Control of Oxidative Metabolism

Question 1

True or false: ATP must be constantly synthesized.

Answer 1

True (we need greater than 200 mol per day, only 0.1 mol available at any one time).

Question 2

How do we get ATP using carbs as energy source?

Answer 2

1) Glycolysis
2) TCA
3) Electron transport
4) Oxidative phosphorylation

Question 3

True or false: ATP can be produced by the body and stored in large amounts.

Answer 3

False

Question 4

True or false: ATP production never exceeds needs.

Answer 4

True

Question 5

What is the control point of electron transport? How do we know?

Answer 5

The terminal step (cytochrome c oxidase’s reduction of O2 to H2O). It is irreversible.

Question 6

What is the controller or cyrtochrome c oxidase?

Answer 6

Substrate availability (substrate = reduced cytochrome c or c2+)

Question 7

What does the concentration of c2+ (reduced cytochrome c) depend on?

Answer 7

Ratios of [NADH]/[NAD+] and [ATP]/[ADP][Pi]

Question 8

What is the ATP mass action ratio?

Answer 8

[ATP]/[ADP][Pi]

Question 9

True or false: The higher the ratio of [NADH]/[NAD+] and the ATP mass action ratio ([ATP]/[ADP][Pi]), the more reduced cytochrome c (c+) is produced and the more active electron transport.

Answer 9

False: The higher the ratio of [NADH]/[NAD+] and the lower the ATPmass action ratio ([ATP]/[ADP][Pi]), the more reduced cytochrome c (c+) is produced and the more active electron transport.

Question 10

When is the ATP mass action ratio highest? What does this do to the rate of oxidative phosphorylation?

Answer 10

When body is at rest; this decreases reduced cytochrome c concentration and, therefore, oxidative phosphoyrulation.

Question 11

When is the ATP mass action ratio increased? What does this do to the rate of oxidative phosphorylation?

Answer 11

When activity is increased; this increases the concentration of reduced cytochrome c, activating cytochrome c oxidase to take O2 to H2O, and increasing oxidative phosphorylation.

Question 12

Why does the ATP mass action ratio ([ATP]/[ADP][Pi]) decrease during minimal activity?

Answer 12

Because less ATP is hydrolyzed to ADP and Pi.

Question 13

What are the concentrations of ATP, ADP, and Pi in the mitochondrial matrix dependent on?

Answer 13

Transport proteins that import from the cytosol (so translocators play a control role in ATP synthesis).

Question 14

Which proteins in the mitochondria regulate ATP synthase?

Answer 14

IF1

Question 15

What happens to IF1 proteins in the mitochondria during times of active respiration and high pH?

Answer 15

IF1 tetramer is inactive

Question 16

What happens to IF1 when the pH of the mitochondria goes below 6.5?

Answer 16

Dissociates into dimers that inhibit ATP synthase by trapping ATP in the alpha3beta3 F1 subunits.

Question 17

Does IF1 activate or inhibit ATP synthesis? In what form is it an inhibitor?

Answer 17

Inhibits; in its dimer form (tetramer form is inactive)

Question 18

What is the purpose of IF1’s deactivation of ATP synthase in times of low O2 availability?

Answer 18

To prevent ATP hydrolysis when respiratory activity and and proton gradient are stopped by lack of O2 (to prevent the reversal of ATP synthase–hydrolysis of ATP–and deprivation of the cell’s remaining energy source).

Question 19

What are the primary sources of electrons that enter the mitochondria?

Answer 19

Glycolysis, TCA cycle, and fatty acid metabolism

Question 20

What control point in glycolysis is a key control point for all of metabolism?

Answer 20

Inhibition of PFK by citrate

Question 21

What activates isocitrate dehydrogenase?

Answer 21

ADP (signals low ATP)

Question 22

What inhibits alpha-ketoglutarate?

Answer 22

ATP

Question 23

What causes the concentration of citrate to go up? What does this increased concentration of citrate effect glycolysis?

Answer 23

High concentrations of ATP (inhibits alpha-ketoglutarate dehydrogenase) and low concentrations of ADP (does not activate isocitrate dehydrogenase); This causes [citrate] to rise, leave the mitochondria, and inhibit glycolysis (stopping further carbohydrate metabolism).