About Krebs cycle, which is the most important cycle in cellular respiration which take place in all aerobic organism and also tells about importance of Krebs cycle. As it place a connecting link between Glycolysis and ETS

1. MALAVIKA PRABHAKARAN
BSc ZOOLOGY

2.  Citric acid cycle.
 Krebs cycle – Sir Hans Krebs in 1937 – Nobel
prize in 1953
 TCA cycle – tricarboxylic acid cycle.

3.  Only in aerobic condition.
 Inside mitochondrial matrix[Eukaryotes].
 Cytosol [Prokaryotes]

5.  Catabolic
 Anabolic

8.  1.Formation of citrate
H2O +
COA
6C

9.  Citrate is converted to isocitrate
[isomerization].

10.  Iso-citrate converted to α-ketoglutarate.
 1st redox reaction,

11.  α-ketoglutarate undergo redox reaction [2nd redox
reaction]
 React with CoA to form succinyl CoA.
4C

12.  succinyl CoA converted to succinyl and CoA by succinyl
synthase.
 Energy released from this reaction is used to
phosphorylate GDP to GTP[Substrate phosphorylation].

13.  Succinate is converted to fumarate by
succinate dehydrogenase.
 Hydrogen is accepted by FAD not NAD.
2

14.  Fumarate – hydration reaction to form malate
by fumarase

15.  Malate is dehydrogenated to oxaloacetate by
malate dehydrogenase.
 Hydrogen is accepted by NAD reduced to
form NADH

16.  Acetyl CoA [2C] used to give 2 CO2.
 Redox reaction gives:
 We convert 3 molecules of NAD to NADH.
 1 molecule of FAD to FADH.
 1 molecule of GDP to GTP.

17. ×2

18.  How many ATPs are produced for 1 molecule
of glucose that enters Krebs cycle.
 1NADH=2.5 ATP
 1FADH=1.5 ATP
 1acetyl CoA= 3NADH,1FADH ,1GTP.
 So ATP for 1 acetyl CoA = 10 ATP
 2acetyl CoA = 20 ATP molecules are
produced per glucose molecules.
2

19.  Required for the regeneration of NAD and
FAD.
 IF NO AIR WHAT WILL HAPPEN?????

20.  YESSS
 ATP
 ETC
 CO2

21. THANK YOU…………