Biochem Exam 1: Set 3 (TCA Cycle, Electron Transport)

Question 1

If there is a positive change in free energy, what direction will the reaction move?

Answer 1

reverse direction

Question 2

What are ways to drive an energetically unfavorable reaction (positive delta G)?

Answer 2

add substrate or remove product

couple the reaction with an energetically favorable one

Question 3

How many high-energy electrons result from one turn of the citric acid cycle?

Answer 3

8

Question 4

What are sources of Acetyl-CoA?

Answer 4

fatty acids, ketone bodies, pyruvate (from glucose and amino acids), ethanol

Question 5

What are the outputs of one turn of the TCA cycle?

Answer 5

2 CO2
1 GTP
3 NADH
1 FADH2

Question 6

What is the final electron acceptor in the electron transport chain?

Answer 6

oxygen

Question 7

What enzyme catalyzes the conversion from pyruvate to acetyl CoA?

Answer 7

Pyruvate Dehydrogenase Complex

Question 8

What is the net reaction catalyzed by pyruvate dehydrogenase complex?

Answer 8

pyruvate + CoA + NAD+ –> acety CoA + CO2 + NADH

Question 9

What are the cofactors for the reaction catalyzed by pyruvate dehydrogenase complex?

Answer 9

thiamine pyrophosphate

lipoic acid, FAD

Question 10

How many subunits do alpha-keto acid dehydrogenase complexes have?

Answer 10

3 (E1, E2, E3)

Question 11

Arsenate/Arsenite effect what subunit of PDC and alpha-ketoglutarate dehydrogenase complex?

Answer 11

E2

Question 12

Vitamin B1 is a component for what subunit of alpha-keto acid dehydrogenase complexes?

Answer 12

E1 (TPP)

Question 13

What are the regulators of PDC?

Answer 13

\+phosphatase
\+Ca2+
\+pyruvate
\+NAD+
-ADP
-acetyl CoA
-NADH

Question 14

What are the components of TCA cycle…

Answer 14

citrate–>isocitrate–>alpha-ketoglutarate–>succinyl CoA–>succinate–>fumarate–>malate–>oxaloacetate

Question 15

What are the enzymes of TCA cycle…

Answer 15

citrate synthase, aconitase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, succinate thiokinase, succinate dehydrogenase, fumarase, malate dehydrogenase

Question 16

Which steps in the TCA cycle produce NADH?

Answer 16

isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, malate dehydrogenase

Question 17

Where is FADH produced in the TCA cycle?

Answer 17

succinate dehydrogenase

Question 18

Where is GTP produced in the TCA cycle?

Answer 18

succinate thiokinase

Question 19

Where is CO2 produced in the TCA cycle?

Answer 19

isocitrate dehydrogenase, a-ketoglutarate dehydrogenase

Question 20

What are the regulators of the TCA cycle?

Answer 20

+ADP
+Ca2+
-NADH
-citrate

Question 21

What are the key regulatory steps of the TCA cycle?

Answer 21

citrate synthase, isocitrate dehydrogenase (biggest regulatory step), a-ketoglutarate dehydrogenase, malate dehydrogenase

Question 22

What intermediates in the TCA cycle can be replenished?

Answer 22

oxaloacetate (by pyruvate), a-ketoglutarate (by glutamate), succinyl CoA (by propionyl CoA from odd-chain fatty acid oxidation)

Question 23

What are the two ways to make ATP?

Answer 23

substrate level phosphorylation, oxidative phosphorylation (electron-transport chain)

Question 24

How is NAD+ reduced to NADH?

Answer 24

accepts 2 electrons and 1 H+ (a hydride ion)

Question 25

How is FAD reduced to FADH?

Answer 25

accepts 1 electron and 1 H+

Question 26

What vitamin is necessary to make NAD/NADH, and what are symptoms from a deficiency in this vitamin?

Answer 26

Niacin (B3) | B3 deficiency = pellagra: dermatitis, dementia, diarrhea

Question 27

What are the five complexes of the electron transport chain?

Answer 27

1. NADH Dehydrogenase 2. Succinate-Q reductase 3. Cytochrome bc1 complex 4. Cytochrome C oxidase 5. ATP Synthase

Question 28

What are the two mobile electron carriers in the inner-mitochondrial membrane?

Answer 28

Coenzyme Q | Cytochrome C

Question 29

What metals are required in the electron transport chain?

Answer 29

Copper and Iron

Question 30

What portion of the mitochondria has the highest concentration of protons?

Answer 30

intermembrane space

Question 31

How many protons are pumped across the membrane by each complex in the ETC?

Answer 31

``` 1 = 4 H+ 2 = 0 H+ 3 = 4 H+ 4 = 2 H+ ```

Question 32

Which reducing agents are used by complexes 1 and 2 in the ETC?

Answer 32

Complex 1 = NADH | Complex 2 = FADH

Question 33

How many protons are required to synthesize one ATP

Answer 33

4 H+ | 3 to turn ATP synthase and 1 to pump ATP out of mitochondria

Question 34

How does ADP get into the mitochondrial matrix?

Answer 34

ATP-ADP translocase

Question 35

How do cyanide and CO disrupt ETC?

Answer 35

bind to heme iron in Complex 4 and stop final transfer of electrons to oxygen

Question 36

If complex 1 is inhibited what happens to ATP production through oxidative phosphorylation?

Answer 36

ATP production is decreased but not halted entirely. Electrons can enter the ETC through complex 2, but the 4 protons transferred by complex 1 do not occur.

Question 37

How do uncoupling agents effect ATP synthesis?

Answer 37

movement of proton not linked to ATP synthesis, energy is lost to heat (brown fat)

Question 38

Why does hypoxia lead to acidosis?

Answer 38

NAD+ is regenerated from NADH anaerobically and lactic acid is produced

Question 39

What are the dangers of aspirin overdose?

Answer 39

Aspirin degradation produces salicylate which is lipid soluble and has a dissociable proton and can act as an uncoupling agent by ferrying protons across the inner mito. membrane

Question 40

How many ATP are synthesized per oxygen consumed

Answer 40

2.5

Question 41

How many ATP are produced per glucose molecule?

Answer 41

30-32 (depending on method of NADH transport)

Question 42

Why are mitochondrial genetic disorders due to mutations in mitochondrial encoded genes?

Answer 42

DNA repair mechanisms aren't as good in the mitochondria as in the nucleus, and inheritance from mother prevents homozygous recessive disorders from being silent in offspring as a heterozygous genotype