CAC and ETC

Question 1

synthesis of Acetyl coA

Answer 1

pyruvate is transported into mitochondria, where it undergoes further oxidation. turning into acetyl coA and CO2 by the pyruvate dehydrogenase complex

Question 2

CAC basic info

Answer 2

8 rxns
oxidizes acetyl coA to 2 CO2
in the matrix of the mitochondria
conserves free energy by reducing NADH and FADH2

Question 3

rxn 1 of CAC

Answer 3

irreversible condensation of acetyl coA w/ oxaloacetate to form citrate
- commited step, uses enzyme citrate synthesis

Question 4

rxn 3 of CAC

Answer 4

irreversible oxidative decarboxylation of isocitrate to alpha-ketoglutarate
- produces the first CO2 and NADH
- uses enzyme isocitrate dehydrogenase

Question 5

rxn 4 of CAC

Answer 5

irreversible oxidative decarboxylation of alpha-ketoglutarate to succinyl-coA
- produces 2nd CO2 and NADH
- uses enzyme alpha-ketoglutarate dehydrogenase

Question 6

ATP and GTP

Answer 6

ATP and GTP are energetically equivalent, are rapidly interconverted through the action of a kinase enzyme

Question 7

What does the CAC generate and what are they used for?

Answer 7

3 NADH and 1 FADH2
- which are used to power the ETC

Question 8

NADH and FADH = ATP equivalent

Answer 8

1 NADH = 3 ATP
1 FADH2 = 2 ATP

Question 9

what are the three rate determining enzyme of the CAC?

Answer 9

1. citrate synthase
2. isocitrate dehydrogenase
3. alpha-ketoglutarate dehydrogenase

Question 10

Net energy produced by CAC

Answer 10

12 ATP equivalents per acetyl coA
- 3 NADH
- 1 FADH2
- 1 GTP
- 2 CO2

Question 11

what are the 3 factors that determine rate of CAC?

Answer 11

1. substrate availability
2. feedback inhibition (products)
3. allosteric feedback of enzymes

Question 12

what downregulates CAC

Answer 12

negative allosteric effectors: ATP & NADH (high energy indicators)

Question 13

what upregulates CAC

Answer 13

positive allosteric effectors: ADP, NAD+, CA2+ (low energy indicators)

Question 14

ETC general info

Answer 14

-series of membrane-associated electron carriers pass electrons from NADH/FADH2 to O2
-this is coupled with proton transport to synthesize ATP

Question 15

ETC mechanism

Answer 15

the passing of electrons is used to transport H+ across the inner mito membrane, producing a proton gradient
- this drives the synthesis of ATP from ADP

Question 16

sequence of ETC

Answer 16

• 4 protein complexes within the inner mito membrane (smaller to greater affinity for electrons)
• 2 mobile electron carriers (CoQ and cytochrome C)
• electrons travel from lower to higher standard reduction potentials

Question 17

how does CoQ and cytochrome C work?

Answer 17

• CoQ carries electrons from complexes I and II to complex III
• cytochrome C carries electrons from complex III to IV

Question 18

role of complex V

Answer 18

catalyzes ATP synthesis (via ATP synthase), through H+ flow from intermembrane space to matrix
- 2 components:
F1: peripheral membrane protein
F2: integral membrane protein

Question 19

chemiosmotic theory

Answer 19

free energy of ETC is conserved by the H+ gradient in the inner mito membrane, which is harnessed to synthesize ATP

Question 20

significance of rxn 6 of CAC

Answer 20

Uses succinate dehydrogenase which is also in the ETC

Question 21

of H+ atoms for each ETC complex

Answer 21

complex I: 4 H+
complex III: 4 H+
complex IV: 2 H+
complex V: 10 H+ (into matrix)

Question 22

does CAC happen in high or low ATP levels

Answer 22

low ATP

Question 23

does ETC happen in high or low ATP levels

Answer 23

low ATP