Microbiology – Fall 2018 – Salcedo
Possible Essay Prompts for Lecture 2 Exam
1. What part of aerobic respiration produces the most ATP? Describe how this process works in
eukaryotes and prokaryotes including where the entering molecules came from, the cellular
location and how the ATP is produced.
The part of aerobic respiration that produces the most ATP is Oxidative Phosphorylation:
electron transport and chemiosmosis. This process makes about 32- 34 ATP which is much
higher than Glycolysis or Tricarboxylic Acid cycle which only make 2 ATP. In eukaryotes, it
occurs in the matrix of the mitochondria and in prokaryotes, it occurs in the cytoplasm where
ETS proteins are located in the cell membrane and protons (H+) are pumped into the periplasmic
space. ATP formation is based on the production of a proton (H+) gradient across a membrane
during electron transport. Movement of the protons across an ATP Synthase causes the formation
of ATP.
2. Compare and contrast the processes of DNA replication in the cell versus in a Polymerase
Chain Reaction (PCR). (You should be able to find several similarities and several differences)
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In PCR, the DNA to be replicated is separated by heat denaturation.
DNA is separated by an ATP-dependent helicase.
DNA primases produce RNA primers in a sequence-independent
manner on exposed single-stranded DNA. 5'->3' exonuclease activity to
degrade RNA primers is therefore unnecessary for PCR.
DNA replication forks do not occur in PCR.
PCR Amplifies DNA (makes copies of the DNA)
in PCR good primer design allows the isolation and amplification of a
particular gene out of the entire genome.
With PCR you only get copies of DNA that are specified between thr
primers, and nothing else
3. Bacteria like E. coli encode certain types of proteins known as receptors that sense nutrients
and allow the bacteria to find food sources. Trace the creation of a protein starting with the
gene in the genome and ending with the protein. (Include enzymes and molecules involved in
the processes)
The creation of a protein starts with
DNA  RNA
mRNA synthesis
RNA strand is then produced by a template of DNA
RNA Polymerase then binds to the DNA at the promoter region and starts transcription, ending
at the termination sequence
RNA  Protein
Protein synthesis
Information contained in the RNA starts the process of decoding mRNA to protein
tRNA reads the codons starting at AUG (methionine acif)
ends at the stop codons (UGA, UAA, UAG)
4. Why are prokaryotes able to react to their environment by producing proteins much more
quickly than eukaryotes? (This should be a complete analysis including multiple differences
between prokaryotic and eukaryotic transcription and translation).
Prokaryotes are able to react to their environment by producing proteins much more quickly than
eukaryotes because they are capable of doing both translation and transcription simultaneously in
the cytoplasm. By doing both of these processes at the same time it greatly increases the protein
production compared to that in eukaryotes.
5. How would you create a genetically-modified corn plant that expresses the human fibrin
protein? (You need to include all techniques, steps, enzymes, etc.)
I would create a genetically-modified corn plant that expresses the human fibrin protein by using
biotechnology. Recombinant DNA Technology is the process of transferring DNA from one
organism to that of a different organism. So with this I would create the transgenic plant of
interest by using agrobacterium to easily transform the plant cells with a large TI plasmid and
inserting the human fibrin protein.
6. If you were a lab technician hired by the Maury Povich Show for an episode on paternity
testing, how could you determine which of 4 possible men was a baby’s biological father?
(Include the theory and techniques involved in the identification).
I would use the process of DNA fingerprinting (DNA profiling) which relies on humans
having differences in their introns. Introns are non-coding regions of DNA that show us
random mutations that occur in the genome that are successfully passed through
generations. These differences in the introns allow us to screen for polymorphisms, which
are differences between human intron DNA sequences. After acquiring the 4 DNA
samples I would then cut their introns with the same restriction endonuclease and use the
process of electrophoresis, which uses charged particles in a fluid or gel under the
influence of an electric field. This process separates the hemoglobin into different bands,
which then we can use to compare the bands to that of the child and whoever’s matches
up will be the father.
7. Imagine that you are planning to treat a patient with the antibiotic Kanamycin for her
Staphylococcus aureus infection. Explain how you would determine both: A) the Minimum
Inhibitory Concentration of Kanamycin for this infection and, B) the Therapeutic Index of
Kanamycin. Include an explanation of why this information is important.
I would determine the minimum inhibitory concentration of Kanamycin for this infection by
having several tubes of growth media with Staphylococcus aureus and adding different doses of
Kanamycin. By doing this I can then see which appropriate dosage will successfully kill off the
infection, making it microbicidal and not microbistatic. The key is to find the lowest dosage of
the antibiotic possible that successfully kills the pathogen. I would then compare it to the
Therapeutic Index by comparing the drug’s toxicity to humans to its effectiveness against the
pathogen. TI= Toxic Dose / MIC. So for example, if the toxic dose to humans is 10 ug/ml and
the MIC is 2 ug/ml then the TI would be 5 ug/ml. The closer the MIC is to the toxic dose the less
safe it is for humans, you always want to go with the drug that has a lower MIC. And a higher TI
means that it is safer for the patient.
8. Analyze the rise of antibiotic-resistant infections including how bacteria become resistant, how
someone gets an antibiotic-resistant superinfection and how our society encourages the
development of antibiotic resistances.
The rise of antibiotic-resistant infections happens because of either the bacteria exhibiting
random mutations or acquiring drug resistance genes from other bacteria. Mechanisms involved
are drug inactivation, block drug entry, drug pumps, altering the drug’s binding site and using
alternative metabolic pathways. Our society encourages the development of antibiotic resistance
due to doctors giving their patients antibiotics even when not needed, so that when it actually is
needed, the bacteria in the body have already acquired genes from others in order to be resistant.
Another issue is the immense usage of antibiotics in our livestock, which we eat, making our
bodies more resistant as well. Bacteria are always finding new ways to survive, so when we
constantly consume things that are the same, the bacteria in our bodies have time to change and
evolve around the antibiotics, creating them useless.