carbohydrates 5- citric acid cycle

Question 1

the Krebs cycle/ the citric acid cycle

• where does it take place?
• how does it produce energy?

Answer 1

1- it takes place in the mitochondrial matrix
2- it produces a high amount of energy through the production of metabolic intermediates- FADH2 and NADH which can then be used to produce ATP

Question 2

how is it controlled?

Answer 2

through pyruvate dehydrogenase
-when there is a high supply of energy then the activity of the pyruvate dehydrogenase is inhibited
-when there is a low supply of energy the activity go the pyruvate dehydrogenase is activated
this controls the breakdown of pyruvate to acetyl CoA which is the main substrate for the cycle

allosterically: ATP and NADP negatively regulate.
- Alpha-ketoglutarate dehydrogenase: switches production from succinyl-CoA to amino acids
- Isocitrate dehydrogenase: prevents isocitrate being converted into alpha-kets glutarate. Citrate will move into the cytoplasm which interrupt glycolysis

Question 3

how do the allosteric inhibitors work?

Answer 3

alpha-ketoglutarate dehydrogenase:
inhibited through ATP, NADH and succinylCoA
causes the build up of ketoglutarate- switches use to aminoacids

isocitrate dehydrogenase:
inhibited through ATP and NADH
activated via ADP
causes the build up of citrate so carried into the cytoplasm where it inhibits phopofructosekinase

Question 4

Products

Answer 4

4Co2
2 ATP
6 NADH + H+
2 FADH2