Kreb's / TCA Cycle

Question 1

Step 1

Answer 1

Citrate synthase ( H2O&raquo_space;CoA)
Only step that makes C-C bonds.
2-C (Acetyl CoA), 4-C (oxaloacetate)

Acetyl CoA + Oxaloacetate -> Citrate

Question 1

Step 3

Answer 1

Isocitrate Dehydrogenase (NAD+ >> NADH + H+, CO2)
Isocitrate -> a-ketoglutarate
Produces NADH, 1st of four ox/redox, CO2 out

Question 2

Step 2

Answer 2

Aconitase

Citrate -> Isocitrate

Question 4

Step 4

Answer 4

a-ketoglutarate dehydrogenase
a-ketoglutarate -> Succinyl CoA
CoA, NAD+&raquo_space; CO2, NADH + H+
Analogous to pyruvate dehydrogenase, a-keto acid is like pyruvate (take off acid, add high energy CoA lose 2nd CO2, get NADH)

Question 5

Step 5

Answer 5

Succinyl CoA Synthetase / Thiokinase (GDP + P1&raquo_space; GTP, CoA)
Succinyl CoA ->Succinate
Produces GTP (GTP = ATP because of y-phosphoryl)

Question 6

Step 6

Answer 6

Succinate Dehydrogenase complex (FAD&raquo_space; FADH2)
Succinate -> Fumarate
Imbedded in Mitochondria membrane (others found in matrix) 2ATP equivalents released.

Question 7

Step 7

Answer 7

Fumarase (H2O > )
Fumarate -> L-Malate
H2O added to double bond

Question 8

Step 8

Answer 8

Malate dehydrogenase (NAD+&raquo_space; NADH + H+)
L-Malate -> Oxaloacetate
Causes oxidation of Malate, makes NADH
Oxaloacetate is generated to react with acetyl CoA to complete the cycle

Question 9

Pyruvate Carboxylase

Answer 9

Anapherotic (“Filling up”) (CO2, ATP&raquo_space; ADP + P1)
pyruvate -> oxaloacetate
regulated by acetyl CoA, replenishes cycle

Question 10

ATP Produced by aerobic conditions in the muscle

Answer 10

30

Question 11

ATP Produced by aerobic conditions in the liver

Answer 11

32

Question 12

ATP Produced by anaerobic conditions in the muscle

Answer 12

2

Question 13

ATP Produced by anaerobic conditions in the liver

Answer 13

2

Question 14

Aerobic Fate of Pyruvate

Answer 14

If aerobic, pyruvate enters mitochondria and generates NADH + H+

Question 15

Anaerboic Fate of Pyruvate

Answer 15

If anaerobic lactate dehydrogenase uses NADH to convert pyruvate to lactate, NAD + is regenerated so that glycolysis can continue.

Question 16

Makes NADH

Answer 16

3 & 8

Question 17

Makes FADH

Answer 17

6

Question 18

Makes GTP

Answer 18

5

Question 19

What happens to NADH generated in the cytosol during glycolysis. Anaerobic conditions

Answer 19

Used to regenerate NAD+ and maintain glycolysis

Question 20

What happens to NADH generated in the cytosol during glycolysis. Aerobic conditions

Answer 20

Travels to mitochondria (via shuttle)