Skip to main content
Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
All textbooksTortora 14th EditionCh. 16 - Innate Immunity: Nonspecific Defenses of the HostProblem 4
Chapter 16, Problem 4

If the following are placed in the order of occurrence, which would be the third step?
a. Activation of C5 through C9
b. Cell lysis
c. Antigen–antibody reaction
d. Activation of C3
e. Activation of C2 through C4

Verified step by step guidance
1
Identify the sequence of events in the classical complement pathway, which is triggered by the antigen–antibody reaction.
Recognize that the first step is the antigen–antibody reaction (option c), where antibodies bind to antigens to initiate the complement cascade.
Next, understand that activation of complement components C2 through C4 (option e) follows, forming the C3 convertase enzyme complex.
Then, the activation of C3 (option d) occurs, which is a critical amplification step in the pathway.
After C3 activation, the terminal components C5 through C9 (option a) are activated, leading to the formation of the membrane attack complex and resulting in cell lysis (option b).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Complement System Activation Pathway

The complement system is a series of proteins that enhance immune responses. Activation begins with antigen–antibody complexes triggering a cascade involving complement proteins C1 through C9, leading to pathogen elimination.
Recommended video:
Guided course
04:40
1) Alternative Pathway

Role of Complement Components C2, C3, C4, and C5-C9

Complement proteins C2, C3, and C4 are activated early in the cascade to form complexes that amplify the response. Activation of C5 through C9 forms the membrane attack complex (MAC), which directly causes cell lysis.
Recommended video:
Guided course
03:18
2) Cell Lysis of Invading Microbes

Sequence of Events in Complement-Mediated Cell Lysis

The sequence starts with antigen–antibody reaction, followed by activation of early complement proteins (C2-C4), then C3 activation, leading to activation of C5-C9, and finally cell lysis by the MAC disrupting the target cell membrane.
Recommended video:
Guided course
03:18
2) Cell Lysis of Invading Microbes
Related Practice
Textbook Question

A human host can prevent a pathogen from getting enough iron by all of the following except

a. reducing dietary intake of iron.

b. binding iron with transferrin.

c. binding iron with hemoglobin.

d. binding iron with ferritin.

e. binding iron with siderophores.

2
views
Textbook Question

How can the complement system cause endotoxic shock?

2
views
Textbook Question

Patients with X-linked chronic granulomatous disease are susceptible to infections because their neutrophils don’t generate an oxidative burst. What is the relation of the oxidative burst to infection?

4
views
Textbook Question

If the following are placed in the order of occurrence, which would be the third step?

a. Diapedesis

b. Digestion

c. Formation of a phagosome

d. Formation of a phagolysosome

e. Margination

1
views
Textbook Question

A decrease in the production of C3 would result in

a. increased susceptibility to infection.

b. increased numbers of white blood cells.

c. increased phagocytosis.

d. activation of C5 through C9.

e. none of the above

2
views
Textbook Question

What are interferons? Discuss their roles in innate immunity.

1
views