[B3] Infection and response

What are pathogens?

Microorganisms which cause infectious disease

What are four types of pathogen?

Viruses, protists, bacteria, fungi

Put the four types of pathogen in order from smallest to largest

(smallest) viruses → bacteria → fungi → protists (largest)

How can pathogens be spread?

• Through air • Through direct contact • Through water (or other ingested substances like food)

Give three words that decsribe diseases that are easily spread

Contagious, Communicable, Infectious

How can the spread of disease can be reduced or prevented?

• Hygiene e.g. washing hands before cooking/after sneezing • Destroying vectors e.g. using insecticides or destroying insects' habitats so that they can't breed • Isolating infected individuals • Vaccination

How do bacteria make us feel ill?

they may produce poisons (toxins) that damage tissues and make us feel ill

How do viruses make us feel ill?

they live and reproduce inside cells, causing cell damage

Name three viral diseases

• Measles • HIV • Tobacco mosaic virus

What are the symptoms of measles?

Fever and red skin rash

How dangerous is measles?

it can be fatal if there are complications For example, it can lead to pneumonia or a brain infection called encephalitis

How is measles spread?

when someone inhales droplets of fluid from an infected person's sneeze or cough

How can measles be treated?

Most people are vaccinated against it when they're young If not vaccinated, the disease cannot be treated (although symptoms may be able to be treated)

What are the symptoms of HIV?

• initially a flu-like illness • then, unless controlled with antiretroviral drugs, the virus attacks the body's immune cells • Late stage HIV infection, or AIDS, occurs when the body's immune system becomes so badly damaged it can no longer deal with other infections or cancers

How is HIV spread?

• Sexual contact • Exchanging bodily fluids, such as blood (e.g. when drug users share needles)

HIV can't be treated; how can it be prevented?

Barrier contraception (like condoms), or not sharing needles

What are the symptoms of TMV (tobacco mosaic virus)?

• Causes a mosaic pattern on leaves (which means parts become discoloured) • Discolouration means that plants can't carry out photosynthesis as well so TMV also inhibits growth

TMV can't be treated; how can it be prevented?

Field hygiene and pest control.

Name two bacterial diseases

• Salmonella • Gonorrhea

What are the symptoms of salmonella?

• fever • stomach cramps • vomiting • diarrhoea

How is salmonella spread?

It is foodborne: eating food contaminated with salmonella bacteria.

How can salmonella be prevented?

• Food hygeine • Most poultry in the UK is vaccinated against salmonella to control the spread

What are the symptoms of gonorrhea?

• Pain when urinating • Thick yellow/green discharge from the vagina or penis

How is gonorrhoea spread?

by sexual contact

How is gonorrhoea treated?

Antibiotics

How should gonorrhea be prevented?

Barrier contraception, e.g. condoms

What type of pathogen causes rose black spot?

Fungi

What are the symptoms of rose black spot?

• Causes purple/black spots to develop on the leaves of rose plants • The leaves can then turn yellow and drop off • Less photosynthesis can happen, so growth is also inhibited

How is rose black spot spread?

Through water and wind.

How can rose black spot be treated?

• Using fungicides • Removing the affected leaves, which should be destroyed so that the fungus can't spread to other plants

What type of pathogen causes malaria?

A protist

What are the symptoms of malaria?

Causes repeating episodes of fever

How dangerous is malaria?

It can be fatal

How is malaria spread?

• mosquitos pick up the protist when feeding on an infected animal • the mosquito infects a new animal by inserting the protist into the animal's blood vessels

How can the spread of malaria be reduced?

• stopping mosquitoes from breeding • using mosquito nets to avoid being bitten

What are the non-specific defence systems of the human body?

• skin • nose • trachea and bronchi • stomach

How does our skin prevent disease?

Skin acts as a barrier and secretes antimicrobial substances which kill pathogens

How does our nose prevent disease?

Hairs and mucus in the nose trap particles that could contain pathogens

How do our trachea and bronchi prevent disease?

• they secrete mucus to trap pathogens • they are lined with ciliated cells which move the mucus up to the back of the throat, where it can be swallowed

How does our stomach prevent disease?

hydrochloric acid in the stomach kills bacteria

How do white blood cells help to defend the body against pathogens?

Phagocytosis, Producing antibodies, Producing antitoxins.

What is phagocytosis?

a type of white blood cell engulfs foreign cells/pathogens and digests them with enzymes

What is a benefit of using vaccinations as opposed to letting the immune system deal with infection?

When infected with a new pathogen, it takes a few days for the immune system to fully respond. By then, you can already be quite ill, so vaccinations help your body to react faster, before you have severe symptoms

What do vaccinations involve?

• a small amount of dead/inactive pathogens are injected into the body • these cause white blood cells to produce specific antibodies, even though the vaccine is harmless • if live pathogens of the same type enter the body after that, they are recognised quickly and the white blood cells can destroy them quickly

What do painkillers do?

they relieve pain and help to reduce symptoms of infection, but don't deal with the cause of disease or kill pathogens.

What do antibiotics do?

they help to cure bacterial disease by killing infective bacteria in the body

Why can't antibiotics be used to treat viruses?

Viruses reproduce inside body cells. This makes it difficult to develop drugs that just kill the virus and not cells as well.

Why are antibiotic-resistant bacteria a problem?

The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. However, the emergence of strains resistant to antibiotics means that some bacteria cannot be treated with antibiotics, and will cause more deaths.

What is an example of an antibiotic-resistant bacteria?

MRSA causes serious wound infections

Give two examples of drugs which were developed from plants

• The heart drug digitalis originates from foxgloves. • The painkiller aspirin originates from willow.

Give an example of a drug which was developed from a microorganism

• Penicillin was discovered by Alexander Fleming from the Penicillium mould (a fungus)

What does the pharmaceutical industry do?

discover and develop medicinal drugs

When testing drugs, what three things are investigated?

• Efficacy (how effective it is) • Toxicity (whether it's harmful) • Dosage (how much, how often)

What is preclinical testing?

tests that are done in a laboratory using cells, tissues and live animals

What are clinical trials?

tests that use healthy volunteers and patients

What are the two main stages of clinical trials?

• Testing on healthy human volunteers (to make sure it doesn't have harmful side effects when the body's working normally). Dosage is gradually increased. • Testing on people suffering from the illness. The optimum dosage is found (most effective, with the fewest side effects).

What is a placebo?

A tablet that does not contain an active drug ingredient

What is the placebo effect?

When a patient expects a treatment to work, so feels better, regardless of whether the drug had any chemical effect in the body

What are blind trials?

• Trials where patients are study are divided into 2 groups; A) receives the drug and B) receives a placebo • The patients are 'blind' so that they don't know whether they have the drug • The doctor can see the actual effect of the drug on the patients

What are double blind trials?

• Trials where patients are study are divided into 2 groups; A) receives the drug and B) receives a placebo • The patients are 'blind' so that they don't know whether they have the drug • The doctors are also 'blind' so they don't know which patient has the drug • This is so that the doctors aren't subconsciously influenced by their knowledge when monitoring and analysing

What are monoclonal antibodies?

Antibodies produced from a single clone of cells

How are monoclonal antibodies produced?

Lymphocytes are stimulated to produce a hybridoma cell which can they divide and make the antibody

How are monoclonal antibodies used?

Pregnancy tests, detecting pathogens, treating certain diseases

What is a drawback of using monoclonal antibodies?

More side effects than initially were expected

How can plant diseases be detectected?

• stunted growth • spots on leaves • areas of decay (rot) • growths • malformed stems or leaves • discolouration • the presence of pests

How can plant diseases be identified?

• reference to a gardening manual or website • taking infected plants to a laboratory to identify the pathogen • using testing kits that contain monoclonal antibodies

What ion deficiency can lead to stunted growth?

Nitrate deficiency

What ion deficiency can lead to chlorosis?

Magnesium deficiency

What are nitrate ions needed for in plants?

Protein synthesis

What are magnesium ionds needed for in plants?

Producing chlorophyl

What are the physical defence systems of plants?

• Cellulose cell walls • Tough waxy cuticle on leaves • Layers of dead cells around stems (bark on trees) which fall off

What are the chemical defence systems of plants?

• Antibacterial chemicals • Poisons to deter herbivores

What are the mechanical adaptations of plants?

• Thorns and hairs deter animals • Leaves which droop or curl when touched • Mimicry to trick animals