Question

Cascade Order in Classical Activation

Once activated, the complement cascade is an ordered process. Each reaction leads to another reaction. This activity asks you to place the cascade reactions in the order they occur, starting with the C1.

Drag the text below into boxes to indicate the correct order of events of complement activation via the classical pathway.

Answer 1

The cascade reactions in complement activation via the classical pathway occur in a specific order, starting with the binding of C1 to antibodies bound to an antigen. Cleavage of C3 and formation of the membrane-attack complex are important steps in this process.

Step-by-step explanation:

The cascade reactions in complement activation via the classical pathway occur in a specific order. The first reaction is the binding of C1 to antibodies bound to an antigen. This step initiates the cascade. Next, the bound C1 triggers the activation of the C4 and C2 proteins. C4 and C2 then generate C3 convertase, which leads to the cleavage of C3. The cleaved C3 fragments, C3a and C3b, play important roles in attracting phagocytes and opsonizing pathogens for destruction. Finally, the cascade culminates in the formation of the membrane-attack complex (MAC) by the proteins C5-C9, which can kill certain pathogens.