2.11 - disease, defense and treatment Flashcards
What are pathogens?
harmful micro-organisms
What are the 4 main types of pathogens?
Virus, bacterium, fungus, protist
What is the life cycle of a pathogen?
They infect a host, reproduce themselves (or replicate, in the case of a virus), spread from their host, and infect other organisms
Diseases caused by pathogens are called communicable diseases. What this mean?
the disease can be transferred from one person to another
Gives the features of a bacterial cell
No nucleus
A cell membrane and cytoplasm
Chromosome that is loose in the cytoplasm
No chloroplasts or mitochondria
Exists as a single cell
Divide by binary fission ( split into two before growing to full size)
A cell wall made murein
Why are viruses not considered alive?
Because they do not complete all of the seven life processes, ie movement, respiration, sensitivity, nutrition, excretion, reproduction and growth
What are viruses made up of?
Relatively short lengths of genetic material DNA which is surrounded by a protein coat
What are the five ways a disease can be spread or transmitted? Give examples.
direct contact - sexual intercourse, shaking hands
Water - dirty water, e.g. chorea bacterium
Air- common cold sneezes, spray thousands of tiny droplets containing virus particles
Unhygienic food prep - undercooked or reheated food can cause bacterial disease ( food poising)
Vector - Any organism that can spread a disease is called a vector
What does HIV stand for? How is it transmitted?
Human Immunodeficiency Virus. Transmitted through body fluids, often during unprotected sex. Also through cuts and injecting drugs using a shared needle
What does AIDS stand for? How is it transmitted?
Acquired Immune Deficiency Virus. Months or years after infection of HIV virus, it becomes active and attack’s patients immune system. At this point HIV has become AIDS.
What are patients given to help slow down the development of AIDS?
Antiviral drugs - drugs that prevent viruses replicating
How is chlamydia transmitted?
Most common sexually transmitted disease. Caused by bacterium chlamydia trachomatis and transmitted by direct contact during sexual intercourse.
How is chlamydia prevented and treated?
Use of condoms in sexual intercourse
Treated by antibiotics
How is Malaria transmitted?
Malaria is a disease spread by mosquitoes which carry the Plasmodium protist. Mosquitoes suck blood containing the protist from an infected person. They then pass the protist to other people when they suck blood from them. Because mosquitoes transmit the disease and do not become ill themselves, they are called vectors.
What are the symptoms of Malaria?
Fever, sweats and chills, headache, vomiting and diarrhoea.
How can Malaria be prevented?
Stopping individuals from being bitten - People sleep under mosquito nets and wear insect repellent to avoid bites. Anti-malarial drugs are also taken, which treat the symptoms and can prevent infection
How does the skin defend the body from pathogens? (non-specific barrier)
Covers almost all parts of the body to prevent infection from pathogens. If cut or grazed it immediately starts healing itself - forming a scab. Prevents infection as skin acts as a physical barrier
Parts of the body that do not have skin have developed other ways to prevent infections. What do the eyes do to prevent infections?
The eyes produce tears which contain enzymes, and these are known as chemical barrier
How does the nose defend the body from infections? (non-specific barrier)
It contains internal hairs that act as physical barriers to infection. Mucus traps pathogens before entering the lung. When the nose is blown mucus and any pathogens trapped in mucus are removed.
The cells that line the trachea (windpipe) have hairs called cilia. These are called ciliated cells. What do they do? (non-specific barrier)
The ciliated cells waft their hairs and move mucus and pathogens upwards towards the throat where they are swallowed into your stomach
What do goblet cells do?
Create the mucus in order to trap pathogens (physical barrier)
How does the stomach defend the body from infections? (non-specific barrier)
It contains hydrochloric acid, and while it does us no harm, it is strong enough to kill any pathogens that have been caught in mucus in the airways or consumed in food or water (chemical barrier)
What is the immune system and what does it consist off?
The body’s defense against the entry of foreign body’s (e.g. pathogens, pollen grain). Consisting of mainly 2 types of white blood cell called phagocytes and lymphocytes.
What do phagocytes do in the immune system?
Attracted to pathogens. They bind then engulf and absorb waste material, harmful microorganism, or other foreign bodies in bloodstreams or tissue
What do lymphocytes do in the immune system?
Recognises proteins on surface of pathogen called antigens. Lymphocytes detect they are foreign and produce antibodies ( may take few days to make). The antibodies cause the pathogens to stick together making it easier for the phagocyte to engulf them.
Some pathogens produce toxins which make you feel ill. Lymphocytes can also produce antitoxins to _______ these toxins. Both the antibodies and antitoxins are highly specific to the antigen on the pathogen, therefore the lymphocytes that produce them are called ____ (specific, non- specific)
neutralise
specific
If your body encounters a particular antigen, your lymphocytes might recognise it. If they do, they _____ themselves in order to make enough antibodies to destroy the pathogen. ______ cells are also created which remain in your bloodstream and produce a quick response if the antigen is encountered again. You are then said to be immune
clone
Memory
Where does the best immunity come from?
Fighting off a disease
What do vaccines do?
They allow a dead or altered form of the disease causing pathogen, which contains a specific antigen, to be introduced into the body.
What do vaccines cause the Immune system to do?
Produce complementary antibodies that target the antigen and attach themselves onto it in order to create memory cells
Immunising increases herd immunity. What is herd immunity
Those who are unable to be vaccinated are protected as outbreaks of disease are prevented because others have been vaccinated and are therefore immune
How do vaccines work (4 stages)
1) Syringe injects an altered form of a pathogen
2) White blood cells release complimentary antibodies to the specific antigens
3) They attach and clump pathogens together
4) White blood cells engulf the pathogens - phagocytosis occurs
What are antibiotics?
Antibiotics are substances that slow down the growth of bacteria. Only effective against bacterial diseases not viral ones
Who discovered the first antibiotic (penicillin)? In what year? How?
Sir Alexander Fleming in 1928
He noticed that some bacteria he had left in a petri dish had been killed by the naturally occurring Penicillium mould.
Antibiotics damage the bacterial cells but do not damage the ___ cells
host
Why are a range of antibiotics needed?
Because different bacteria cause different disease. One particular antibiotic may only work against a few types of bacteria
Why can’t viral diseases be cured by antibiotics?
because they reproduce inside the host cells
Give reasons to why commonly prescribed antibiotics are becoming less effective?
Overuse of antibiotics
Failing to complete the fully prescribed course by doctor
Use of antibiotics in farming
What is resistant bacteria also known as?
Super bugs
One superbug is MRSA. What control measures are in place to prevent spread of this disease?
Hand washing
Thorough cleaning of hospital wards
Use of alcoholic gels
MRSA screening
Why are most drugs made at pharmaceutical companies?
Because these companies have synthetic (chemical processed material, not natural) versions of plant extracts
What are the stages of preclinical drug testing?
1) Drugs are tested using computer models and human cells grown in a lab
2) If drug passes 1st stage it is then used on animals - typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side effects
What are the stages of clinical trials?
If drug passed animal testing:
3) Tested on healthy volunteers to check if they are safe
4) Tested on people with illness to ensure they work
What is a placebo?
A pill that has no effect on the patient and doesn’t contain the active ingredient
What is a blind trial?
When patients aren’t told if they are on the placebo
What is a double blind trial?
Neither patient nor the doctor administering the drug knows if the patient is receiving the drug or a placebo (eliminate bias all together)
What does monoclonal antibodies mean?
‘Mono’ means one and ‘clone’ means identical copy. Monoclonal antibodies are, therefore, identical copies of one type of antibody.
What are antibodies?
A protein produced by the immune system (lymphocytes) that attacks foreign organisms (antigens) that get into the body
Pathogens have ____ on their surface called antigens. When a pathogen infects the body, the lymphocytes recognise these antigens as foreign and attack them by producing _____
Proteins
antibodies
What are the 5 stages of the formation of monoclonal antibodies
1) An antigen is injected into a mouse
2) The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen
3) Spleen cells which produce lymphocytes are removed during a a small operation
4) The spleen cells are fused with human cancerous white blood cells called myeloma cells ( a tumor cell ) to form hybridoma cells which divide indefinitely
5) The hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen
What are tumor markers?
A protein on the surface of a tumor that can be recognised by the immune system
Describe the process in how monoclonal antibodies be used to treat cancer?
Tumor markers allow monoclonal antibodies to be produced to bind specifically with these antigens. They will bind with these cancer cells and clump them together.
How can monoclonal antibodies treat cancer?
1) carrying drugs that have been attached to them to the tumour
2) encouraging your immune system to attack the cancer cells directly
Monoclonal antibodies have been attached to dyes that will glow fluorescent under _____ or when radioactive labels are used
UV light
Why is tissue typing used?
It’s used to determine the extent to which the immune system of the recipient of a donor organ will react against the donor organ antigens. A poor match could result in the rejection of a donor organ.
Monoclonal antibodies have been developed which can prevent rejection. They combine with and inactivate helper T cells, without helper T cells the lymphocytes that produce antibodies against the transplanted organ won’t work. What are helper T cells
cells that signal to other cells of the immune system that an antigen is present
