Complement 1 Classical Pathway

The video tutorial explains the complement system, a crucial part of the immune system, focusing on the classical pathway. It details the structure and function of antibodies, particularly IgG and IgM, and their role in activating the complement system. The process involves proteins like C1Q, C1R, and C1S, leading to the formation of C3 and C5 convertase. The tutorial also covers the role of C4 and C2, the instability of thioester bonds, and the formation of the membrane attack complex, which ultimately lyses pathogens.

What are the three pathways of complement system activation?

• Alternative, Intrinsic, Lectin

• Classical, Intrinsic, Extrinsic

• Classical, Alternative, Lectin

• Intrinsic, Extrinsic, Lectin

Which antibodies are primarily involved in activating the complement system?

• IgD and IgE

• IgA and IgE

• IgG and IgM

• IgA and IgD

What is the role of C1Q in the complement system?

• It inhibits the complement cascade.

• It activates C3 directly.

• It binds to the FC portion of the antibody.

• It binds to the antigen directly.

What is the function of C1S in the complement cascade?

• It binds to the antigen.

• It activates C4 and C2.

• It inhibits C1R.

• It deactivates C3.

What is the significance of the C3 convertase in the complement system?

• It inhibits C1Q.

• It splits C3 into C3A and C3B.

• It binds to the antigen.

• It deactivates C5.

What is the role of C3B in the complement system?

• It forms a complex with C5.

• It initiates the membrane attack complex.

• It binds to the antigen directly.

• It acts as a C3 convertase.

What is the function of C5 convertase in the complement cascade?

• It binds to the antigen.

• It splits C5 into C5A and C5B.

• It inhibits C3B.

• It deactivates C4.

What is the role of C5B in the complement system?

• It binds to the antigen directly.

• It forms a complex with C3.

• It initiates the membrane attack complex.

• It inhibits C1Q.

What is the purpose of the membrane attack complex?

• To activate C1Q.

• To inhibit C3 convertase.

• To lyse the pathogen.

• To bind to antibodies.

How does the body prevent complement activation on its own cells?

• By activating C1Q.

• By stabilizing the thioester bond.

• By hydrolyzing the thioester bond.

• By inhibiting C3B.