6.2.6Unit 6: Practical Skills in Biology II
Developing Immunity — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 5 parts Lesson 12 of 48 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Primary Response
The first meeting with an antigen is slow because few suitable lymphocytes are present.
1
On first exposure to an antigen, few lymphocytes have the right receptor.
2
Activated T and B cells must divide and differentiate, which takes several days.
3
Plasma cells then start to make antibodies, so the person usually has symptoms.
4
Memory cells are formed during this response and remain in the blood.
5
The person is now immune to that pathogen.
Part 2 of 5Secondary Response
Faster
- Faster Memory cells are more numerous than the original matching lymphocytes, so they detect and respond to the antigen quickly.
Stronger
- Stronger More plasma cells form, so antibodies are made faster and in larger quantity.
Outcome
- Outcome The pathogen is often removed before symptoms develop.
Memory
- Memory This long-term protection depends on memory cells staying in the body.
Antibody level
- Antibody level The antibody concentration in the blood rises much higher and more quickly in the secondary response than in the primary one.
Part 3 of 5Active and Passive Immunity
In passive immunity, no memory cells are produced, so protection is short lived.
Active and Passive Immunity
Active natural
- Active natural Gained by catching the disease, when the person makes their own antibodies and memory cells.
Active artificial
- Active artificial Gained through vaccination, which triggers the immune response without causing the disease.
Passive natural
- Passive natural Antibodies pass from mother to foetus across the placenta or to a baby in breast milk.
Passive artificial
- Passive artificial Antibodies are injected, as in an antitoxin, and give quick but temporary protection.
| Feature | Active | Passive |
|---|---|---|
| Antibodies made by | The person | Another source |
| Memory cells | Yes | No |
| Protection | Long term | Short term |
Part 4 of 5Vaccination
Vaccines are the main application of the primary and secondary response.
Content
- Content Vaccines contain antigens, in the form of weakened or dead pathogens, antigens alone, or genetic material coding for them.
Effect
- Effect The primary response creates memory cells, so a later infection triggers a rapid secondary response.
Delivery
- Delivery Vaccines are given by injection or by mouth.
Antigenic variation
- Antigenic variation Mutations change pathogen antigens, so some vaccines must be updated regularly.
Herd effect
- Herd effect When many people are vaccinated, fewer people can pass on the pathogen, which also protects those who are not immune.
Part 5 of 5Exam Checklist & Tips
6.2.6 – Key Points for the Exam
- Primary response The slower immune response when an antigen is first encountered.
- Secondary response The faster, larger response when the same antigen is met again.
- Vaccine A preparation containing antigens that is given to produce immunity.
- Passive immunity Protection from antibodies obtained from another source.
- Memory cell A long-lived lymphocyte that remains after an infection and enables a faster secondary response.
Common Mistakes
- Writing that vaccines contain antibodies; most contain antigens.
- Saying passive immunity makes memory cells, when it does not.
- Forgetting that the secondary response is faster because memory cells are already present.
- Describing the primary response as having no symptoms; symptoms usually occur while it builds.
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