Biology - Topic 3 - Infection and Response
Biology - Topic 3 - Infection and Response
Monoclonal antibodies (mAb)
Pregnancy tests - rely on mAbs that bind to the hormone Human Choronic Gonadotropin (HCG) that is made in the early stages of pregnancy.
Research - Used to locate or identify specific molecules in a cell or tissue.
Diagnosis - Made to bind to specific antigens or blood clots or cancer cells. May also carry markers that make it easy for doctors to see where they have built up.
Measuring and monitoring - mAbs can monitor the levels of hormones and of other chemicals in the blood. For example screening blood for HIV infections, detecting drugs and detecting infections such as syphillis.
How they are produced
mAbs are made from Hybridoma cells. These are made of B-Cells and Myelona cells. Monoclonal means cloned from a single hybridoma.
Lymphocytes (B-Cell) produce the antibodies.
Phagocytes (B-Cell) follow the signal from the antibody.
Pregnancy tests- the antibodies on the strip attach to a hormone called HCG in the wee that only pregnant women the beads and the hormone bind to the antibodies on the strip turning it blue.
Types of pathogens
Measles- Spread by droplets from a sneeze or cough, people develop red skin and have a fever, measles can sometimes lead to pneumonia or encephalitis.
Tobacco mosaic virus- causes mosaic pattern on the leaves of the plants (parts become discoloured) means the plant cant carry out photosynthesis as well.
HIV- Spread by sexual contact or bodily fluids such as blood, the virus attacks the immune cells, if the body's immune system is damaged badly it cant cope with other infections such as cancers at this stage it is known as aids.
Fungi- Rose black spot is a fungus causes black or purple spots to develop on the leaves of rose plants causing them to drop which affects photosynthesis ( less chlorophyll less chloroplasts so less photosynthesis)
spreading through water or wind treated b fungicides or stripping pants of affected leaves.
Protists- All eukaryotes, some are parasites which live in other organisms and can cause them damage transferred by a vector e.g mosquito.
Malaria is caused by a protist, life cycle of the malarial protist includes phases in the mosquito and mammal. Malarial protist causes episodes of fever (affects the liver) can be fatal. Spread of malaria can be controlled by :- controlling the vectors from breeding and by preventing the vector from biting ( using nets).
Vaccines help control lots of communicable diseases that were once common in the UK. Smallpox no longer occurs and polio infections have fallen by 99%.
Big outbreaks of disease called epidemics can be prevented if a large percentage of the population is vaccinated. Therefore there will be fewer people able to pass it on.
If majority of population are vaccinated it protects individual who cannot be vaccinated ( too old too young too ill immunocompromised) this provides HERD IMMUNITY.
Protects from future infections
Involves injecting small amounts of dead or inactive pathogens. These carry antigens which causes your body to produce antibodies to attack them.
If pathogens of the same type appear after that, WBC can rapidly mass-produce antibodies to kill off the pathogen.
When infected with a new pathogen, it takes your WBC a few days to learn how to deal with it. You can become pretty ill in this time.
They don't always work, sometimes they don't give you immunity.
Can also have a bad reaction to a vaccine e.g swelling or something more serious like fever or seizures. But bad reactions are very rare.
Plant Diseases and defences
Plants can get diseases
1) Plants can be infected by viral, bacterial and fungal pathogens. They can also be infected and damaged by insects. For example aphids are an insect that can cause huge damage to plants.
2) Common signs of a plant have a disease are: Stunted growth, spots on their leaves, patches of decay (rot), abnormal growths e.g lumps, malformed stems or leaves, discolouration.
3) Infestations of pests are easy to spot too- you should be able to see them on plants.
4) Different plant diseases have different signs. They can be identified by:
1) Looking up the signs in a garden manual or gardening websites.
2) Taking the infected plant to a lab, where scientists can identify the pathogen,
3) Using testing kits that identify the pathogen using monoclonal antibodies.
Plants need mineral ions
1) Nitrates are needed to make proteins and therefore for growth. A lack of nitrates cause stunted growth.
2) Magnesium ions are needed for making chlorophyll, which is needed for photosynthesis. Plants without enough magnesium suffer from chlorosis and have yellow leaves.
Plants need mineral ions from the soil, if there aren't enough plants suffer deficiency symptoms.
2) Other plants produce poisons which can deter herbivores e.g tobacco plants, foxgloves and deadly nightshade.
1) Some can produce antibacterial chemicals which kill bacteria- e.g the mint plant and witch hazel
2) Other plants have leaves that droop or curl, this prevents them being eaten by knocking insects off themselves and moving away from things.
3) Others cleverly mimic other organisms. For example the passion flower has bright yellow spots which look like butterfly eggs, stopping butterflies laying eggs there. Several species of plant in southern Africa in the "ice plant family" look like stones and pebbles. Tricking animal into not eating them.
1) Some plants adapted to have thorns and hairs which stop animals touching and eating them.
2) Plant cells are surrounded by cell walls made from cellulose. These form a physical barrier for pathogens that get past the waxy cuticle.
3) Layers of dead cells around their stems. For example the outer part of bark on a tree. These act as a barrier to stop pathogens entering .
1) Most plants leaves and stems have a waxy cuticle, which provides a barrier to stop pathogens entering.
Gonorrhoea - caused by bacteria and is a STD, passed through sexual contact, was treated by a antibiotic called penicillin but there has become strains that are resistant to it. To stop people should use contraception such as condoms. Will get pain when they urinate and thick yellow or green discharge from the vagina or penis.
Salmonella- Causes food poisoning, caused by the toxins that the bacteria produce. Get it by eating food that has the bacteria such of raw chicken. Causes fever, stomach cramps, vomiting and diarrhoea
Body has a pretty sophisticated defence
3)The trachea and bronchi secrete mucus to trap pathogens.
4)The trachea and bronchi are lined with cilia, these are hair like structures which waft mucus up.
2)Hairs and mucus in your nose trap particles that could contain pathogens.
5)The stomach produces hydrochloric acid.
1)Skin acts as a barrier to pathogens.
Immune system can attack pathogens
When some types of white blood cell come across a foreign antigen, they produce proteins called antibodies that lock on to the invading cell so it can be found and destroyed by other white blood cells.
Antibodies are then produced rapidly and carried around the body to find all similar bacteria or viruses
Every invading pathogen has unique molecules on its surface.
If the person is infected with the same pathogen again the white bold cells will rapidly produce the antibodies to kill it.
3)Producing Antitoxins, these counteract toxins produced by the invading bacteria.
1) Consuming them, white blood cells can engulf foreign cells and digest them. This is called phagocytosis.
Bacteria can become resistant to Antibiotics
3) This means only non-resistant strains of bacteria will be killed.
4) The individual resistant bacteria will survive and reproduce and the population of resistant strain will increase.
2) If you have an infection, some of the bacteria might be resistant to antibiotics
5) The resistant strain could cause a serious infection that cant be treated by antibiotics. E.g: MRSA causes serious wound infections and is resistant to powerful antibiotics.
1) Bacteria can mutate- sometimes the mutations cause them to be resistant to an antibiotic
6) To slow down the rate of this reproduction. It is important for doctors to not over-prescribe antibiotics.
7) It is important that you finish the course of antibiotics, and don't stop after you feel better.
Many drugs originally come from plants
2) Some of these chemicals can be used in drugs to treat human diseases or relieve symptoms. For example:
Aspirin is used as a painkiller and to lower fever. It was developed from a chemical found in willow
1) Plants produce a variety of chemicals to defend themselves against pests and pathogens.
Digitalis is used to treat heart conditions. It was developed from a chemical found in foxgloves.
Alexander Fleming was clearing out some petri dishes containing bacteria. He noticed one of the dishes had mould on it and the area around the mould was free of bacteria.
3) Some drugs are extracted from microorganisms for example:
He found that the mould was producing a substance that killed bacteria- this substance was penicillin.
4) Now drugs are made on a larger scale in the pharmaceutical industry. This process still might start with a chemical extracted from a plant.
Some drugs relieve symptoms- others cure the problem
3) Antibiotics don't destroy viruses. Viruses reproduce using your body cells, making it difficult to develop drugs that destroy only the virus.
4) Antibiotics has greatly reduced the number of deaths from communicable diseases caused by bacteria.
2) Antibiotics kill or prevent growth of the bacteria without killing your body cells. Different antibiotics kill different types of bacteria.
1) Painkillers are drugs that relieve pain. They don't tackle the cause they just help reduce symptoms
There are 3 main stages in drug testing.
once a target compound is identified as possibly having therapeutic effects - this could be synthesised based on a chemical extracted from a plant
1) Preclinical testing, drugs are tested on human cells and tissues.
2) However you cant do this with drugs that affect whole or multiple body systems, for example testing a drug for blood pressure must be done on a whole animal because it has an intact circulatory system.
1) Next step is to test on live animals. This is to test efficiency, to find out about its toxicity (how harmful it is) and to find the best dosage.
2) The law in Britain is that any new drug need to be tested on two different live mammals. People disagree with this, but others believe its the safest way to check a drug before giving it to humans.
1) If it passes the tests on animals it is then tested on human volunteers in a clinic trial
2) First it is tested on healthy human volunteers to check for any side effects. To begin a low dose is given but this is gradually increased.
3)If these results are good, the drugs can be tested on those suffering with illness. The right dose is found, most effective with fewest side effects.
4)To test how well it works, patients are randomly put into two groups. One group is given the new drug, the other group given a placebo ( a substance similar to the drug but one that doesn't do anything. This is so the doctor can see the difference the drug makes.
5) The patients and sometimes the doctors don't know which drug is being given to which group. This is so doctors monitoring aren't subconsciously influenced by their knowledge. This is known as a double blind trial
6) The results aren't published until they have been through peer review. This helps to prevent false claims.
7) drug will be licensed and allowed to be prescribed - information will continue to be gathered about any side effects seen and long term effects of the drug when used regularly in patients
Water - Drinking or bathing in dirty water e.g cholera.
Air - Can be breathed, some are carried in air droplets produced when sneeze or cough e,g influenza virus.
Direct Contact - Touching contaminated surfaces e.g athletes foot.
Microorganisms that enter the body and cause disease.
Isolating infected individuals