Question

Microbiology study guide questions. Please Help!

s. which of the following statements about water activity is not true? a) many fungi can tolerate aw levels of 07-0.8 b) many microorganisms grow well at an aw of 0.98 e sear water has an aw of 0.98 e-xerephiles thrive in dry conditions DNA typically becomes disordered below an a of o.90 Which of the following descriptions about ribosome structure is not true? a) 80s is the size of the intact functional ribosome in Archaea b) 28s rRNA is found in the 60s ribosomal subunit in eukaryotes c) 5.8 s rRNA is found in the 60s ribosomal subunit in eukaryotes d) 16s rRNA is found in the 30s ribosomal subunit in Bacteria e) 18s rRNA is found in the 40s ribosomal subunit in eukaryotes 7. Which of the following statements about cell division in Caulobacter is not true? a) a stalked cell is capable of undergoing division, but a swarmer cell is not b) a stalked cell eventually loses its stalk and forms a fla cell cycle gella during the normal Caulobacter c) the type of differentiation that occurs in cell division in Caulobacter happens during the normal cell cycle, and is not specific to stressful conditions d) certain genes that are involved in flagella function are more likely to be expressed in the swarmer cell than the stalked cell e) the stalk structure that forms contains an area in the tip that has a high amount of polysaccharides with an adhesive property 8. Which of the following statements about mechanisms to deal with the toxic effects of oxygen gas is true? a) catalase converts water and oxygen gas to hydrogen peroxide b) carotenoid pigments convert singlet oxygen to hydrogen peroxide c) peroxidase works with the coenzyme NADH to convert hydrogen peroxide to water d) superoxide dismutase converts singlet oxygen to hydrogen peroxide and oxygen gas (uncharged) e) superoxide reductase works with rubredoxin to convert the superoxide radical to oxygen gas (uncharged) a iw hich of the following statements about regulation by catabolite repression is not ra the lac operon, CAP -cyclic AMP binds upstream of the promoten polymerase binding to the promoter b) glucose allosterically binds to CAP, changing the conformation so that CAP canno DNA target site e) cyclic AMP allosterically interacts with CAP, which allows CAP binding to the DNA target site d) RNA polymerase can still ind to the lac operon promoter, even without the presence of CAP nearby e) c yclic AMP binds to CAP at a section on the protein that is not the same as the section of CAP that binds to its DNA target site 10. Which of the following statements about the glucose transport/phosphotransferase system of E coli is not true? a) the unphosphorylated form of the transport system lowers the efficiency of Lac permease b) as glucose gets transported into the cell, the activity of adenyl cyclase is reduced c) as glucose gets transported into the cell, the transport system donates a phosphate group to glucose d) the phosphorylated transport system results in a decrease in cyclic AMP levels e) the unphosphorylated form of the system results in a decrease in the ability of lactose to be transported into the cell 11. Which of the following statements about the EnvZ signal transduction system is true? a) OmpR, in an unphosphorylated form, binds to a DNA regulatory site to upregulate the ompC gene b) the EnvZ protein is positioned in the membrane so that its N-terminus and C-terminus is protruding into the periplasm e) high osmotic pressure would result in increased levels of the OmpC porin relative to the OmpF porin d) OmpR, in its phosphorylated form, binds to a DNA regulatory site to upregulate the ompF gene e) under high osmotic conditions, EnvZ gets phosphorylated near its N-terminus 12. Which of the following environmental conditions would result in the highest amount of expression of the E. coli lac operon? a) lactose absent, glucose absent b) lactose present, glucose absent c) cAMP present, glucose absent d) lactose absent, glucose present e) lactose present, glucose present 13. Which of the following statements about the frp orehanging the conformation a) tryptophan binds to the Trp allosten in E. coli is not true? p repressor allosterically, changing the conformation of the repressor so that it binds to the operator b) the proteins encoded by the operon function to break down tryptophan c) when the Trp bi p repressor binds to the operator, it blocks RNA polymerase from binding to the promoter d) the promoter of this operon is not regulated by CAP-cAMP complex e) high levels of tryptophan result in down-regulation of the operon 14. Which of the following statements about the maltose operon of E. coli is true? a) the CAP-CAMP complex binds at a DNA site near the promoter of the maltose operon directly upregulates transcription of this promoter b) the Mal repressor protein binds to the operator site to down-regulate the expression of and this operon c) the proteins encoded by this operon function to synthesize maltose d) MalT directly upregulates the promoter of the maltose operon e) all of the above 15. Which of the following statements about all kinds of things is not true? a) in an exponentially growing culture, a round of DNA replication can begin before the current round of replication is complete b) in the type of bacterial transcription termination discussed in lecture, RNA polymerase reads the signals for termination in the RNA sequence, not the DNA sequence c) Agrobacterium uses a pilus-like system to introduce the T, plasmid into plant cells d) a chape allowing it to slither out through the cellular surface layers e) an oligotrophic bacterium is defined as growing optimally in relatively high nutrient rone protein facilitates secretion of a protein in bacteria by unwinding the protein, environments

Answer 1

5. c). DNA typically becomes disordered below an a_w of 0.90.

6. a). 80s is the size of the intact functional ribosome in Archaea

7. b). a stalked cell eventually loses its stalk and forms a flagella during the normal Caulobacter cell cycle

8. a). catalase converts water and oxygen gas to hydrogen peroxide

9. b). glucose allosterically bind t CAP, changing the confirmation so that CAP cannot bind to its DNA target site.

10. d). the phosphorylated form transport system results in a decrease in cyclic AMP levels

11. d). OmpR, in its phosphorylated form, binds to a DNA regulatory site to upregulate the ompF gene

12. b). lactose present, glucose absent

13. b). the proteins encoded by the operon function to break down tryptophan

14. b). the Mal repressor protein binds to the operator site to down-regulate the expression of this operon

15. e). an oligotrophic bacterium is defined as growing optimally in relatively high nutrient environments