Question at position 9 Which of the following is TRUE about the C5 convertase?All of the answers are true.None of the answers are true.C5 convertase is an important player in the production of the MAC.C5 convertase cleaves C5 into C5a and C5b, with the b chain attached to the pathogen surface and the chain dissociating away to serve as a potent proinflammatory chemotactic factor.C5 convertase can consist of the membrane-bound components C3b2Bb.

Question

Question at position 9 Which of the following is TRUE about the C5 convertase?All of the answers are true.None of the answers are true.C5 convertase is an important player in the production of the MAC.C5 convertase cleaves C5 into C5a and C5b, with the b chain attached to the pathogen surface and the chain dissociating away to serve as a potent proinflammatory chemotactic factor.C5 convertase can consist of the membrane-bound components C3b2Bb.

BlackTom AI · Accepted Answer

C5 convertase cleaves C5 into C5a and C5b, so start with the core complement biology: C5 convertase is the enzyme complex that generates C5a (a small diffusible anaphylatoxin/chemoattractant) and C5b (the larger fragment that initiates membrane attack complex formation).

1) Relevant knowledge points and concepts
- Complement activation proceeds through classical, lectin, and alternative pathways; all pathways produce C3 convertases that then generate C3b and assemble C5 convertases.
- C5 convertase function: enzymatic cleavage of C5 → C5a + C5b.
- Biological roles: C5a is a potent proinflammatory chemoattractant and anaphylatoxin; C5b remains bound and nucleates MAC (C5b–C6–C7–C8–C9).
- Composition: classical/lectin C5 convertase = C4b2a3b; alternative C5 convertase = C3b2Bb (often written as C3bBb with an additional C3b = C3b2Bb), and these are membrane-bound.

2) Step-by-step reasoning
- Option “C5 convertase cleaves C5 into C5a and C5b…”: True because enzymatic cleavage produces C5a (diffuses, chemoattractant) and C5b (binds pathogen surface and initiates MAC).
- Option “C5 convertase is an important player in the production of the MAC.”: True because C5b generated by C5 convertase is required to start MAC assembly.
- Option “C5 convertase can consist of the membrane-bound components C3b2Bb.”: True; that composition describes the alternative-pathway C5 convertase (membrane associated).
- “None of the answers are true.” is therefore false.
- “All of the answers are true.” is supported because each specific factual statement above is correct.

3) Intermediate steps (mechanistic sequence)
- C3 convertase generates surface C3b → additional C3b attaches to form C5 convertase (classical: C4b2a + C3b → C4b2a3b; alternative: C3bBb + C3b → C3b2Bb).
- C5 convertase binds C5 and cleaves it → C5a released; C5b remains bound → C5b recruits C6–C9 → MAC formed.

4) Why the correct answer is correct
- Each listed factual statement accurately describes C5 convertase’s composition, activity, and role in inflammation and MAC formation; therefore the collective choice “All of the answers are true” is correct.

5) Why other options are incorrect
- “None of the answers are true.” contradicts established complement biochemistry and is false.
- The individual factual options are correct, so selecting any single one instead of “All” is incomplete.

Conclusion: All provided statements about C5 convertase are true; thus the correct answer is “All of the answers are true.” This matches the given answer.

类似问题

Question at position 51 To which of the following is MBL MOST structurally similar?C5bNone of the answers are correct.BbC1qC3b

Question at position 40 Which of the following acts as a serine protease that, with cofactors, cleaves C3b and C4b?Factor HMCP (CD46)ProperdinDAF (CD55)Factor I

Question at position 20 Which of the following provides serine protease activity in the classical complement activation pathway?Both C1r and C1s act in the classical pathway.C1rMASP-2None of the answers acts in the classical pathway.C1s

Question at position 17 The MAC consists of a multimeric complex of which of the following proteins that, by their association, forms a pore in the surface of the attacked cell?C6C9C5bC3bC4b

Question at position 14 Of the molecules listed, which can be considered the key molecule in complement pathways?IgMC1C5 convertaseNone of the answers are correct.MBL

Question at position 10 Which of the following complement fixation pathways can be initiated by a soluble C3 convertase?All of the answers are correct.AlternativeNone of the answers are correct.LectinClassical

What is the term for a group of proteins in serum that finish off the work of antibodies to destroy bacteria and other cells?

The complement system refers to:

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