Kreb's Cycle, energetics and significance (Trick)

1. Citric acid cycle/Krebs
Cycle/TCA cycle
Presented By – Shubhrat Maheshwari

2. Introduction
CITRIC ACID CYCLE= TCA CYCLE =KREBS CYCLE
(TCA = Tricarboxylic acid cycle)
• In 1937, Sir Hans krebs proposed a complete cycle, and in 1953 got Nobel prize for it.
Definition:
• Acetyl CoA is completely oxidized to CO2 in a cycle of reactions with simultaneous production of energy is
termed as the citric acid cycle.
• Acetyl-CoA, is derived from pyruvate and other metabolites.
• All enzymes are in the mitochondrial matrix.

3. Functions of TCA cycle
• Final common oxidative pathway that oxidizes acetyl CoA to CO2.
• The source of reduced coenzymes that provide the substrate for the respiratory chain.
• The link between catabolic and anabolic pathways (amphibolic role).
• Provides precursors for synthesis of amino acids and nucleotides.
• Components of the cycle have a direct or indirect controlling effects on key enzymes of the pathways.
The citric acid cycle is final common oxidative pathway
CO2

4. Citric Acid Cycle
• After Glycolysis, Pyruvate inter in mitochondria
• Pyruvate decarboxylated and converted in Acetyl CoA. This step catalyzed by pyruvate dehydrogenase
enzyme. This reaction is a link between glycolysis and TCA (Tricarboxlic acid) cycle.
Fig :Conversion of pyruvate to acetyl-CoA

6. (Where: GTP= Guanine triphosphate;
GDP= Guanine Diphosphate;
FAD = Flavin adenine dinucleotide,
FADH2= Flavin adenine dinucleotide dihydride;
NAD= Nicotinamide adenine dinucleotide;
NADH= Nicotinamide adenine dinucleotide hydride)

7. Energetics
• Energetics of TCA Cycle=
• 3ATP (1 NADH, Step 3) + 3ATP (1 NADH, Step 4) + 1ATP (1 GTP, Step 5) + 2ATP (1 FADH2, Step 6) +
3ATP (1 NADH, Step 7) = 12 ATP generated.
• Overall TCA cycle produce 2CO2 molecule and generated 12 ATP.
• Hence, 2 Acetyl Co A produce total energy= 12 x 2= 24
• Energetic in complete oxidation of a glucose molecule:

8. Significance of TCA Cycle

9. Trick to learn krebs cycle
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Smart Staff For Main Office
Cricket – citrate
Coach – cis- Aconitate
India – Isocitrate
Appoints – alpha ketoglutarate
Smart – succinyl- CoA
Staff- Succinate
For- Fumarate
Main- Malate
Office- oxaloacetate