Topic 3 - Infection and response - Pathogens and communicable diseases

Question 1

What are pathogens?

Answer 1

Microorganisms that enter the body and cause disease

Question 2

What type of disease to pathogens cause?

Answer 2

Communicable diseases - ones that are easily spread

Question 3

What is bacteria?

Answer 3

1. Bacteria are very small living cells
2. They are about 1/100th the size of your body cells
3. They can reproduce rapidly inside your body
4. They can make you feel ill by producing toxins that damage your cells and tissues

Question 4

What are viruses?

Answer 4

1. Viruses are not cells. They are tiny. About 1/100th the size of a bacterium
2. Like bacteria, they can reproduce rapidly inside your body
3. They live inside your cells and replicate themselves using the cells’ machinery to produce many copies of themselves. The cell will usually then burst, releasing all the new viruses
4. This cell damage is what makes you feel ill

Question 5

What are protists?

Answer 5

1. Protists are single-cell Eukaryotes
2. Some protists are parasites. Parasites live on or inside other organisms and can cause them damage. They are often transferred to the organism by a vector, which doesn’t get the disease itself. E.g. a mosquito is a vector for malaria

Question 6

What are fungi?

Answer 6

1. Some fungi are single celled. Others have a body which is made up of hyphae
2. These hyphae can grow and penetrate human skin and the surface of plants, causing diseases
3. The hyphae can produce spores, which can be spread to other plants and animals

Question 7

How can pathogens be spread?

Answer 7

1. Water. Some pathogens can be picked up by drinking or bathing in dirty water. E.g cholera is a bacterial infection that is spread by drinking water contaminated with the diarrhoea of other sufferers.
2. Air. Pathogens can be carried in the air and can then be breathed in. Some airborne pathogens are carried in the air in droplets produced when you cough or sneeze. E.g. the influenza virus that causes flu is spread like this
3. Direct contact. Some pathogens can be picked up by touching contaminated sursfaces, including the skin. E.g. athlete’s foot is a fungus which makes skin itch and flake off. It is most commonly spread by touching the same things an as infected person e.g. shower floors and towels

Question 8

What are three viral diseases?

Answer 8

1. Measles
2. HIV
3. Tobacco mosaic virus (TMV)

Question 9

Describe measles?

Answer 9

1. Measles is a viral disease. It is spread by droplets from an infrected person’s sneeze or cough
2. People with measles develop a red skin rash, and they’ll show signs of a fever
3. Measles can be very serious, or even fatal, if there are complications. Measles can sometimes lead to pneumonia (a lung infection) or encephalitis (imflammation of the brain)
4. Most people are vaccinated against measles when they are young

Question 10

Describe HIV?

Answer 10

1. HIV is a virus spread by sexual contact, or by exchanging bodily fluids such as blood. This can happen when people share needles when taking drugs
2. HIV initially causes flu-like sypmtoms for a few weeks. Usually, the person doesn’t then experience any symptoms for several years. During this time, HIV can be controlled with antiretroviral. These stop the virus replicating inside the body
3. The virus attacks the immune cells
4. If the body’s immune system is badly damaged, it can’t cope with other infections or cancers. At this stage, the virus is known as late stage HIV infection, or AIDS

Question 11

Describe TMV?

Answer 11

1. Tobacco Mosaic Virus is a virusthat affects many species of plants, e.g. tomatoes
2. It causes a mosaic pattern on the leaves of the plants - parts of the leaves become discoloured
3. The discolouration means the plant can’t carry out photosynthesis as well, so the virus affects growth

Question 12

Example of a fungal disease?

Answer 12

Rose black spot

Question 13

Describe rose black spot?

Answer 13

1. Rose black spot is a fungus that causes purple or black spots to develop on leaves of rose plants. The leaves can then turn yellow and drop off
2. This means that less photosynthesis can happen, so the plant doesn’t grow very well
3. It spreads through the environment in water or by the wind
4. It can be treated using fungacides and by stripping the plant of its affected leaves. These leaves then need to be destroyed so that the fungus can’t spread to other rose plants

Question 14

Example of a disease spread by a protist?

Answer 14

Malaria

Question 15

Describe malaria?

Answer 15

1. Malaria is caused by a protist
2. Mosquitos are vectors - they pick up the malarial protist when they feed on an infected animal
3. Every time the mosquito feeds on another animal, it infects it by inserting the protist into the animal’s blood vessels
4. Malaria causes repeating episodes of fever. It can be fatal
5. The spread of malaria can be reduced by stopping the mosquitos from breeding
6. People can be protectred from mosquitos by using insecticides and mosquito nets

Question 16

Examples of bacterial diseases?

Answer 16

1. Salmonella
2. Gonorrhoea

Question 17

Describe salmonella?

Answer 17

1. Salmonella is a type of bacteria that causes food poisoning
2. Infected people can suffer from fever, stomach cramps, vomiting and diarrhoea
3. These symptoms are caused by toxins that the bacteria produces
4. You can get salmonella food poisoning by eating food that’s been contaminated with salmonella bacteria e.g. eating a chicken that caught the disease while it was alive or eating food that was prepared in unhygeinic conditions
5. In the UK, most pultry is given a vaccination against salmonella. This is to control the spread of the disease

Question 18

Describe gonorrhoea?

Answer 18

1. It is a sexually transmitted disease (STD)
2. It is passed on by sexual contact like having unprotected sex
3. Gonorrhoea is caused by bacteria
4. A person with gonorrhoea will experience pain when they urinate. Another symptom is a thick yellow or green discharge from the vagina or penis
5. It was originally treated with an antibiotic called penicillin, but strains of the bacteria have become resistant to it
6. To prevent it from spreading, people can be treated with antibiotics and should use barrier methods of contraception such as condoms

Question 19

How can the spread of disease be reduced or prevented?

Answer 19

1. Being hygeinic. E.g. washing hands regularly
2. Destroying vectors. By getting rid of the organisms that spread disease, you can prevent the disease from being passed on. You can use insecticides or destroy their habitat so they cant breed
3. Isolating infected individuals. If you isolate someone with a communicable disease, it prevents them from passing it on to anyone else
4. Vaccination. People that are vaccinated are less likely to develop infection and then pass it on. Can’t protect plants against infection - they don’t have an immune system

Question 20

Why do plants need nitrate ions?

Answer 20

1.Nitrates are needed to make proteins and therefore for growth
2. A lack of nitrates causes stunted growth

Question 21

Why do plants need magnesium ions?

Answer 21

1. Magnesium ions are needed to make chlorophyll which is needed for photosynthesis
2. Plants without enough magnesium suffer from chlorosis and have yellow leaves

Question 22

How to identify plant diseases?

Answer 22

1. Looking up the signs in a gardening manual or on a gardening website
2. Taking the infected plant to a laboratory, where scientists can identify the pathogen
3. Using testing kits that identify the pathogen using monoclonal antibodies