Quiz 1 (Bioenergetics)

Question 1

The TCA cycle is an ___ pathway and takes place in the ___.

Answer 1

amphibolic / mitochondria

*both catabolic and anabolic

Question 2

What enzyme allows pyruvate to enter the mitochondrial matrix?

What enzyme splits pyruvate into acetyl-CoA?

Answer 2

Mitochondrial Pyruvate Carrier (MPC)

Pyruvate Dehydrogenase (PDC)

Question 3

PDC produces…

Answer 3

1 NADH / 1 carbon dioxide / 1 acetylene-CoA

Question 4

What enzyme links glycolysis to the TCA Cycle?

Answer 4

Pyruvate Dehydrogenase Complex (PDC)

Question 5

PDC is made of:

Answer 5

3 enzymes (E1 / E2 / E3)

+

5 coenzymes (TPP / CoA / Lipoic Acid / FAD / NAD+)

• TPP is derived from Vitamin B1
• FAD is derived from Vitamin B2
• NAD+ is derived from Vitamin B3
• CoA is derived from Vitamin B5

Question 6

Phosphorylation of the PDC occurs in coenzyme ____ of the enzyme ___.

Answer 6

Thiamine Pyrophosphate (TPP)

E1

Question 7

PDC regulation:

Answer 7

Pyruvate Dehydrogenase Kinase (PDK) =>
+Po = inactive PDC

Pyruvate Dehydrogenase Phosphatase (PDP) =>
-Po = ACTIVE PDC

• insulin activates PDK
• activators = Calcium / Magnesium / ADP / CoA / NAD+ / pyruvate
• inhibitors = Acetyl-CoA / NADH / ATP / Arsenite

Question 8

When ___ phosphorylates PDC, PDC will become ___.

Answer 8

PDK / inactive

Question 9

What 3 enzymes are associated with highly regulates steps in the TCA cycle?

Answer 9

Citrate Synthase

Isocitrate Dehydrogenase

Alpha-ketoglutarate Dehydrogenase

Question 10

What enzyme is responsible for generation of an ATP equivalent in the TCA cycle?

Answer 10

Succinate Thiokinase

*generates GTP

Question 11

What enzyme produces FADH2 in the TCA cycle?

Answer 11

Succinate Dehydrogenase (aka. Complex II of ETC)

Question 12

When the cellular ATP levels are low, the activity of the TCA cycle is ___.

Answer 12

Increased

Question 13

___ reaction replenish intermediates of the TCA cycle.

Examples

Answer 13

Anaplerotic

• FED: Pyruvate —> OAA
• FASTING: Asn —> Asp —> OAA
• FASTING: Gln / Pro / His / Arg —> Glu —> alpha-ketoglutarate
• FASTING: Thr / Met / Ile / Val —> Propionyl CoA —> Succinyl CoA
• FASTING: Phe / Tyr / Asp —> Fumarate

Question 14

___ inhibits Pyruvate Carboxylase from converting Pyruvate into OAA.

Answer 14

Insulin

Question 15

Oncometabolites of the TCA cycle include ___ and ___.

Answer 15

Citrate

2-hydroxyl glutarate

Question 16

OxPhos takes place in the ___.

Answer 16

Inner-mitochondrial membrane

Question 17

Goals of OxPhos:

Answer 17

1. Transfer electrons (from NADH/FADH2 to oxygen)
2. Establish a proton gradient
3. Synthesize ATP

Question 18

Proton motive force is made by:

Answer 18

1. pH gradient (Direction of H+ flow)

2. Membrane potential (“non-leakiness” of membrane)

Question 19

___ inhibits ATPase by disrupting the proton transport through the channel.

Answer 19

Oligomycin

Question 20

1 mol ATP requires passage of ____ H+.

Answer 20

3+1

Question 21

___ is the only ETC complex that does not pump protons across the innermembrane.

Answer 21

Complex II

Question 22

___ transfers electron to molecular oxygen.

Answer 22

Complex IV

Question 23

Inhibition of electron transfer down the ETC causes a ___ in the pumping of protons.

Answer 23

Decrease

Question 24

OxPhos is sensitive to ___ and ___.

Answer 24

Oxygen

[ATP/ADP] ratio

Question 25

____ disrupts the proton gradient and causes heat production instead of ATP synthesis.

Answer 25

Uncoupling (proton leak)

Question 26

DNP is an _____ that disrupts the proton gradient, thereby causing a ___ in ATP synthesis.

Answer 26

Uncoupling agent / decrease

Question 27

Shuttles are important because ____ cannot enter the mitochondria on its own.

Answer 27

NADH

Question 28

Malate-Aspartate Shuttle Vs. Glycerophosphate Shuttle

Answer 28

Malate-Aspartate Shuttle - occurs in heart / liver / kidney - NADH is shuttled into the mitochondrial matrix - NADH enters ETC at Complex I - reversible (depends on the fact that OAA cannot pass membranes) Glycerophosphate Shuttle - occurs in muscle and brain - electrons from FADH2 are shuttled into CoQ - irreversible