infection and response (everything)

how are pathogens spread?

Water, air and direct contact

how to stop pathogens from spreading

vaccination, quarantine, basic hygiene and kill the vectors

what are pathogens

disease causing microorganisms

what are non communicable diseases

Diseases that cannot be transmitted from one person to another

What are communicable diseases?

Diseases caused by pathogens that can be transmitted from one individual to another

what is measles?

a viral disease spread when an infected person coughs or sneezes, causes people to develop a red rash across their body and face, children in the UK are vaccinated with the MMR vaccine when they are children

what is HIV

a viral disease that attacks the body's immune system, it has flu like/cold symptoms, can cause AIDS( disease where immune system can't cope anymore and is susceptible to many diseases), spread by sexual contact and sharing needles/exchanging bodily fluids, antiretroviral drugs stop the virus from getting worse if caught early

What is TMV (Tobacco Mosaic Virus)?

a plant virus that causes yellow/discoloured leaves so photosynthesis cannot take place in these yellow areas reducing crop yields, spread by direct contact between healthy and infected plants, no cure farmers just develop TMV resistant plant strains

how do viruses cause disease?

they invade a host cell, once they get inside they replicate/ make lots of copies of themselves and eventually the cell bursts(lysis) making us feel ill and the virus spreads to other cells

what are bacteria

a unicellular prokaryotic micro-organism, they are 100x smaller than an animal cell, diameter of 10^-6 metres

What is salmonella?

a bacterial disease that causes food poisoning, mostly caught from eating chickens/eggs that haven't been vaccinated against it, symptoms include fever. abdominal cramps, vomiting and diarrhoea, usually passes within a week, to prevent cook food properly and wash hands after handling raw meat, usually passes within a week

What is gonnorhea?

STD, passed on by having unprotected sex, symptoms include pain when urinating and thick yellow or green discharge, treatment= penicillin however there are lots of strains becoming antibiotic resistance

how do bacteria damage cells?

they produce toxins that directly damage cells

how to combat antibiotic resistance

only prescribe antibiotics for serious infections and patients take it for the full course

what are fungi?

eukaryotic organisms, some have long thread like structures called hyphae that can penetrate skin and cause disease they also release spores which can also spread them

how is rose black spot spread?

water or wind

What is rose black spot?

A fungal disease where purple or black spots develop on leaves reducing the plant's ability to photosynthesise so it can't grow well

how to treat rose black spot?

chop off infected leaves and burn them or spray with fungicides

what are protists

multicellular or unicellular eukaryote that can cause disease, they are transported by vectors eg. mosquito transports malaria(the vectors don't get the disease themselves)

symptoms of malaria

fever and headaches, comes and goes, can be fatal

how to prevent protists?

stop the vectors, destroy their breeding sites, kill them with insecticides, mosquito nets

what is an antigen?

a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies

what's an antibody?

An antibody is a protein made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction

what's an antitoxin?

An antitoxin is a protein/chemical produced by WBC that can bind and counteract the toxins that pathogens produce

How does the skin protect the body from disease?

acts as a physical barrier, helpful good bacteria live on the skin providing competition for pathogens, secretes oils/antimicrobial substances which kill pathogens

How do tears defend against infection?

there are enzymes in tears(called lysozymes)

how does the trachea defend against infection?

lined with a layer of mucus via goblet cells that traps particles, also lined with cilia which are tiny hair like structures they move mucus and trapped particles up to the back of the throat to either be swallowed and killed by stomach acid or spat out

How does the stomach defend against infection?

contains hydrochloric acid that kills pathogens

How does the nose defend against pathogens?

The nose has cilia and mucus which trap particles that could contain pathogens.

What do lymphocytes do?

produce antibodies

What are phagocytes and what do they do?

a type of white blood cell that via phagocytosis they track the pathogen, bind to it and engulf it and destroy it via enzymes within it

how do antibodies work? ( 6)

- they lock onto a foreign antigen and act as a signal for phagocytes to come and destroy them,

- the shape of each antibody is specific to the antigen

- once our immune system knows which shape the antibody has to take to bind to the antigen, memory cells in our immune system remember this for next time so the immune system can produce antibodies quicker and can get rid of the pathogen before it affects our body (immunity)

- Furthermore, the binding of antibodies to antigens causes pathogens to clump together making them easier to destroy

what are two cons of vaccines?

- don't always work/don't always grant full immunity

- we sometimes have bad reactions to them eg. swelling at the injection site, seizures, fever

What are vaccines?

Weakened pathogens/contains an inert version of the pathogen that stimulate the body's immune system to produce antibodies to the antigen so that in the future memory cells will make specific antibodies quicker before the person gets ill/infected

how do vaccines help us develop immunity?

because the weakened pathogen still contains the same antigen our body still treats it as if we have the actual pathogen so it produces antibodies therefore making us develop immunity

What is herd immunity?

when the majority of people in a population are immune to a pathogen, the pathogen won't have any people to spread to even if a few people aren't vaccinated they are unlikely to catch it, as the majority of people around them are immune

4 pros of vaccines

- herd immunity,

- prevents outbreaks/epidemics,

- protection from diseases,

- control of common diseases eg. smallpox, measles, whooping cough

What is immunity

The ability of the body to defend itself against pathogens

how are monoclonal antibodies made

They are produced by stimulating mouse lymphocytes to make a particular antibody(by injecting the mouse with a particular antigen) . The lymphocytes are combined with a particular kind of tumour cell(myeloma) to make a cell called a hybridoma cell. The hybridoma cell can both divide rapidly (like a tumour cell) and make the antibody.(we leave them to divide in a petri dish) Single hybridoma cells are cloned to produce many identical cells that all produce the same antibody. The antibodies can then be collected and purified.

which part of a pregnancy test does the woman wee on?

the orange bit on the end

How does a pregnancy test work?

The pregnant woman wees on the end of the test strip in the reaction zone. The reaction zone contains mobile antibodies specific to HCG and they contain a blue dye. The HCG in the pregnant woman’s urine bidns to the antibodies. the woman’s wee flows over the test strip carrying the mobile beads from the reaction zone to the result window. the result window contains immobile antibodies specific to HCG, so the HCG in her urine binds to the antibodies here and a blue line is shown to indicate a positive result. The unfixed beads from the reaction zone then flow to the control window. The antibodies here are specific to the reaction zone antibodies and are fixed and so the reaction zone antibodies bind to the control window antibodies

describe three ways monoclonal antibodies can be used to treat cancer

-They bind to receptors on the outside of cancer cells preventing them from growing/diving by mitosis
-They signal to the immune system/white blood cells and cause them to attack/destroy the cancer cells
-They can carry drugs/radioactive chemicals to target the cancer cells directly;

3. describe the control window on a pregnancy test

non-mobile antibodies complementary to the reaction zone antibodies

what are monoclonal antibodies

Antibodies produced from a single group of genetically identical B-lymphocytes

What are the uses of monoclonal antibodies?

- pregnancy tests
- detecting diseases
- treating cancer
-locate or identify specific molecules in a cell or tissue

what hormone do pregnant women excrete in their urine that a pregnancy test detects?

HCG

what happens if you wee on the test and you're not pregnant?

the urine will wash the unfixed beads along the test strip so they'll flow right over the fixed antibodies on the right and nothing will happen so the test strip won't go blue

where are the lymphocytes removed from a mouse to make monoclonal antibodies

In monoclonal antibody production, lymphocytes are extracted from the spleen of a mouse after it has been immunized with a specific antigen

why is it necessary to produce a hybridoma cell instead of using a white blood cell alone to produce monoclonal antibodies?

lymphocytes cannot divide continuously this means we wouldn't be able to produce monoclonal antibodies on a large scale

1. describe the reaction zone on a pregnancy test

HCG-specific antibodies are here, they are mobile and contain a blue dye

2. describe the result window on a pregnancy test

non-mobile HCG-specific antibodies are found here

how does an enzyme in a pregnancy test help show a positive result?

The enzyme catalyses a reaction in the reaction zone that produces a change in colour

how was penicllin discovered

Alexander Flemming returned to his lab after a holiday and a fungus was growing in his petri dish killing surrounding bacteria, as the genus of the fungus was penicillum he named the antibiotic penicillin

what is aspririn

common painkiller, developed from a chemical found in the bark of willow trees

what is digitalis?

used to treat heart problems like heart failure, originally developed from a chemical found in a plant called foxglove

What is the efficacy of a drug?

how well the drug works eg. how well a painkiller reduces your pain

what is dosage

how much of the drug/ concentration should be given

what is toxicity?

how harmful it is eg. does it damage any cells, any side effects?

step 1 of pre clinical trials

substance is tested on human cells and tissues which can be grown in a lab. this way we can easily and cheaply test lots of substances however it doesn't tell us how it would affect an entire organism or particular organ.

step 2 of pre clinical trials

testing on live animals, gives us a good idea of efficacy and toxicity of the drug

step 1 of clinical testing

give the drug to healthy volunteers at a low dosage then slowly increase the dose keeping a close eye on the individual(trying to find maximum dosage here)

step 2 of clinical testing

give the drug to people with the illness and slowly increase the dose(this time we're looking for the optimum dosage where efficacy is maximised and toxicity minimised)

what is a placebo

like the real drug but doesn't do anything(made of sugar)

what is a placebo used for?

to help test the effectiveness of a new health care treatment, such as a medication, by using it as a control to compare

what is a double blind trial?

Where the patients AND researchers don't know which patients have the drug or placebo

what's the importance of a peer review?

It is when scientists check each other's work
It is important to prevent false claims

what are the symptoms of a plant disease?

-patches of decay
-spots of discolouration
-presence of pests
-abnormal growths/lumps
-malformed stems/leaves

How to identify plant diseases

- Referencing a garden manual or website
- Taking the infected plant to a laboratory for testing
- Using testing kits which contain monoclonal antibodies

what are the symptoms of a nitrate deficiency in plants?

stunted growth as nitrates are needed to make proteins and therefore for growth

what are the symptoms of a magnesium deficiency in plants?

chlorosis/yellow leaves as magnesium ions are needed to make chlorophyll(a green pigment in plants that absorbs light for photosynthesis)

what are a plant's physical defences?

- cellulose cell walls
-tough waxy cuticles on leaves
-layers of dead cells around stems(bark on trees) which fall off

what are a plant's chemical defences?

-Antibacterial chemicals
-Poisons to deter herbivores

what are a plant's mechanical defences/adaptations?

-thorns and hairs deter animals
-leaves which droop or curl when touched
- mimicry to trick animals eg. fake insect eggs on leaves