Pathogen
Disease-causing microoganism
Toxin
Harmful chemical produced by microorganism
Protist
Example of a microoganism
Positive effects of using bacteria
Assist in digesting food
Some bacteria produce vaccines, antibiotics and/or drugs
Act as decomposers
Pathogens can enter the body by:
Water (eg drinking contaminated water)
Air (eg breathing in droplets)
Direct contact (eg touching an infected person)
Droplet infection
An infection spread from one person to another by droplets of water released from the upper respiratory tract by sneezing/coughing. Can be prevented by wearing masks.
Bacteria
Single celled organisms
Have a circular strand of DNA rather than a nucleus
Do not contain mitochondria
May have a flagellum
Living cells
Viruses
NOT cells
Smaller than bacteria
Consist of genetic material and a protein coat
How do bacteria cause disease
Reproduce rapidly by splitting in 2 (binary fission) and produce toxins which can damage cells
How do viruses cause disease
Live and reproduce rapidly inside host cells, continuing until the cell bursts. Cell damage is what causes people to feel unwell
Health
A state of physical and mental wellbeing
2 examples of how health problems interact
Viruses can trigger changes in cells leading to cancer
Defects in the immune system mean someone is more likely to suffer from infectious diseases
Reactions initially caused by a pathogen can trigger allergies such as asthma and skin rashes
Poor physical health can lead to mental illnesses such as depression
Malnutrition can link to other conditions such as obesity, cancer, type 2 diabetes and a weakened immune system
4 types of pathogens
Bacteria
Fungus
Viruses
Protists
Louis Pasteur
Developed the germ theory of disasae, showing that it was caused by living microoganisms
Joseph Lister
Introduced the use of carbolic acid to sterilise instruments and to clean wounds in surgeries
Ignaz Semmelweis
Proved that hand-washing could dramatically reduce the number of deaths during childbirth
Florence Nightengale
Introduced handwashing and other hygienic practices into hospitals
How to prevent the spread of infection
Hygiene- cleans away/kills pathogens
Isolating infected individuals- reduces the spread by limiting contact
Destroying/controlling vectors- reduces spread of pathogens
Vaccination- Strengthens immune systems defences against the disease
Symptoms of measles
Cold-like symptoms
Sore, red and swollen eyes
Red skin rash
Fever
Aches and pains
Loss of appetite
Tiredness
How is measles spread
Droplet infection and direct contact
Symptoms of HIV
Fever
Fatigue
Swollen lymph nodes
Diarrhoea
Weight loss
Other flu-like symptoms
How is HIV spread
Direct sexual contact and sharing blood (eg sharing needles)
TMV symptoms
Mottled leaves
Stunted growth
Reduced yields in affected crops
How is TMV spread
Mechanically- from infected plants to scratched/damaged leaves of normal plants
Salmonella symptoms
Fever
Cramps
Vomiting
Diarrhoea
How is salmonella spread
By bacteria ingested in food or on food prepared in unhygienic conditions
How is the spread of salmonella managed
Poultry are vaccinated against it
Gonorrhoea symptoms
Thick yellow/green discharge
Pain on urinating
How is gonorrhoea spread
Direct sexual contact
How is the spread of gonorrhoea controlled
Treated with antibiotics (although some strains are resistant)
Barrier method of contraception (eg condoms)
Physical defences of plants against disease
Waxy cuticle
Cell walls made from cellulose
Layers of dead cells around stems (eg bark on trees)
Chemical defences of plants against disease
Some plants produce antibacterial chemicals- eg mint and witch hazel