Krebs Cycle

Question 1

What does TCA stand for?

Answer 1

Tricarboxylic acid cycle

Question 2

What does each turn produce?

Answer 2

2CO2
3NADH
1GTP
1FADH2

Question 3

Step 1

Answer 3

Thioester linkage hydrolysed
2C acetyl group accepted by oxaloacetate
Gives 6C Citrate

Question 4

Step 2

Answer 4

Isomerisation yields isocitrate

Question 5

Step 3

Answer 5

Series of oxidative decarboxylations

Produces reduced co-factors (NADH)

Question 6

Step 4

Answer 6

Back to 4C compound

Question 7

Step 5

Answer 7

Produces GTP analogous to ATP

Has high energy phosphoanhydride bond

Question 8

Step 6+7

Answer 8

More redox

Produces FADH2 and more NADH

Question 9

Step 8

Answer 9

Return back to oxaloacetate to restart cycle

Question 10

What is transamination?

Answer 10

An amine group is transferred from an amino acid to a keto acid forming a new pair of amino and keto acids

E.g alanine and alpha-ketoglutarate —> pyruvate and glutamate

Amine group excreted as urea

Question 11

Name two ways NADH’s high energy electrons are transported from cytosol to matrix

Answer 11

The glycerol phosphate shuffle (skeletal muscle and brain)

The malate aspartate shuffle (liver, kidney, heart)

Question 12

What is step one of the glycerol phosphate shuffle?

Answer 12

Cytosolic glycerol-3-phosphate dehydrogenase transfers e- from NADH to DHAP
Generate glycerol-3-phosphate

Question 13

What is step 2 of the glycerol phosphate shuffle?

Answer 13

Membrane bound form of glycerol-3-phosphate dehydrogenase transfer e- to FAD
Then passed to co-enzyme Q (ETC)

Question 14

What is step 1 of the malate-aspartate shuffle?

Answer 14

Malate dehydrogenase converts oxaloacetate to malate
Malate transported into mitochondria
MDH converts malate back to oxaloacetate releasing NADH

Question 15

What is step 2 of the malate-aspartate shuffle?

Answer 15

Oxaloacetate converted to aspartate by aspartate transaminase
Aspartate exits the mitochondria