Page 124 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

Choose the best correct answers in each of the following statements

1- The complement system is an enzyme cascade that helps defend against
infection. There are several pathways of complement activation. Which of
the following activation pathways occurs when components of microbial cell

surfaces or immunoglobulins cleave small amounts of C3?
a) Alternative
b) Lectin

c) Classical antibody-dependent
d) Classical antibody-independent

2- In the classical pathway, the antibody activated the C1 complex consisting
of the C1q, C1r & C1s subunits.
Which of the following subunit binds to the antibody?
a) C1q b) C1r
c) C1s d) All answers are true

3- The membrane attack complex consists of five different complement
proteins C5, C6, C7, C8, and C9. Which of the following subunits bind to
the surface and provide a binding site for a subsequent component?
a) C5a b) C5b
c) C6a d) All answers are false

4- In the classical pathway, after the proteolysis of the C3 complement
pathway. Which component is cleaved by C4bC2aC3b and initiates the
formation of membrane attack complex?
a) C5 b) C6
c) C7 d) C8

General Microbiology & Immunology (PM 401) theoretical handbook Page 113