In a sandwich ELISA (enzyme-linked immunosorbent assay) used to monitor cardiac troponin levels in a patient suspected of having a myocardial infarction, a microtitre well is pre-coated with monoclonal capture antibodies. After the patient's serum is added and incubated, the well is washed, and a second monoclonal antibody conjugated to an enzyme is added. Which of the following best explains the role of this second enzyme-conjugated monoclonal antibody?
It binds specifically to the constant region of the capture antibody to initiate a cascade that cleaves the bound troponin, releasing a fluorescent marker into the solution.
It enzymatically degrades any non-specific serum proteins remaining in the well to prevent false-positive results caused by non-specific binding.
It binds to a different epitope on the cardiac troponin molecule, and the conjugated enzyme catalyses a reaction with an added substrate to produce a color change proportional to the troponin concentration.
It acts as a competitive antagonist, displacing the bound cardiac troponin from the capture antibody to allow direct mass spectrometry of the supernatant.
97 exam-style questions on OCR GCSE Biology 6.3 Monitoring and maintaining health, covering 6.3.1 Health and disease, 6.3.2 Interactions between diseases, 6.3.3 Spread of communicable diseases, 6.3.4 Common infections and diseases, 6.3.5 Physical plant defence responses, 6.3.6 Chemical plant defence responses, 6.3.7 Detecting and identifying plant diseases, 6.3.8 White blood cells and platelets, 6.3.9 Non-specific defence systems, 6.3.10 The immune system, 6.3.11 Monoclonal antibodies, 6.3.12 Vaccines and medicines, 6.3.13 Aseptic techniques, 6.3.14 Discovery and development of new medicines, 6.3.15 Causes of non-communicable diseases, 6.3.16 Treatments for cardiovascular disease, 6.3.17 Lifestyle factors and non-communicable diseases, 6.3.18 Cancer, 6.3.19 Stem cells in medicine, 6.3.20 Gene technology in medicine, and 6.3.21 The human genome and medicine. Each one has a worked solution and a mark scheme showing where the marks go.