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Biology - Natural Defences (AQA)
Colds and 'flu are viral infections so antibiotics have no effect on them.

Biology - Natural Defences (AQA)

Discover how your body blocks pathogens using skin, mucus, cilia and chemical barriers, and how these natural defences work together to keep you healthy.

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Fascinating Fact:

Cilia in your airways beat like tiny oars, sweeping trapped pathogens up and out.

In GCSE Science Biology (AQA), you learn about the body's natural defence systems. These include physical barriers, mucus and cilia in the airways, and chemical defences that help stop pathogens causing disease.

  • Cilia: Tiny hair-like structures lining the airways that move mucus containing dust and microorganisms away from the lungs.
  • Mucus: A sticky fluid that traps microorganisms and particles on surfaces such as the nose and windpipe.
  • Physical barrier: A structure like skin that helps prevent pathogens from entering the body.
What are the body's natural defences in GCSE Biology?

The body's natural defences include the skin, blood clotting, mucus and cilia in the airways, stomach acid, and tears. Together they help stop pathogens entering or surviving in the body.

How do cilia and mucus protect the lungs from infection?

Mucus traps dust and microbes in the airways, while cilia move in waves to push this mucus toward the throat, where it can be swallowed and destroyed by stomach acid.

What is the difference between physical and chemical barriers?

Physical barriers, such as skin and cilia, block or remove pathogens. Chemical barriers, like stomach acid and enzymes in tears, kill or damage microorganisms that reach those surfaces.

1 .
Which of the following statements about white blood cells is incorrect?
They engulf and ingest pathogens
They expel the pathogens from the bloodstream via the liver
They produce antibodies which neutralise pathogens
They produce antitoxins to neutralise the effects of the toxins from pathogens
The surface of every cell is covered with molecules called antigens which are usually fragments of protein or carbohydrate molecule. The antigens on the surface of pathogenic cells are different from those on the surface of your own cells which means that your white blood cells can recognise pathogens
2 .
Your body can develop a natural immunity to certain pathogens. What is the name of the cells responsible for this?
Lymphocytes
Leucocytes
Phagocytes
Virocytes
Lymphocytes are one type of white blood cell
3 .
What is produced by a lymphocyte that enables it to neutralise pathogens?
Antigens
Antipaths
Antibodies
Antibacts
Each lymphocyte produces a specific type of antibody that matches a specific antigen. Each pathogen has its own unique antigen. When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte is triggered to reproduce quickly which makes many copies of the antibody to neutralise the pathogen
4 .
Which of the following statements is correct?
Passive immunity involves receiving antibodies
Antibiotics work because the prevent the toxins from being poisonous to the host
White blood cells produce antigens to protect the body
Viruses cause cholera and typhoid in poor areas of the world
Active immunity is where the white blood cells have 'learnt' how to defend agains a pathogen because you have been exposed to it before. Sometimes you may be treated for infection by receiving antibodies from someone else. That's passive immunity. Protection from passive immunity lasts only a few weeks or months. For example, antibodies passed from the mother to the baby before birth give passive immunity to the baby for the first 4-6 months after being born
5 .
Which of the following also help your body defend itself against infection?
Mucus and cilia in the respiratory system
Hydrochloric acid in the stomach
Lysozyme (an enzyme) in tears
All three of the above
As well as these examples, there is also the skin (which acts a physical barrier) and saliva (which contains enzymes)
6 .
Which of the following is not one of the ways that white blood cells provide active immunity?
They destroy invading pathogens by eating them
They produce antibodies to destroy pathogens
They produce antitoxins that neutralise toxins from pathogens
They destroy pathogens by ingesting them
This question tests if you know that you must use the word ingest and not 'eat' when describing how white blood cells work. Do remember not to be caught out by this please - it is a silly way to lose a mark in your exams
7 .
Which of the following are the two main groups of white blood cells?
Phagocytes and lymphocytes
Stem cells and platelets
Macrophages and bacteriophages
Erythrocytes and monocytes
Another word for phagocytes is macrophages
8 .
The lymphocytes produce antibodies. How do antibodies work?
They penetrate inside the pathogen and destroy its nucleus
They penetrate inside the pathogen and change the chemical composition of the cytoplasm
They attach to the pathogens and cause them to clump together making it easy for phagocytes to find and ingest them
They attach to the pathogens and take them to the liver where they are destroyed
Antibodies also exist that attach to the target pathogen and damage or destroy it
9 .
Vaccination is used to immunise people against diseases. Pick the false statement:
Edward Jenner is credited with the discovery of vaccination
Vaccines contain the antibodies needed to protect your body from infection
Each vaccine protects you from a specific disease
Some vaccines contain the pathogen that causes the disease
20 years before Jenner a Dorset Farmer, Benjamin Jesty, had carried out the same procedure to protect his family against smallpox but rarely gets any credit. A vaccine protects from a single disease but they can be combined, for example, the MMR vaccine against measles, mumps and rubella. Vaccines can be made from the pathogen itself - but either a weakened or inactivated version
10 .
Why are antibiotics no good for treating colds and 'flu?
Colds and 'flu are viral infections
Cold and 'flu mutate too quickly so the antibiotics only work for a very short time
Colds and 'flu are 'superbugs' and totally resistant to antibiotics
Antibiotics cannot work fast enough to treat colds and 'flu
This question is testing if you realise that colds and 'flu are caused by viruses and that antibiotics only work against bacteria
You can find more about this topic by visiting BBC Bitesize - Infection and response

Author:  Kev Woodward (PGCE, Science & Chemistry Teacher, Quiz Writer)

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