M1 L6

Question 1

describe the importance of enzyme control for correct cellular function

Answer 1

Enzyme gene transcriptional control allows a cell to respond to changes in its biochemical status and/or environment.

Question 2

explain substrate/product level control of enzyme activity

pathways

Answer 2

they are organized into cellular metabolic pathways. they overlap, have branch-points requiring switching and some parts are reversible

Question 3

explain feedback control of enzyme activity and allosteric enzymes.

Answer 3

feedback control allows communication between enzyme-catalyzed reactions. allosteric enzymes have their activity regulated by the other effector molecules enabling feedback control.

Question 4

describe the control of enzyme activity by the controlling expression of the enzyme gene.

effector molecules

Answer 4

Non-substrate ‘Effector’ molecules control allosteric enzyme activity. Effectors bind elsewhere to the active site.
Negative allosteric effectors (inhibitors) stabilize the low activity T-state.
Positive allosteric effectors (activators) stabilize the high activity R state.

Question 5

Describe the reversible modification of enzymes by phosphorylation to regulate enzyme activity

Answer 5

The phosphorylated form of the enzyme has a different activity to the non-phosphorylated form. A kinase (ATP-dependent enzyme) adds the covalent phosphate, while phosphatase removes it.

Question 6

Describe/explain the irreversible modification of zymogens by proteolytic cleavage to regulate enzyme activity.

Answer 6

proteolytic enzymes activate zymogens when they are in the correct tissue location. they are irreversibly activated by proteolysis (hydrolysis) which is a peptide bond of their protein main-chain
digestive proteases are synthesized in the pancreas in an inactive zymogen form so the pancreas wont digest itself

Question 7

Understand the example of AT Case as an allosteric enzyme.

Answer 7

its a key enzyme in the pyrimidine synthesis (uracil, thymidine and cytosine) pathway, and is feedback regulated by cellular pyrimidine requirements

Question 8

talk about the blood-clotting cascade that sequentially activates enzyme clotting factors resulting in blood clot formation

Answer 8

inactive zymogen proteases are activated, resulting in the final conversion of prothrombin to thrombin at the site of the wound producing blood clot. the correct regulation of blood clotting is very important

Question 9

what’s an allosteric enzyme

Answer 9

enzymes that their activity is changed by a molecule (effectors) other than a subtrate