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medical sciences
biology
Questions and Answers of
Biology
Explain why Pseudomonas putida goes into the production of polyhydroxyalkanoate (PHA) when the available nitrogen supply is severely reduced.
a. Outline the steps in the production of an antibiotic, starting with a newly discovered mold. b. Review chapter 10 and describe several ways that recombinant DNA technology can be used in
From chapter 7, figure 7.6. What method of food preservation exploits the principles that are illustrated here?Figure 7.6
From chapter 8, figure 8.24. Correlate the stages in this figure with corresponding steps in wine making, starting with grapes. Where do champagne bubbles come from? What causes wine to go sour?
What are the two major themes of microbiology and how do they differ in their focus?
What were the major microbiological interests of Martinus Beijerinck and Sergei Winogradsky? It can be said that both men discovered nitrogen fixation. Explain.
Select one major subdiscipline of microbiology from each of the two major categories of Table 1.3. Why do you think the subdiscipline is “basic” or “applied”?
How can prokaryotic and eukaryotic cells be distinguished? List the major activities carried out by cells, and in each case, describe why the activity occurs.
Why did the evolution of cyanobacteria change Earth forever? How many domains of life are there and how are they related?
What is an ecosystem? What effects can microorganisms have on their ecosystems?
How would you convince a friend that microorganisms are much more than just agents of disease?
For what contributions are Robert Hooke and Antoni van Leeuwenhoek most remembered in microbiology? What time period were these scientists active?
Explain the principle behind the Pasteur flask in studies on spontaneous generation. Why were the results of this experiment inconsistent with the theory of spontaneous generation?
What is a pure culture and how can one be obtained? Why are pure cultures important for medical microbiology and other areas of microbiology?
What are Koch’s postulates and how did they influence the development of microbiology? Why are Koch’s postulates still relevant today?
Pasteur’s experiments on spontaneous generation contributed to the methodology of microbiology, understanding of the origin of life, and techniques for the preservation of food. Explain briefly how
Describe the lines of proof Robert Koch used to definitively associate the bacterium Mycobacterium tuberculosis with the disease tuberculosis. How would his proof have been flawed if any of the tools
Imagine that all microorganisms suddenly disappeared from Earth. From what you have learned in this chapter, why do you think that animals would eventually disappear from Earth? Why would plants
Why is the rigid layer of the bacterial cell wall called peptidoglycan? What are the structural reasons for the rigidity that is conferred on the cell wall by the peptidoglycan structure?
List several functions of the outer membrane in gram- negative Bacteria. What is the chemical composition of the outer membrane?
What cell wall polysaccharide common in Bacteria is absent from Archaea? What is unusual about S- layers compared to other cell walls of prokaryotes? What types of cell walls are found in Archaea?
What function(s) do polysaccharide layers outside the cell wall have in prokaryotes?
What types of cytoplasmic inclusions are formed by prokaryotes? How does an inclusion of poly-ß-hydroxybutyric acid differ from a magnetosome in composition and metabolic role?
What is the function of gas vesicles? How are these structures made such that they can remain gas tight?
In a few sentences, indicate how the bacterial endospore differs from the vegetative cell in structure, chemical composition, and ability to resist extreme environmental conditions.
Define the following terms: mature endospore, vegetative cell, and germination.
Describe the structure and function of a bacterial flagellum. What is the energy source for the flagellum? How do the flagella of Bacteria differ from those of Archaea in both size and composition?
Contrast the mechanism for motility in Flavobacterium from that in Escherichia coli.
What is the function of staining in light microscopy? What is the advantage of phase- contrast microscopy over bright- field microscopy? What is the advantage of DIC microscopy over bright- field
In a few sentences, explain how a motile bacterium is able to sense the direction of an attractant and move toward it.
In the experiment described in Figure, what is the control and why is it essential?
List at least three features of eukaryotic cells that clearly differentiate them from prokaryotic cells. What are histones and what do they do?
How are the mitochondrion and the hydrogenosome similar structurally? How do they differ? How do they differ metabolically?
What major physiological processes occur in the chloroplast?
What evidence exists that supports the idea that the major organelles of eukaryotes were once Bacteria.
What are the functions of the following eukaryotic cell structures: endoplasmic reticulum, Golgi complex, and lysosomes?
What is the major advantage of electron microscopes over light microscopes? What type of electron microscope would be used to view the three- dimensional features of a cell?
How large can a prokaryote be? How small? Why is it that we likely know the lower limit more accurately than the upper limit? What are the dimensions of the rod- shaped bacterium Escherichia coli?
Describe in a single sentence the structure of a unit membrane.
Describe the major structural differences between membranes of Bacteria and Archaea.
Cells of Escherichia coli take up lactose via lac permease, glucose via the phosphotransferase system, and maltose via an ABC- type transporter. For each of these sugars describe: (1) the components
Calculate the surface-to-volume ratio of a spherical cell 15 mm in diameter and of a cell 2 mm in diameter. What are the consequences of these differences in surface-to-volume ratio for cell function?
Assume you are given two cultures, one of a species of gram-negative Bacteria and one of a species of Archaea. Discuss at least four different ways you could tell which culture was which.
Calculate the amount of time it would take a cell of Escherichia coli (1 x 2 mm) swimming at maximum speed (60 cell lengths per second) to travel all the way up a 3-cm-long capillary tube containing
Assume you are given two cultures of rod-shaped bacteria, one gram-positive and the other gram-negative. How could you differentiate them using(a) Light microscopy;(b) Electron microscopy;(c)
Why are amino acids so named? Write a general structure for an amino acid. What is the importance of the R group to final protein structure? Why does the amino acid cysteine have special significance
What are aminoacyl-tRNA synthetases and what types of reactions do they carry out? How does a synthetase recognize its correct substrates?
Define the types of protein structure: primary, secondary, tertiary, and quaternary. Which of these structures are altered by denaturation?
Genes were discovered before their chemical nature was known. First, define a gene without mentioning its chemical nature. Then name the chemicals that compose a gene.
DNA molecules that are AT-rich separate into two strands more easily when the temperature rises than do DNA molecules that are GC-rich. Explain this based on the properties of AT and GC base pairing.
What are R plasmids and why are they of medical concern?
With reference to DNA, what is meant by the terms semiconservative, complementary, and antiparallel?
A structure commonly seen in circular DNA during replication is the theta structure. Draw a diagram of the replication process and show how a theta structure could arise.
Why are errors in DNA replication so rare? What enzymatic activity, in addition to polymerization, is associated with DNA polymerase III and how does it reduce errors?
The genome of the bacterium Neisseria gonorrhoeae consists of one double- stranded DNA molecule that contains 2220 kilobase pairs. Calculate the length of this DNA molecule in centimeters. If 85% of
Compare and contrast the activity of DNA and RNA polymerases. What is the function of each? What are the substrates of each? What is the main difference in the behavior of the two polymerases?
What would be the result (in terms of protein synthesis) if RNA polymerase initiated transcription one base upstream of its normal starting point? Why? What would be the result (in terms of protein
In Chapter 10 we will learn about mutations, inheritable changes in the sequence of nucleotides in the genome. By inspecting Table, discuss how the genetic code has evolved to help minimize the
Describe the key molecular processes that occur when a cell grows and divides.
Examine the graph describing the relationship between growth rate and temperature. Give an explanation, in biochemical terms, of why the optimum temperature for an organism is usually closer to its
Describe a habitat where you would find a psychrophile, and one where you would find a hyperthermophile. How can these organisms survive under such harsh conditions?
Concerning the pH of the environment and of the cell, in what ways are acidophiles and alkaliphiles different? In what ways are they similar?
Contrast an aerotolerant and an obligate anaerobe in terms of sensitivity to O2 and ability to grow in the presence of O2. How does an aerotolerant anaerobe differ from a microaerophile?
Compare and contrast the enzymes catalase, superoxide dismutase, and superoxide reductase as regards their substrates and products.
Contrast the terms thermal death time and decimal reduction time. How would the presence of bacterial endospores affect either value?
Describe the principle of the autoclave. How does it differ from simple boiling? Microbial culture media does not boil in the autoclave; why not?
Describe the role of proteins present at the divisome. Does the FtsZ ring form before or after chromosome replication?
Describe the procedure for obtaining the minimum inhibitory concentration (MIC) for a chemical that is bacteriocidal for Escherichia coli.
Contrast the action of disinfectants and antiseptics. Disinfectants are not used on living tissue; why not?
How do cells of Escherichia coli that carry a mutation in mreB ( the gene encoding the protein MreB) look different microscopically from wild- type ( unmutated) cells? What is the reason for this?
Describe how new peptidoglycan subunits are inserted into the growing cell wall. How does the antibiotic penicillin kill bacterial cells, and why does it kill only growing cells?
What is the difference between the specific growth rate (k) of an organism and its generation time (g)?
Describe the growth cycle of a population of bacterial cells from the time this population is first inoculated into fresh medium.
How does a chemostat regulate growth rate and cell numbers independently?
How can turbidity be used as a measure of cell numbers?
Calculate g and k in a growth experiment in which a medium was inoculated with 5 x 106 cells/ ml of Escherichia coli cells and, following a 1-h lag, grew exponentially for 5 h, after which the
Escherichia coli but not Pyrolobus fumarii will grow at 40° C, while P. fumarii but not E. coli will grow at 110° C. What is happening (or not happening) to prevent growth of each organism at the
Why do dideoxynucleotides function as chain terminators?
Why is investigation of the metabolome lagging behind that of the proteome?
What are the objectives of systems biology?
Most of the genetic information on our planet does not belong to cellular organisms. Discuss.
What is the major difference in how duplications have contributed to the evolution of prokaryotic versus eukaryotic genomes?
Explain how horizontally transferred genes can be detected in a genome.
Explain how transposable elements promote the genome evolution of Bacteria.
Explain how chromosomal islands might move between different bacterial hosts.
What are pathogenicity islands and why are they important?
What characteristics are used to identify open reading frames using sequence data?
What is the relationship between genome size and open reading frame content of prokaryotic genomes?
Which genomes are larger, those of chloroplasts or those of mitochondria? Describe one unusual feature each for the chloroplast and mitochondrial genomes.
How does your genome compare with that of yeast in overall size and gene number?
Distinguish between the terms genome, proteome, and transcriptome.
What does a 2D protein gel show? How can the results of such a gel be correlated with protein function?
Apart from genome size, what factors make complete assembly of a eukaryotic genome more difficult than assembly of a prokaryotic genome?
Describe how one might determine which proteins in Escherichia coli are repressed when a culture is shifted from a minimal medium (containing only a single carbon source) to a rich medium containing
The gene encoding the beta subunit of RNA polymerase from Escherichia coli is said to be orthologous to the rpoB gene of Bacillus subtilis. What does that mean about the relationship between the two
Describe the proteins produced when cells of Escherichia coli experience a heat shock. Of what value are they to the cell?
Explain how alternative sigma factors control sporulation in Bacillus.
How does regulation by sRNA differ from that of riboswitches?
Describe how transcriptional attenuation works. What is actually being “attenuated”?
Contrast regulation of DAHP synthase and glutamine synthetase.
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