session 3-enzyme activity,zymogens and clot breakdown

Question 1

What is Km?

Answer 1

substrate concentration that gives 1/2 Vmax

Question 2

What is Vmax?

Answer 2

maximum rate of reaction when enzyme is saturated with substrate

Question 3

What happens to Vmax and Km during non competitive inhibition?

Answer 3

• Vmax=not reached because active site shape is changed and so max velocity cannot be reached
• Km=unaffected

Question 4

What happens to Vmax and km in competitive inhibition?

Answer 4

• Km=increased due to blocking of active site and therefore a higher velocity is reached before enzyme is saturated with substrate (adding substrate will overcome effect of inhibitor)
• Vmax=unaffected

Question 5

what is allosteric control?

Answer 5

Binding of an activator/inhibitor at a place other than the active site of protein to regulate it and could change how enzyme functions

Question 6

What is positive/negative cooperativity when referring to allosteric effectors?

Answer 6

-inhibit or activate an enzyme

Question 7

what type of enzymes add and remove phosphate groups to proteins?

Answer 7

• add=kinase

- remove=phosphatase

Question 8

what is a zymogen?

Answer 8

-inactive precursor of an enzyme which is converted into an enzyme when activated by another enzyme

Question 9

what activates PFK in glycolysis?

Answer 9

AMP and fructose-2,6-bisphosphate

Question 10

what is the Michaelis-Menten equation?

Answer 10

Vo= Vmax [s]/Km + [s]

Question 11

what inhibits PFK in glycolysis?

Answer 11

ATP,citrate and H+

Question 12

how do phosphate groups affect enzymes?

Answer 12

• bulky and charged

- affect enzyme conformation and substrate binding

Question 13

Zymogens are inactive precursors of enzymes. Name an enzyme and zymogen located in the stomach

Answer 13

zymogen=pepsinogen

enzyme=pepsin

Question 14

give 2 examples of a zymogen and its enzyme in the pancreas

Answer 14

Zymogen=proelastase
Enzyme=elastase

Zymogen=chymotrypsinogen
Enzyme=chymotrypsin

Question 15

what does the concentration of zymogens do in terms of clot formation and breakdown?

Answer 15

• dilute clotting factors by blood flow

- removed by liver

Question 16

How do proteases breakdown clot?

Answer 16

-Digested e.g. 8a degraded by protein C

Question 17

What does AT3 (antithrombin 3) do?

Answer 17

-Breaks down thrombin with the help of HEPARIN

Question 18

what does fibrinolysis mean?

Answer 18

breaking down of clot

Question 19

what does T-PA stand for and what does it do?

Answer 19

tissue plasminogen activator-breaks down blood clots by turning plasminogen into plasmin which in turn causes fibrin to turn into fragments. (with the help of STREPTOKINASE)

Question 20

Activation of Zymogens in the pancreas are controlled by what enzyme?

Answer 20

Trypsin

Question 21

Describe in 3 steps how emphysema is caused-(clue:deficiency in protein enzyme inhibitor)

Answer 21

• deficiency in alpha-anti trypsin protein inhibitor
• needed to stop trypsin activity (which activates other enzymes including elastase)
• therefore continuous activation of elastase occurs=destroys alveolus walls

Question 22

What do the Kringle domains do on prothrombin?

Answer 22

Keeps thrombin in inactive form

Question 23

What is the role of gal domains?

Answer 23

Localise clot to site of damage

Question 24

Which enzyme, when activated from the pro…. Version of itself by thrombin, catalyses cross linking between fibrin to form clot?

Answer 24

Transglutaminase

Question 25

What three ways can an enzyme be changed?

Answer 25

• allosteric regulation
• covalent modification
• proteolytic cleavage

Question 26

Give an example of an enzyme that is allosterically controlled. Hint:glycolysis

Answer 26

PFK

Question 27

Give an example of covalent modification.

Answer 27

Phosphorylation (addition of phosphate=kinase, removal=phosphatase)

Question 28

Give 3 examples of proteolytic cleavage enzyme activation.

Answer 28

• insulin (preproinsulin)
• digestive enzyme
• blood clotting
• apoptosis

Question 29

What is an isoenzyme?

Answer 29

Each of two or more enzymes which same function but different structure