Use Advanced Search to search by activities, standards, and more. Modern physicians frequently prescribe antibiotic medications to help people fight infections. One of the first antibiotics discovered was penicillin.
Penicillin was first used to treat bacterial infections in and is derived from the fungus Penicillium sp. When used as an antibiotic treatment, penicillin operates by a very specific mechanism. Penicillin interferes with the production of a molecule called peptidoglycan. Peptidoglycan molecules form strong links that give the bacterial cell strength as well as preventing leakage from the cytoplasm.
Nearly every bacterium has a peptidoglycan cell wall. The composition of the cell wall differs depending on the type of organism, so penicillin does not affect other organisms. The cell walls of plants, for example, are made from cellulose. The cell walls of algae are highly variable.
Algae cell walls can be made of cellulose, xylan, silica, carrageenan or a variety of other materials. The cell walls of most fungi are made from chitin. Composition of the cell wall in the archaea is more diverse.
Within bacteria, there are two types of bacterial cell walls. The predatory bacterium, Bdellovibrio bacteriophorus, drills into a prey bacterium and, once inside, digests it. In an attack upon a gram-negative bacterium that has a slimy cell covering which can inhibit phagocytosis, what is the correct sequence of structures penetrated by B.
Jams, jellies, preserves, honey, and other foodstuffs with a high sugar content hardly ever become contaminated by bacteria, even when the food containers are left open at room temperature. This is because bacteria that encounter such an environment A undergo death by plasmolysis. B are unable to metabolize the glucose or fructose, and thus starve to death.
C undergo death by lysis. D are obligate anaerobes. E are unable to swim through these thick and viscous materials. In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located together on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the result should be A a transformed bacterium.
B the rapid spread of tetracycline resistance to other bacteria in that habitat. C the subsequent loss of tetracycline resistance from this bacterium. E the temporary possession by this bacterium of a completely diploid genome. In a bacterium that possesses antibiotic resistance and the potential to persist through very adverse conditions, such as freezing, drying, or high temperatures, DNA should be located within, or be part of, which structures?
Which two structures play direct roles in permitting bacteria to adhere to each other, or to other surfaces?
B an external covering provided by the plasma membrane. Prokaryotic ribosomes differ from those present in eukaryotic cytosol. Because of this, which of the following is correct? A Some selective antibiotics can block protein synthesis of bacteria without effects on protein synthesis in the eukaryotic host.
B Eukaryotes did not evolve from prokaryotes. C Translation can occur at the same time as transcription in eukaryotes but not in prokaryotes. D Some antibiotics can block the synthesis of peptidoglycan in the walls of bacteria. E Prokaryotes are able to use a much greater variety of molecules as food sources than can eukaryotes.
Which statement about the genomes of prokaryotes is correct? A Prokaryotic genomes are diploid throughout most of the cell cycle. B Prokaryotic chromosomes are sometimes called plasmids. D The prokaryotic chromosome is not contained within a nucleus but, rather, is found at the nucleoid region.
If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell, the regenerated bacterium will probably A lack antibiotic-resistant genes. B lack a cell wall. C lack a chromosome. D lose base pairs from its chromosome. E be unable to survive in its normal environment.
Which of the following requires ATP to function, and permits some species to respond to taxes plural of taxis? A endospore B sex pilus C flagellum D cell wall E capsule. Not present in all bacteria, this cell covering enables cells that possess it to resist the defenses of host organisms: A endospore B sex pilus C flagellum D cell wall E capsule. Not present in all bacteria, this structure enables those that possess it to germinate after exposure to harsh conditions, such as boiling: A endospore B sex pilus C flagellum D cell wall E capsule.
Which of the following is a structure that permits conjugation to occur? Which of the following is an important source of endotoxin in gram-negative species? If this structure connects the cytoplasm of two bacteria, one of these cells may gain new genetic material: A endospore B sex pilus C flagellum D cell wall E capsule. Which of the following contains a copy of the chromosome, along with a small amount of dehydrated cytoplasm, within a tough wall?
Regarding prokaryotic reproduction, which statement is correct? A Prokaryotes form gametes by meiosis. B Prokaryotes feature the union of haploid gametes, as do eukaryotes. C Prokaryotes exchange some of their genes by conjugation, the union of haploid gametes, and transduction. D Mutation is a primary source of variation in prokaryote populations.
E Prokaryotes skip sexual life cycles because their life cycle is too short. Which of these statements about prokaryotes is correct? A Bacterial cells conjugate to mutually exchange genetic material. A endospore B sex pilus C flagellum D cell wall E capsule. Not present in all bacteria, this cell covering enables cells that possess it to resist the defenses of host organisms: A endospore B sex pilus C flagellum D cell wall E capsule.
Not present in all bacteria, this structure enables those that possess it to germinate after exposure to harsh conditions, such as boiling: A endospore B sex pilus C flagellum D cell wall E Capsule.
Which of the following is a structure that permits conjugation to occur? If this structure connects the cytoplasm of two bacteria, one of these cells may gain new genetic material: A Endospore B Sex pilus C flagellum D capsule. Which of the following contains a copy of the chromosome, along with a small amount of dehydrated cytoplasm, w within a tough wall A endospore B sex pilus C flagellum D cell wall E capsule.
B Prokaryotes feature the union of haploid gametes, as do eukaryotes. D Mutation is a primary source of variation in prokaryote populations.
E Prokaryotes skip sexual life cycles because their life cycle is too short. Which of these statements about prokaryotes is correct? A Bacterial cells conjugate to mutually exchange genetic material.
B Their genetic material is confined within a nuclear envelope. C They divide by binary fission, without mitosis or meiosis. D The persistence of bacteria throughout evolutionary time is due to their genetic homogeneity i. E Genetic variation in bacteria is not known to occur, nor should it occur, because of their asexual mode of reproduction.
A microevolution B speciation C adaptive radiation D sexual selection E stabilizing selection. What can be inferred from figure A Most of the genetic change that permitted adaptation to the new, low-glucose environment occurred toward the conclusion of the experiment. B Rates of mitosis increased over the course of the experiment. C The highest rate of genetic change occurred during the first quarter of the experiment.
A number of daughter cells produced per mother cell per generation B amount of ATP generated per cell per unit time C average swimming speed of cells through the growth medium D amount of glucose synthesized per unit time E number of generations per unit time. If new genetic variations in the experimental populations arose solely by spontaneous mutations, then the most effective process for subsequently increasing the prevalence of the beneficial mutations in the population over the course of generations is A transduction.
B binary fission. C conjugation. D transformation. E meiosis. A Generation time should be the same as in the typical environment. B Generation time should be faster than in the typical environment. C Generation time should be slower than in the typical environment. Which term is least closely associated with the others? How is the recipient cell different at Time D than it was at Time A? A It has a greater number of genes. E It has a greater number of introns. Which two processes are responsible for the shape of the curve at Time B?
C What forces are generally responsible for disrupting the mating bridge? D How is it that a recipient cell does not necessarily become an Hfr cell as the result of conjugation with an Hfr cell?
Which of the following are responsible for many human diseases? A photoautotrophs B photoheterotrophs C chemoautotrophs D chemoheterotrophs that perform decomposition E parasitic chemoheterotrophs. Cyanobacteria are A photoautotrophs. E parasitic chemoheterotrophs. Which of the following use light energy to synthesize organic compounds from CO2? Which of the following obtain energy by oxidizing inorganic substances; energy that is used, in part, to fix co2 A photoautotrophs B photoheterotrophs C chemoautotrophs D chemoheterotrophs that perform decomposition E parasitic chemoheterotrophs.
Which of the following use light energy to generate ATP, but do not release oxygen? Modes of obtaining nutrients, used by at least some bacteria, include all of the following except A chemoautotrophy. B photoautotrophy. C heteroautotrophy. D chemoheterotrophy. E photoheterotrophy. A They may breathe it in from air that has experienced lightning discharges. B They may ingest nitrogen fixers. D They may ingest other animals that had done either B or C above.
E Answers B , C , and D above are all possible. B Light-dependent reaction rates must be highest between hours and hours. C Atmospheric N2 levels increase at night because plants are no longer metabolizing this gas, so are not absorbing this gas through their stomata.
D Heterocyte walls become less permeable to N2 influx during darkness. A horizontal gene transfer B binary fission C alternative gene splicing D meiosis E plasmolysis. A microscopic examination of staining characteristics of the cell wall B metabolic characteristics such as the production of methane gas C metabolic characteristics such as chemoautotrophy and photosynthesis D genetic characteristics such as ribosomal RNA sequences E ecological characteristics such as the ability to survive in extreme environments.
Which statement about the domain Archaea is false? A Genetic prospecting has recently revealed the existence of many previously unknown archean species. B Some archaeans can reduce CO2 to methane. C The genomes of archaeans are unique, containing no genes that originated within bacteria. E Some archaeans are adapted to waters with temperatures above the boiling point. E Archaeans should lack cell walls.
Which of the following traits do archaeans and bacteria share? A extreme halophiles B extreme thermophiles C methanogens D cyanobacteria E nitrogen-fixing bacteria that live in root nodules. The optimal pH of its enzymes will lie above pH 7.
The optimal pH of its enzymes will lie below pH 7. What is the primary ecological role of prokaryotes? A parasitizing eukaryotes, thus causing diseases B breaking down organic matter C metabolizing materials in extreme environments D adding methane to the atmosphere E serving as primary producers in terrestrial environments.
B Human populations would thrive in the absence of disease. E There would be no more pathogens on Earth. How can prokaryotes be considered to be more successful on Earth than humans? A Prokaryotes are much more numerous and have more biomass.
B Prokaryotes occupy more diverse habitats. C Prokaryotes are more diverse in metabolism. D Only B and C are correct. E A, B, and C are correct. A The antibiotic administered may kill viruses that had been keeping the bacteria in check. B Antibiotics may cause other side effects in patients. C Overuse of antibiotics can select for antibiotic-resistant strains of bacteria. D Particular patients may be allergic to the antibiotic. E Antibiotics may interfere with the ability to identify the bacteria present.
Consequently, assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient who is receiving broad-spectrum antibiotics is most likely to become A unable to fix carbon dioxide. B antibiotic resistant.
C unable to fix nitrogen. D unable to synthesize peptidoglycan. E deficient in certain vitamins. Which statement about gram-negative bacteria is correct? A Penicillins are the best antibiotics to use against them. B They often possess an outer membrane containing toxic lipopolysaccharides. C Their chromosomes are composed of DNA tightly wrapped around large amounts of histone proteins. D Their cell walls are primarily composed of peptidoglycan. Protists are alike in that all are A unicellular.
B eukaryotic. C symbionts. D monophyletic. E autotrophic. A Many species within this kingdom were once classified as monerans. B Animals, plants, and fungi arose from different protist ancestors.
D Chloroplasts among various protists are similar to those found in prokaryotes. E Some protists, all animals, and all fungi share a protist common ancestor, but these protists, animals, and fungi are currently assigned to three different kingdoms.
A nuclei and chloroplasts B mitochondria and chloroplasts C cilia and mitochondria D mitochondria and nuclei E mitochondria and cilia. A from infoldings of the plasma membrane, coupled with mutations of genes for proteins in energy-transfer reactions B from engulfed, originally free-living prokaryotes C by secondary endosymbiosis D from the nuclear envelope folding outward and forming mitochondrial membranes E when a protoeukaryote engaged in a symbiotic relationship with a protobiont Answer: B.
Such organelles A are roughly the same size as bacteria. B can be cultured on agar, because they make all their own proteins. C contain circular DNA molecules. D have ribosomes that are similar to those of bacteria.
A conjugation B horizontal gene transfer C binary fission D phagocytosis E meiosis. A autotrophic euglenids B diatoms C dinoflagellates D red algae E cyanobacteria. C It engulfs organic material by phagocytosis or by absorption. D It has an endospore. E It is protected by a siliceous case. Which of these was not derived from an ancestral alpha proteobacterium? A chloroplast B mitochondrion C hydrogenosome D mitosome E kinetoplast.
A red algae B dinoflagellates C diplomonads D euglenids E golden algae. Which of the following pairs of protists and their characteristics is mismatched? A apicomplexans : internal parasites B golden algae : planktonic producers C euglenozoans : unicellular flagellates D ciliates : red tide organisms E entamoebas : ingestive heterotrophs.
Which of these statements about dinoflagellates is false? A They possess two flagella. B Some cause red tides. C Their walls are composed of cellulose plates. D Many types contain chlorophyll. A ciliates B apicomplexans C dinoflagellates D brown algae E golden algae.
A foraminiferans B radiolarians C ciliates D kinetoplastids E slime molds. D Most live as solitary cells in fresh water. E They have two or more nuclei. A budding B meiotic division C mitotic division D conjugation E binary fission.
A Fungi are closely related to the water molds. B Body shape reflects ancestor-descendant relationships among organisms. D Filamentous body shape is evolutionarily ancestral for all eukaryotes.
E Both A and B are correct. The Irish potato famine was caused by an organism that belongs to which group? A ciliates B oomycetes C diatoms D apicomplexans E dinoflagellates. If one were to apply the most recent technique used to fight potato late blight to the fight against the malarial infection of humans, then one would A increase the dosage of the least-expensive antimalarial drug administered to humans.
B increase the dosage of the most common pesticide used to kill Anopheles mosquitoes. C introduce a predator of the malarial parasite into infected humans. E insert genes from a Plasmodium-resistant strain of mosquito into Anopheles mosquitoes.
Which question would be most important for one interested in the day-to-day survival of individual diatoms? A How does carbon dioxide get into these protists with their glasslike valves? C How do diatoms with their glasslike valves keep from sinking into poorly lit waters? D How do diatoms with their glasslike valves avoid being shattered by the action of waves? E How do diatom sperm cells locate diatom egg cells?
A thalli B bladders C blades D holdfasts E gel-forming polysaccharides. E a feeding plasmodium.
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