The citric acid cycle (CAC) – also known as the TCA cycle (tricarboxylic acid cycle) or the Krebs cycle – is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. here u will find every detail of KREBS cycle.

1. Krebs cycle
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2.  The citric acid cycle (CAC) – also known as the TCA
cycle (tricarboxylic acid cycle) or the Krebs cycle – is a
series of chemical reactions used by all aerobic
organisms to release stored energy through
the oxidation of acetyl-CoA derived
from carbohydrates, fats, and proteins.
 In addition, the cycle provides precursors of certain
amino acids, as well as the reducing agent NADH, that
are used in numerous other reactions.

3.  The name of this metabolic pathway is derived from the citric
acid (a tricarboxylic acid, often called citrate, as the ionized
form predominates at biological pH) that is consumed and
then regenerated by this sequence of reactions to complete
the cycle.
 The cycle consumes acetate (in the form of acetyl-CoA)
and water, reduces NAD+ to NADH, releasing carbon dioxide.
 The NADH generated by the citric acid cycle is fed into
the oxidative phosphorylation (electron transport) pathway.
 The net result of these two closely linked pathways is the
oxidation of nutrients to produce usable chemical energy in
the form of ATP.

4.  In eukaryotic cells, the citric acid cycle occurs in
the matrix of the mitochondrion.
 In prokaryotic cells, such as bacteria, which lack
mitochondria, the citric acid cycle reaction
sequence is performed in the cytosol

5.  The citric acid cycle itself was finally
identified in 1937 by Hans Adolf Krebs

6.  The citric cycle is a central driver of cellular respiration.
 It takes acetyl CoA—produced by the oxidation of pyruvate and
originally derived from glucose—as its starting material and, in a
series of redox reactions, harvests much of its bond energy in
the form of NADH,FADH2 and ATP molecules.
 The reduced electron carriers NADH and FADH2—generated in
the TCA cycle will pass their electrons into the electron transport
chain and, through oxidative phosphorylation, will generate
most of the ATP produced in cellular respiration.

9. STEPS ENZYMES
• CONDENSATION •Citric acid synthase
• ISOMERISATION •Aconitase
•Aconitase
• DEHYDROGENATION-1 •Isocitrate dehydrogenase
• DECARBOXYLATION •Oxalosuccinate decarboxylase
• OXIDATIVE DECARBOXYLATION •α-ketoglutarate dehydrogenase
complex succinate thiokinase
• DEHYDROGENATION-3 •Succinate dehydrogenase
• HYDRATION •Fumarase
• DEHYDROGENATION-4 •Malate dehydrogenase

10.  Citrate Is A Special Substrate For Making Oxaloacetate.

11.  Products of the first turn of the cycle are one GTP (or ATP),
three NADH, one QH2 and two CO2.
 Because two acetyl-CoA molecules are produced from
each glucose molecule, two cycles are required per glucose
molecule. Therefore, at the end of two cycles, the products are:
two GTP, six NADH, two QH2, and four CO2.
 The total number of ATP molecules obtained after complete
oxidation of one glucose in glycolysis, citric acid cycle,
and oxidative phosphorylation is estimated to be between 30
and 38.