Biology · Edexcel Paper 1
Human Defences and Immunity
How the body stops pathogens from getting in, how the immune system destroys those that do, how vaccination prepares the body for infection, and why antibiotics work against bacteria but not viruses. It also covers herd immunity and the evaluation of vaccination for separate Biology. Matches Edexcel 5.12 to 5.16. Lessons 1, 2, 3 and 5 are for both Combined Science and separate Biology at Foundation and Higher. Lesson 4, Herd Immunity and Evaluating Vaccination, is for separate Biology only.
Lessons
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1
Physical and Chemical Barriers
Most of the time, pathogens never get inside you. This lesson looks at the body's first line of defence: physical barriers such as the skin, mucus and cilia…
9 terms -
2
The Immune System
When a pathogen gets past the barriers, the immune system takes over. This lesson explains how white blood cells recognise antigens, make antibodies and memory…
9 terms -
3
Immunisation
Vaccination has saved more lives than almost any other medical advance. This lesson explains how a vaccine that contains an inactive form of a pathogen makes…
9 terms -
4
Herd Immunity and Evaluating Vaccination
When enough people are vaccinated, even those who are not protected are safer. This lesson is for separate Biology only: Combined Science students do not need…
9 terms -
5
Antibiotics
Antibiotics changed medicine, but they only work on bacteria. This lesson explains how antibiotics kill bacteria without harming human cells, why they do not…
9 terms
Key terms in this chapter
All 45, gathered from every lesson.
- Non-specific defence
- A defence that works against all pathogens in the same way.
- Barrier
- A structure that stops pathogens from entering the body.
- Mucus
- A sticky liquid made by goblet cells, which traps pathogens and dust.
- Cilia
- Tiny hair-like structures on cells that move in waves, to move mucus.
- Goblet cell
- A cell in the airway lining that makes mucus.
- Lysozyme
- An enzyme in tears and saliva that breaks down the cell walls of bacteria.
- Hydrochloric acid
- The acid made in the stomach, which kills most pathogens.
- Sebum
- An oily substance made by the skin, which can kill some bacteria.
- Platelet
- A cell fragment in the blood that helps it to clot.
- Antigen
- A molecule on the surface of a cell or pathogen that the immune system recognises.
- Antibody
- A protein made by lymphocytes that binds to a specific antigen.
- Lymphocyte
- A type of white blood cell that makes antibodies.
- Phagocyte
- A white blood cell that engulfs and digests pathogens.
- Phagocytosis
- The engulfing and digesting of pathogens by a phagocyte.
- Memory lymphocyte
- A lymphocyte that stays in the body after an infection, ready to respond quickly to the same antigen again.
- Primary response
- The slow, small immune response the first time a pathogen is met.
- Secondary response
- The fast, large immune response the second time a pathogen is met.
- Immune
- Protected from a particular disease, because of memory lymphocytes.
- Vaccine
- A preparation containing inactive or weakened pathogens, or their antigens, that makes the body immune to a disease.
- Immunisation
- Making a person immune to a disease, by giving a vaccine.
- Inactive pathogen
- A pathogen that has been killed or changed so that it cannot cause disease, but still has its antigens.
- Booster
- An extra dose of a vaccine to increase immunity.
- Placebo
- A harmless substance that has no effect, used in tests as a comparison.
- Eradicate
- To wipe out a disease completely.
- Strain
- A type of a pathogen with its own genetic features.
- Immune
- Protected against a disease because of memory lymphocytes.
- Influenza
- A viral disease, also called flu, that changes often.
- Herd immunity
- The protection of unvaccinated people from a disease, because so many others are immune that the disease cannot spread.
- Vaccination programme
- A plan to vaccinate a whole population against a disease.
- Uptake
- The proportion of people who accept a vaccine.
- Threshold
- The level that must be reached before an effect happens, such as the proportion that must be immune.
- Side effect
- An unwanted effect of a treatment.
- Eradication
- The complete removal of a disease.
- Outbreak
- A sudden rise in the number of cases of a disease.
- Vulnerable
- Likely to be harmed, such as people with weak immune systems.
- Retracted
- Withdrawn by a journal because the research was found to be unreliable.
- Antibiotic
- A drug that kills bacteria or stops them growing.
- Penicillin
- The first widely used antibiotic, made from the mould Penicillium.
- Cell wall
- A rigid layer outside the cell membrane of a bacterium, which human cells do not have.
- Ribosome
- A structure where proteins are made. Bacterial ribosomes differ from human ones.
- Broad-spectrum antibiotic
- An antibiotic that works against many types of bacteria.
- Antiviral drug
- A drug that is designed to stop a particular virus from reproducing.
- Selective
- Affecting some things but not others.
- Zone of inhibition
- A clear area on an agar plate where bacteria cannot grow.
- Mould
- A type of fungus that grows as a furry mass.