BIO 250 Final Exam 2023 with verified questions and answers

A pure culture A) is sterile. B) is a population of identical cells. C) is made of a precisely defined chemical medium. D) contains one microbial cell. b Microbial cells first evolved on Earth approximately ________ _______ years ago. A) 1.6 to 1.8 million B) 7.0 to 7.2 million C) 3.8 to 3.9 billion D) 10.5 to 11.5 billion E) None of the above c Predict how Pasteur's conclusions on spontaneous generation with swan flasks would have changed if he worked with and maintained the flasks in a laminar flow hood (where the air is sterile). A) Sterilization of the swan flask solutions would not have been necessary to reject spontaneous generation. If he did sterilize the flasks, the spontaneous generation hypothesis would have been supported. B) His incubation times would not have been sufficient to refute spontaneous generation. C) Pasteur's flasks never would have putrefied, and the experiment would not have refuted spontaneous generation. D) Viruses would have still been present, and his conclusion would have been unchanged. c Of the structures listed below, which one is found in the outer most membrane of a Gram-negative cell? A) Ribosomes B) The peptidoglycan layer C) The periplasm D) LPS (lipopolysaccharide) layer d Gram-positive bacteria stain _____ with a Gram stain reaction because they have a __________ peptidoglycan layer than Gram-negative bacteria. A) red / thinner B) purple/ thinner C) purple / thicker D) red / thicker c Which of the following statement(s) is/are correct? A) Flagella allow bacteria to glide B) Flagella allow bacteria to swim C) The directed movement of bacterial cells in response to a gradient of a chemical, is called chemotaxis D) A and C are correct E) B and C are correct e Electron microscopy has _________ ________ than light microscopy, because the wavelengths of electrons are much ___________ than the wavelength of visible light. A) higher resolution/smaller B) lower magnification/larger C) higher resolution/larger D) lower resolution/smaller a Which of the following statements are false: A) Poly-β-alkanoates (PHA) such as poly-β-hydroxybutyrate (PHB) are carbon- and energy-storing polymers that can be used to produce biodegradable plastics. B) A major function of prokaryotic gas vesicles is to confer buoyancy on cells by decreasing their density C) A major function of the cytoplasmic membrane in prokaryotes is to act as a permeability barrier. D) Scanning electron microscopy can be used to visualize the different layers of the cell membrane(s) and cell wall d Beta-lactam antibiotics such as penicillin A) interfere with chromosome replication B) prevent the transpeptidase from cross-linking two glycan chains in the peptidoglycan layer of a growing cell wall C) prevent the cytoplasmic membrane from forming D) cannot penetrate the cell b From the standpoint of the microorganism, in glycolysis the useful product(s) are A) Anabolic intermediates B) ATP C) Fermentation products such as lactic acid and ethanol D) Both (A) and (B) E) (A), (B), and (C) d During respiration electrons from the __________ of substrates are used to ________ a terminal electron acceptor that is either oxygen (aerobic respiration) or some other inorganic compound (anaerobic respiration) A) reduction / oxidize B) transport / degrade C) oxidation / reduce D) none of the above c Which intermediate compound(s) in the citric acid cycle is/are often used for biosynthetic pathways as well as carbon catabolism? A) α-ketoglutarate B) oxaloacetate C) acetyl~CoA D) All of the above E) None of the above d Which pathway(s) are used to obtain anabolic intermediates: A) Pentose phosphate pathway B) Glycolysis C) Citric acid cycle D) All the above E) None of the above d Which statement is FALSE? A) Electron transport systems mediate transfer of electrons and conserve some of the energy released during transfer and use it to synthesize ATP B) In electron transport systems, the electron carriers are membrane associated. C) Fermentation requires a fully functional electron transport chain so that a proton gradient can be formed and drive the synthesis of ATP. D) The proton motive force drives the conversion of ADP to ATP through ATP synthase c By controlling the concentration of nutrients continuously added to a chemostat, cells can constantly be maintained at the A) exponential growth phase. B) stationary growth phase. C) lag growth phase. D) death growth phase. a A bacterial cell doubles every 30 minutes under given laboratory conditions. When a liquid broth is inoculated with 10 cells, how many cells will the culture contain after 4 hours? A) 40 B) 80 C) 160 D) 2560 E) None of the above d To determine the number of bacteria in a water sample, a laboratory technician used the pour-plate method: 1 ml of 10-4 dilution was inoculated in a Petri dish and molten agar was poured over it. After incubation, he counted 95 colonies on that plate. How many cells (or colony forming units, CFU) were present in 1 ml of the water sample? A) 95 CFU/ml B) 360 CFU/ml C) 9.5 X 104 CFU/ml D) 9.5 x 105 CFU/ml E) 9.5 x 106 CFU/ml d Which of the statements A-D is FALSE: A) Biofilms consist of bacterial cells that are embedded in an attached polysaccharide matrix and can affect human health, water distribution systems, and fuel storage B) When a microbial population is growing exponentially, it means that the number of cells will double during a specific time interval C) The time between inoculation of a bacterial culture and the beginning of growth is usually called the stationary phase D) If a bacteria cell like Escherichia coli (10-12 g/cell) could grow without any restrictions, their mass could be that of planet earth (5 x 1027 g) in about two days time. E) All of the above are false c Which statement is CORRECT: A) Bacteria that are able to grow in humans and cause disease would be classified as thermophiles B) Enumerating cells that clump together is challenging for direct counting by microscopy, measuring turbidity, and viability counts by spread plating. C) The time interval required for the formation of two cells from one is called the growth rate D) Smaller bacteria generally grow slower than larger ones due to a higher surfacearea-to-volume ratio. E) All the above are correct b A ___________ agent is a chemical that inhibits bacteria from reproducing, but does NOT necessarily kill them. a. bacteriocidal b. bacteriolytic c. bacteriological d. bacteriostatic d Which of the statements is NOT true? a. The removal or destruction of all microorganisms is called pasteurization b. Autoclaving requires maintaining steam at 121°C and high pressure for about 15 minutes c. The instrument used for autoclaving is called an autoclave d. A bacterium is resistant to antibiotic A but not B. In a disk diffusion assay the zone of inhibition will be smaller for a disk with antibiotic A than with antibiotic B. a Plasmids can be a. beneficial to their bacterial host b. transferred by conjugation c. replicated in the nucleus of bacteria d. Both (a) and (b) are correct e. (a), (b), and (c) are correct d Because there are three hydrogen bonds between the bases guanine and cytosine, and two between adenine and thymine, GC-rich DNA will denature/melt a. at the same temperature as AT-rich DNA, with some minor variations b. at a higher temperature than AT-rich DNA c. at a lower temperature than AT-rich DNA d. in accordance with the animal or plant from which it was taken b Which statement is correct? a. All strains of the species Escherichia coli have virtually the same genome size and gene content. b. DNA replication in prokaryotes makes a lot of mistakes, leading to mutation rates of 1/1000. c. DNA replication in prokaryotes requires no primer. d. DNA replication in prokaryotes occurs at a single replication fork because their DNA is linear e. DNA replication always proceeds from the 5'-phosphate of the incoming nucleotide to the 3'-hydroxyl group of the previously added nucleotide e A polymerase chain reaction (PCR) a. can amplify a specific DNA sequence roughly 1 billion-fold. b. consists of three mains steps that are repeated many times: for example, incubation at 94°C to denature DNA strands, incubation at 60°C for primer hybridization, and incubation at 72°C for DNA synthesis c. translate DNA into proteins d. both (a) and (b) are correct e. both (b) and (c) are correct d Transfer RNA (tRNA) molecules a. function to transfer ribonucleotides to RNA polymerase during transcription. b. function to transfer the correct amino acids to the ribosome during translation. c. encode a codon that is the same as the sequence of nucleotides in mRNA d. do not function as described in (a), (b), and (c) e. function as described in a), (b), and (c) b When a codon reads AGC, one of the possible anticodons on the tRNA is a. AGC b. TCG c. UCG d. GCA e. None of the above c In negative control of transcription, how does the presence of a co-repressor like the amino acids tryptophan or arginine affect transcription? a. The co-repressor causes the repressor to bind to the operator, which blocks transcription. b. The co-repressor binds to the repressor, which allows transcription to proceed. c. The co-repressor binds to the operator, blocking a Proteins that are needed in the cell at about the same level under all growth conditions, require ____________ expression a. inducible b. promotable c. repressible d. constitutive d Enzyme induction occurs a. when the substrate of the enzyme is depleted. b. when the inducer binds to the operator in the DNA c. when the substrate is present. d. continuously. c Which of the following is correct: a. In catabolite repression, cells always use the best carbon source first b. Some regulatory proteins that bind to DNA block transcription, whereas others activate transcription c. A two-component regulatory system usually involves a sensor kinase and a response regulator. d. All of the above are correct e. None of the above are correct d Which of the following is NOT true about retroviruses? a. They code for the enzyme reverse transcriptase b. They never integrate in the host chromosome c. They are medically important viruses because they include the virus that causes AIDS. d. They can synthesize DNA with RNA as the template b Which of the following is true about viruses: a. HIV stands for Human Immunodeficiency Virus b. In influenza the H and N in for example H3N2 stands for the number of hydroxyl and amino groups on the surface of the virus c. In the case of both bacterial and animal viruses the entire viral particle can penetrate the cell d. Viruses can infect any cells within a large group; they are not very specific because they attach to many different proteins on the surface of a cell. a Based on the table in this exam: If the codon AAA is changed to AAU, it is an example of a a. silent mutation b. nonsense mutation, because a stop codon is generated c. frameshift mutation d. dimer formation e. missense mutation e Horizontal gene transfer has been thoroughly documented for genes involved in a. DNA replication and repair. b. antibiotic resistance genes. c. virulence and degradation functions. d. (a) and (b) e. (b) and (c) e Horizontal gene transfer a. is the transfer of DNA from one bacterial cell to another, and can even occur between distantly related organisms b. only occurs in eukaryotes. c. is very rare and only occurs between closely related strains. d. does not occur in natural environments a You have performed the following mating experiment using an Hfr strain of Escherichia coli as donor and an F- strain of Escherichia coli as recipient: Hfr (his+ leu+ RifS) X F- (his- leu- RifR). (his+: able to synthesize the essential amino acid histidine; leu+ : able to synthesize the essential amino acid leucine; StrS: sensitive to killing by the antibiotic rifampicin; and StrR : resistant to rifampicin) Which of the following selective media would you use to score recombinant colonies? a. minimal medium + glucose +rifampicin b. minimal medium + glucose c. minimal medium + glucose + histidine and leucine d. minimal medium + glucose + rifampicin + histidine and leucine a Which of the following is FALSE: a. Intercalating agents, like acridine orange and ethidium bromide, lead to mutagenesis by pushing DNA base pairs apart, which can lead to insertions or deletions. b. Transposons are only found on the chromosomes of bacteria c. A typical mutation rate for a bacterium is in the range of 10-9 to 10-10 per bp. d. The use of transposons to generate mutations is a convenient way to create bacterial mutations in the laboratory. b The horizontal gene transfer mechanism called "____________________" was discovered by Frederick Griffith through an experiment in which he inoculated mice with dead ___________ cells and live ______ cellsand found that the combination killed the mice, apparently due to transfer of ___________ from the _____________________ cells to the _______________ cells a. transformation/ non-virulent/ virulent/ DNA/ live virulent/ dead non-virulent cells b. transformation/ virulent / non-virulent/DNA/ dead virulent/ live non-virulent cells c. transformation/ virulent / non-virulent/RNA/ dead virulent/ live non-virulent cells d. transduction/ virulent / non-virulent/DNA/ dead virulent/ live non-virulent cells e. transduction/ non-virulent / virulent/DNA/ live non-virulent/ dead virulent cells b In specialized transduction, a. the virus never integrates in the bacterial chromosome b. virtually any genetic marker can be transferred from donor to recipient. c. genetic information is transferred from one cell to another mediated by a plasmid d. transduction occurs at high efficiency for only a restricted group of genes near the insertion site of the phage. d What occurs when an inducer is added to an environment containing an organism with a metabolic pathway controlled by a repressor? a. The inducer binds to the DNA and thereby allows transcription of the pathway. b. The inducer combines with the substrate and blocks induction. c. The inducer combines with the repressor and thereby allows transcription of the pathway. d. The inducer combines with the repressor and blocks transcription of the pathway c During transcription the enzyme RNA polymerase a. binds to a structural gene b. synthesizes a strand of RNA that is complimentary to mRNA c. binds to a so-called "promotor sequence" found in DNA d. does all of the above e. does none of the above c Mutations a. may be neutral, beneficial, or harmful b. are a permanent change in the nucleotide sequence of DNA c. can be spontaneous d. All of the above are true for mutations e. None of the above are true for mutations d Chemotaxis in bacteria occurs through the use of... a. prions. b. quorum sensing. c. autoinduction. d. a two-component regulatory system. d In agarose electrophoresis a DNA fragment of 2,000 bp will end up ___________________________ in the agarose gel than a 20,000-bp fragment, because it migrates __________________________through the agarose than the larger fragment. a. closer to the negative electrode / more slowly b. closer to the negative electrode / more rapidly c. further away from the negative electrode / more rapidly d. further away from the negative electrode / more slowly c Which choice below lists the steps necessary for genetic cloning in the correct order? a. fragment the DNA; insert DNA into vector; insert vector into host; host replication of recombinant vector; isolate DNA of interest b. isolate DNA of interest; fragment the DNA; insert vector into host; insert DNA into vector; host replication of recombinant vector c. isolate DNA of interest; fragment the DNA; host replication of recombinant vector; insert DNA into vector; insert vector into host d. isolate DNA of interest; fragment the DNA; insert DNA into vector; insert vector into host; host replication of recombinant vector d Restriction enzymes are enzymes that a. are rare in prokaryotes b. can only degrade DNA molecules from the end of a strand, moving inward c. cut DNA in random sites and therefore they are not useful for gene cloning purposes d. typically recognize a specific DNA sequence of 4 to 8 bp and can result in sticky as well as blunt ends d Which statement most closely expresses our present understanding? a. The chloroplast arose from the incorporation of a cyanobacterial-like organism b. The chloroplast is an ancestor of the cyanobacteria c. The chloroplast and the cyanobacteria are not closely (or specifically) related d. The cyanobacteria are descendents of the chloroplast a The currently understood phylogeny of biological life distinguishes a. Three phyla b. Three domains c. Three orders d. Four domains e. Four phyla b The very first DNA sequencing technology called the Sanger method relies on a. nuclear magnetic resonance (NMR) analysis. b. the release of protons whenever a new nucleotide is added to a growing strand of DNA. c. the detection of pyrophosphate d. the incorporation in the DNA strand of labeled deoxynucleotides that terminate chain extension during DNA synthesis. e. the incorporation in the DNA strand of dideoxynucleotides that terminate chain extension during DNA synthesis. e Chromosomal islands contain clusters of genes for a. virulence, biodegradation of pollutants, or symbiotic relationships. b. central metabolism. c. virulence or glycolysis. d. DNA replication and repair. e. translation, cell wall synthesis, or symbiotic relationships a The pan genome of a species is the genomic content that is a. encoded by mobile genetic elements b. expressed under all environmental conditions. c. present in one or more strains of the same species. d. shared with all other prokaryotes. e. shared between all strains of a species c The phenomenon whereby H2 consumption by one organism positively affects the energetics of the reaction of the H2 producer (making it an exothermic reaction) is called a. auxotrophy b. syntrophy c. phototropy d. chemolithotrophy e. none of the above b Which of the following is NOT true about nitrification: a. Nitrifying bacteria develop particularly well in lakes and streams receiving sewage because of the ammonium (NH4+ ) present in the sewage. b. It is the process whereby NO3- is used as terminal electron acceptor in anaerobic respiration c. It is carried out by bacteria able to grow chemolithotrophically at the expense of reduced inorganic nitrogen compounds d. It is the conversion of ammonium to nitrate over nitrite. b Which of the following is NOT true: a. Sulfate (SO42-) is a substrate that sulfur-oxidizing bacteria commonly use to support growth. b. BTEX, a group of compounds found in gasoline, can be oxidized by bacteria c. Iron oxidizing bacteria are chemolithotrophs d. Chemolithotrophs do not require organic compounds as energy source e. So far as we know, denitrification and nitrogen fixation can only be carried out by bacteria a Hydrogen oxidizing bacteria obtain a lot of energy from oxidizing hydrogen to water with oxygen because a. they use light as their energy source b. it doesn't require uptake of sugars c. the two half reactions' redox couples (E0′) are relatively close to each other. d. the two half reactions' redox couples (E0′) are very far from each other. e. None of the above d Chemoorganotrophs a. can live from air and minerals only b. require an organic compound as energy source c. can be phototrophs d. are always anaerobic bacteria e. are none of the above b Which statement is true: a. Staphylococcus aureus is osmotolerant b. The maximum temperature at which Archaea have been shown to grow is 80 °C c. Rhizobium species are plant pathogens d. Malaria is caused by Giardia species e. Members of the genus Pseudomonas are most abundant in the large intestine of humans and none of them cause disease in humans, plants or animals. a Which statement is false? a. In brown rot the cellulose is attacked preferentially, and the lignin is left unmetabolized. b. Most fungi are aquatic and primarily marine c. Fungi share a more recent common ancestor with animals than any other group of eukaryotic organisms d. There are at least 80 phyla within the domain Bacteria e. The Irish potato famine was caused by Phytophtora infestans b The spirochete _____________, which causes the sexually transmitted disease, syphilis, has remained unculturable despite many efforts. a. Thermus aquaticus b. Salmonella enterica c. Mycobacterium tuberculosis d. Treponema pallidum e. Staphylococcus aureus d Many species of bacteria are able to ferment sugars. This process: a. requires a fully functional electron transport chain so that a proton gradient can be generated to drive the synthesis of ATP b. involves the reduction of organic compounds, which serve as terminal electron acceptors. c. involves the oxidation of NADH to NAD+ d. Answers (b) and (c) are both correct. e. Answers (a), (b), and (c) are all correct. d Which statement is correct: a. Lactobacillus is the name of the genus of Gram-positive, rod-shaped bacteria used in the production of fermented milk products b. Gastric ulcers can be caused by Helicobacter pylori c. Archaea lack peptidoglycan in their cell walls d. Saccharomyces cerevisiae is also called baker's yeast e. All of the above are correct e A gram-positive microorganism has the following traits: filamentous, forms spores at the end of mycelia, produces antibiotics, produces an earthy smell, is nutritionally versatile, yields compact "dusty" colonies on agar culture media. These traits describe the genus a. Neisseria b. Streptobacillus. c. Streptomyces. d. Mycobacterium. e. Streptococcus c Some organisms are capable of using aerobic respiration or anaerobic respiration but use aerobic respiration preferentially. Why do they use aerobic respiration when possible? a. Using aerobic respiration allows them to use fermentation as well. b. Respiration with oxygen as a terminal electron acceptor generates more energy than respiration with other terminal electron acceptors. c. It is more efficient to focus on one process than to use two simultaneously, so aerobic respiration is the default and anaerobic respiration is used only as a backup. d. Aerobic respiration generates more oxygen, which is needed by many organisms. b Which statement is false: a. Escherichia coli is an important indicator group used to monitor fecal contamination of food and water. b. E. coli belongs to a broader group referred to as coliforms. Coliforms are defined as Gram-negative rods that ferment lactose to acid and gas at 37 C within 18-48 hrs. c. Members of the Pseudomonodales are ubiquitous organisms (found everywhere) in soil and water d. The causative agent of cholera is Mycoplasma cholerae e. Members of the genus Bacteroides are the most abundant bacteria present in the large intestine of humans d Based on oxygen requirements, the genus Clostridium is classified as _______________ a. aerobic b. facultative aerobic c. obligate anaerobic d. microaerophilic e. none of the above c . The Archaea ... a. are phylogenetically diverse, but functionally restricted to extremophiles and chemolithotrophs. b. are diverse microorganisms that inhabit almost every environment on Earth, including the colon of humans and other mammals. c. Are a domain of microorganisms, some of which are extreme halophiles that can grow in water that has up to 33% sodium chloride d. (a) and (c) are correct e. (b) and (c) are correct e Halobacterium pumps large quantities of K+ ions (potassium) into its cytoplasm from the environment so that the high quantities of Na+ cations in the environment do not diffuse into the cell. By doing this, death by___________________________ is avoided. a. sodium toxicity b. potassium toxicity c. osmolysis (rupture of the cell membrane) d. DNA replication arrest e. Dehydration e Which statement is true? a. Genetic drift is a random process through which gene frequencies change. b. The earliest nucleic acid was probably a simple DNA molecule. c. The atmosphere of primitive Earth is usually described as an oxidizing atmosphere. d. In the molecular clock approach, it is assumed that nucleotide changes are subject to intense selective pressure. e. LUCA is the individual ancestor of each of the domains of life a