Bridge Step and Krebs Cycle

Question 1

Bridge Step

Answer 1

pyruvate - acetyl-CoA

enzyme is pyruvate dehydrogenase complex (E1+E2+E3)

referred to as oxidative decarboxylation

inhibited by ATP, acetyl-CoA, NADH, fatty acids

activated by AMP, CoA, NAD+, Ca2+

Question 2

Step 1

Answer 2

Acetyl-CoA + Oxaloacetate - citrate

H20 - CoA-SH

enzyme is citrate synthase

irreversible reaction

inhibited by NADH, succinyl-CoA, citrate, ATP

activated by ADP

Question 3

Step 2

Answer 3

cirate - isocitrate

enzyme is aconitase

Question 4

Step 3

Answer 4

Isocitrate - alpha-Ketoglutarate

NAD+ - NADH + CO2

enzyme is isocitrate dehydrogenase

inhibited by ATP

activated by Ca2+, ADP

Question 5

Step 4

Answer 5

alpha-ketoglutarate - succinyl-COA

CoA-SH + NAD+ - NADH + CO2

enzyme is alpha-ketoglutarate dehydrogenase complex

irreversible

inhibited by succinyl-CoA, NADH

activated by Ca2+

Question 6

Step 5

Answer 6

succinyl-CoA - succinate

GDP + Pi - GTP + HS-CoA

enzyme is succinyl-CoA synthetase

Question 7

Step 6

Answer 7

Succinate - Fumarate

FAD - FADH2

Q - QH2

FADH2 is the intermediate product

enzyme is succinate dehydrogenase

Question 8

Step 7

Answer 8

Fumarate - Malate

enzyme is fumarase

Question 9

Step 8

Answer 9

Malate - Oxaloacetate

NAD+ - NADH + H+

enzyme is malate dehydrogenase