6A Flashcards
What is DNA virus
Have DNA as their genetic material
Lambda phage
What is RNA virus
Viruses that have RNA as the genetic material
TMV and Ebola
RNA retrovirus
RNA that produces DNA
- reverse transcriptase catalyse the production of viral DNA from single strand of RNA
The new viral DNA is incorporated into the host DNA where it acts as a template to produce viral protein and RNA
Process of lysogenic step 1
Bacteriophage attaches to bacterium
Process of lysogenic step 2
Phage DNA is injected into host cell. It brings about the synthesis of viral enzyme
Process of lysogenic step 3a
Viral DNA is incorporated into host cell DNA
Process of lysogenic step 3a2
Viral DNA is replicated each time the bacterium divides without causing any damage
Process of lysogenic step 2 to 3B
Phage DNA inactivated the host DNA and takes over the cell biochemistry
Lag phase
Population increase slowly as the population adjust to the new environment and starts to reproduce
Log phase
Lots of nutrients and space - exponential growth of the population double each divisions
Stationary phase
Population reaches it maximum as it is limited by its environment
Eg. Lack of resources and toxic waste product
During this phase the no. Of microorganisms dying equals the number being produced by binary fission and the growth curve level off
Death phase
Lack of nutrients and build up of toxic waste , death rate exceed rate of reproduction- population decline
Death rate increases:
Nutrients insufficient for growth
Accumulating waste —> lower pH —> bacteria can’t grow
How are tuberculosis spread
By droplets infection airborne
Why is it difficult to control TB by vaccination
Increased in elderly people: less effective immune system
HIV:increase TB
Increased poverty:overcrowding
Wars and political unrest : densely populated
Mobile population: tourism , global trade and refugees
Where does the TB initially infect
Affects the respiratory system, damaging and destroying lung tissue
It suppresses the immune system making the body less able to fight the disease
Symptoms of TB
Fever
Fatigue
Coughing
Lung inflammation
May spread to other parts of the body which can cause organ failure
What happens in primary infection
Bacteria is inhaled into the lungs and slowly multiply causing no symptoms
If the immune system is fully active it will cause a localised inflammatory response , engulfing the bacteria and for making a mass of tissue called tubercule
After a while the inflammation would fully disappear and lungs heal
What happens in the active stage
Some bacteria is able to survive past the primary infection stage as they have an thick waxy outer layer which protects them from enzyme of the macrophages
—>which allows them to do so allowing them to remain dormant and reproduce until the immune system is weak the will cause active tuberculosis
Active stage continued step 1
Active TB result in deactivation of old or controlled infections
The bacteria reproduce rapidly causing rather noticeable symptoms
—> night sweat
Loss of appetite and weight loss
Active stage continued step 2
Patient will start to cough out liquid produced by the lungs called septum
If the infection gets more severe the lungs is damaged heavily the patient will start to cough blood
Active stage continued step 3
Alveoli start to breakdown and produce large inefficient air sacs
The bacteria also attacks T cell to stop production of antibodies
Although the body raise its temperature to kill bacteria
The bacteria can survive up until 42c and the metabolic enzyme start to denature at 40c
Eventually the patient dies due to organ failure no respiration or due to invasion by opportunistic disease
What microorganisms provides to grow
Nutrients —> glucose/amino acids
=respiration —> energy
Oxygen —> respiration
*anaerobic microorganisms would require the absence of oxygen
Optimum pH - enzyme reaction
Optimum temperature- enzyme reaction
Why microorganisms should be cultured with great care
- always risk that a mutation could lead to the formation of pathogenic strains
-pathogenic bacteria from the environment could contaminate the bacterial culture being investigated
State the hazard and precautions of this practical
Naked flame: keep away from flammable material
Bacteria is biohazard use disinfectant and wash hands, dispose of bacteria safely
Disinfectant is flammable keep away from naked flame
Why should the lid not be completely taped to the Petri dish
To allow oxygen to enter the Petri dish preventing the growth of harmful anaerobic bacteria
Why is the Petri dish incubated upside down
To prevent condensation from forming on the lid and dripping down onto the agar
Aseptic technique
Buying sterile equipment or sterilizing reusable equipment with a Bunsen burner flame and ethanol
Cleaning surface before and after with ethanol
Using Bunsen burner or other flame to heat the air causing it to rise and carry away airborne microorganisms
Stomach acid
If you eat or drink something that contains pathogens
—> killed by stomach acid due to acidic conditions of the stomach
Some may survive and pass into the intestines where they can invade cells of the gut wall and cause disease
How can the Skin prevent infection
Acts as a physical barrier to pathogen
*if there is damage your skin , pathogen on the surface can enter your bloodstream
The blood clots at the area of damage to prevent pathogens from entering but some may get in before the clot form
When Gut and skin flora prevent infection
Your intestine and skin are naturally covered with harmless microorganisms
Lactic acid is also released which kills bacteria
They compete with pathogens for nutrients and space
—> limit the number of pathogen living in the gut on the skin and make it harder for them to infect the body
What can sebum protect against
An oily substance produced by the skin which contains chemical that inhibit the growth of microorganisms
*washing - using antibacterial soap can reduce your resistance to disease by destroying the natural pH balance and surface flora of the skin
What is lysozyme prevent infection
Mucosal surface produce secretion . These secretion contain an enzyme lysozyme
—> lysozyme kill bacteria by damaging their cell wall
——-> makes bacteria burst open (lyse)
Define endotoxins
Lipopolysaccharides that are integral part of the outer layer of the cell wall of gram negative bacteria and act s toxin to other cell
- effect around site of bacterial infection
—fever
— vomiting
—diarrhoea
Define exotoxins
Soluble protein produced and released into the body by the bacteria as they metabolism and reproduce in the cell of their host; these proteins act as toxin in different ways
Host tissue invasion
Pathogen is by invading host tissue and damaging the cells. The response of the host organism cell damage causes the symptoms of disease
Eukaryotic vs bacteria
Bacteria contains:
-Cytoplasm that doesn’t have membrane bound organelle
-ribosome that are smaller (70s)
-no nucleus
Capsule function
- prevent dehydration of the bacteria
-protects the bacteria as it cover the marker receptors
Function of flagellum
Long hair like structure that rotates to make the prokaryotes cell move
Function of pilli
- attachment to host cell
-for sexual reproduction ( gene transfer)
Define plasmid
Small circular piece of DNA that code for specific aspect of bacterial phenotype
Define nucleiod
The area in a bacterium containing the single circular loop of coiled DNA
What does gram positive bacteria contain
Thick layer of peptidoglycan- teichoic acid
The crystal violet complex in the gram stain is trapped in the thick peptidoglycan layer and resist de colouring when bacteria are dehydrated using alcohol
Bacteria don’t pick up the red safranin counterstain and appear purple
Gram negative bacteria
Thin layer of peptidoglycan with no teichoic acid between the two layers of membrane
Outer membrane is made up of lipopolysaccharides
This layer dissolves when the bacteria are ethanol
—> exposes the thin peptidoglycan layer and the crystal violet is washed out
The peptidoglycan takes up the red safranin counterstain - red
What does virus have
1) all viruses have capsid made out of capsomere
2) nucleiod acid of DNA or RNA and antigens known as VAPs which target proteins in the host cell surface membrane
3) envelope
Lysis step 1
The viral genetic material is transcribed and translated to produce new viral components
Lysis step 2
The component assembled into mature virus that accumulated inside the host cell
Lysis step 3
Eventually the host cell will burst which release large no. Of virus each of which can infect the new host cell - cell lysis
Retrovirus
1) viral RNA entered the host cell.
2) viral RNA is translated to viral DNA by reverse transcriptase in the cytoplasm
3)viral DNA is incorporated into the host DNA in the nucleus where it acts as a template to produce viral proteins and RNA
Method of spread vectors
Living organism that transmit from one host to another
Inhalation
When you cough sneeze or talk droplets are expelled from your respiratory tract
1) when the droplets are inhaled by another individual the pathogens enter into a new respiratory tract and another infection is established
Ingestion
Many pathogens that caus egut disease to be transmitted by faecally contaminated food or drink
Describe the sequence of symptoms that result in the death of a person infected with mycobacterium tuberculosis
1) in the beginning the person will have breathing problems
2) as the infection become worse, lung tissue becomes damaged and blood is coughed up in the sputum
3) then TB causes suppression of immune system as T cell and antibodies reduces
4) the patient will high fever
5) as the lungs becomes less capable to take in oxygen for respiration death of the patient may result
