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Flashcards in Session 3 Deck (17)
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1
Q

Define Km

A

Substrate concentration that gives ½ Vmax.

2
Q

Define Vmax

A

Maximum rate when enzyme is saturated with substrate

3
Q

How are enzyme kinetics effected by non competitive inhibitors?

A

Vmax is not reached

Km is uneffected

4
Q

How are enzyme kinetics effected by competitive inhibitors?

A

Can be overcome by adding more substrate

5
Q

Define Allosteric control

A

Binding of a substrate to one active site enhances substrate binding to the other active sites.

6
Q

Define Covalent modification

A

Many different types of group can be attached covalently to proteins via amino acids

7
Q

Define Proteolytic activation

A

Enzyme secreted as an inactive protein precursor and cleaved by proteases to the active enzyme

8
Q

Why is Phosphofructokinase important?

A

Sets rate of glycolysis due to allosteric regulation.
Activators – AMP
Inhibitors – ATP

9
Q

How do phosphate groups effect enzyme activity?

A

The bulky, charged groups that can significantly affect enzyme conformation and substrate binding
Kinases transfer the phosphate group from ATP to the –OH group
Phosphatases remove phosphate groups through hydrolytic activity.

10
Q

Define Zymogen

A

Inactive precursors of enzymes.

11
Q

What is the Zymogen of Pepsin?

A

Pepsinogen in the Stomach

12
Q

What is the Zymogen of Trypsin?

A

Trypsinogen in the Pancreas

13
Q

What is the Zymogen of Elastase?

A

Proelastase in the Pancreas

14
Q

What are the 2 pathways in the clotting cascade?

A

The Intrinsic pathway - damaged membrane of blood cells promotes the binding of Factor XI
The Extrinsic pathway - trauma releases tissue factor (factor III)

15
Q

How does positive feedback work in the clotting cascade?

A

Activation of Thrombin promotes further activation in the cascade. Allows formation of clot from the activation of a very small amount of initial factor

16
Q

What are the key steps in the clotting cascade?

A

Factor X –> Factor Xa
Factor Xa causes Prothrombin –> Thrombin
Thrombin causes Fibrinogen –> Fibrin

17
Q

What mechanisms are involved in regulation of clot formation/breakdown?

A

The concentration of Zymogens (Dilution of clotting factors by blood flow, removed by Liver)
Digestion by proteases
Specific inhibitors (Antithrombin III, enhanced by Heparin binding)
Fibrinolysis