from oxidative phosphorylation), most carbon released as CO2, electrons reduce an external electron acceptor (like oxygen) - Fermentation: low ATP yield (primarily from glycolysis), electrons from catabolism end up back on partially oxidized substrate, most carbon remains in organic form - Both: important for catabolism of sugars, NADH is the major electron carrier, pyruvate is the major intermediate
Sugars are used by many chemoheterotrophs as an important source of carbon and energy. Indeed, complete oxidation of glucose using oxygen as a terminal electron acceptor has a free energy change of -2,883.0 kJ/mol. What strategy do cells use to minimize the amount of that energy that is lost as heat during the catabolism of sugars? Choose one: A. The oxidation reaction occurs within insulated organelles. B. Energy is harvested using a series of smaller oxidations. C. The cells employ high-capacity energy carriers (e.g., ΔG°' of hydrolysis ~ -1000 kJ/mol). D. Oxidations of sugars directly power membrane-bound ATP synthases. E. Oxidation is directly coupled to biomass synthesis.
B
The classical pathway for complement activation is initiated by A) Factors released from phagocytes. B) Antigen-antibody reactions. C) C5-C9. D) Factors released from damaged
B
The first living organisms on earth likely were most similar to which of the following groups of present-day organisms? a.Cyanobacteria b.Archaea c.Algae d.Protozoa
B
A Streptococcus pneumoniae mutant does not produce a capsule. What will be the most likely result of this mutation if the bacteria infect a host?Choose one: A. Without the capsule, the bacteria no longer produce MAMPs and so will escape detection by the host's immune system. B. The loss of the capsule will protect the bacteria from the oxidative burst in the phagolysosome and allow them to survive within phagocytes. C. Without the capsule, opsonization of the mutant will not be required for host macrophages to ingest the microbe, making it less pathogenic. D. Without the capsule, the bacteria are more likely to cause septicemia (an infection of the blood) because they will enter the blood by extravasation more easily than encapsulated bacteria.
C
A mutant strain of Listeria that failed to polymerize actin would be less able to: Choose one: A. direct host cell motility. B. survive in the cytoplasm. C. invade neighboring cells. D. detoxify digestive enzymes. E. multiply in the cytoplasm.
C
All of the following statements about antibodies are true EXCEPT a) IgA is secreted as a dimer. b) IgEis involved in inflammation. c) IgGis the largest antibody. d) IgDis found on the surface of B cells. e) IgMis the first antibody detected in an immune response.
C
An organism's phylogeny describes what? Choose one: A. acquisition of genes by horizontal gene transfer B. codon usage compared to other organisms C. genetic relatedness to other species D. chemical composition (percentage of C, N, P, etc.) E. genomic G+C content
C
Certain endophytic Frankia associate with alder trees to form nodules (such as this one shown here) that: (bundle of cells on the root of the plant) Choose one: A. slowly starve the plant. B. store water for the plant. C. provide fixed nitrogen for the plant .D. secrete antibiotics to kill potential plant pathogens .E. fix carbon for the plant.
C
Which of the following statements best describes how an organism's fitness is influenced by its environment? Choose one: A. Any mutation that results in a faster generation time will increase fitness across environments. B. Organisms in dilute, nutrient-poor environments are more fit if they have large genomes. C. A given mutation may be beneficial in some environments but a disadvantage in others. D. Mutations negatively affect fitness in a given environment, but acquisition of genes enhances it. E. In order to become fixed in a population, mutations must enhance fitness in all environments.
C
Astrobiologists believe that microbes likely make up the majority of biospheres that may exist in the universe. The reasoning for this is that microbes inhabit a wider range of conditions than do multicellular organisms. For example, on Earth, microbes are known to live in all of the following conditions except which one? Choose one: A. in the absence of carbon B. in the absence of oxygen C. in the absence of light D. in below-freezing temperatures
A
Imagine that you are an early microbiologist attempting to reproduce Louis Pasteur's famous experiments which helped disprove spontaneous generation. You first prepare a hay infusion (a type of nutrient broth), then boil it for 20 minutes in a swan-necked flask of the same design that Pasteur used. Upon cooling and incubation at room temperature, you notice that your broth has become cloudy (turbid) only a few days later. What did your broth contain that Pasteur's likely did not? Choose one: A. endospores B. akinetes C. myxospores D. sufficient oxygen E. sufficient nutrients F. hyperthermophilic archaea
A
Nitrosomas spp. are betaproteobacteria which mediate which important step in the nitrogen cycle? Choose one: A. ammonia oxidation B. ammonification C. nitrite oxidation D. denitrification E. nitrate reduction
A
The three tubes in the photograph contain a fermentable carbohydrate (e.g., glucose) and the pH indicator phenol red. The middle and left tubes were inoculated with bacteria, and the right tube was left uninoculated as a control. Which of the tubes shows evidence of fermentation? A. left tube B. middle tube C. both D. none E. impossible to tell without further analysis
A
Why do the pathogens Rickettsia rickettsii and Listeria monocytogenes resemble each other? Choose one or more: A. their ability to live intracellularly B. their mode of entry into new host organisms C. their Gram reaction D. their ability to move directly between host cells E. their ability to live independently of a host F. their ability to polymerize host actin
A,D & F
All of the following are part of the mechanism of action of alpha and beta interferons EXCEPT A) They bind to the surface of uninfected cells. B) They bind to viruses to kill them. C) They initiate manufacture of antiviral proteins. D) They interfere with various stages of viral multiplication. E) They initiate cellular transcription of antiviral genes.
B
Animals and most microorganisms are classified as chemoorganoheterotrophs. The prefixes "chemo," "organo," and "hetero" refer to how the organism meets its needs, respectively, for: Choose one: A. carbon, energy, and electrons B. energy, electrons, and carbon C. electrons, carbon, and energy D. carbon, electrons, and energy E. electrons, energy, and carbon
B
Both the carbon and nitrogen cycles are vital for life on Earth. Which of the following is not a similarity between these two elemental cycles?Choose one: A. Both affect the biochemical oxygen demand in bodies of water B. Fixation of both elements is only conducted by prokaryotes. C. Both produce greenhouse gases. D. The atmosphere is the main organismal source for both elements.
B
Organs have varied mechanisms for limiting the amount and types of colonizing microbiota. In the choices below, organs are matched with one of their microbiota-limiting mechanisms. Which organ and mechanism are mismatched? Choose one: A. lungs - action of the mucociliary escalator B. bladder - presence of bile salts C. intestine - secretion of lectins that separate the microbiome from the host mucosal cells D. skin - presence of dry, high-salt environments E. eye - constant washing action with antimicrobial factors such as lysozyme
B
The chloroplasts found in every plant cell on Earth are descended from a species of endosymbiotic ____ .
cyanobacteria
The explosive gas, H2, may be produced by commensal E. coli metabolizing sugars via ___ fermentation.
mixed-acid
Members of the phylum Actinobacteria have had a profound impact on human health over the course of civilization. One member of the genus ____ causes a deadly disease which has likely claimed over 1 billion victims, while another of the genus _____ yielded the first effective drug to combat this ancient scourge.
mycobacterium streptomyces
The production of _____ by cyanobacteria is believed to have resulted in one of Earth's earliest mass extinctions.
oxygen
Which of the following is the correct order in the taxonomic hierarchy? a. Kingdom—phylum—class—order—family—genus—species b. Kingdom—class—order—family—phylum—genus —species c. Species—genus—family—order—class—phylum —kingdom d. Phylum—kingdom—class—order—genus—family—species
A
Which of the following statements about macrophages is false? Choose one: A. Macrophages differentiate only from monocytes. B. Macrophages present microbial peptide antigens on major histocompatibility complexes. C. Macrophages are involved only in innate immunity. D. Macrophages are phagocytic.
A
Which of the following statements is true? A) Interferon is a secreted protein that is induced by a viral infection. B) Interferon directly kills invading viruses. C) Interferon interacts with viruses thus blocks viral entry into cells. D) Interferon causes cell lysis.
A
Why is it so difficult to arrive at a simple species definition for prokaryotes? Choose one: A. They engage in extensive horizontal gene transfer. B. They don't have nuclei. C. Their chromosomes are usually circular. D. Their genes are frequently arranged as operons. E. Their generation times are much faster than eukaryotes.
A
Stromatolites are the ancient fossilized remains of layered communities of what? Choose one: A. photoautotrophic bacteria B. corals C. marine mosses D. haloarchaea E. kelp
A or Cyanobacteria
Which of the following nitrogen cycle processes returns N2 to the atmosphere? Choose one or more :A. denitrification B. nitrification C. anammox reaction D. nitrogen fixation
A&C
Which of the following processes of the nitrogen cycle is an aerobic process? Choose one: A. denitrification B. anammox reaction C. nitrification D. nitrogen fixation
C
Which of the following traits of bacterial cells differ significantly from the other domains of life?Choose one or more: A. peptidoglycan in cell envelope B. type of RNA polymerase C. phospholipids in membrane D. DNA as genetic material E. translation elongation factors F. nature of genetic code
A,B, &E
Which of the following are considered requirements for the emergence of life? Choose one or more: A. liquid water B. molecular oxygen (O2) C. essential elements for organic molecules D. DNA E. continual source of energy
A,C,E
Which of the following symbionts may be found in lichens? Choose one or more: A. fungus B. cyanobacterium C. moss D. chemoautotroph E. alga F. zooxanthella
A,E, & B
The first step in PCB degradation requires an unusual dechlorination reaction. Imagine that you are conducting a long-term study of a PCB-affected site and detect organisms capable of PCB dechlorination. This is intriguing because none had been detected at the same site 20 years earlier. What is the best explanation for your finding? Choose one: A. PCB dechlorinators from nearby areas detected the PCBs and migrated to the site using chemotaxis. B. PCB dechlorinators were always present in very small (i.e., nondetectable) numbers but became selectively enriched over time. C. Bacteria at the site detected a novel substrate and evolved the necessary pathways to use it. D. The PCBs induced elevated rates of mutation in resident microbes that resulted in the evolution of PCB-degrading abilities.
B
The phylogenetic classification of the Domain Bacteria is based________. a. cell morphology b.rRNAsequences c. Gram stain reaction d.habitat
B
Ultimately, respiration and fermentation are simply different ways to conclude sugar catabolism. Following the energy-yielding reactions, respiring cells pass electrons to oxygen (or other external inorganic oxidant), while fermenting cells dump electrons back onto a partially oxidized organic molecule (such as pyruvate), which then exits the cell as a waste product. Either way, the goal is to do which of the following? Choose one: A. fully oxidize NADH into CO2 and H2O B. recycle NADH back to NAD+ C. generate as much NADH as possible (then synthesize more NAD+ if necessary) D. break down NADH into biosynthetic precursors E. stimulate de novo production of NAD+
B
What is the minimum number of NADH molecules that must be oxidized for oxygen to be reduced to water? Choose one: A. 1 B. 2 C. 3 D. None; the electrons to reduce water are picked up free from the cytoplasm.
B
Which of the following represents an important limitation of small-subunit (SSU) rRNA analysis from a metagenome? Choose one: A. The method requires sophisticated culturing techniques. B. The "universal" primers for amplification of target genes may actually miss many uncharacterized taxa. C. Methods do not yet exist for obtaining data on the archaeal fraction of communities. D. The method cannot be used on mixed-species communities. E. Small-subunit rRNA analysis cannot identify microbes below the level of phylum.
B
Which of the following statements about the acquisition of the human microbiome is true? Choose one: A. The human microbiome begins to develop before birth .B. The microbiome of babies less than 3 years old is less diverse than that in adults. C. The first bacteria to colonize the intestines are strict anaerobes. D. The genitourinary microbiome is first acquired in adulthood.
B
Ethanolic fermentation results in which of the following end product(s)? Choose one or more: A. acetone B. carbon dioxide C. water D. lactic acid E. oxygen F. alcohol
B&F
Mollicutes such as Mycoplasma are distinguished from related Firmicutes by their inability to :Choose one or more: A. live extracellularly. B. make amino acids. C. synthesize phospholipids. D. retain the Gram-stain (i.e., they stain Gram-negative). E. make ribosomes. F. be independently motile.
B,C&D
A bacterial phylum is generally defined based on: Choose one: A. morphology and shared habitats. B. shared habitats and common ancestor. C. ancestry and key traits. D. key traits regardless of ancestry. E. genetic relatedness only.
C
Consider the following sequence of events where the blue lines represent a nucleic acid and the brown shapes are proteins The nucleic acid is not necessarily eliminated at the end, but may be enclosed by protein components. Which of the following might have evolved by the process shown here? Choose one: A. viruses B. membranes C. ribosomes D. tRNA E. DNA
C
Fungi compose a very minor component of life in marine ecosystems yet are vital to the health of terrestrial ones. This is primarily due to their ability to: Choose one: A. contribute to primary production. B. oxygenate the soils. C. break down lignin .D. form nitrogen-fixing nodules on legumes. E. oxidize reduced inorganic substrates.
C
Molecular clocks use genes that: a. code for TCA cycle enzymes b. are found primarily on plasmid DNA c. are involved in transcription and translation d. are acquired though transduction e. encode enzymes for glycolysis
C
Once inside the host, how does Listeria evade phagocyte-mediated killing? Choose one: A. It prevents fusion of a phagosome with a lysosome. B. It produces toxins that lyse host cells. C. It uses a toxin to escape the phagosome .D. It has evolved resistance to host digestive enzymes. E. It produces a capsule which makes the cells difficult to phagocytose.
C
The binomial system of nomenclature assigns each organism a scientific name consisting of a.speciesand strain. b.kingdomand species. c.genusand species. kingdomand genus.
C
The class of immunoglobulin transferred from mother to infant during breast-feeding is A. IgA. B. IgD. C. IgG. D. IgM.
C
Which of the following cells produce perforinsand granzymes? a) Memory B cells b) Plasma B cells c) Cytotoxic T cells d) Helper T cells e) Antigen-presenting cells
C
Which of the following is not a function of the Fc portion of the immunoglobulin molecule? A. Binding to host cells including some cells of the immune system and some phagocytic cells. B. Binding to a component of the complement system. C. Binding to the antigen. D. All of the choices.
C
§In immunology, the term "clonal selection" best refers to a) Multiple types of cells needed to generate an antigenic-specific response. b) Ability of one B cell to produce multiple isotypes of antibodies. c) Ability of specific lymphocyte subsets to proliferate upon exposure to a specific epitope. d) Ability of memory cells to induce a quick secondary antibody response. e) Process of opsonizing antigen for rapid phagocytic degradation.
C
Which of the following represent prokaryotic primary producers? Choose one or more: A. protists B. moss C. cyanobacteria D. seaweed E. fungi F. viruses G. lithoautotrophs
C&G
Which of the following produce large amounts of methane (a potent greenhouse gas) as part of their normal digestion? Choose one or more: A. mosquitoes B. cats C. termites D. sheep E. cattle F. humans
C,D & E
Eukaryotic organelle structures that are thought to have arisen from endosymbioticrelationships include: a. rough and smooth endoplasmic reticulum b. vacuoles and Golgi apparatuses c. nuclei and lysosomes d. mitochondria and chloroplasts e. carboxysomesand chloroplasts
D
In which of the following body sites would the mere presence of microbes indicate an infection?Choose one: A. lungs B. stomach C. skin D. blood E. bladder
D
Many microorganisms, especially those in the Firmicutes phylum, are of great practical importance for industrial, commercial, and/or medical applications. As an example, which of the species listed here may help limit the spread and impact of the emerging Zika virus? Choose one: A. Geobacillus stearothermophilus B. Streptomyces spp. C. Clostridium botulinum D. Bacillus thuringiensis E. Dehalobacter restrictus
D
The Gibbs free energy change of a reaction can be calculated using the equation ΔG = ΔH - TΔS. A biochemical reaction that can provide energy for cellular metabolism would be one in which: Choose one: A. all terms on the right are positive. B. ΔG was positive. C. all terms on the right are negative. D. ΔG was negative.
D
The nitrogen and sulfur cycles are analogous in many ways. Which of the following is a characteristic that both cycles share? Choose one: A. The atmosphere is the main source in both cycles. B. Both cycles provide nutrients that are limiting in most ecosystems. C. In both cycles, only the most reduced cycled inorganic compound is assimilated into biomass. D. Most of the redox reactions of the cycles are performed only by prokaryotes.
D
The purposes of Taxonomy include _______. a.Classification b.Identification c.Nomenclature d.noneof these e.allof these
D
The video explains how O2 becomes reduced to H2O during aerobic respiration. In the example of the bacterial ETS that was given, how many protons were actually lost from the cytoplasm for every O2 molecule that was consumed? Choose one: A. 4 B. 8 C. 28 D. 20 E. 16
D
Which of the following is a common virulence factor produced by Proteobacteria but is entirely lacking among Firmicutes pathogens? Choose one: A. enterotoxin B. cytotoxin C. AB toxin D. endotoxin E. neurotoxin
D
Which of the following is the most direct cause of a rise in biochemical oxygen demand (BOD) in bodies of water? Choose one: A. chemosynthesis by lithotrophs B. photosynthesis by cyanobacteria C. methanogenesis by methanogens D. respiration by heterotrophs
D
A molecular clock is best described as what? Choose one: A. a biomolecule (such as DNA) whose sequence can be used to deduce ancestry B. the amount of divergence within DNA resulting from horizontal gene transfer C. the relative accuracy of DNA polymerases between two organisms D. the rate at which nonsense mutations are acquired within a gene
A
Which of the following are pathogenic species within the Firmicutes phylum?Choose one or more: A. Epulopiscium fishelsoni B. Salmonella enterica C. Lactobacillus lactis D. Streptococcus pyogenes E. Staphylococcus aureus F. Clostridium botulinum
D,E, &F
The final step in glycolysis catalyzed by pyruvate kinase couples the hydrolysis of phosphoenolpyruvate (PEP) to the formation of ATP via substrate-level phosphorylation of ADP. If the ΔG°' of ATP + H2O → ADP + Pi + H+ is -30.5 kJ/mol and the ΔG°' of the coupled reaction is -31.4 kJ/mol, what is the ΔG°' of PEP + H2O → pyruvate + Pi? Choose one: A. +61.9 kJ/mol B. More information is needed C. -0.9 kJ/mol D. +0.9 kJ/mol E. -61.9 kJ/mol
E
The gamma class of the Proteobacteria includes many medically important genera in the families Enterobacteriaceae and Pseudomonadaceae. Which of the following characteristics allows differentiation between these two groups? Choose one: A. Gram reaction B. ability to form biofilms C. ability to grow autotrophically D. morphology (rods versus cocci) E. ability to grow anaerobically
E