Topic 5 - Health & Disease Flashcards
Definition of Health
Health – “a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity.” – World Health Organisation
Describe the difference between communicable & non-communicable diseases
• Communicable diseases can be spread between individuals. This might be through air particles from coughing (known as droplet infection), e.g. a flu, a cold & parasite infections
• Non-communicable diseases can’t be transmitted between individuals, e.g. cancer, heart disease, asthma & diabetes
Explain why the presence of one disease can lead to a higher susceptibility to other diseases
If you are affected by one disease, it could make you more susceptible to others – your immune system/body becomes weakened by the disease, so it’s less likely to fight off the other disease, causing another one due to infections caused by bacteria, viruses & fungi.
Describe a pathogen as a disease-causing organism, including viruses, bacteria, fungi & protists
Pathogens are organisms such as viruses, bacteria, fungi & protists that cause communicable diseases
Describe some common infections, including: cholera, tuberculosis, chalara ash dieback, malaria, HIV, stomach ulcers & Ebola
• CHOLERA is a bacteria that causes diarrhoea.
• TUBERCULOSIS is a bacteria that causes lung damage.
• CHALARA ASH DIEBACK is a fungi that causes leaf loss & bark lesions.
• MALARIA is caused by a protist that causes damage to red blood cells & liver.
• HIV is a virus that destroys white blood cells, leading to the onset of AIDS
• Stomach ulcers are caused by a bacterium called Helicobacter
• Ebola is a virus that causes haemorrhagic fever (a fever with bleeding).
Explain how pathogens are spread & how this spread can be reduced / prevented
CHOLERA (bacteria)
• How it spreads: by contaminated water sources
• How to prevent transmission: make sure people have access to clean water supplies
TUBERCULOSIS (bacteria)
• How it spreads: through the air when infected individuals cough (airborne)
• How to prevent: infected people should avoid crowded public spaces, practise good hygiene & sleep alone. Their homes should be well-ventilated.
CHALARA ASH DIEBACK (fungi)
• How it spreads: it’s carried through the air by the wind. (Also when diseased ash trees are moved between areas)
• How to prevent: by removing young, infected ash trees & replanting with different species. + Restricting the import / movement of ash trees
MALARIA (protists)
• How it spreads: Mosquitoes act as animal vectors (carriers) – they pass on the protist to humans but they don’t get the disease themselves.
• How to prevent: use mosquito nets & insect repellent to prevent mosquitoes carrying the pathogen from biting people.
Stomach ulcers caused by Helicobacter (bacteria)
• How it spreads: Oral transmission e.g. swallowing contaminated water / food
• How to prevent: have clean water supplies & hygienic living conditions
EBOLA (virus)
• How it spreads: bodily fluids
• How to prevent: by isolating infected individuals & sterilising any areas where the virus may be present.
Describe the lifecycle of a virus, including lysogenic & lytic pathways
LYTIC PATHWAY
• The virus attaches itself to a specific host cell and injects its genetic material into the cell.
• The virus uses proteins & enzymes in the host cell to replicate its DNA and to produce the components of new viruses.
• The viral components assemble (join together)
• The host cell bursts in a process called lysis, releasing new viruses, which infects more cells.
LYSOGENIC PATHWAY
• The virus uses restriction enzymes to insert its DNA into the host cell DNA
• The viral genetic material & host DNA gets replicated every time the host cell divides – but the virus is dormant as no new viruses are made.
• A chemical trigger causes the viral genetic material to leave the genome and enter the lytic pathway.
Explain how STIs are spread & how this spread can be reduced / prevented
STIs are infections that spread through sexual contact, e.g. sexual intercourse.
CHLAMYDIA (bacteria)
• spread through sexual contact —> pregnant woman can give chlamydia to their baby during childbirth.
• can be reduced by wearing a condom
• screening individuals so they can be treated for the infection
• avoid sexual contact
HIV (virus)
• spreads through bodily fluids (e.g. blood, semen, vaginal fluids)
• can be reduced by wearing a condom
• drug users should avoid sharing needles
• medication
Describe how some plants defend themselves against attack from pests & pathogens by physical and chemical barriers
PHYSICAL BARRIERS
Plants have:
• a waxy cuticle on the surface of the leaf – acts as a barrier to stop pathogens entering the leaf or pests from damaging them. It can also stop water collecting on the leaf, which could reduce the risk of infection by pathogens that are transferred between plants in water.
• a thick cellulose cell wall – provides support for the plant and prevents pathogens entering the plant that make it past the waxy cuticle
CHEMICAL BARRIERS
• plants produce chemicals called antiseptics —> which kill bacterial and fungal pathogens
• plants produce chemicals to deter pests from feeding on their leaves.
Some of these chemicals can be used as frugs to treat human diseases / relieve symptoms
e.g. Quinine —> comes from the bark os the cinchona tree. Treats malaria. //
Aspirin —> developed from a chemical found in the bark and leaves of willow trees. Relieves pain & fever
Describe different ways plant diseases can be detected & identified in the field and in the lab
IN THE FIELD (by observations)
• galls (abnormal growths) might indicate crown gall disease in many different types of plant —> apple/other fruit trees.
• diseased plants will have yellow leaves due to environmental causes, such as a nutrient deficiency.
• analyse the distribution of diseased plants —> e.g. patches of diseased plants suggests that the disease is spread through the soul , and a random distribution may suggest an airborne pathogen.
IN THE LAB
• cuttings are taken from the diseased plant. The pathogen causing the disease is grown on an agar plate. Yhe pathogen is tested and identified using a monoclonal antibody testing kit (ELISA kit).
• the pathogen’s DNA will be present in the plant’s tissues if a plant is infected with a pathogen.
Describe how the physical & chemical barriers of the human body provide protection from pathogens
PHYSICAL BARRIERS
• the skin acts as a barrier to pathogens. If it gets damaged, blood clots quickly seal cuts & keeps microorganisms out
• hairs and mucus in your nose trap particles that could contain pathogens
• cells in your trachea & bronchi (airways in the lungs) also produce mucus —> traps pathogens .
• cilia (hair-like structure) wafts the mucus up to the back of the throat where it can be swallowed, so it can be killed by hydrochloric acid
CHEMICAL BARRIERS
•the stomach produces hydrochloric acid —> this kills most pathogens that are swallowed
• the eyes produce a chemical called lysozyme (in tears) which kills bacteria on the surface of the eye
Explain how the immune system acts as a defence against disease
• When a pathogen enters the body for the first time, the immune response is slow because there aren’t many B-lymphocytes that can produce the antibody needed to lock on to the antigen.
• memory lymphocytes are also produced due to the antigen.
• if you become infected with the same pathogen again, the antibodies will be produced at a faster rate as more cells will recognise it.
• the secondary response often gets rid of the pathogen before you begin to show symptoms.
Explain the body’s response to immunisation using an inactive form of a pathogen
• Immunisation involves injecting dead or inactive pathogens into the body. These are antigenic (they carry antigens) —> even though they’re harmless, your body produces antibodies to help destroy pathogens.
• antigens also trigger memory lymphocytes
• so, if the same type of pathogen gets into the body, there will already be memory lymphocytes that can cause a fast secondary immune response. This means that you’re less likely to get the disease .
Discuss the advantages and disadvantages of immunisation
ADVANTAGES
• epidemics can be prevented if a large population are immunised. Even the people who aren’t immunised are unlikely to catch the disease as there is fewer people able to pass it on – this is known as herd immunity.
• some diseases, e.g. smallpox, has been wiped out by immunisation programmes
DISADVANTAGES
• Immunisation isn’t always effective in providing immunity
• Bad reactions (e.g. fevers, swelling, seizures) can occur in response to vaccines —> but it’s very rare .
