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The presence of which of the following feature would best indicate a eukaryotic cell?
Organelles are only found in eukaryotic cells which set them apart from prokaryotic cells.
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Gram staining prepares bacteria to be visualized under light microscope.
What allows a bacteria to stain positively with gram stain?
Gram-positive bacteria are able to retain the crystal violet stain found in gram stain because of their thick peptidoglycan cell walls. Consequently, these bacteria stain dark blue or purple by gram staining. Alternatively, gram-negative bacteria appear red or pink because they are unable to retain the dye due to thinner cell walls and less peptidoglycan.
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Which of the following would not be found an E. Coli sample?
E. Coli is a type of bacteria. Because bacteria are prokaryotes, they do not contain membrane-bound organelles. A nucleus is a membrane-bound organelle and therefore would not be found in bacteria.
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All of the following are true about bacilli bacteria except:
I. All bacilli are rod-shaped
II. All bacilli are gram positive
III. All bacilli are aerobic
Bacilli is a genus of bacteria that are characterized by their rod-shaped cells. Bacilli can be either gram positive, such as Bacillus anthracis, or gram negative, such as Salmonella enterica. Bacilli bacteria can be either aerobic (require oxygen) or facultative anaerobes (can thrive in both oxygen rich and oxygen poor environment). Bacilli are not exclusively aerobic, nor are they exclusively gram positive.
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What characteristic do both all plants and fungi have in common?
Both plants and fungi consist of eukaryotic cells. Their cells contain membrane-enclosed nuclei and organelles which is a defining characteristic of eukaryotic cells.
Fungi do not photosynthesize. While seedless plants and fungi use spores, this trait is not common to all plants. Plant cell walls are composed of collagen, while fungi use chitin.
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An antifungal cream advertises to chemically attack the fungal cells without harming the skin. The antifungal chemical most likely acts on which of the following?
The antifungal compound is likely specific to chitin, as it is a common material of many fungi cell wall structures. Chitin is resistant to breakdown, and is actually found in insect exoskeletons. The incorrect answers are found in skin cells as well as fungal cells, and would harm the skin if the chemical attacked these structures.
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Which of these processes is the means by which a bacterium can directly uptake and incorporate foreign DNA from the environment into its genome?
Transformation is defined as the process by which bacteria can incorporate exogenous DNA from the environment into their genome via direct uptake. Transduction and conjugation are also processes by which exogenous DNA is incorporated, but involve other methods.
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Reverse transcriptase is most likely to be found in which of the following?
Reverse transcriptase is commonly used by retroviruses, such as human immunodeficiency virus (HIV). Reverse transcriptase is used to convert the virus RNA into DNA, which can then be inserted into the host genome.
Bacteria, protists, and fungi have DNA genomes and do not require an enzyme to convert RNA back to DNA. Double-stranded DNA (dsDNA) viruses also have no need for this conversion, as their DNA can be directly incorporated into their hosts.
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Viral genomic material can be comprised of which types of nucleic acids?
I. Single-stranded DNA
II. Double-stranded DNA
III. Single-stranded RNA
IV. Double-stranded RNA
Different classes of viruses store genetic material in different forms.
Double-stranded RNA (dsRNA) viruses, single-stranded RNA (ssRNA) viruses, double-stranded DNA (dsDNA) viruses, and single-stranded DNA (ssDNA) viruses are all large classes of viral classification. Retroviruses can be classified as ssRNA viruses, but are often left in their own category.
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Which of the following is not found in a virus?
Viruses use the hosts ribosomes to translate their genes, and do not possess their own organelles for replication. Viruses are made of a protein buffy coat with genetic material (DNA or RNA) inside.
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Slides containing bacteria are stained with crystal violet and iodine, destained with alcohol, and counterstained with safranin. Under the mircoscope, the bacteria appear a bluish-purple color. Which class of bacteria are on the slide?
The technique explained in the question is the "Gram stain". Bacteria that are Gram-positive will stain a bluish-purple color, while Gram-negative bacteria will stain a red or pink color. This difference in color occurs because of the large cell wall present on Gram-positive bacteria, and is a response to increased peptidoglycan expression. Additionally, some bacteria (such as mycobacteria and helicobacter) are not easily stained using this method.
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An unidentified class of bacteria are placed into a test tube containing liquid and set on top of a lab bench. After the liquid and bacteria has a chance to settle, the bacteria are found distributed throughout the liquid (as opposed to located primarily at the top or bottom of the liquid). What type of bacteria is in the tube?
In order for the bacteria to be distributed throughout the liquid, it must be able to survive in either the presence or absence of oxygen. Facultative anaerobic bacteria can surive in both cases, although, they prefer oxygen. In the absence of oxygen, they can produce energy through fermentation. Both microaerophiles and obligate aerobic bacteria require oxygen to survive and, in this experiment, would be found near the top of the tube. Oxygen is toxic to obligate anaerobic bacteria, which would be found at the bottom.
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Which of the statements below describes eukaryotic, but not prokaryotic cells?
Post-transcriptional modifications, such as the splicing out of introns, only occur in eukaryotic cells. They cannot occur in prokaryotes because in those cells, trancription and translation happen concurrently in the cytoplasm.
Both types of cell contain ribosomes, so this answer does not fulfill the question criteria. Cells that lack membrane-bound organelles and a nuclear membrane are prokaryotes, not eukaryotes. Similarly, only prokaryotes are capable of coupled transcription and translation mechanisms. Finally, the choice that references external plasmids also describes prokaryotes.
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Which of the following is not a tenet of the Cell Theory?
All of the answer choices are tenets of the Cell Theory, except for the one concerning organelles. Not every cells has membrane-bound organelles (e.g. prokaryotic cells).
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An unknown cell type has been isolated. It is suspected that this cell is prokaryotic. The presence of which of these cell structures would confirm that the cell is prokaryotic?
Cytoplasm is found in all types of cells. Flagella is found in all cells that are mobile. Spores can be found in bacteria but also fungi. Ribosomes are found in prokaryotic cells albeit smaller in size compared to those in eukaryotic cells.
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Which of the following components of an animal cell would NOT also be observed in a bacterial cell?
This question is asking about one of the differences between eukaryotes and prokaryotes. While both eukaryotes and prokaryotes use DNA to encode their genetic information, making "DNA" incorrect, remember that prokaryotes lack membrane-bound organelles. \This makes both "ribosomes" and "phospholipid cell membrane" incorrect, because neither of them are membrane-bound organelles. We are left with "nucleus," which is the correct answer.
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Which of the following would not be found in a prokaryotic cell?
One of the key differences between prokaryotes and eukaryotes is that prokaryotes have no membrane bound organelles, therefore, prokaryotes would not have mitochondria. Prokaryotes have a plasma membrane for protection, ribosomes for protein production, RNA in the form of mRNA, tRNA, and rRNA, and DNA polymerase to replicate their DNA.
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A scientist studying a culture of bacteria finds an organism he hadn't seen before. He thinks it might be some kind of single-celled eukaryote. What observed characteristic would support the scientists prediction?
The characteristic that defines a eukaryote is the presence of membrane bound organelles, such as the nucleus, mitochondria, Golgi body, and chloroplasts. Both eukaryotes and prokaryotes have ribosomes, DNA and RNA, and and electron trasnsport chain. Bacteria and plants have cell walls but not all eukaryotes do, so it is not a defining characteristic.
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Which of the following is not a characteristic of prokaryotes?
Prokaryotes do not have membrane-bound organelles, such as the nucleus or mitochondria. In fact, endosymbiotic theory suggests that mitochondria evolved from symbiotic prokaryotic relationships. Prokaryotes are often associated with all of the other characteristics listed.
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Which of the following would not help determine whether a cell was eukaryotic or prokaryotic?
Membrane bound organelles are specific only to eukaryotes. Circular DNA is only present in prokaryotes. Rough endoplasmic reticulum is only present in eukaryotes, as all prokaryotic ribosomes are cytoplasmic. Although prokaryotes have circular DNA, both eukaryotes and prokaryotes have double-stranded DNA.
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