PM1A hard to learn Flashcards
Bacterial cells have inclusion bodies. Examples of inclusion bodies are volutin granules and gas vacuoles. explain what those are
Volutin granules- store polymerised inorganic phopshates which can be used in metabolism and assist in formation of biofilms
Gas vacuoles- accumulations of small, protein-lined vesicles of gas that allow the bacteria to alter their buoyancy in water.
BACTERIA TOPIC:
FLAGELLA MOVEMENT:
What is the difference between taxis and chemotaxis?
Taxis- is a motile response to an environment stimulus.
Chemotaxis- is a response to a chemical gradient of attractant or repellent molecules in the bacterium’s environment.
In an environment that lacks a gradient of attractant or repellent, the bacterium will move randomly, the bacterium keeps searching for a gradient.
In an environment that has a gradient of attractant or repellent, the net movement of bacterium is towards the attractant and away from the repellent.
BACTERIA TOPIC :
Describe chemotaxis of bacterium with peritrichous flagella
Chemotaxis is regulated by chemoreceptors in the membrane of the bacterium- these bind chemical attractants or repellents.
This triggers either a clockwise or anticlockwise rotation of the flagellum.
Increasing conc of attractant or decreasing conc of repellent (both conditons beneficial) causes less tumbling and longer runs.
Decreasing conc of attractant or increasing conc of repellent (both conditions harmful) causes normal tumbling and a greater chance of reorienting in a better direction.
As a result the organisms net movement is toward the optimum environment.
VIRUSES TOPIC:
Describe where in the cell DNA viruses and RNA viruses replicate in eukaryotic cells.
Where in the cell do bacteriophages (viruses that infect bacteria) replicate in bacteria?
In eukaryotic cells, most DNA viruses can replicate inside the nucleus, with an exception observed in the large DNA viruses, such as the poxviruses, that replicate in the cytoplasm
RNA viruses that infect animal cells often replicate in the cytoplasm.
Bacteriophages replicate ONLY in the cytoplasm of bacteria, since prokaryotic cells do not have a nucleus.
VIRUSES TOPIC:
What is the mode of mRNA production for a single stranded RNA (+) virus?
What is the mode of mRNA production for a single stranded RNA (-) virus?
What is the mode of mRNA production for a single stranded RNA virus with reverse transcriptase?
RNA (+) virus: genome functions as mRNA.
RNA(-) virus: mRNA is transcribed from the RNA genome.
RNA with reverse transcriptase:
reverse transcriptase makes DNA from RNA genome, DNA is then incorporated in the host genome, mRNA is transcribed from the incorporated DNA.
VIRUSES TOPIC:
Describe the budding of influenza virus (process)
- Influenza virus becomes attached to a target epithelial cell.
- The cell engulfs the virus by endocytosis.
- Viral contents are released. Viral RNA enters the nucleus where it is replicated by the viral RNA polymerase.
- Viral mRNA is used to make viral proteins.
- New viral particles are made and released into the extracellular fluid.
- The cell which is not killed in the process continues to make new virus.
BACTERIAL GROWTH TOPIC:
Describe when batch culture and continuous culture is used in industry
What is the name for the process of maintaining microbial cells in the log or exponential phase?
batch culture is used for the purification of secondary metabolites (antibiotics, pigments) derived from primary metabolites, not involved in growth and are produced in the stationary phase.
Continuous culture is used to extract primary metabolites (amino acids, organic acids) from bacteria.
Primary metabolites are produced at the highest rate when the microorganisms are in the log exponential phase of growth.
In continuous culture, the growth rate of microbials is maintained in the exponential phase, the cells could not reach the stationary phase of growth.
This is because there will be no nutrient depletion as nutrients are continuously supplied into the reservoir.
steady-state phase of growth is the name for process of maintaining microbial cells in the log or exponential phase of growth
BACTERIAL GROWTH TOPIC:
compare batch and continuous culture.
In batch nutrients are added at the start whereas in culture nutrients are continuously added.
In batch product removed when fermentation stops, whereas in continuous, product continuously removed.
Batch: growth rates and product formation slower because of limiting factors e.g. substrate levels, build up of toxins. slower growth rates= larger vessels used.
Continuous: microbial cells held in exponential growth phase giving higher productivity and can be on a smaller scale.
Batch: easy to set up and maintain whereas in continuous can be difficult to maintain microbial cells in exponential phase.
Batch: if contamination occurs only one batch is wasted whereas in continuous huge volume of product/organism wasted.
Batch: less efficient, more time wasted as shutting down, removing product and starting up again, whereas continuous culture is more efficient as continuous.
Batch: product quality can vary between batches, whereas in continuous product quality more consistent.
BACTERIAL DISEASE TOPIC
Describe the THREE stages of the mycobacterial infection tuberculosis (10 marks)
Primary infection – TB bacteria first enter body (1 mk) only a few people become sick immediately after tuberculosis bacteria enter their body (1 mk).
In most cases, TB bacteria that enter the lungs are immediately killed by the body’s defenses (1 mk)
Latent (inactive infection)-
Bacteria that survive are engulfed by white blood cells called macrophages (1 mk)
The engulfed bacteria can remain alive inside these cells in a dormant state for many years (1 mk)
The body walls off the bacteria inside a collection of cells, which form tiny scars (1 mk)
The dormant bacteria do not multiply or cause symptoms- in most cases, these bacteria remain dormant and never cause any further problems (1 mk)
The infection is not contagious during latent infection (1 mk)
Active disease - In a small percentage of infected people, the dormant tuberculosis bacteria eventually start to multiply and cause active disease/reactivate (1 mk)
At this stage, infected people actually become sick and can spread the disease (1 mk)
BACTERIAL GROWTH TOPIC
Describe what turbidity is in the indirect methods of measuring cell number
Indirect detection of CELL DENSITY.
The turbidity (cloudiness) of a sample of bacteria in a LIQUID suspension is measured using a spectrophotometer.
The spectrophotometer transmits a light beam through the bacterial suspension and this light is measured by a detector to give an absorbance value.
As no of bacteria in suspension increases, turbidity also increases and causes less light to reach detector.
The decrease in light passing through the sample is associated with a decrease in percent transmission and an increase in absorbance measured by the spectrophotometer.
BACTERIA TOPIC:
what is the difference between nucleoid and plasmids?
Nucleoid: bacterial chromosomes are circular, haploid (unpaired) and not bound by nuclear membrane.
Conc with dna and dna associated proteins
DNA interfere with nucleoid associated proteins
(NAPs) which assist in the organisation and packaging of chromosomes.
Plasmids: extra chromosomal dna not found in chromosomes is found in plasmids.
DNA is shorter, circular, double stranded.
Bacteria are not the only one which have plasmids, archaea and eukaryotes do.
REPLICATION AND TRANSCRIPTION TOPIC:
Outline the basics steps on DNA replication
Initiation:
1.Enzyme helicase unwinds double helix and exposes the comp strands.
2. Primase puts down a short piece of RNA called a primer.
Primer: is an existing group of RNA nucleotides with a 3’-OH to which a new nucleotide can be added, usually 10-12 nucleotides long. Provides a starting point for DNA synthesis.
Elongation:
3. DNA polymerase reads (3’-5’) along each single strand and adds comp nucleotides.
4. Each nucleotide strand serves as a template for building a new comp strand.
5. The RNA primers present on the newly formed strand need to be replaced by DNA.
6. After primer removal is completed, the lagging strand still contains gaps (between the okazaki fragments).
7. Ligase enzyme identifies and seals these gaps by creating phosphodiester bond between the 5’ phosphate and 3’ OH groups of adjacent regions.
Termination:
8. Replication stops at a specific termination site which is made up of a unique nucleotide sequence.
9. This sequence is identified by specialised proteins called tus, which bind onto these sites, blocking the path of helicase.
REPLICATION AND TRANSCRIPTION TOPIC:
Describe the process of transcription, its machinery and end products.
- Template recognition:
Recognises the promoters
RNA polymerase binds to DNA
DNA unwinds - Initiation
- Elongation:
RNA polymerase moves ( 3’-5’) and synthesises RNA (5’-3’), unwound region moves. - Termination:
RNA polymerase reaches the end and transcription stops by releasing RNA polymerase and RNA.
DNA duplex REOFRMS
End product is a single stranded RNA molecule.
