MIC 102 Exam 1 Questions with Correct Answers

MIC 102 Exam 1 Questions with Correct Answers Which type of cell is most susceptible to osmotic lysis in an environment with a very low concentration of solutes (hypotonic)? - Answer-Mycoplasma Which of the following cellular structures self-assemble (purified monomers can assemble into the structure without added factors or the input of energy)? - Answer- Flagellar filament Phospholipid bilayer S layer mycoplasma - Answer-only prokaryotic group listed that do not have a cell wall to resist high osmotic pressure caused by water moving into the solute-rich cell While Mycoplasma are highly successful inside the relatively isotonic environment inside a host's body, they do not fare well in hypotonic environments or culture media. how does phospholipid bilayer assemble? - Answer-phospholipid nonpolar tails are attracted to each other to escape the hydrophilic environment surrounding them how does flagellar filament assemble? - Answer-Flagellin aggregates spontaneously at the tip of the flagellar filament during flagellar assembly how does the S layer assemble? - Answer-The S-layer is a lattice of a single protein that will self-assemble into highly-ordered arrays how do pili assemble? - Answer-built of monomers of the protein pilin that are added to the base of the pilus filament What distinguishes an organelle (such as a mitochrondrion or chloroplast) from a carboxysome or enterosome? - Answer-Organelles may contain DNA carboxysomes - Answer-protein-enclosed compartments where bacteria concentrate the enzymes and substrates forcarbon fixation enterosomes - Answer-protein-enclosed compartments where bacteria concentrate the enzymes and substrates for propanediol and ethanolamine metabolism DNA may be observed in which forms inside Bacterial cells? - Answer-Circular chromosomes what is bacterial DNA like? - Answer-single circular chromosome bound by DNA- condensing proteins Positively-charged cations in the cytoplasm reduce the electrostatic repulsion of negatively-charged DNA and allow its condensation into higher-ordered loops and supercoiled structures Bacteria may also have circular plasmids, which encode functions not essential for survival (note: a cell may be "cured" of a plasmid but never of a chromosome) T/F: Only prokaryotes can transcribe and translate a gene at the same time. - Answer-true Why can't eukaryotes transcribe and translate a gene at the same time? - Answer- transcription and translation are separated in time and space: transcription can only happen inside the nucleus while translation takes place in the cytoplasm or endoplasmic reticulum Why can prokaryotes transcribe and translate a gene at the same time? - Answer-they do not have a membrane enclosing their DNA, DNA replication machinery, RNA polymerase, and ribosomes can all access the DNA/RNA at the same time and place Which of the following are NOT influenced by cell size? - Answer-Presence of a phospholipid membrane all cellular organisms have phospholipid membrane Which of the following are influenced by cell size? - Answer-Type of microscopy used to image cells Acquisition of nutrients from the environment Microbial growth rate (how quickly they replicate) Surface area/volume ratio Which statement provides evidence that the Eukarya lineage arose by the "ingestion" of an ancestral bacterium by an ancestral archaeaon (cell from Archaea lineage)? - Answer-Eukaryotic DNA replication and transcription enzymes are most similar to the the equivalent enzymes in modern Archaea T/F: All cellular organisms grow best at 37oC although some extremophiles can tolerate much higher or lower temperatures. - Answer-false Extremophiles are highly adapted to the environments they are found in and would find "normal" human temperatures incompatible with survival and/or growth Which molecule is NOT a constituent of the gram-negative bacterial envelope? - Answer-Lipoteichoic acid Which molecule is a constituent of the gram-negative bacterial envelope? - Answer- Lipopolysaccharide Periplasm Peptidoglycan T/F: All microscopes use light or electrons to image cellular structures. - Answer-false Scanning probe microscopes use a metal tip to probe the contours and properties of surface structures. Does the traditional concept of species apply to prokaryotes? - Answer-No, because prokaryotes are asexual and exchange genes by horizontal transfer "traditional" concept of species - Answer-organisms are considered the same species if they breed (or have the potential to breed) and produce fertile offspring β-‐‐lactam antibiotics, such as penicillin, inhibit transpeptidase activity during cell wall synthesis. What will happen to a gram-‐‐positive bacterial cell in a hypertonic environment after penicillin treatment? - Answer-The cytoplasm will shrink (plasmolysis) Why do bacteria store excess nutrients (phosphate, PHA, glycogen) in granules rather than in solution in the cytoplasm? - Answer-To decrease its concentration inside the cytosol and allow the cell to take up more of the nutrient overall. Which of these proteins is most likely to need a chaperone to retain its function? - Answer-Glycolytic enzyme of a hyperthermophile The "stem" F0 component of the ATP synthase in an acidophile Helicobacter pylori isolated from the gastric epithelium does not grow well under room atmosphere but early researchers discovered that it could grow in a candle jar. Is H. pylori likely to be (an): - Answer-Facultative anaerobe