tca cycle Flashcards
What is the TCA cycle
A series of 8 enzymatic reactions for the oxidation of acetyl coA
- Oxaloacetate is both a reactant and regenerated at the end of the cycle
What are the products of TCA cycle and what they are produced by
- NADH- Produced by three dehyfrogenase reactions
-FADH- Produced by 1 dehydrogenase
-C02- released in 2 decarboxylation reactions
-GTP- generated via substrate level phosphorylation
What is the role of the TCA cycle in Metabolism
- Serves as a sharded metabolic pathway for all fuels
What are the 2 major Dual functions of the TCA cycle
- Energy production: Facilitates ATP production
- Biosynthesis: Produces intermediates for various biosynthesis processes
Describe 3 major functions of the TCA cycle
- It provides a common ground for the interconversion of metabolites and fuel
- Four oxidative steps produce free energy for ATP synthesis
- Acetyl-CoA is common product
Where is Acetly-CoA loacted
Mitochondrial matrix
What are the 2 roles Acetly coA has-
- Mitochondrial Role
-Cytoplasmic Role
What is the function of Citrate synthesis
- Catalyses the first reaction of the TCA cycle, condensing Acteyl CoA and Oxaloacetate to form citrate
What is the energy source for citrate synthesis
- The splitting of high energy thioester bonds in a citroyl-coA
What is the role of Citrate
-Serves as a percursor for de novo lipogenesis
What is the name of the first and second enzyme used in the TCA cycle
- Citrate synthesis
-Aconitase
What is the function of Aconitase
- It catalyses the reversible isomerization of citrate to isocitrate via the intermediate cis-aconitate
What are the 2 steps in which the reaction involed in Aconitase role in TCA cycle
- dehydration followed by hydration
Explain Aconitases specificity
- It specifically acts on the oxaloacetate end of the molecule
What is the name of the 3rd and 4th enzymes used in the TCA cycle
isocitrate dehydrogenase
- a-ketogluturate dehydrogenase
What is the role of both isocitrate dehydrogenase and a -ketogluturate dehydrogenase
- Catalyze reactions converting isocitrate to a-ketogluturate then to succinyl coA, while reducing NAD+ to NADH and releasing C02
What is Isocitrate dehydrogenase
-What is it inhibited and activated by and its function
- Regulatory enzyme that is imhibited by high levels of NADH and ATP
- Activated by NAD+ and ADP
- Converts isocitrate to a -ketogluturate
What is the function of a -ketogluturate dehydrogenase
converts a -ketogluturate to suxxinyl coA, NADH and C02
Why does the net carbon yield of the TCA cycle remain zero
- 2 caarbons enter as acetyl coA
- 2 C are releases as C02, so they cancel eachother out
What is the function of succinyl-coA synthetase
- Catalyzes the conversion of succinyl-coA to succinate and a free coA
-And GTP is formed
How is GTP formed from succinyl coA synthetase
- Energy from the high energy thioester bond in succinyl coA is conserved in the formation of GTP from GDP and pi
What is the role of GTP
It is utilised in:
- Gluconeogenesis
-Protein synthesis
-Cell signaling processes
What is succinate dehydrohenase
- Flavoprotein with FAD as a prosthetic group
Where is succinate dehydrogenase located
- In the inner mitochondrial membrane
Name the enzymes invoved in the TCA CYCLE
1.Citrate synthesis
2.Aconitase
3.Isocitrate dehydrogenase
4.a-ketogluturate dehydrogenase
5.Succinyl-coA synthetase
6.Succinate dehydrogenase
7.Fumerase
8.Malate Dehydrogenase
What is the function of succinate dehydrogenase
- It catalyzes the oxidation of succinate to fumarate while reducing FAD to FADH2
What is the role of fumerase
- It catalyzes the addition of water across the trans double bond of fumerate to form L-malate
- Water is released
What is the function of malate Dehydrogenase
- Catalyses the oxidation of L-malate to Oxaloacetate.
- Regenerates NADH
What does the activity of the TCA cycle depend on
- ## Availability of NAD+
What is Pyruvate Dehydogenase complex inhibited by
- NADH,ATP,acteyl coA(negative effectors)
What is pyruvate Dehydrogenase complex activated by
- low conc of NADH,ATP and acetyl coA
- Insulin
What is Anaplerosis
- The replenishment of the TCA cycle intermediates to maintains its activity
Name the key anaplerotic enzymes
- pyruvate carboxylase- converts pyruvate oAA
-Malic enzyme- Converst pyruvate to malate
Aspartate Transamination
Name the major anaplerotic pathways
-Pyruvate carboxylase converts pyruvate to oxaloacetate (OAA).
-Glutamate converted α-ketoglutarate
-Valine, isoleucine, and odd-chain fatty acids → Succinyl-CoA.
-Some amino acids → Fumarate.
-Other amino acids → Oxaloacetate (OAA)
What are the fuctions of Anapolerotic rections in the TCA cycle
- Restore TCA intermediates to maintain cycle function
Name the 2 key regulatroy enzymes in TCA cycle
- Pyruvate dehydrogenase
-Isocitrate dehydrogenase
