4D 1.1 Biochem i.6

Question 1

Q19 drugs that work as a platelet ADP receptor antagonist are referred to as what.

Answer 1

AP drugs

Question 2

Q41what does anti-thrombin III do

Answer 2

A plasma protein that forms an irreversible complex with thrombin

Question 3

Q44 what are the 4 functions of thrombin

Answer 3

Converts Fibrinogen to Fibrin

Activates Factor XIII to stabilise Fibrin mesh by crosslinking

Enhances its own activation by positive feedback

Enhances platelet aggregation

Question 4

Q26 what does A clot on top of platelet plug do

Answer 4

strengthens the plug and reinforces the seal

Question 5

Q11 Platelets can be ACTIVATED by several factors: what are they

Answer 5

1. ADP (adenosine diphosphate) - released by platelets, erythrocytes & endothelial cells
2. COLLAGEN – in the connective tissue, exposed by vessel damage
3. THROMBIN – made by enzymatic cleavage of prothrombin
4. PAF – platelet activating factor (phospholipid) from the vessel wall & other cells

Question 6

Q50 wound healing Occurs by 4 continuous, overlapping and precisely programmed phases

Answer 6

Rapid Haemostasis

Appropriate Inflammation

Proliferation

Tissue Remodelling

Question 7

Q30 which factor converts prothrombin to thrombin

Answer 7

Factor X (10), Factor V (5), Ca2+, PF3

Question 8

Q21 excessive bleeding can occur through acquired disorders such as

Answer 8

Vitamin C deficiency

Excessive exogenous (gym)

Endogenous glucocorticoids (drugs)

Question 9

Q47 warfarin and dicoumarol are examples of

Answer 9

Vitamin k antagonists

Question 10

Q2 Haemostasis is a complex system involving 3 major steps, what are they?

Answer 10

1 vascular spasm.

2 formation of a platelet plug.

3 blood coagulation (clotting)

Question 11

Q32 which factor from the intrinsic pathway converts factor x (10)

Answer 11

Factor IX (9), Factor VIII (8), ca2+, PF3

Question 12

Q4 Muscle cells contract

Constriction reduces blood flow

limits blood loss

occur during?

Answer 12

Vasoconstriction

Question 13

Q48 anti-thrombin (synthesised in the liver), Heparin (synthesised in mast cells), protein c and s (synthesised in liver) and tissue factor pathway inhibitor, are all responsible for what

Answer 13

Preventing inappropriate clotting

Question 14

Q36 what causes the fibrin to cross link

Answer 14

Activated factor XIII (XIIIa)

Question 15

Q12 What are the Effects of ACTIVATION on Platelets:

Answer 15

1. Change shape from disc to sphere with extended pseudopodia
2. Granules release in aid of haemostasis e.g ADP, serotonin, fibronectin and vWF
3. Aggregate
4. Adhere to vessel wall
5. Synthesis thromboxane

Question 16

Q8 where are platelets derived from

Answer 16

small fragments derived from bone marrow cells called megakaryocytes

Question 17

Q27 what is fibrin

Answer 17

insoluble, threadlike molecule, which forms a loose, mesh that traps blood cells

Question 18

Q10 under what conditions, allow platelets to not stick to the endothelium

Answer 18

Normal

Question 19

Q13 Outline the stages of formation for a platelet plug

Answer 19

Platelet adhesion to vessel wall -> Platelet activation -> Platelet aggregate (build Platelet mass) -> mass forms primary haemostatic plug -> plug is stabilised by fibrin.

Question 20

Q38 protein c is activated by what

Answer 20

Thrombin

Question 21

Q49 plasminogen is a serum protein synthesised by the liver, what is its function

Answer 21

Binds to fibrin and converts to plasmin, which slowly degrades fibrin.

Phagocytic white blood cells remove debris.

Question 22

Q45 which vitamin is essential for the synthesis of prothrombin

Answer 22

Vitamin K

Question 23

Q5 vasoconstriction is mediated by which platelet-derived products?

Answer 23

Serotonin and thromboxane

Question 24

Q34 how many peptide bonds does thrombin cleave

Answer 24

4 peptide bonds (releasing fibrinopeptides)

Question 25

Q29 what is the function of thrombin

Answer 25

catalyses conversion of fibrinogen to fibrin activates Factor XIII

Question 27

Q43. What converts prothrombin to thrombin when required?

Answer 27

BLOOD CLOTTING CASCADE 12 plasma clotting factors synthesised by the liver some steps require Ca²⁺ and platelet factor 3 (PF3)

Question 28

Q24 both pathways result in the conversion of fibrinogen to

Answer 28

Fibrin – needed to stabilise blood plug

Question 29

Q35 what is the name of the cleaved product

Answer 29

Fibrin monomer

Question 30

q17 Antiplatelet drugs are used to treat arterial thrombosis, they decrease platelet aggregation and inhibit thrombus formation. Give an example of an AP drug

Answer 30

aspirin – reduce thromboxane

Question 31

Q16 what is von Willebrand disease

Answer 31

vWD is an autosomal disease, located in chromosome 12 affecting the vWF

Question 32

Q31 which factor from the extrinsic pathway converts Factor X (10)

Answer 32

Factor VII (7), Ca2+

Question 33

q18 drugs that are platelet receptor antagonists (target GpIIb which binds vWF) are referred to as what.

Answer 33

AP drugs

Question 34

Q14 a normal/damage endothelium will produce which mediators

Answer 34

Question 35

Q7 platelets are also known as

Answer 35

Thrombocytes

Question 36

Q1 What is the definition of haemostasis

Answer 36

the stopping of a flow of blood.

Question 37

Q20 Ehlers-Danlos Syndrome is an example of

Answer 37

A congenital disorder that affects connective tissues supporting the skin, which causes excessive bleeding.

Question 38

Q25 A fibrin clot is formed by

Answer 38

interaction between the intrinsic, extrinsic and final common pathways

Question 39

Q42 what stops blood from clotting

Answer 39

Fibrinogen is always present in blood, but thrombin must not be present Thrombin present as an inactive precursor, prothrombin

Question 40

Q39 which factors are digested by protein C

Answer 40

Factors Va and VIIIa

Question 41

Q3 Why must Haemostasis be appropriately controlled:

Answer 41

1 To avoid inappropriate clot formation. 2 Clots must be eventually degraded. 3 Clots are a temporary solution

Question 42

Q28 where is fibrin generated from

Answer 42

generated from FIBRINOGEN a large, soluble plasma protein synthesised by the liver

Question 43

Q15 what is the role of vWF and platelet receptors

Answer 43

vWF is produced by platelets and endothelial cells, which bind to Gplb and Gpllb/llla receptors of the platelets to encourage aggregation and adhesion.

Question 44

Q22 exposure of flowing blood to sub-endothelial collagen, exposed by vessel damage, activates which pathway

Answer 44

Intrinsic pathway

Question 45

Q6 Example of vasodilators and inhibitors of platelet aggregation are?

Answer 45

Prostacyclin and nitric oxide

Question 46

Q33 how many polypeptide chains does fibrinogen consists of

Answer 46

Fibrinogen consists of 6 polypeptide chains

Question 47

Q9 what allows the megakaryocyte to contract

Answer 47

High levels of actin and myosin

Question 48

Q23 exposure of flowing blood to a protein called tissue factor (TF) through tissue damage, activates which pathway

Answer 48

Extrinsic pathway

Question 49

Q46 what is the role of Ca2+

Answer 49

Anchors prothrombin to platelet membrane surface after injury Brings prothrombin near clotting factors (Xa and Va)

Question 50

Q37 clotting factors are labile, what is responsible for the removal of clotting factors

Answer 50

Dilution of blood flow, liver and degradation of proteases

Question 51

Q40 thrombin has dual function, what does this mean

Answer 51

Catalyses formation of fibrin Initiates the deactivation of the clotting cascade