B3- Infection and response Flashcards
What are the four types of pathogen?
Virus, protozoa, bacteria, fungus.
Which pathogen needs a host cell to reproduce and what does this make them?
Viruses. They are therefore not cells and are always pathogens.
Describe how a virus invades a cell.
- Virus enters cell.
- Substances in the cell break down the virus’ outer membrane.
- The virus’ nucleic acid is released.
- The acid enters the cell’s chemical manufacturing system.
- The virus overpowers the cell; the cell begins producing viruses.
- The viruses are released once there are too many for the cell to hold- the cell is killed.
What are pathogens?
Microorganisms which cause communicable disease.
From smallest to largest, what order do the types of pathogens come?
Viruses → bacteria → fungi → protozoa.
What is a eukaryote?
An organism which has cells with nuclei or a cell with a nucleus. Eukaryotes are complex and include all animals and plants.
Describe bacteria.
- They are very small prokaryotic cells, about 1/100th the size of a body cell
- They reproduce rapidly inside the body
- They make you feel ill by producing toxins that damage cells and tissues
- However, they aren’t always parasites
Describe viruses.
- Not cells
- About 1/100th the size of a bacterium
- Make you feel ill by reproducing rapidly inside cells
Describe protozoa.
- They’re all eukaryotes and some are single-celled
- Some are parasites
- Parasites live on or inside organisms and cause damage
- They are often transferred to the organism via a vector which doesn’t get the disease itself
Describe funghi.
- Not always parasites
- Some are single-celled
- Others have a body made of threadlike structures called hyphae
- Hyphae can grow and penetrate human skin and the surface of plants, causing diseases
- Hyphae produce spores which can be spread to other plants and animals
In what ways can pathogens be spread?
- Ingested substances (water, food)
- Air
- Direct contact
Name 3 viral diseases.
- Measles
- HIV
- Tobacco mosaic virus
How is measles spread?
By droplets of fluid from an infected person’s sneeze/cough.
What are the symptoms of measles?
- Fever and red skin rash
- Can be fatal if there are complications
- E.g. can lead to pneumonia or a brain infection called encephalitis
How can measles be treated?
- Most people are vaccinated against it when they’re young
- If not, the disease must run its course
How is HIV spread?
- Sexual contact
- Exchanging bodily fluids, such as blood- e.g. when sharing needles taking drugs
What are the symptoms of HIV?
- Initially, flu-like symptoms for a few weeks
- Usually, no other symptoms are experienced for several years
- During this time, HIV can be controlled by antiretroviral drugs which stop the virus replicating
- The virus weakens the immune system by attacking immune cells. If it’s badly damaged, the body can’t cope with other infections, or cancers
- At this stage, HIV is known as late stage HIV infection or AIDS
HIV cannot be cured; how can it be prevented?
- Barrier contraception
- Not sharing needles
Why can’t HIV be cured, by our immune system or by drugs?
- When HIV copies its genes, it mutates into many different strains. As a result, the virus overpowers the body’s immune defenses
- It is a virus so reproduces inside cells. This means that it’s hard to kill it without damaging many of our cells
How is TMV spread? What does it affect?
Via vectors. Affects many species of plants.
What are the symptoms of TMV?
- Causes a mosaic pattern on leaves- parts become discoloured
- Discolouration means that plants can’t carry out photosynthesis as well
- TMV therefore inhibits growth
TMV can’t be treated; how can it be prevented?
Field hygeine and pest control.
What kind of disease is rose black spot?
Fungal.
How is rose black spot spread?
Through water and wind.
What are the symptoms of rose black spot?
- Causes purple/black spots to develop on the leaves of rose plants
- The leaves can then turn yellow and drop off
- Therefore, less photosynthesis can happen, so growth is inhibited
*
How can rose black spot be treated?
- Using fungicides
- Stripping the plant of its affected leaves, which should be destroyed so that the fungus can’t spread to other plants
What causes malaria?
A protist.
How is malaria spread?
- Part of the malarial protist’s life cycle takes place inside the mosquito
- The mosquitoes are vectors- they pick up the protist when feeding on an infected animal
- When a mosquito feeds on an infected animal, it infects it by inserting the protist into the animal’s blood vessels
What are the symptoms of malaria?
Causes repeating episodes of fever. It can be fatal.
How can the spread of malaria be reduced?
Stopping mosquitoes from breeding.
How can people be protected from getting malaria from mosquitoes?
- Using insecticides
- Using mosquito nets
Why is malaria so difficult to eradicate?
- It is spread by mosquitoes
- It is constantly evolving
- It has several stages to its life cycle; each stage requires different ways to eradicate
Name 2 bacterial diseases.
- Salmonella
- Gonorrhea
How is salmonella spread?
It is foodborne: eating food contaminated with salmonella bacteria.