PBL 2 Flashcards
What are the different shapes of bacteria?
Spherical - cocci
Cylindrical - bacilli or rods
Helical - spirochaetes
What does the arrangement of bacteria depend on?
The plane of successive cell divisions
What are examples of bacteria arrangements?
Chains, Clusters, pairs, angled pairs or palisades
What does gram stain divide bacteria into?
Gram positive and gram negative
In which type of bacteria does the peptidoglycan form a thick layer external to the cell membrane?
Gram-positive bacteria
In which type of bacteria does the peptidoglycan form a thin layer with an overlying outer membrane?
Gram-negative bacteria
What are the principal molecules of the outer membrane?
Lipopolysaccharides and lipoproteins
What causes the peptidoglycan to be highly polar?
The polysaccharides and the charged amino acids
What is a function of the highly polar peptidoglycan membrane?
to form a thick hydrophilic surface
What does the property of hydrophilia allow?
It allows gram - positive organisms to resist the bile in the gut
Are gram negative bacteria hydrophilic or hydrophobic?
The outer membrane is hydrophilic but the lipid components give hydrophobic properties as well
what are the three main types of bacteria?
Bacillus (rod), Coccus (sphere), and spirallus (spiral)
What are pili?
Another form of bacterial surface protection. pili are more rigid than flagella`
What is the function of pilli?
Attachment either to other bacteria (sex pili) orto host cells (common pili)
What does bacterial growth rate depend on?
The environment they are in
What is the lag phase?
The initial period of adjustment
What is the log/exponential phase?
The period where the population doubles at a constant rate (generation time)
What is the death phase?
As nutrients are depleted and toxic products accumulate cell growth slows to a stop and cells eventually begin to die
What is the structure of the bacterial genome?
Circular
What is the origin of replication (OriC)?
The singular point on the circular bacterial genome where replication begins
Which enzymes are used to unwind and separate the two DNA strands?
helicases and topoisomerases
What do the separated DNA strands serve as?
Templates for DNA polymerase
What do the two copies of the genome consist of?
One parent strand and one daughter strand
What does the process of cell division involve?
- segregation of replicated genomes
- formation of a septum in the middle of the cell
- separation of the two cells
How is the septum formed?
An invagination of the cytoplasmic membrane and ingrowth of the cell wall
What is quorum sensing?
The mechanism by which specific gene transcription is activated in response to bacterial concentration.
What happens when quorum sensing bacteria reach appropriate numbers?
The signalling compounds they produce are at a sufficient concentration to activate the transcription of specific genes
What are endospores?
Highly resistant spores within bacterial cells
What are the functions of endospores?
To enable the bacteria to survive adverse conditions
When are endospores formed?
When the cells are unable to grow e.g. when the environment changes or when nutrients are exhausted but never by actively growing cells.
What is the structure of the bacterial spore?
A complex multi-layered coat surrounding a new bacterial cell
What gives the bacteria their extreme resistance to heat and chemicals?
The presence of Dipicolinic acid and high calcium content
How long do endospores remain dormant?
many years
When do endospores return to a normal bacterial state?
When the conditions improve a new bacterial cell emerges and resumes normal life
Why are viruses not considered to be alive?
They require a host cell to reproduce
How much smaller than bacteria are viruses roughly?
10x
What does the general structure of viruses include?
Nucleic acid, protein subunits, cell membrane and a vural envelope
What is most viral genetic material made of?
RNA but some do have DNA
What genetic material do retroviruses have?
Genetic material that swaps between RNA and DNA
What is the virus envelope?
A liquid bilayer that surrounds the virus.
What does the virus envelope contain?
virus proteins that are important for infecting other cells
How is the virus envelope formed?
When the virus buds from the surface of cells they acquire this extra layer.
What extra enzyme do viruses with RNA have?
They always have their own replicase as humans dont have enzymes to replicate RNA
What do viruses need in order to replicate?
A host cell to make copies of its genetic material and the proteins and enzymes it requires to replicate
What is the cellular process that all viral cells require?
Protein translation on the ribosomes
Where does replication of DNA/RNA take place?
In most cases the nucleus but for some viruses in the cytoplasm
What is the final stage of viral replication?
the assembly and release of the new virus
Where is the nucleocapsid formed?
Either the nucleus or cytoplasm of the host cell
How are viruses released?
- Budding through the cell membrane
- Cell lysis
- Cell death
What is cell lysis?
When a cell bursts
Why do viruses with RNA have a lot of mutations?
RNA polymerase makes a lot of mistakes
What is a lytic infection?
When the virus causes the host cells to burst when the virus replicates
What is a persistent infection?
When the virus is released slowly and consistently by the cell.
In these infections people can be symptomless for a long time but still carry and spread the virus
What is a latent infection?
The virus’ genetic material may be dormant in the host cells cytoplasm or even incorporated in its genome until it is triggered
What is malignant transformation?
When viruses cause ‘normal’ host cells to turn into tumour or cancer cells
Do cancer inducing viruses have DNA or RNA?
They can have either DNA or RNA
What is Hepatitis A?
A virus that can impair liver function. It is most common in countries with poor sanitation
How can Hep A be prevented?
Travellers are advised to be vaccinated. Generally the illness doesn’t present severe symptoms
What is Cholera?
Caused by a bacteria that leads to an acute gastrointestinal infection.
It is spread through un-sanitary water and food due to poor sanitation
How can Cholera be prevented?
Travellers are advised to be vaccinated as cholera can be very severe and sometimes even be fatal
What is Typhoid?
Can be caused by some strains of salmonella and is prevalent in india,S/SE Asia, some parts of Africa and Central America
How can typhoid be prevented?
Travellers should be vaccinated
What is Shigellosis?
Caused by a bacteria this causes symptoms like nausea,diarrheoa and abdominal cramps.
This is mostly in countries with poor sanitation but has been know to occur in the UK
How can illnesses that are caused by poor sanitation be avoided?
- Using bottled water
- Don’t have ice in your drink
- Only eat salad/fruit if you prepared it yourself
- Avoid eating unpasteurised dairy products
What is Zika virus?
An infection transmitted by an infected female mosquito. It is common in Brazil and other American countries.
The symptoms are not severe unless pregnant, it can then have a severe effect on the baby
What is Malaria?
Transmitted through the bite of a parasite. Mainly found in Africa, some parts of Asia and South America. The effects of malaria are more severe in pregnant women, children, and the elderly
How can Malaria be prevented?
Anti-malarial medication should be taken
What is Dengue fever?
Caused by a viral infection that is spread by mosquitos. It is mainly found in S/SE Asia, Africa and the Carribean. It causes flu-like symptoms.
How can mosquito transmitted illnesses be prevented?
- Stay indoors between dusk and dawn
- Use products containing DEET as a repellent
- Wear loose fitting clothes
- sleep under a net
- try not to go to highly infested areas
What are neutrophils?
The most common WBC, they make up 50-60% of WBCs
What is the function of neutrophils?
They phagocytose pathogens and infected cells and play a big part in inflammation
What is the function of Lymphocytes?
Lymphocytes are divided into T&B lymphocytes. They produce antibodies which play a big part in the bodies defence against infection. They can also recognise antigens and destroy them
What are monocytes?
When the monocytes are in tissue they are known as macrophages.
They are formed in the bone marrow and then are released into the blood and tissue
What is the function of monocytes?
Phagocytose pathogens
What are eosinophils?
They are usually found in tissue.
What is the function of eosinophils?
Combat parasitic infection and to phagocytose antibody-antigen complexes
