Exam 1 Review Flashcards
List and explain how a t4 bacteriophage infects a host cell.
- First the tail fibers of the phage attach to the LPS on the outmembrane of gram negative bacteria.
- Next the phage penetrates the cell and nucleic acid is injected.
- Next nucleic acids and proteins are synthesized.
- Then, new virus particles are assembled and packaged. Lastly, the cell is lysed and mature virions are released from the host cell.
Explain the difference between the lytic pathway and the lysogenic pathway in a virion.
Lytic- lytic infection is very fast and almost immediately stops host DNA synthesis. The process results in cell death.
Lysogenic- The virus enters the cell and incorporates viral dna into the host genome. The synthesis of mRNA for the late proteins of the lytic cycle is repressed until the cell enters a stressful environment. Thus lysogeny does not kill the cell and the viral genome replicates with the host genome.
Contrast the main differences between animal viruses and bacteriophages
Animal viruses- whole virion enters host cell. Virion often has an envelope. Virus is replicated in the nucleus.
Bacteriophages- just nucleic acid enters cell. Most are naked (no envelope). Virus replicates in cytoplasm
Compare and contrast prokaryotic and eukaryotic cells
Prokaryotes:
Smaller, no organelles, dna in cytoplasm (nucleoid form),most have cell walls, most circular DNA, haploid, coupling of transcription and translation, polycistronic
Eukaryotes:
Larger, membrane bound organelles, nucleus, linear DNA , diploid, energy centers ( mitochondria/ chloroplasts),
What color do gram positive cells stain? What color do gram negative cells stain? Explain why. Include diagrams.
a. Gram positive- purple bc of thick peptidoglycan layer
b. Gram negative – pink because they have thin layer of peptidoglycan
- Why are bacteria cells small? And how has it helped them evolve.
Large surface to volume ratio, faster nutrient exchange , divides faster leading to more mutations which means faster adaptation thus it can evolve quicker
What is the distinction between oxidative and substrate-level phosphorylation in ATP formation?
Oxidative phosphorylation is the result of the proton motive force and ATP synthase interaction to produce ATP. Substrate-level phosphorylation involves the transfer of phosphate from high-energy intermediates to ADP to form ATP. The main difference is the efficiency of ATP production between the two methods, with oxidative phosphorylation being more efficient.
Explain how the proton motive force results in an electrochemical gradient. Why is it both electrical and chemical?
The proton motive force results in a chemical gradient due to a H+ ion gradient on the outside of the cell membrane. The electrical gradient refers to the net accumulation of positive charges (H+) on the outside and negative charges (-OH) on the inside of the cell membrane.
- Explain how NADH/NAD+ are utilized in glycolysis and fermentation.
In the first redox reaction in glycolysis, glyceraldehyde 3 phosphate (three carbon intermediates) is oxidized and the electron go to NAD+, (NAD+ get reduced=NADH)
NAD+ is recycled when pyruvate is reduced by NADH.
Describe how Koch was able to identify the pathogen responsible for causing disease and provide two reasons why it is difficult to use Koch’s postulate for diseases today.
- Identify pathogen in all diseased organisms
- Grow pathogen in a pure culture
- Inoculate healthy host and it must get sick
- Isolate disease causing pathogen again
- Human models are not available because the pathogen that causes a disease in humans does not always cause the disease in animals, asymptomatic host, can’t culture many pathogens, multiple pathogens that cause the disease
List 5 examples of why microorganisms are essential to our world
- Agriculture - reduces dependence and over use of fertilizers because they recycle nutrients
- Medicinal applications – maintain sterile conditions, grow pathogen in culture and test antibiotics
- Digestion in humans and ruminant animals
- Recycles nutrients in the sediment of ponds and lakes
- Recycles organic material to make natural gas
- Bioremediation – used to clean up spilled solvents or oil
- Production of alcohol, cheese, bread
- EBPR
- Wastewater and drinking water
- Thanks for the oxygen
How did Pasteur defeat the notion of spontaneous generation.
The idea that something came from nothing.
Heated the mixture of media.
Developed swan neck flask to trap microbes and particulates in neck.
If the flask wasn’t tipped nothing grew.
Tipped the flask so the media touched the microbes in the neck, and it turned cloudy
Describe and provide an example of negative control, positive control, and global control.
Negative control prevents transcription via repressors and inducers. Ex: arg or lac operon.
Positive control promotes transcription when an activator protein binds RNA polymerase to DNA. Ex: maltose operon
Global control responds to environmental signals by regulating many genes. Ex: lac and maltose operon
How does a riboswitch affect translation?
By binding to a metabolite that disrupts the normal folding of the mRNA, the shine-dalgamo sequence becomes unavailable to the ribosome. This inhibits translation.
What are antisense RNA’s and how do they affect gene regulation?
They are small sequences of RNA that bind to mRNA compliments to form dsRNAs that cannot be translated. The dsRNA’s are then targeted for degradation.
Why and how does supercoiling occur? Draw a simple sketch along with your explanation.
Supercoiling happens in order to fit the large amount of DNA material into a small prokaryotic cell. Class II topoisomerases (DNA gyrase) make double-stranded breaks, passes the double helix through the break, and reseal the break.
