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33 Cards in this Set
- Front
- Back
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What is the function of a protease?
Name 4 types of these. Which type of protease will we focus on in our class? |
Proteases catalyze the hydrolysis of a peptide bond.
ex) serine protease, cysteine protease, aspartic acid protease and metalloprotease We focus on Serine protease |
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What is the enzyme that converts trypsinogen to trypsin?
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enterokinase
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Describe how a serine protease breaks a peptide bond.
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Serine-OH becomes deprotonated by HIS side chain. The O- in SER_O- makes a nucleophilic attack on the peptide bond in question, hydrolyzing it. ASP_O- comes in and stabilizes the N+ in the histidine.
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What deprotonates serine in serine protease rxn?
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Histidine
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What stabilizes the HIS-N+ left from a serine protease rxn?
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Aspartate
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State 3 mechanisms of stopping bloodflow.
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1. vasoconstriction
2. mechanical obstruction 3. formation of clots (insoluble cross-linked proteins) |
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What stimulated aggregation of platelets after vessel damage?
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Increased ADP
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What does Von Willibrand Factor do?
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Von WIllibrand factor causes big plasma cells to adhere to collagen/foreign material when blood is spilled. (Part of formation of clots)
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What signals vasoconstriction?
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when platelets disintegrate as they touch collagen - they clump and release 5-hydroxytryptamine (Seratonin) - which causes vasoconstriction.
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What kind of protease is thrombin?
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endopepsidase
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What rxn does thrombin use to make Fibrin out of fibrinogen?
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Serine protease rxn!
Hydrolysis of arginylglycine bond by nucleophilic attack by a serine molecule that was deprotonated by Histidine. |
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What is a serpin?
What does it do? |
serine protease inhibitor. It inhibits serine mediated proteases.
Would work against clotting. |
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Fibrin is made from fibrinogen by the cleavage of what bond specifically? What does this do?
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Arginylglycine bond.
This causes fibrinogen a and b to fall off of Fibrin to activate it. |
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What is made of 29 disulfide bonds holding 6 chains together?
describe this with symbols. |
Fibrinogen = alpha2beta2gamma2
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What factor hardens a soft fibrinogen clot?
What kind of enzyme is this? |
XIIIa.
XIIIa is a transglutaminase - it forms cross-links in the fibrin. |
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What does it mean to say that XIIIa is a transglutaminase?
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A transglutaminase transfers a carbonyl from a GLU to the amine group on a LYS on ANOTHER chain = cross-link formation.
THIS HARDENS THE SOFT CLOT |
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Where does XIIIa (the factor that hardens a clot) come from?
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It starts as XIII and is made into XIIIa by THROMBIN and Ca+.
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Why does XIII need Ca+ and Thrombin to make XIIIa?
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XIII exists in two forms, alpha2beta2 (plasma) and alpha2 (platelet).
Thrombin cleaves alpha subs Ca+ cleaves beta subs. |
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What cleaves prothrombin into thrombin?
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Xa (Stuart factor)
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What accelerates the conversion of prothrombin to thrombin by Xa?
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Va
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Which clotting pathway includes plasma components ONLY?
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Intrinsic pathway includes plasma components only.
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Which clotting pathway includes non-plasma components and tissue factor?
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Extrinsic pathway includes tissue factors but not plasma components.
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Which clotting factors are vitamin K dependent?
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II (prothrombin), VII, IX, X.
Also protein c and s..but they inhibit clotting. |
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How do protein C and S inhibit clotting? By acting on what factor?
What disease is caused by protein C deficiency? |
Protein c and s inhibit clotting by proteolysis of VIIIa (which makes Xa from X w Vit K) and Va
Deficiency of Protein C and S causes Purpura Fulminans = increased clotting = death as baby |
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Which factors can be accelerated by increased concentration of Thrombin?
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Thrombin can activate V, VII and VII
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Which factors can be inhibited by Thrombin?
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II (prothrombin), Va, VIIIa, Xa
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Protein C and S can stop which factor?
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VIIIa
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Intrinsic pathway:
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XII --->XI--->IX--->X->thrombin
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Which clotting factor in the Extrinsic pathway is bound to Tissue Factor?
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VII
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What post-translational modification takes place to pre-prothrombin to make prothrombin?
What else does this require? |
carboxylation of several of its glutamates.
Vitamin K is REQUIRED for carboxylation |
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What does the carboxylation of pre-prothrombin do?
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carboxylation enhances -charge of glutamate and allows side chain to recognize and ligate a Ca+ ion.
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What does coumadin do?
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Competitive inhibitor for epoxide reductase
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What does epoxide reductase do?
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Takes Vit K epoxide (junk) and turns it back into usable Vit KH2
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