Citric acid cycle

Question 1

Step 1

Answer 1

-Acetyl-CoA joins with a four carbon molecule, oxaloacetate, releasing the CoA group and making a six carbon molecule called citrate

Question 2

Step 2

Answer 2

-Citrate is converted into its isomer, isocitrate, which actually has two steps: the removal and then addition of a water molecule.

Question 3

Step 3

Answer 3

-Isocitrate is oxidized and releases a carbon dioxide, leaving behind a five carbon molecule- a-ketoglutarate
-NAD+ is reduced to NADH
-Enzyme that catalyzes this reaction is isocitrate dehydrogenase
-Rate limiting step f

Question 4

Step 4

Answer 4

• a-ketoglutarate is oxidized releasing another carbon dioxide molecule
  -The remaining four carbon molecule picks up Coenzyme A to form succinyl CoA (unstable)
• NAD+ is reduced to NADH
  -enzyme that catalyzes this reaction is a-ketoglutarate dehydrogenase

Question 5

Step 5

Answer 5

-the CoA of succinyl CoA is replaced by a phosphate group, which is then transferred to ADP to make ATP (or GDP to GTP). Molecule produced is called succinate

Question 6

Step 6

Answer 6

-Succinate is oxidized forming fumarate
-Two hydrogen atoms are transferred to FAD producing an FADH2

Question 7

Step 7

Answer 7

Water is added to fumarate and turns it into another four carbon molecule called malate

Question 8

Step 8

Answer 8

-Malate is oxidized to regenerate the starting molecule oxaloacetate
-NAD+ is reduced to NADH