Krebs cycle for Bio Tech in Grade 9 .pptx

Kreb cycle is the further process of glycolysis

1. TCA Cycle By: Carl Benedict Ave Winchester Unciano Jillian Alexa Beran John Ryan Paraggua Princess Angel Dizon

2. TCA Cycle Also known as Krebs cycle TCA cycle essentially involves the oxidation of acetyl CoA to CO 2 and H 2 O. TCA cycle –the central metabolic pathway The TCA cycle is the final common oxidative pathway for carbohydrates, fats, amino acids.

3. TCA cycle supplies energy & also provides many intermediates required for the synthesis of amino acids, glucose, heme etc. TCA cycle is the most important central pathway connecting almost all the individual metabolic pathways.

4. Definition Citric acid cycle or TCA cycle or tricarboxylic acid cycle essentially involves the oxidation of acetyl CoA to CO 2 & H 2 O. Location of the TCA cycle Reactions of occur in mitochondrial matrix, in close proximity to the ETC.

5. Krebs Cycle is a part of Cellular Respiration Cellular respiration is a catabolic reaction taking place in the cells. It is a biochemical process by which nutrients are broken down to release energy, which gets stored in the form of ATP and waste products are released . In aerobic respiration, oxygen is required. Cellular respiration is a four-stage process. In the process, glucose is oxidised to carbon dioxide and oxygen is reduced to water. The energy released in the process is stored in the form of ATPs. 36 to 38 ATPs are formed from each glucose molecule.

6. Reactions of TCA cycle Oxidative decarboxylation of pyruvate to acetyl CoA by PDH complex. This step is connecting link between glycolysis and TCA cycle. Glycolysis: Partial oxidation of a glucose molecule to form 2 molecules of pyruvate. This process takes place in the cytosol

7. Reactions of TCA Cycle Step:1 Formation of citrate Oxaloacetate condenses with acetyl CoA to form Citrate , catalysed by the enzyme citrate synthase Inhibited by: ATP, NADH, Citrate - competitive inhibitor of oxaloacetate.

8. Steps 2 & 3 Citrate is isomerized to isocitrate Citrate is isomerized to isocitrate by the enzyme aconitase This is achieved in a two stage reaction of dehydration followed by hydration through the formation of an intermediate - cis-aconiase

9. Steps 4 & 5 Formation of - ketoglutarate Isocitrate dehydrogenase (ICDH) catalyses the conversion of (oxidative decarboxylation ) of isocitrate to oxalosuccinate & then to - ketoglutarate . The formation of NADH & the liberation of CO 2 occure at this stage. Stimulated (cooperative) by isocitrate , NAD + , Mg 2+ , ADP, Ca 2+ (links with contraction). Inhibited by NADH & ATP

10. Step: 6 Conversion of - ketoglutarate to succinyl CoA Occurs through oxidative decarboxylation , catalysed by - ketoglutarate dehydrogenase complex. - ketoglutarate dehydrogenase is an multienzyme complex. At this stage of TCA cycle, second NADH is produced & the second CO 2 is liberated.

11. Step: 7 Formation of succinate Succinyl CoA is converted to succinate by succinate thiokinase . This reaction is coupled with the phosphorylation of GDP to GTP. This is a substrate level phosphorylation . GTP is converted to ATP by the enzyme nucleoside diphosphate kinase .

12. Step: 8 Conversion of succinate to fumarate Succinate is oxidized by succinate dehydrogenase to fumarate . This reaction results in the production of FADH 2 . Step: 9 Formation of malate: The enzyme fumarase catalyses the conversion of fumarate to malate with the addition of H 2 O.

13. Step:10 Conversion of malate to oxaloacetate Malate is then oxidized to oxaloacetate by malate dehydrogenase . The third & final synthesis of NADH occurs at this stage. The oxaloacetate is regenerated which can combine with another molecule of acetyl CoA & continue the cycle.

14. Pyruvate Acetyl CoA Citrate Cis-Aconitase Iso -citrate Oxalosuccinate ɑ- Ketoglutarate Succinyl CoA Succinate Fumarate Malate Oxaloacatete PDH CO 2 , NADH + H + NAD + - H 2 O - H 2 O NADH + H + NAD + - CO 2 CO 2 , NADH + H + NAD + GDP+Pi GTP FADH 2 FAD - H 2 O NADH + H + NAD + Citrate synthase Aconitase Aconitase ICDH ICDH ɑ- KGDH Succinate Thiokinase SDH Fumarase MDH TCA

15. Regeneration of oxaloacetate The TCA cycle basically involves the oxidation of acetyl CoA to CO 2 with the simultaneous regeneration of oxaloacetate . There is no net consumption of oxaloacetate or any other intermediate in the cycle.

16. Significance of TCA cycle Complete oxidation of acetyl CoA . ATP generation. Final common oxidative pathway. Integration of major metabolic pathways. Fat is burned on the wick of carbohydrates. Excess carbohydrates are converted as neutral fat No net synthesis of carbohydrates from fat. Carbon skeleton of amino acids finally enter the TCA cycle.

17. Requirement of O 2 by TCA cycle There is no direct participation of O 2 in TCA cycle. Operates only under aerobic conditions. This is due to, NAD + & FAD required for the operation of the cycle can be regenerated in the respiratory chain only in presence of O 2 . Therefore, citric acid cycle is strictly aerobic.

18. Energetics of TCA Cycle Oxidation of 3 NADH by ETC coupled with oxidative phosphorylation results in the synthesis of 9ATP. FADH 2 leads to the formation of 2ATP. One substrate level phosphorylation . Thus, a total of 12 ATP are produced from one acetyl CoA.

19. Regulation of TCA Cycle Three regulatory enzymes 1. Citrate synthase 2. Isocitrate dehydrogenase 3. α - ketoglutarate dehydrogenase

20. Citrate synthase is inhibited by ATP, NADH, acyl CoA & succinyl CoA . Isocitrate dehydrogenase is activated by ADP & inhibited by ATP and NADH α - ketoglutarate dehydrogenase is inhibited by succinyl CoA & NADH. Availability of ADP is very important for TCA cycle to proceed.

21. Transamination Transamination is a process where an amino acid transfers its amino group to a keto group and itself gets converted to a keto acid. The formation of Alpha ketoglutarate & oxaloacetate occures by this mechanism.

22. 1.It’s also Known as Krebs Cycle
A.TCA Cycle C.ATC Cycle
B.ACT Cycle. D.CAT Cycle 2.What does TCA Cycle Stands for? A.Tricarbocylic Acid Cycle. C.Thricarboxylic Acid Cycle B.Tricarboxylic Acid Cycle D.Tricarbonxylic Acid Cycle 3.TCA Cycle essentially involves the oxidation of acetyl CoA to……
A.CH4 and SO₂
B. H₂O and CH3Cl
C.N2 and CO₂
D. H₂O and CO₂ 4.What is the importance of the kreb cycle? A. It produces the majority of energy used by aerobic cells
B. to maintain the proper contents of salts, proteins, ions, and nutrients in the cell
C. to assist the cell in movement
D. to provide tensile strength and protection against mechanical and osmotic stress 5.What required O₂ by TCA cycle A.The TCA cycle itself directly require to oxygen. B.Oxygen is a subordinate in the TCA Cycle.
C.NAD+&FAD required for this operation of the cycle D.The TCA cycle cannot occur without oxygen. Direction: Answer the Following Questions in Capital Letters

23. 6.What is Cellular Respiration? A.Is a Catabolic Reaction taking place in the cells. B.A biochemical process by which nutrients are broken down to release energy, which gets stored in the form of ATP and waste products are released. C.A four-stage process where glucose is oxidised to carbon dioxide and oxygen is reduced to water. D.All of the above 7.TCA Cycle is the final common oxidative for? A.Nutrients , Protein, Acid B.Water , Amino Acid, Glucose C.Amino Acids, Fats, Carbohydrates D.None of the Above 8.What step is the Formation of succinate. A.Step 2-3 C.Step 4-5 B.Step 7 D.Step 6 9.Citrate is isomerized to isocitrate A.Step 10 C.Step 2-3 B.Step 4-5 D.Step 8 10.The enzyme fumarase catalyses the conversion of fumarate to malate with the addition of H2O. A.Formation of succinate B.Conversion of - ketoglutarate to succinyl CoA C.Citrate is isomerized to isocitrate D.Formation of malate

24. 11.Which doesn’t tell about the Significance of the TCA Cycle? A.Excess carbohydrates are converted as neutral fat. B.Operates only under aerobic conditions. C.Complete oxidation of acetyl CoA. D.ATP generation 12.The following are the regulatory enzymes except. A.Citrate synthase B.α- ketoglutarate dehydrogenase C.Isocitrate dehydrogenase D.Oxidative decarboxylation 13.What is Transamination? A.Oxidation of 3 NADH by ETC coupled with oxidative phosphorylation results in the synthesis of 9ATP. B.Partial oxidation of a glucose molecule to form 2 molecules of pyruvate C.A process where an amino acid transfers its amino group to a keto group and itself gets converted to a keto acid. D.The oxidation of acetyl CoA to CO2 with the simultaneous regeneration of oxaloacetate. 14.Occurs through oxidative decarboxylation A.Conversion of malate to oxaloacetate B.Conversion of succinate to fumarate C.Citrate is isomerized to isocitrate D.Conversion of - ketoglutarate to succinyl CoA 15.Cellular respiration is a four-stage process. In the process, ________ is oxidised to carbon dioxide and oxygen is reduced to water. A.Glucose B.Enzymes C.Citric acid D.Succinyl

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