Quick revision: every question with its correct answer. For the full explanation, open the test and tap View Solution.
3.4 Antigen–Antibody Interactions — Test 1
Q1. Affinity of an antibody refers to:✓ The strength of binding between one paratope and one epitope
Q2. Avidity differs from affinity in that avidity is:✓ The overall strength from multiple binding sites acting together
Q3. Antibody titre is defined as:✓ The highest dilution of serum still giving a positive reaction
Q4. The bonds responsible for antigen–antibody binding are:✓ Non-covalent (hydrogen, ionic, hydrophobic, van der Waals)
Q5. A precipitation reaction occurs optimally at the:✓ Zone of equivalence
Q6. The prozone phenomenon is a false-negative result caused by:✓ Antibody excess
Q7. Agglutination differs from precipitation in that agglutination involves:✓ Particulate antigens clumping together
Q8. IgM is a more efficient agglutinin than IgG mainly because IgM has:✓ High valence (up to 10 binding sites)
Q9. Affinity maturation during an immune response results in:✓ Production of antibodies with progressively higher affinity
Q10. The equilibrium dissociation constant (Kd) of an antibody relates to affinity such that:✓ A lower Kd indicates higher affinity
Q11. Cross-reactivity in a serological test means the antibody:✓ Reacts with an antigen sharing similar epitopes
Q12. Single radial immunodiffusion (Mancini) quantifies antigen by measuring:✓ The diameter of the precipitin ring
Q13. In the Ouchterlony double-diffusion test, a continuous (fused) precipitin line indicates:✓ Identity (shared epitopes) between antigens
Q14. The law of mass action applied to antibody binding means binding is:✓ Reversible and concentration-dependent
Q15. Complement fixation as a serological test detects:✓ Antigen–antibody complexes by consumption of complement
Q16. Neutralisation by antibody refers to:✓ Blocking the biological activity of a toxin or virus
Q17. Multivalent binding contributes to high avidity because:✓ Simultaneous bonds make complete dissociation much less likely
Q18. A high-affinity antibody compared with a low-affinity one will:✓ Bind antigen more tightly and dissociate more slowly
Q19. In immunoassays, the specificity of antigen–antibody binding allows:✓ Detection of a target analyte in a complex mixture
Q20. The overall strength of binding between an antibody and a multivalent antigen is called:✓ Avidity
Q21. Precipitation of soluble antigen by antibody in solution depends mainly on:✓ Antibody being at least bivalent (cross-linking into a lattice)
Q22. Match each term with its correct description and select the correct option.✓ A-iii, B-iv, C-i, D-ii