Classical Pathway of Complement Activation

The video explains the classical pathway of complement activation, emphasizing the role of antibodies. It details how antibodies bind to antigens, leading to the activation of complement proteins like C1, which then trigger a cascade involving C3 and C5 convertases. This cascade results in the formation of the membrane attack complex (MAC), which disrupts pathogen cell membranes. The video also compares the classical pathway with the lectin and alternative pathways, highlighting their differences and similarities.

Which pathway of complement activation is typically the last to be activated upon initial exposure to an antigen?

• Lectin pathway

• None of the above

• Classical pathway

• Alternative pathway

What is required for the activation of the classical pathway of complement?

• Sugars on the bacterial surface

• Antibodies

• Direct pathogen recognition

• None of the above

Which classes of antibodies are capable of activating the complement system?

• IgA and IgD

• IgD and IgE

• IgM and IgG

• IgA and IgE

What happens to the FC loop of an antibody when it binds to an antigen?

• It detaches from the antibody

• It changes color

• It becomes hidden

• It becomes exposed

Which protein initiates the complement activation cascade by binding to the antibody?

• C9

• C5A

• C3B

• C1Q

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

• To bind antibodies

• To split C3 into C3A and C3B

• To form the membrane attack complex

• To activate C1Q

What is the significance of the thioester bond in complement proteins like C3B?

• It prevents protein activation

• It allows proteins to float away

• It helps proteins bind to bacterial surfaces

• It changes the protein's color

What is the function of the membrane attack complex (MAC) in the complement system?

• To activate C1Q

• To form a pore in the pathogen's membrane

• To split C3 into C3A and C3B

• To bind antibodies

Which of the following pathways does not require antibodies for complement activation?

• Classical pathway

• Lectin pathway

• Alternative pathway

• Both B and C

What is the primary difference between the lectin pathway and the classical pathway?

• The lectin pathway does not lead to cell lysis

• The lectin pathway is slower

• The lectin pathway requires sugars on the bacterial surface

• The lectin pathway requires antibodies