4.2 Kreb's Cycle

Question 1

_ enzyme-catalyzed rxns
_ take place in the mitochondrial matrix
_ binds to the matrix side of the inner mitochondrial matrix

Answer 1

8, 7, 1

Question 2

Why must the cycle turn twice?

Answer 2

for all c in original glucose to be fully consumed and released as CO2

Question 3

step 1

Answer 3

2C acetyl group carried by coenzyme A is transferred to oxaloacetate, forming citrate

Question 4

citrate is rearranged into isocitrate (it’s isomer)

Answer 4

step 2

Question 5

step 3

Answer 5

isocitrate is oxidized to a-ketoglutarate; one C is removed and released as CO2 and NAD is reduced to NADH and H+

Question 6

step 4

Answer 6

a-ketoglutarate is oxidized to succinyl CoA; one C is removed to be released as CO2 and NAD is reduced to NADH and H+

Question 7

step 5

Answer 7

• the release of CoA from succinyl CoA produced succinate
• the energy released converts GDP to GTP, which converts ADP into ATP by substrate-level phosphorylation
• the only ATP made directly in the citric acid cycle

Question 8

step 6

Answer 8

• succinate is oxidized to fumarate

- two protons removed and two e- removed are transferred to FAD, producing FADH2

Question 9

fumarate is converted into malate by the addition of a molecule of water

Answer 9

step 7

Question 10

malate is oxidized to oxaloacetate, reducing NAD into NADH and H+
- oxaloacetate can react with acetyl-CoA to reenter the cycle for the second round

Answer 10

step 8

Question 11

the acetyl group is completely oxidized into

Answer 11

CO2

Question 12

What molecules are synthesized at the end of the cycle?

Answer 12

2 ATP, 6 NADH- and 2 FADH2