The Complement System Made Easy

The video tutorial by Leslie Samuel from Interactive Biology TV explains the complement system, a part of the immune response involving proteins made in the liver and activated in the blood. It covers the classical and alternative pathways, detailing how proteins like C1 to C9 interact to destroy pathogens. The classical pathway starts with an antigen-antibody complex, while the alternative pathway begins with C3 binding directly to the pathogen. Both pathways recruit phagocytes, tag pathogens for destruction, and form a membrane attack complex to eliminate pathogens. The video concludes with a preview of the next topic on T cells.

What is the primary function of complement proteins in the blood?

• To regulate blood pressure

• To participate in immune responses

• To aid in digestion

• To transport oxygen

In the classical pathway, which protein is the first to bind to the antigen-antibody complex?

• C9

• C1

• C5

• C3

What is the role of C3a in the classical pathway?

• To bind to the pathogen

• To split C5 into C5a and C5b

• To attract phagocytes to the infection site

• To form the membrane attack complex

Which proteins form the membrane attack complex in the classical pathway?

• C1, C2, C3, C4

• C5b, C6, C7, C8, C9

• C3a, C3b, C5a

• C1, C3, C5, C7

How does the alternative pathway differ from the classical pathway?

• It requires antigen recognition

• It involves direct activation of C3

• It does not form a membrane attack complex

• It starts with C1 binding to an antibody

Which proteins interact with C3 in the alternative pathway?

• Factor P, B, and D

• Factor A, B, and C

• C1, C2, and C4

• C5, C6, and C7

What is a common outcome of both the classical and alternative pathways?

• Production of red blood cells

• Formation of antibodies

• Recruitment of phagocytes and formation of the membrane attack complex

• Activation of T cells