Topic 3 Infection and response

Q: What is a pathogen?

A: A microorganism that causes infectious disease.

Q: Name four types of pathogens.

A: Bacteria, viruses, fungi, and protists.

Q: How do bacteria reproduce?

A: By binary fission; they can divide every 20 minutes under ideal conditions.

Q: How do bacteria cause illness?

A: They reproduce rapidly and release toxins that damage tissues and make us feel ill.

Q: What is a virus?

A: A pathogen that can only reproduce inside a host cell.

Q: Why are viruses different from bacteria?

A: Viruses cannot reproduce on their own and must infect host cells.

Q: How do viruses cause illness?

A: They enter host cells, reproduce inside them, and damage or burst the cells.

Q: Give an example of a viral disease.

A: HIV (which can lead to AIDS).

Q: How can pathogens spread through the air?

A: In water droplets (e.g. influenza).

Q: How can pathogens spread through water?

A: By drinking contaminated water (e.g. cholera).

Q: How can pathogens spread by direct contact?

A: Through sexual contact or sharing needles (e.g. HIV).

Q: Describe ways to reduce the spread of communicable diseases.

A: Good hygiene reduces transmission, clean water prevents infection, reducing contact lowers spread, isolation prevents outbreaks, and vaccination reduces the number of susceptible individuals.

Q: Can antibiotics kill viruses?.

A: No – antibiotics do not work against viruses

Q: What are the early symptoms of measles?

A: A high temperature (fever).

Q: How is measles spread?

: By inhaling droplets released when an infected person coughs or sneezes.

Q: How is measles prevented?

A: By vaccination, usually in early childhood.

Q: What happens to the immune system after HIV infection?

A: HIV attacks immune cells, gradually damaging the immune system.

Q: What is AIDS?

A: The late stage of HIV when the immune system is severely damaged.

Q: Give two ways HIV can be spread.

A: Unprotected sexual intercourse and sharing infected needles.

Q: How is HIV treated?

A: With antiretroviral drugs.

Q: Describe the stages and treatment of HIV infection.

A: HIV initially causes flu-like symptoms and then damages the immune system. In late stages (AIDS), the immune system cannot fight infections or cancer. Antiretroviral drugs stop the virus multiplying and prevent AIDS but are not a cure.

Q: Describe how salmonella food poisoning is caused and spread.

A: Salmonella is caused by bacteria ingested in contaminated food. The bacteria release toxins that cause symptoms such as fever, vomiting, and diarrhoea.

Q: Describe the symptoms, treatment, and prevention of gonorrhoea.

A: Gonorrhoea causes discharge and pain when urinating. It is treated with antibiotics, although some strains are resistant. The spread can be reduced by using condoms and testing people who have unprotected sex.

Q: Why is salmonella less common in the UK now?

A: Poultry such as chicken are vaccinated against salmonella.

Q: What are the symptoms of gonorrhoea?

A: Thick yellow or green discharge from the penis or vagina and pain when urinating.

Q: Why is gonorrhoea harder to treat now?

A: Some strains are antibiotic resistant.

Q: What causes malaria?

A: A pathogen called a protist.

Q: Describe how malaria is spread.

A: Malaria is spread by mosquitoes. When a mosquito bites an infected person, it picks up the malaria pathogen. The mosquito then bites another person and passes the pathogen on.

Q: Describe two ways the spread of malaria can be reduced.

A: The spread of malaria can be reduced by stopping mosquitoes from breeding by draining still water or using insecticides. It can also be reduced by preventing mosquitoes from biting humans using mosquito nets, especially those treated with insecticide.

Q: What is the vector for malaria?

A: A mosquito.

Q: What are the two main defence systems of the human body?.

A: The non-specific defence system and the immune system

Q: How does the skin protect the body from pathogens?

A: It forms a protective barrier.

Q: Why is the outer layer of skin effective against pathogens?

A: It is made of dead cells that are hard for pathogens to penetrate.

Q: How does the body prevent pathogens entering through cuts in the skin?

A: The skin forms a scab.

Q: What do cilia do to protect the body?

A: They waft mucus upwards towards the throat.

Q: How does the stomach protect against pathogens?

A: It contains hydrochloric acid.

Q: Which cells are involved in the immune system?.

A: White blood cells.

Q: What are the two main functions of the immune system?

A:

1. Destroy pathogens and toxins

2. Protect against future infection by the same pathogen

Q: Name the three ways white blood cells protect the body.

A:

1. Phagocytosis

2. Producing antibodies

3. Producing antitoxins

Q: What is phagocytosis?

A: The process where white blood cells ingest and destroy pathogens.

Q: How does a white blood cell find a pathogen?

A: It detects chemicals released by the pathogen.

Q: What are antibodies?

A: Protein molecules produced by white blood cells.

Q: How do antibodies work?

A: They bind to pathogens and mark them for destruction.

Q: How do antibodies provide long-term protection?

A: They remain in the blood and protect against reinfection.

Q: What are toxins?

A: Harmful chemicals released by some bacteria.

Q: What are antitoxins?

A: Chemicals produced by white blood cells that neutralise toxins.

Q: Name the two infectious plant diseases you need to know for GCSE.

A:

• Tobacco mosaic virus (TMV)

• Rose black spot

Q: Describe the symptoms and effects of tobacco mosaic virus.

A: TMV causes leaves to become discoloured in a mosaic pattern. This reduces the rate of photosynthesis, which leads to reduced growth of the plant.

Q: Compare tobacco mosaic virus and rose black spot.

A: Tobacco mosaic virus is caused by a virus and causes mosaic discolouration of leaves. Rose black spot is caused by a fungus and causes black or purple spots, yellowing and leaf loss. Both diseases reduce photosynthesis and therefore reduce plant growth.

Q: What is vaccination?

: The introduction of small quantities of dead or inactive pathogens into the body.

Q: What are antibiotics?

A: Medicines that kill bacteria inside the body without harming human cells.

Q: Name two diseases that can be treated with antibiotics.

A: Salmonella food poisoning and gonorrhoea.

Q: Why are antibiotics not prescribed unless necessary?

A: To reduce the risk of antibiotic resistance developing.

Q: What is antibiotic resistance?

A: When bacteria evolve so that antibiotics no longer kill them.

Q: What causes antibiotic resistance?

A: Overuse and misuse of antibiotics.

Q: Why can’t antibiotics treat viral diseases?

A: Viruses live and reproduce inside body cells, making them hard to target without damaging tissues.

Q: What do painkillers do?

A: Relieve symptoms such as pain.

Q: Which plant was used to make the heart drug digitalis?.

A: Foxglove

Q: Where did the painkiller aspirin originally come from?

A: Willow trees.

Q: Who discovered penicillin and where did it come from?

A: Alexander Fleming; from the mould Penicillium.

Q: Why must all new medicines be tested?

A: To check they are safe, effective, and to find the correct dose.

Q: What three things are tested when developing a new drug?

A:

1. Toxicity (safety)

2. Effectiveness

3. Best dose

Q: What is pre-clinical testing?

A: Testing a drug before it is used on humans.

Q: What is used in pre-clinical testing?

A: Cells, tissues, or live animals.

Q: What is clinical testing?

A: Testing drugs on humans.

Q: Who is given the drug first in clinical trials?

A: Healthy volunteers.

Q: What happens after a drug is shown to be safe?

A: Tests continue to find the optimal dose with the fewest side effects.

Q: What is a placebo?

A: A dummy drug with no active ingredient.

Q: Why can a placebo make people feel better?

A: Because they believe they are being treated.

Q: What is a double-blind trial?

A: A trial where neither patients nor doctors know who gets the real drug or the placebo.

Q: Explain why double-blind trials are used when testing medicines.

A: A placebo is used to compare results with the real drug. Neither doctors nor patients know who receives the real drug, preventing bias. This ensures results are reliable and shows whether the drug is truly effective.