Biology- B5: Health, Disease and the Development of Medicines

Define health.

A state of complete physical, mental and social well-being (as defined by the World Health Organisation, WHO).

Define disease.

A disorder of the body or mind that negatively affects and individual’s health.

What are the two types of disease?

-Communicable.

-Non-communicable.

What is a communicable disease?

-A disease that is passed directly between individuals.

-Caused by a pathogen.

Define pathogen.

A disease-causing organism e.g. virus, fungi, bacteria, protists.

What is a non-communicable disease?

-A disease that cannot be transmitted between individuals.

-Generally long lasting with a slow-onset.

-Caused by lifestyle, environmental conditions, genetic mutations etc.

What is a symptom?

A change experienced by an organism that indicates disease.

Why does having an illness make an individual more likely to contract another disease?

A disease may weaken an individual’s immune system making them increasingly susceptible to other infections.

Describe cholera.

-Caused by Vibrio cholerae bacterium.

-Spread by drinking water or washing in water that has been contaminated with infectious faeces.

-Symptoms: diarrhoea, vomiting.

How can the incidence of cholera be reduced?

-Access to clean water.

-Improved sanitation (sewage disposal etc).

Describe tuberculosis (TB).

-Caused by Mycobacterium tuberculosis bacterium.

-It is an airborne bacteria spread by droplet infection.

-Symptoms: lung damage, chesty cough, wheezing.

How can the transmission of TB be reduced?

-Improved hygiene (washing hands, sneezing into tissues etc).

-Infected individuals should avoid crowded areas.

-Increased ventilation in the individual’s home.

Describe Chalara ash dieback.

-Caused by a fungus that infects ash trees.

-Spread via airborne spores which are carried by the wind.

-Caused dark lesions on bark and blackened leaves which wilt and eventually die.

How can the transmission of Chalara ash dieback disease be reduced?

-Control the movement of ash trees.

-Kill infected plants.

-Replant with a different species.

Describe malaria.

-Caused by plasmodium protist.

-Spread by mosquito vectors which pick up the plasmodium protist when feeding on the blood of an infected organism and transmit malaria to other organisms during feeding.

-Flu-like symptoms, damage to red blood cells, liver damage.

How can the incidence of malaria be reduced?

-Mosquito nets.

-Insect repellent.

Cover arms and legs.

Describe stomach ulcers.

-Caused by Helicobacter pylori bacterium.

-Transmitted orally by eating infected foods or drinking infected water.

-Symptoms: stomach pain, vomiting, nausea.

How can the transmission of Helicobacter pylori be reduced?

-Access to clean water.

-Improved hygiene.

-Improved sanitation (sewage disposal etc).

Describe Ebola.

-Caused by Ebola virus.

-Spread by direct contact with infected body fluids e.g. blood, semen, saliva, mucus, vomit.

-Symptoms: fever, diarrhoea, vomiting, internal bleeding.

How can the transmission of Ebola be reduced?

-Improved hygiene.

-Isolating infected individuals.

-Sterilisation of outbreak areas.

Describe simply how viruses cause disease.

They enter host cells and replicate inside of them. The host cells rupture, releasing new viruses.

How do viruses differ from other microorganisms e.g. bacteria, fungi?

Viruses are not living organisms. They do not reproduce and can only replicate inside a host cell.

By what two pathways do viruses replicate inside living cells?

-Lytic pathway.

-Lysogenic pathway.

Describe the lytic pathway.

1) Virus binds to specific receptors on host cell.

2) Virus injects its DNA into host cell and replicates its DNA using host cell machinery.

3) New viral structures are produced and assembled.

4) Host cell ruptures, releasing new viruses.

Describe the lysogenic pathway.

1) Virus binds to specific receptors on host cell.

2) Viral DNA injected into host cell and becomes integrated into host cell genome.

3) Viral DNA replicates each time the host cell divides. However, the call remains normal.

4) Trigger causes the activation of viral DNA. It enters lytic pathway.

Describe HIV.

-Caused by human immunodeficiency virus.

-Spread by direct contact with infected body fluids e.g. blood, semen, breast milk.

-Destroys white blood cells making the individual immunodeficient and increasingly susceptible to other diseases. Leads to AIDS.

How can the spread of HIV be reduced?

-Use of condoms and protected sex.

-Needle exchange.

-Screening blood for HIV.

-Deterring infected mothers from breastfeeding.

Describe Chlamydia.

-Caused by Chlamydia bacterium.

-Spread through sexual contact or direct contact with infected genital fluids.

-Can result in infertility.

How can the spread of Chlamydia be reduced?

-Use of condoms and protected sex.

-Screening.

Describe the physical defence system within plants.

-Waterproof waxy cuticle- surface barrier preventing the entry of pathogens.

-Cellulose cell wall- further barrier against pathogens.

Give some examples of chemical barriers in plants.

-Secretion of toxins to reduce damage by pests e.g. stinging nettles.

-Production of antibacterial chemicals that kill bacterial pathogens.

Why are chemicals produced by plants useful?

They produce physiological effects on the body so can be used in medicines to treat disease.

Why are chemicals produced by plants useful?

They produce physiological effects on the body so can be used in medicines to treat disease.

Give an example of a medicine derived from plants.

-Quinine- antimalarial, bark of Cinchona sp.

-Aspirin- painkiller, bark/leaves of Salix alba.

Why are plant defence systems important?

-Plants are producers so all organisms higher up in food chains rely upon their survival and ability to fight disease.

-Important in maintaining human food security.