Session 3 Flashcards
Define Km
Substrate concentration that gives ½ Vmax.
Define Vmax
Maximum rate when enzyme is saturated with substrate
How are enzyme kinetics effected by non competitive inhibitors?
Vmax is not reached
Km is uneffected
How are enzyme kinetics effected by competitive inhibitors?
Can be overcome by adding more substrate
Define Allosteric control
Binding of a substrate to one active site enhances substrate binding to the other active sites.
Define Covalent modification
Many different types of group can be attached covalently to proteins via amino acids
Define Proteolytic activation
Enzyme secreted as an inactive protein precursor and cleaved by proteases to the active enzyme
Why is Phosphofructokinase important?
Sets rate of glycolysis due to allosteric regulation.
Activators – AMP
Inhibitors – ATP
How do phosphate groups effect enzyme activity?
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.
Define Zymogen
Inactive precursors of enzymes.
What is the Zymogen of Pepsin?
Pepsinogen in the Stomach
What is the Zymogen of Trypsin?
Trypsinogen in the Pancreas
What is the Zymogen of Elastase?
Proelastase in the Pancreas
What are the 2 pathways in the clotting cascade?
The Intrinsic pathway - damaged membrane of blood cells promotes the binding of Factor XI
The Extrinsic pathway - trauma releases tissue factor (factor III)
How does positive feedback work in the clotting cascade?
Activation of Thrombin promotes further activation in the cascade. Allows formation of clot from the activation of a very small amount of initial factor
