What is complement? How does it cause bacterial lysis? What ar...

Question

What is complement? How does it cause bacterial lysis? What are some of the other roles of complement?

Accepted Answer

Hi, everybody. Let's look at our next problem. It says the complement system functions as a defense mechanism against microbial infections, specifically bacteria by initiating a cascade of reactions resulting in the destruction of foreign invaders. Which of the following statements best describes the mechanism of destruction of bacteria by the complement system. A formation of antibodies that bind to the bacteria and enhance their phagocytosis. B ization of bacteria by C three B which can covalent bind to the surface of bacteria and enhance their phagocytosis. Choice, C release of cytotoxic substances to kill the bacteria directly in a way similar to cytotoxic T cell mediated destruction of pathogens or D membrane attack complex formation, which consists of complement proteins. C five BC six, C seven, C eight and multiple copies of C nine causing the formation of a poor like structure in the bacterial membrane, disrupting the bacterial cell wall and membrane choice. E both B and D and Choice F all of the above. So this question is specifically asking us what is the mechanism of destruction of the bacteria by the complement system. So there's a lot of things associated with the complement system, but we want to specifically focus on this mechanism by which the bacteria is destroyed. So that has two parts in a complement system. The first thing IZATION was essentially marking the pathogen. I put, marking in quotation marks it's not a scientific term but marking the pathogen sort of labeling it for destruction. And the second part is the formation of the M AC or membrane attack complex. And this is going to have a bunch of complement proteins that will cause the disruption of the bacterial cell wall by forming a pore like structure in it. So with those two things in mind, let's work through our answer. Choices. Choice A says formation of antibodies that bind to the bacteria enhance their pago cytosis. Um Antibodies are um the uh antibody binding is a form of ops. It binds directly to the pathogen marks it for destruction. But the formation of the antibodies is not part of the complement system that would be taking place in the B cells. Once the antibodies bind that antibody antigen complex can, can trigger the complement system. But this keyword here is formation. So the formation of antibodies is not part of the complement system. So that's why choice A is not our correct answer. So we'll cross that off Choice B ization of the bacteria by C three B which can covalent bind and enhance their pago cytosis. This is, that's that number one that we wrote down IZATION C three B is a complement protein. So this would definitely be part of this mechanism. So I'm not going to circle it as our answer because we do have the possibility of more than one correct answer. So choice B will mark with a dot To say that it's a correct answer. Then choice C release of cytotoxic substances to kill the bacteria directly similar to the way cytotoxic T cells work. Uh This would not be the mechanism of destruction. Again, they act to form this poor like structure that disrupts the membrane, but they don't release directly cytotoxic substances. So choice C not correct. So I'll just say not the mechanism. And that's why choice C is not our answer. Um We can also eliminate choice f all of the above. We've already crossed out two answers. That's not going to be our answer. So let's move on to choice D membrane attacks complex membrane attack complex formation. And it lists the complement proteins that make that up saying that it forms a poor like structure disrupts the bacterial cell wall and membrane. And yes, this is part of that mechanism of destruction of bacteria caused by the complement system, those complement proteins. That's a big clue here. Our answer has right in it, complement proteins. So choice D marking with a dot Also another correct answer. So therefore our overall answer must be choice E both B and D as both correctly describe that mechanism by which the complement system destroys bacteria cells. So choice E both B and D is our answer here. See you on the next video.

What is complement? How does it cause bacterial lysis? What are some of the other roles of complement?

Key Concepts

Complement System

Bacterial Lysis

Roles of Complement

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