12.1 Disease (Cambridge (CIE) O Level Biology): Flashcards
Exam code: 5090
1/790Still learning
Know0
- FrontPathogens & Barriers
Define pathogen.
Was this flashcard helpful?
Cards in this collection (79)
Define pathogen.
A disease-causing organism.
Define transmissible disease.
A disease in which the pathogen can be passed from one host to another.
What is the difference between direct and indirect transmission of a pathogen?
In direct transmission the pathogen passes straight from one host to another, e.g. through body fluids such as blood.
In indirect transmission the pathogen leaves the host and is carried to another person, e.g. in air, food or water.
Cholera, typhoid and dysentery are transmitted through contaminated .
Cholera, typhoid and dysentery are transmitted through contaminated food or water.
Give two mechanical (physical) barriers that prevent pathogens entering the body.
Two mechanical barriers are:
skin
mucus and hairs in the nose and airways
How do mucus and hairs in the nose and airways defend against pathogens?
Mucus traps pathogens and the hairs waft the mucus out of the airways, stopping pathogens reaching the lungs.
The stomach produces , which is strong enough to kill pathogens that are swallowed.
The stomach produces hydrochloric acid, which is strong enough to kill pathogens that are swallowed.
True or False?
The hydrochloric acid in the stomach can kill pathogens that are swallowed.
True.
Stomach acid is strong enough to kill many pathogens before they can cause disease.
How does the skin act as a barrier to pathogens?
The skin covers the body to keep pathogens out; if it is cut or grazed it heals itself, often by forming a scab.
Define sebum.
An oily substance produced by the skin that helps to kill pathogens.
True or False?
Phagocytes and antibodies are barriers to the entry of pathogens.
False.
Phagocytes and antibodies only act once a pathogen has entered the body, so they are not barriers to entry.
Define vector.
An organism that carries a pathogen from one host to another.
What type of organism causes malaria?
A protoctist called Plasmodium.
Which organism is the vector of malaria?
The female Anopheles mosquito.
The female Anopheles mosquito feeds on human blood to obtain the she needs to develop her eggs.
The female Anopheles mosquito feeds on human blood to obtain the protein she needs to develop her eggs.
True or False?
The mosquito is the cause of malaria.
False.
The mosquito is the vector; the cause of malaria is the protoctist Plasmodium.
How does a mosquito transmit Plasmodium between people?
The mosquito takes up Plasmodium when it bites an infected person, then passes it into the blood of the next person it bites.
Other than mosquito bites, give two ways malaria can be transmitted.
Malaria can also be transmitted by:
blood transfusion with infected blood
unsterilised (shared) needles
from mother to child across the placenta
Give two ways the spread of the Anopheles mosquito can be controlled.
Ways to control the mosquito include:
spraying with insecticides (e.g. DDT)
spreading oil over water surfaces
draining marshes and still water
stocking water with fish that eat the larvae
Spreading over the surface of water stops mosquito larvae breathing air at the surface.
Spreading oil over the surface of water stops mosquito larvae breathing air at the surface.
How can an individual reduce their risk of catching malaria?
sleep under (insecticide-treated) bed nets
avoid exposing skin at dusk, when mosquitoes are most active
take antimalarial drugs (e.g. chloroquine, mefloquine)
True or False?
Sleeping under an insecticide-treated bed net helps to prevent malaria.
True.
Bed nets stop mosquitoes biting at night, reducing the chance of Plasmodium being transmitted.
Define STI.
A sexually transmitted infection — a pathogen passed between people during sexual contact.
Define HIV.
Human Immunodeficiency Virus — the virus that usually leads to AIDS.
Define AIDS.
Acquired Immunodeficiency Syndrome — a condition in which the immune system shuts down.
What effect does AIDS have on the body?
It causes the immune system to malfunction and eventually shut down, so the body cannot fight infections.
Why do people with AIDS often die from infections such as pneumonia?
Their immune system no longer works, so they can no longer fight off infections they would normally overcome.
HIV is a that usually leads to the development of AIDS.
HIV is a virus that usually leads to the development of AIDS.
Give three ways in which HIV can be transmitted.
HIV can be transmitted by:
unprotected sex (exchange of body fluids)
sharing needles with an infected person
blood transfusion with infected blood
mother to baby across the placenta or through breast milk
True or False?
HIV can be passed from a mother to her baby through breast milk.
True.
HIV is present in body fluids, so it can be passed to a baby during breastfeeding.
True or False?
HIV can be caught by shaking hands with an infected person.
False.
HIV is spread through body fluids, not through everyday contact such as shaking hands.
How can the spread of HIV be controlled?
limit the number of sexual partners
always use a condom / avoid unprotected sex
get tested
raise awareness through education programmes
Using a during sex helps to prevent the transmission of HIV.
Using a condom during sex helps to prevent the transmission of HIV.
Define cholera.
A disease caused by the bacterium Vibrio cholerae, resulting in severe diarrhoea.
Where in the gut does Vibrio cholerae attach and act?
To the wall of the small intestine.
How is cholera transmitted?
Through infected (contaminated) water or food.
Define diarrhoea.
The loss of large volumes of watery faeces from the anus.
Why can severe diarrhoea lead to death?
The body loses large amounts of water and ions, causing dehydration, so tissues and organs stop working properly.
How is cholera treated?
With oral rehydration therapy — a drink containing small amounts of salt and sugar dissolved in water.
Oral rehydration therapy is a drink containing small amounts of and dissolved in water.
Oral rehydration therapy is a drink containing small amounts of salt and sugar dissolved in water.
How does Vibrio cholerae cause water to be lost into the intestine?
The bacteria release a toxin that makes the intestine cells release chloride ions into the lumen; this lowers the water concentration, so water moves out of the cells by osmosis.
The cholera toxin makes the cells lining the intestine release into the lumen.
The cholera toxin makes the cells lining the intestine release chloride ions into the lumen.
True or False?
Cholera is caused by a virus.
False.
Cholera is caused by the bacterium Vibrio cholerae.
True or False?
During cholera infection, water moves out of the intestine cells into the lumen by osmosis.
True.
Chloride ions lower the water concentration in the lumen, so water leaves the cells by osmosis.
What is the simplest way to prevent the spread of disease?
To stop pathogens from spreading, using good hygiene, sanitation and safe waste disposal.
Define vector.
An organism, such as a fly, that carries a pathogen from one place or host to another.
Give two ways to prepare food hygienically to prevent disease.
keep food cold so microbes reproduce slowly
cook food well to kill microbes
cover food to keep off flies
use separate chopping boards for raw meat
Why should food be stored cold?
So that bacteria and fungi reproduce more slowly.
Cooking food well helps to prevent disease because the high temperature will bacteria and fungi.
Cooking food well helps to prevent disease because the high temperature will kill bacteria and fungi.
How does washing with soap help prevent the spread of pathogens?
Soap removes pathogens from the skin, along with the substances that trap them.
Why is the safe disposal of waste food important?
Waste food attracts flies, which act as vectors that can spread pathogens to human food.
How does good sanitation help to prevent disease?
Drains and plumbing remove faeces and waste safely, and raw sewage is treated to kill pathogens before it is released.
Raw sewage should be to remove solid waste and kill pathogens before it is released into the environment.
Raw sewage should be treated to remove solid waste and kill pathogens before it is released into the environment.
True or False?
Keeping food cold slows down the reproduction of bacteria and fungi.
True.
Low temperatures slow the reproduction of microbes, keeping food safe for longer.
True or False?
Raw sewage can be released into the environment without any treatment.
False.
Raw sewage must be treated to remove solids and kill pathogens before release.
Define ethanol.
The type of alcohol found in wines, beers and spirits.
Define depressant.
A drug that slows down signals in the nerves and brain.
Why are there legal limits for drinking and driving?
Alcohol increases reaction times by slowing the brain, which makes driving dangerous.
Alcohol is a depressant, so it slows down signals in the nerves and .
Alcohol is a depressant, so it slows down signals in the nerves and brain.
Give two short-term effects of alcohol abuse.
vomiting
impaired judgement and reduced self-control
impaired balance and muscle control
sleepiness or unconsciousness
Give two long-term effects of alcohol abuse.
damage to the brain (memory loss and confusion)
damage to the liver (cirrhosis)
social isolation
Which organ removes alcohol from the blood?
The liver.
Why can long-term alcohol abuse damage the liver?
The liver's enzymes break down alcohol, but the products are toxic, so over time the liver becomes irreparably damaged.
Define cirrhosis.
Liver damage caused by long-term heavy alcohol abuse.
Long-term alcohol abuse can damage the brain, causing memory loss and .
Long-term alcohol abuse can damage the brain, causing memory loss and confusion.
True or False?
Alcohol is a stimulant that speeds up the body's reactions.
False.
Alcohol is a depressant; it slows down the brain and increases reaction times.
True or False?
Alcohol can be an addictive drug.
True.
In many people alcohol is very addictive.
Define carcinogen.
A substance that causes cancer.
Name three harmful chemicals found in tobacco smoke.
tar
nicotine
carbon monoxide
What harm does tar do in the lungs?
Tar is a carcinogen. It also destroys cilia and stimulates extra mucus, leading to chronic bronchitis and COPD.
How does carbon monoxide affect the blood?
It binds irreversibly to haemoglobin, reducing the blood's capacity to carry oxygen.
Carbon monoxide binds irreversibly to , reducing the oxygen-carrying capacity of the blood.
Carbon monoxide binds irreversibly to haemoglobin, reducing the oxygen-carrying capacity of the blood.
What two effects does nicotine have on the body?
Nicotine is addictive and narrows blood vessels, which raises blood pressure.
How does smoking lead to emphysema?
Frequent infection attracts phagocytes that release elastase, which breaks down elastin in the alveoli walls; the alveoli burst, reducing the surface area for gas exchange.
Define emphysema.
A lung disease in which the alveoli walls break down, reducing the surface area for gas exchange.
In emphysema, the enzyme elastase breaks down in the walls of the alveoli.
In emphysema, the enzyme elastase breaks down elastin in the walls of the alveoli.
Name three diseases linked to smoking.
lung cancer
COPD (chronic bronchitis and emphysema)
coronary heart disease
True or False?
The tar in tobacco smoke is a carcinogen.
True.
Tar is a carcinogen and increases the risk of lung cancer.
True or False?
Nicotine widens blood vessels and lowers blood pressure.
False.
Nicotine narrows blood vessels and raises blood pressure.
Sign up to unlock flashcards
or