Complement 3

Question 1

What happens to C3 in the alternative pathway?

Answer 1

It is cleaved spontaneously into C3a and C3b

Question 2

What happens to C3b in the alternative pathway if there is no microbe?

Answer 2

It gets hydrolysed and remove to the liver

Question 3

What happens to C3b in the alternative pathway if there is a microbe?

Answer 3

C3b binds to the microbial surface

Question 4

What does C3b do once bound to the microbe in the alternative pathway?

Answer 4

It associates with factor B

Question 5

What happens to factor B after it associates with C3b in the alternative pathway?

Answer 5

It is cleaved into Bb (which stays attached to C3b) by factor D

Question 6

What can the C3b, Bb complex do in the alternative pathway?

Answer 6

Cleave many C3s

Question 7

How is the alternative pathway an amplifying pathway?

Answer 7

Cleavage of C3 ends up leading t even more cleavage of C3

Question 8

In the alternative pathway, what is C5 convertase made up of?

Answer 8

C3b, Bb and another C3b

Question 9

What does C5 convertase do in the alternative pathway?

Answer 9

Cleave C5 into C5a and C5b

Question 10

What stabilises the 3b, Bb complex?

Answer 10

Factor P

Question 11

Other than on the surface of cells where can C3 convertase assemble?

Answer 11

The blood

Question 12

What is the soluble c3 convertase made up of?

Answer 12

C3b and factor B

Question 13

Lifespan of soluble c3 convertase?

Answer 13

v short

Question 14

Why is complement not activated on self cells?

Answer 14

There are complement control proteins that stop it from being activated

Question 15

Which type of bacteria is not sensitive to the membrane attack complex?

Answer 15

Gram +ves

Question 16

What is similar about c4 and c4?

Answer 16

They both have an internal thioester bond

Question 17

What happens once C5b is formed?

Answer 17

It joins with C6 and C7

Question 18

Where is the C5b, C6 and C7 complex found?

Answer 18

On the membrane

Question 19

What happens once the C5b, C6, C7 complex is formed?

Answer 19

C8 can join

Question 20

What does C8 joining C5b, C6, C7 trigger?

Answer 20

The formation of a multimeric C9 MAC

Question 21

What is the most potent anaphylatoxin?

Answer 21

C5a

Question 22

How does the formation of the membrane attack complex/pore/C9 thing kill cells?

Answer 22

It allows extracellular fluids to enter

Question 23

What can all complement control proteins (except DAF) do?

Answer 23

Recruit factor I enzyme which can cleave the complex

Question 24

Examples of complement control proteins?

Answer 24

DAF, Factor I, Factor H, MCP, CR1, C4BP

Question 25

What can decay accelerating factor (DAF) do?

Answer 25

Break down the C3b, Bb complex

Question 26

What can factor I do?

Answer 26

Cleave C3b and C4b--> break down the c3 convertase enzyme

Question 27

What is factor H?

Answer 27

A cofactor for Factor I

Question 28

What are the cofactors of Factor I?

Answer 28

Factor H, CD46 (membrane cofactor protein), and CD35 (complement receptor 1)

Question 29

What is a positive regulator of complement?

Answer 29

Factor P (properdin)

Question 30

What does properdin do?

Answer 30

Stabilizes the alternative pathway c3 convertase on the bacterial surface

Question 31

What does factor H do?

Answer 31

It can remove factor Bb from C3b Factor H then binds to C3b instead

Question 32

What happens once factor H is bound to C3b?

Answer 32

Factor I is recruited, and C3 is cleaved into non functional components

Question 33

What does complement receptor 1 do?

Answer 33

Removes Bb from C3b, binds to C3b, recruits Factor I which then cleaves C3b

Question 34

What does membrane cofactor protein do?

Answer 34

Act as a cofactor for factor I binding to C3b and Bb