Download The Krebs Cycle (Citric Acid Cycle)

The Krebs Cycle
(Citric Acid Cycle)
By Zuzana Kollarova
Krebs Cycle

Enzymes in the matrix of the mitochondria catalyze a
cycle of reactions called the Krebs cycle.
 The common pathway to completely oxidize fuel
molecules which mostly is acetyl CoA ,the product from
the oxidative decarboxylation of pyruvate
 It enters the cycle and passes ten steps of reactions that
yield energy and CO2
 These reactions can only occur if oxygen is available
and so are part aerobic cell respiration
 Prokaryotic cells – occurs in the cytoplasm
 Eukaryotic cells – occurs in the mitochondria
Steps:
1.
2.
3.
4.
In the first reaction of the cycle an acetyl group is
transferred from acetyl CoA to a four-carbon
compound (oxyloacetate) to form a six-carbon
compound (Citrate).
Citrate is converted to isocitrate.
The 6-carbon isocitrate is oxidized by NAD+ to
produce reduced NADH and 5-carbon alphaketoglutarate. One carbon is lost as CO2
(decarboxylation). CO2 is waste product.
The 5-carbon alpha-ketoglutarate is oxidized by NAD+
to produce reduced NADH and 4-carbon succinyl-CoA.
(One carbon is lost as CO2.)
5. Hydrogen is removed – Oxidation of
succinyl-CoA produces succinate and
one GTP that is converted to ATP.
Oxidation reactions release energy,
much of which is stored by the carriers
when they accept hydrogen.
6. Oxidation of succinate by FAD produces
reduced FADH2 and fumarate.
7. Fumarate is converted into malate
8. Oxidation of malate by NAD+ produces
reduced NADH and oxaloacetate
 Animation:
http://www.youtube.com/watch?v=aCypoN
3X7KQ