Disease (Edexcel GCSE Combined Science: Biology): Flashcards
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Health
A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (WHO definition).
Communicable disease
A disease caused by a pathogen that can spread between individuals (or between animals and individuals).
How does the World Health Organisation (WHO) define health?
A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.
What is a non-communicable disease? Give two examples.
A disease that is not caused by a pathogen and cannot be passed between individuals.
Examples: asthma, coronary heart disease (CHD), most cancers.
Name three factors that can increase the risk of developing a non-communicable disease.
Diet, stress and a person's life situation (e.g. income and where they live).
Why might someone suffering from one disease become more susceptible to other diseases?
Their immune system may be compromised, or the diseases may interact in ways that further damage health.
How can a virus living in cells trigger cancer? Give an example.
The virus can cause cells to become cancerous.
For example, the HPV virus can infect cells of the cervix and lead to cervical cancer.
How does HIV infection make a person more susceptible to other infections?
It reduces the number of lymphocytes, weakening the immune system so the body cannot fight off opportunistic infections such as pneumonia.
How can poor diet affect health?
It can lead to deficiencies, obesity, diabetes and poor mental health.
Communicable diseases are caused by , whereas non-communicable diseases are caused by these.
Communicable diseases are caused by pathogens , whereas non-communicable diseases are not caused by these.
Severe physical ill health can lead to and other mental illness, which can negatively impact the immune system.
Severe physical ill health can lead to depression and other mental illness, which can negatively impact the immune system.
True or False?
Non-communicable diseases can be passed from one person to another.
False.
Non-communicable diseases are not caused by pathogens, so they cannot be spread between individuals. Only communicable diseases can be passed on.
Pathogen
Any microorganism that causes disease in another organism (e.g. in plants or animals).
Communicable disease
A disease that is spread by pathogens from one organism to another.
Name the four types of pathogen.
Bacteria, fungi, protists (protoctists) and viruses.
Why are all viruses described as pathogenic, but not all bacteria, fungi and protists?
All viruses can only exist by living inside the living cells of other organisms, so they always cause harm. Many bacteria, fungi and protists are harmless and do not cause disease.
How do pathogenic bacteria cause damage to the body?
They reproduce very quickly and produce toxins that damage cells.
Name a disease caused by a pathogenic bacterium.
Tuberculosis (TB), bacterial meningitis, stomach ulcers or cholera.
How do fungi infect other organisms?
They produce spores, which allow them to spread and infect other organisms.
Give an example of a fungal disease that affects plants.
Black Sigatoka (in bananas) or Chalara ash dieback (in ash trees).
What is a protist, and name a serious disease caused by one?
A protist is a (usually unicellular) parasite that needs a host to survive.
For example, Plasmodium falciparum causes malaria.
A pathogen is a that causes disease in another organism.
A pathogen is a microorganism that causes disease in another organism.
The protist causes severe forms of malaria in humans.
The protist Plasmodium falciparum causes severe forms of malaria in humans.
True or False?
Viruses can only reproduce inside the living cells of another organism.
True.
Viruses have no cellular machinery of their own, so they must use a host cell to replicate. This is why all viruses are pathogens, unlike bacteria, fungi and protists, many of which are harmless.
Transmissible disease
A disease caused by a pathogen that can pass from one host to another.
Which bacterium causes cholera, and what are its symptoms?
Vibrio cholerae infects the intestines, causing diarrhoea, vomiting and leg cramps. It can lead to death if not treated quickly.
Which bacterium causes tuberculosis (TB), and what are its symptoms?
Mycobacterium tuberculosis infects the lungs, causing a chronic cough and bloody mucus.
What type of infection is chlamydia, and what can it cause if untreated?
Chlamydia is a sexually transmitted infection caused by Chlamydia trachomatis. If left untreated it can cause infertility.
How does HIV affect the body?
It destroys lymphocytes (white blood cells), reducing the number of antibodies that can be made.
This weakens the immune system, eventually leading to AIDS.
How does HIV avoid being destroyed by the immune system?
It repeatedly changes its protein coat, so lymphocytes cannot recognise it.
How is malaria spread, and what are its symptoms?
It is spread by mosquitoes (an animal vector) and damages the blood and liver, causing fever, chills and fatigue.
How is the fungal disease Chalara ash dieback spread between trees?
Its spores travel large distances in the wind.
How can the spread of waterborne diseases such as cholera be prevented?
By avoiding poor quality water and making sure people have access to clean water.
Give three ways the sexual transmission of HIV and chlamydia can be reduced.
Wearing condoms, screening to detect cases, and limiting the number of sexual partners (also education programmes and avoiding sharing needles).
Malaria is spread by mosquitoes, which act as an animal , carrying the pathogen between hosts.
Malaria is spread by mosquitoes, which act as an animal vector , carrying the pathogen between hosts.
Diseases such as influenza and tuberculosis are spread by transmission, in droplets travelling through the air.
Diseases such as influenza and tuberculosis are spread by airborne transmission, in droplets travelling through the air.
True or False?
HIV can be passed on through infected blood as well as through sexual contact.
True.
HIV is carried in body fluids, so it can be transmitted through infected blood (for example through shared needles or blood products) as well as through sexual contact. It is not spread by everyday contact such as touching or sharing cutlery.
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