B3 : Infection and Response

What is the scientific definition of health?

The state of physical or mental well-being

What are communicable diseases?

Diseases that can spread from one person to the other (spread by a pathogen)

What are non-communicable diseases?

Diseases that can’t spread from one person to the other

What is a pathogen?

A microorganism that causes disease

What are the 4 type of pathogens?

• Bacteria

• Virus

• Protist

• Fungi

How do bacteria make people ill? (2)

• They reproduce rapidly

• They make you ill by producing toxins that damage cells and tissue

Name the 2 bacterial diseases

• Salmonella

• Gonorrhoea

What does salmonella cause?

Food poisoning

How can you get salmonella? (2)

• By eating uncontaminated food that is contaminated with the salmonella bacteria

• By eating food that was prepared in unhygienic conditions

What are the symptoms of salmonella? (4)

• Fever

• Stomach cramps

• Vomiting

• Diarrhoea

How can the spread of salmonella prevented?

In the UK chickens (and other meat sources) are given a vaccination again salmonella

What is gonorrhoea?

A sexually transmitted disease (STD)

How can you get gonorrhoea?

Via sexual contact (having unprotected sex)

What are the symptoms of gonorrhoea? (2)

• Pain when urinating

• Yellow or green discharge

What can prevent the spread of gonorrhoea? (2)

• Treated with antibiotics

• Usage of barrier methods such as condoms

Why has gonorrhoea become trickier to treat with antibiotics? + Which antibiotic?

The antibiotic used is penicillin but this has become harder because some bacteria has become resistant

How do viruses make people ill? (3)

• They reproduce rapidly

• Live inside your cells, replicate themselves and cause cells to burst leading to the virus spreading to other cells and infecting them

• The cell damage makes us ill

What are the 3 types of viral diseases?

• Measles

• HIV

• Tobacco mosaic virus (TMR)

How can viruses not be killed?

By antibiotics

How is measles spread?

From droplets from an infected persons sneeze or cough

What are the symptoms of measles? (2)

• Red skin rash

• Fever

What can measles sometimes cause?

Damage to the breathing systems and the brain

How do you prevent the spread of measles?

By getting vaccinated when you’re young

How is HIV spread? (2)

• By sexual contact

• Exchanging bodily fluids

What are the symptoms of HIV?

Flu like symptoms

What does HIV attack?

The immune system

How can HIV be prevented in the early stages?

Antiretroviral drugs (stop virus replicating + must be taken for the rest of their lives)

What can HIV cause in its later stages?

Aids

How is TMV spread?

By entering the wounds of plants

What are the symptoms of TMV?

A mosaic pattern is caused by discolouration which means plants can’t photosynthesise and therefore affects plant growth

How do protists spread disease?

Through a vector (an insect which doesn’t get the disease itself only carries and spreads it)

What disease is caused by protists?

Malaria

How is Malaria spread?

Via infected mosquitos biting humans

What are the symptoms of Malaria? (3)

• Repeating episodes of a fever

• Headaches

• Vomiting

How can malaria be prevented? (3)

• Stopping mosquitos from breeding (mosquitos breed in still water so we need to find areas of still water and drain them)

• Using insecticides

• Using mosquito nets when sleeping

What are fungal diseases?

Diseases caused by fungi

What disease is causes by fungi?

Rose black spot

How is Rose black spot spread?

Through the wind or in water

What organism does rose black spot infect?

Plants (roses)

What are the symptoms of rose black spot? (3)

• Purple or black spots on leaves

• Less photosynthesis occurs and leaves struggle to grow

• Leaves eventually turn yellow and drop off

How can the spread of rose black spot be prevented? (2)

• Gardeners use fungicides

• Gardeners strip the plant of its infected leaves and burn them so the fungi can’t spread

How can the spread of diseases be reduced or prevented? (4)

• Being hygienic → washing hands

• Destroying vectors

• Isolating infected individuals

• Vaccination

What 4 body parts have specific functions to keep pathogens out of the body?

• Skin

• Nose (nostrils)

• Trachea + Bronchi

• Stomach

How does the skin prevent pathogens from entering the body? (3)

• Acts as a barrier (protective layer)

• Secretes antimicrobial substances (substances used to prevent or treat infections)

• If skin is damaged, scabs are formed to stop pathogens from entering

How does the nose prevent pathogens from entering the body?

Contain hairs and mucus which trap pathogens before they enter the breathing system (but can’t always prevent this)

How do the trachea and bronchi prevent pathogens from entering the body? (2)

• Both are covered in cilia

• Cilia are covered in mucus to trap pathogens + then waft the mucus to the throat where it is swallowed into the stomach

How does the stomach prevent pathogens from harming the body?

Contains hydrochloric acid (pH of 2) which kills pathogens before they enter the digestive system

What defence system would kill pathogens if the stomach does not kill them?

The immune system

What are the 2 main function of the immune system?

• They destroy pathogens and toxins

• They protect us in the future if the pathogens ever re enter

What cell does the immune system have?

White blood cells

What are the 3 functions white blood cells have?

• Phagocytosis

• Producing antibodies

• Producing antitoxins

Explain what happens when white blood cells carry out phagocytosis

White blood cells detect the pathogens and engulf (ingest) them and then kill them

What are antigens?

A molecule on the surface of a pathogen

Explain what happen when white blood cells produce antibodies (3)

• When white blood cells come across a foreign pathogen they rapidly produce proteins called antibodies

• The antibodies lock onto the antigens of a pathogen so they can be found and destroyed by other white blood cells

• The antibodies are specific to the antigen

What happens if if a person is infected with the same pathogen?

The white blood cells will recognise the pathogen and kill it immediately eventually leading to immunity

Explain what happens when white blood cells produce antitoxins

White blood cells produce antitoxins to counteract toxins produced by pathogens to prevent you from getting ill

How does vaccination work? (4)

• When getting a vaccine, dead or inactive forms of the pathogen are injected into your body (so they don’t actually cause harm)

• The white blood cells then produce antibodies specific to the pathogen which bind to the antigens and are later engulfed by white blood cells

• If the pathogen ever re enters the white blood cell will immediately make the correct antibodies for the pathogen

• This will eventually give you immunity

What is herd immunity?

When a large group of people are vaccinated against a disease , it protects unvaccinated people because the unvaccinated person can’t catch the disease because no one is there to pass the pathogen on

What are the pros of vaccinations? (2)

• Control outbreaks of diseases such as epidemics

• Leads to herd immunity

What are the cons of vaccinations? (2)

• Don’t always lead to immunity

• Can have bad reaction (rare)

What are painkillers (give example)? + What is their job?

Painkillers, such as aspirin, are drugs that relieve the pain and reduce symptoms (don’t actually kill the pathogen)

What are antibiotics (give example)? + What is their job?

Antibiotics, such as penicillin, kill or prevent the growth of the bacteria without causing harm to your cells

What do antibiotics not work on + why?

Viruses because viruses reproduce inside of cells and it would be hard to kill them without also damaging your cells

What happens when bacteria mutate?

They become resistant to antibiotics and can no longer be treated by antibiotics meaning they can cause serious infection

How would doctors slow the rate of development of resistive bacteria?

They avoid overprescribing antibiotics

Why is it important to finish the whole course of antibiotics?

Because antibiotics will kill the non resistant strain of bacteria but the resistant strain of bacteria will still be left + if you stop taking the antibiotics the left over bacteria will then reproduce and you will feel ill again

What is aspirin + how was it developed?

Aspirin is a painkiller + was developed from a chemical found in willows

What is Digitalis + how was it developed?

Digitalis is used to treat heart conditions + was developed from a chemical found in foxgloves

What is penicillin + how was it developed?

Penicillin is a drug that kills bacteria + was found by Alexander Fleming on a petri dish on which grew bacteria resistant mould now known as penicillin

What are the 5 stages of developing drugs? (5)

1. Preclinical testing (begins)

2. Preclinical testing (continue)

3. Clinical Trials

4. Double-blind trials

5. Peer review

What happens in the first stage of developing drugs (preclinical trials begin)?

Tests of the drug are done in a laboratory using cells and tissues

What happens in the second stage of developing drugs (preclinical trials continue)?

Tests of the drug are done on live animals to determine for toxicity (is it safe) + efficacy (does it work)

What happens in the third stage of developing drugs (Clinical trials)? (3)

• Tests of the drug are done healthy volunteers and patients

• Initially a small dose is given to see if there are any harmful side effects (when given to healthy people)

• If the drug is found to be safe further trial are carried to find the optimum dose (the most effective with the least amount of side effects)

What happens in the fourth stage of developing drugs (Double-blind trials)? (3)

• To see how well the drug works patients are put in 2 different groups

• Half of them are given the real drug + the other half are given a placebo (fake drug)

• This is to see if the drug actually works and isn’t in everyone’s head

Why are double-blind trials called that + why are they done? (2)

• Because the doctor and the patients don’t know who was given a placebo or the real drug

• This eliminates bias

What happens in the fifth stage of developing drugs (Peer review)?

Other scientists review the medicine + check for any mistakes

When new medicine is in use why is it monitored?

To see if there are any long term side effects

What type of white blood cell produces antibodies?

B-lymphocytes

How are monoclonal antibodies produced? (6)

1. A mouse is injected with the chosen antigen

2. This triggers the B-lymphocytes (a type of white blood cell that produces antibodies) to be produced which will produce antibodies specific to the antigen

3. Then the B-lymphocytes are collected from the mouse

4. The B-lymphocytes produced won’t divide on their own so they are fused with a tumour cell to make a hybridoma + will divide rapidly

5. The hybridoma then divides rapidly

6. The antibodies will be collected and purified

What do pregnancy tests detect + where is this hormone found?

They detect the hormone HCG which is found in the urine of pregnant women

How are monoclonal antibodies used in pregnancy tests? (8)

1. On a pregnancy test, there is a bit of the stick where you wee on that has antibodies stuck into it with a blue head

2. The test strip (the bit which indicates you’re pregnant) has antibodies stuck onto it so they can’t move

3. If you’re pregnant, when you wee on the stick

   • the hormones bind to the blue antibodies

   • the urine moves up the stick + carrying the hormones + blue antibodies up

   • The blue antibodies bind with the antibodies stuck onto the stip

   • So it turns blue (or any other colour) indicating you’re pregnant

4. If you aren’t pregnant non of this happens because the blue antibodies didn’t have any hormones to bind with leading to no indication of pregnancy

How are monoclonal antibodies used to treat cancer? (5)

1. Cancer cells have specific antigens called tumour makers

2. Monoclonal antibodies can be produced to bind specifically to tumour markers

3. An anti-cancer drug will be attached to these antibodies which may be a radioactive substance, a toxic drug or a chemical that stops cancer from growing + dividing

4. The antibodies are given to a patient via a drip

5. The drug attached to the antibodies will then attach to the tumour marker + this will kill the cancer cells but not normal body cells

How are monoclonal antibodies used to locate specific molecules in a cell or tissue? (3)

1. Monoclonal antibodies specific to the molecule will be made

2. Then they will be bound with fluorescent dye

3. If the molecule is present the monoclonal antibodies will attach to it and will be detected using dye

What are 2 other ways monoclonal antibodies can be used?

• To bind to hormones + other chemicals to measure their levels

• Test blood samples for specific pathogens

What side effects do monoclonal antibodies cause? (3)

• Vomiting

• Fever

• Low blood pressure

What are the 2 main mineral ions plants need?

• Nitrate ions

• Magnesium ions

Why do plants need nitrate + what happens if they don’t get it?

Nitrate is needed to make proteins for growth + lack of nitrate causes stunted growth

Why do plants need magnesium ions + what happens if they don’t get it?

Magnesium ions are needed to make chlorophyll which absorbs sunlight for photosynthesis + a lack of magnesium ions causes chlorosis (causes plants to stop making photosynthesis) + yellow leaves

What are the 7 common signs of disease in a plant?

• Stunted growth

• Spots on leaves

• Patches of decay

• Abnormal growth (lumps)

• Malformed stems or leaves

• Discolouration

• Pests

What 3 ways can plant diseases be identified by?

• Looking it up in a garden manual or a gardening website

• Taken to a lab where scientists identify the pathogen

• Using test kits that identify the pathogens using monoclonal antibodies

What are the physical defences of a plant? (3)

• Waxy cuticle → Barrier to stop pathogens from entering

• Plant cells are surrounded by a cell wall made of cellulose

• A layer of dead cells around their stems/barks → acts as a barrier to stop pathogens from entering

What are the mechanical defences of a plant? (3)

• Have thorns + hairs → stops animals from touching + eating them

• Leaves droop + curl when touched → prevent them from being eaten

• Mimicry of other organisms → fools insects into not eating them

What are the chemical defences of a plant? (2)

• Produce antibacterial chemicals → kill bacteria

• Produce poison → deter herbivores