M7 - Infectious disease Flashcards
classifying different pathogens that cause disease in plants and animals
Bacteria prokaryotic cells Have cell walls Unicellular DNA present but no nucleus Eg. c. tetani
Fungi Eukaryotic cells Have cell walls Unicellular or multicellular DNA inside of nucleus Eg. yeast, mould
Protozoa Eukaryotic cells No cell wall Unicellular Eg. malaria, giardia
Viruses
Non cellular
Protein outer case that protects internal nucleic acid (DNA or RNA)
Eg. influenza, measles, polio, rabies
Prions
Non cellular
Protein
BSE prion (Mad Cows disease)
Macroscopic parasites
Eukaryotic
Multicellular
Eg. ticks, fleas, leeches (Lyme disease), tapeworm
investigate modes of transmission of infectious diseases, including direct contact, indirect contact and vector transmission
Direct contact - Individuals physically transferring the pathogens eg. touching, kissing, sexual intercourse
Indirect contact - objects being contaminated with pathogens eg. used tissue, used bed sheets, contaminated medical equipment. Contaminated objects are called fomites
Vehicle transmission - spread of pathogens by contaminated air, food or water eg. eating raw meat, sharing drinks
Vector transmission - animals assisting in the transfer of pathogens between individuals
Biological vectors - eg. mosquitoes, transfer the pathogen from one individual to another, but the pathogen also undergoes part of its life cycle in the vector
Mechanical vectors - eg. flies, physically transfer the pathogen from one person to another, without being infected themselves
design and conduct a practical investigation relating to the microbial testing of water or food samples
Water purification experiment
We took water from the local creek. We purified one sample with a chemical tablet and the other by boiling it. We then put each sample and one control sample onto an agar plate and incubated it to allow microbes to grow. It was found that boiling the water killed more microbes in the water.
investigate the work of Robert Koch and Louis Pasteur, to explain the causes and transmission of infectious diseases,
Robert Koch
Robert Koch developed new equipment and technology eg. agar plates technique that allowed bacteria to be studied. He aided our understanding of the cause and transmission of disease by identifying the specific type of bacteria that caused several diseases, eg. anthrax, tuberculosis and cholera.
Koch’s Postulates
He conducted experiments involving transferring specific bacteria into a healthy animal which showed this animal developed the disease. This developed Koch’s Postulates, conditions that can be used to determine the specific pathogens that cause a disease.
He first collect pathogen from a diseased organism
Then he isolated the causative agent and grew it in pure culture
Then the cultured agent was injected into a healthy organism
The healthy organism was found to get the same disease as the original organism
Louis Pasteur
He disproved the theory of spontaneous generation and contributed to the germ theory. He experimentally showed that live microbes eg. yeast, caused fermentation and that when smaller microbes eg. bacteria were present, acetic acid was produced - making the wine sour. His observations that the microbes were causing “diseases” in wines led him to the belief that microbes could also cause diseases in humans.
Pasteur’s experiment on microbial contamination
He sent up two flasks, both containing broth. One of the flasks had a swan neck, one had the neck removed. The one with the neck remained free of microbes, while the one without the neck had grown microbes. This was because microbes cannot move against gravity through the upwards part of the neck. Microbes only developed in the flask open to the air, thus refuting the idea of spontaneous generation. This helped people to realise that microbes did not spontaneously generate in sick people, but were carried in the air, or by other means, as suggested by the germ theory.
analyse responses to the presence of pathogens by assessing the physical and chemical changes that occur in the host animal’s cells and tissues
Barriers to entry
Skin - hard for microbes to penetrate, difficult environment for microbes to grow on
Secretions - eg. tears, contains antibacterial enzyme
Mucous membranes - line the natural body openings of mouth and throat, and urinary and reproductive tracts. They secrete mucus which traps the pathogens
Chemical barriers - eg. acid in stomach which kills most pathogens
Flushing mechanism - regular emptying of the bladder to flush microbes out. Production of tears washes microbes from the eyes.
Reflex actions - coughing, sneezing and vomiting, removes trapped pathogens
Innate immune response
This response is triggered by pathogens that get through the barriers. Innate immune responses are not specific to a particular pathogen.
Phagocytosis
White blood cells act as phagocytes that carry out phagocytosis
The phagocyte can engulf microbes via endocytosis.
The vacuole formed from endocytosis then fuses with a lysosome, allowing chemicals and enzymes to destroy the microbes
Inflammation response
Triggered by the release of chemicals caused by injuries to body tissues
These chemicals cause increased blood flow to the injured area, as well as causing blood capillary and enter the tissues
The inflammation allow blood components to exit the capillary and enter the tissues eg. phagocytes which help clear cellular debris and microbes
Secretion of antimicrobial proteins and natural killer cells
Lysozymes: enzymes that directly attack bacterial antigens by breaking down their cell walls
Complement system: causes the cells of the invading microbes to burst (cell lysis)
Interferon: released when the cell is infected by a virus to signal other cells to undergo apoptosis (cell suicide)
Natural killer cells (NKC) : specialised white blood cells that can recognise body cells infected with viruses. They attach themselves to the infected cells and release chemicals that cause the cells to undergo apoptosis.
Lymphatic system at
Drainage system that collect blood plasma that seeped out of the capillaries
There are special chambers called lymph nodes which defend against diseases as they contain many phagocytes which “eats” any foreign cells, and lymphocyte cells which can target specific pathogens and destroy them.
When fighting the infection, the lymph nodes will become swollen which can indicate the location of the infection.
Adaptive immune response
Involves specialised leukocytes (white blood cells) that can mount a specific response to an antigen.
Includes two types of cells that are produced in bone marrow: T cells and B cells
T cells or T-lymphocytes are produced in the bone marrow and multiply in the Thymus glands. They attack body cells that are infected by pathogens, or growing abnormally as cancers
B cells or B-lymphocytes are produced and mature in bone marrow. They produce antibodies which attack pathogens which are not inside body cells but in the blood, lymph or tissue fluid.
explain how the immune system responds after primary exposure to a pathogen, including innate and acquired immunity
1st line of defence - barriers to entry
2nd line of defence - innate immune system, don’t target specific pathogens
3rd line of defence - adaptive immune system, lymphocytes can identify specific pathogens by their antigen and adapt the defences to accurately target each one, meaning future immunity as well.
Helper T cells - activate and direct other immune cells
Cytotoxic T cells - use chemicals to kill antigens-specific antibodies
Memory T or B cells - provide future immunity by remaining in the body after primary exposure to allow for a more effective secondary response should re-exposure to the same antigen occur again.
Plasma B cells - produce antigen-specific antibodies
investigate procedures that can be employed to prevent the spread of disease, including but not limited to vaccination, including passive and active immunity
Passive immunity
- occurs when an individual is given antibodies from another person or organism which can provide temporary immunity
- can occur naturally eg. baby receives antibodies from mother’s breast milk
- can occur artificially eg. after a snake bite, a person can be given an injection of antivenom which contains antibodies extracted from a horse.
Active immunity
When an individual’s immune system produces antibodies and develops specific memory B and T cells for the causative agent.
Can occur naturally through previous exposure to a disease
Can occur artificially by receiving a vaccination that contains a safe form of the disease
investigate and assess the effectiveness of pharmaceuticals as treatment strategies for the control of infectious disease,
Antivirals
Do not tend to cure the disease but try to prevent death by managing the symptoms
Antiviral drugs exist for only some diseases caused by virus eg. influenza and HIV. Tamiflu inhibits the enzyme that the replicated influenza virus needs to exit the infected cells
Not effective for killing or inhibiting the virus, only the management of symptoms
Only have antivirals for a limited amount of viruses
Antibiotics
Antibiotics stop cell wall and protein synthesis from occurring in bacteria
Eg. vancomycin disrupts cell wall synthesis
Effectiveness is only short-term due to rapid increase in antibiotic resistance in pathogens
Each type of antibiotic only works for certain types of bacteria.
Only a limited number of antibiotics can treat fungal and protozoan diseases
Side effects include, deafness, vertigo and nausea
compare the adaptations of different pathogens that facilitate their entry into and transmission between hosts
B.Anthracis
- Produces dormant spores - aids its spread in the environment
- Spores have tough, triple protein like coat - protects spores
- Rods have tough coating - provides resistance to antibodies
- Toxic production - cause sudden death of host
- Spores activate when inside the host - allows formation of rods inside host
- Rods can reproduce rapidly - increase number of rods, spores, and amount of toxin produces
E.coli
- Produces haemolysin - a chemical that helps the bacteria form pores in host cells membranes in the digestive tract
Mycobacteria
- Has high lipid content in their cell walls - helps them to survive in the environment by resisting chemicals and dehydration
Tapeworms
- Have hooks and suckers - can attach to the walls of hosts digestive systems
Giardia
- When in external environment can switch to cyst form - more durable
investigate the response of a named Australian plant to a named pathogen through practical and/or secondary-source investigation
Ipomoea costata (Potato Plant).
pathogen: Phytophthora Infestans (Fungi).
disease: Late Blight (or Potato Blight).
response: Their pattern recognition receptors can recognise beta-glucans that are present on the phytophthora infestans’ cell wall. When the pattern recognition receptor recognises it, protease protein is produced as a response to stop the growth of the pathogen.
