tca cycle

Question 1

What is the TCA cycle

Answer 1

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

Question 2

What are the products of TCA cycle and what they are produced by

Answer 2

• NADH- Produced by three dehyfrogenase reactions
  -FADH- Produced by 1 dehydrogenase
  -C02- released in 2 decarboxylation reactions
  -GTP- generated via substrate level phosphorylation

Question 3

What is the role of the TCA cycle in Metabolism

Answer 3

• Serves as a sharded metabolic pathway for all fuels

Question 4

What are the 2 major Dual functions of the TCA cycle

Answer 4

• Energy production: Facilitates ATP production
• Biosynthesis: Produces intermediates for various biosynthesis processes

Question 5

Describe 3 major functions of the TCA cycle

Answer 5

• 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

Question 6

Where is Acetly-CoA loacted

Answer 6

Mitochondrial matrix

Question 7

What are the 2 roles Acetly coA has-

Answer 7

• Mitochondrial Role
  -Cytoplasmic Role

Question 8

What is the function of Citrate synthesis

Answer 8

• Catalyses the first reaction of the TCA cycle, condensing Acteyl CoA and Oxaloacetate to form citrate

Question 9

What is the energy source for citrate synthesis

Answer 9

• The splitting of high energy thioester bonds in a citroyl-coA

Question 10

What is the role of Citrate

Answer 10

-Serves as a percursor for de novo lipogenesis

Question 11

What is the name of the first and second enzyme used in the TCA cycle

Answer 11

• Citrate synthesis
  -Aconitase

Question 12

What is the function of Aconitase

Answer 12

• It catalyses the reversible isomerization of citrate to isocitrate via the intermediate cis-aconitate

Question 13

What are the 2 steps in which the reaction involed in Aconitase role in TCA cycle

Answer 13

• dehydration followed by hydration

Question 14

Explain Aconitases specificity

Answer 14

• It specifically acts on the oxaloacetate end of the molecule

Question 15

What is the name of the 3rd and 4th enzymes used in the TCA cycle

Answer 15

isocitrate dehydrogenase
- a-ketogluturate dehydrogenase

Question 16

What is the role of both isocitrate dehydrogenase and a -ketogluturate dehydrogenase

Answer 16

• Catalyze reactions converting isocitrate to a-ketogluturate then to succinyl coA, while reducing NAD+ to NADH and releasing C02

Question 17

What is Isocitrate dehydrogenase
-What is it inhibited and activated by and its function

Answer 17

• Regulatory enzyme that is imhibited by high levels of NADH and ATP
• Activated by NAD+ and ADP
• Converts isocitrate to a -ketogluturate

Question 18

What is the function of a -ketogluturate dehydrogenase

Answer 18

converts a -ketogluturate to suxxinyl coA, NADH and C02

Question 19

Why does the net carbon yield of the TCA cycle remain zero

Answer 19

• 2 caarbons enter as acetyl coA
• 2 C are releases as C02, so they cancel eachother out

Question 20

What is the function of succinyl-coA synthetase

Answer 20

• Catalyzes the conversion of succinyl-coA to succinate and a free coA
  -And GTP is formed

Question 21

How is GTP formed from succinyl coA synthetase

Answer 21

• Energy from the high energy thioester bond in succinyl coA is conserved in the formation of GTP from GDP and pi

Question 22

What is the role of GTP

Answer 22

It is utilised in:
- Gluconeogenesis
-Protein synthesis
-Cell signaling processes

Question 23

What is succinate dehydrohenase

Answer 23

• Flavoprotein with FAD as a prosthetic group

Question 24

Where is succinate dehydrogenase located

Answer 24

• In the inner mitochondrial membrane

Question 25

Name the enzymes invoved in the TCA CYCLE

Answer 25

1.Citrate synthesis 2.Aconitase 3.Isocitrate dehydrogenase 4.a-ketogluturate dehydrogenase 5.Succinyl-coA synthetase 6.Succinate dehydrogenase 7.Fumerase 8.Malate Dehydrogenase

Question 26

What is the function of succinate dehydrogenase

Answer 26

- It catalyzes the oxidation of succinate to fumarate while reducing FAD to FADH2

Question 27

What is the role of fumerase

Answer 27

- It catalyzes the addition of water across the trans double bond of fumerate to form L-malate - Water is released

Question 28

What is the function of malate Dehydrogenase

Answer 28

- Catalyses the oxidation of L-malate to Oxaloacetate. - Regenerates NADH

Question 29

What does the activity of the TCA cycle depend on

Answer 29

- Availability of NAD+ -

Question 30

What is Pyruvate Dehydogenase complex inhibited by

Answer 30

- NADH,ATP,acteyl coA(negative effectors)

Question 31

What is pyruvate Dehydrogenase complex activated by

Answer 31

- low conc of NADH,ATP and acetyl coA - Insulin

Question 32

What is Anaplerosis

Answer 32

- The replenishment of the TCA cycle intermediates to maintains its activity

Question 33

Name the key anaplerotic enzymes

Answer 33

- pyruvate carboxylase- converts pyruvate oAA -Malic enzyme- Converst pyruvate to malate Aspartate Transamination

Question 34

Name the major anaplerotic pathways

Answer 34

-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)

Question 35

What are the fuctions of Anapolerotic rections in the TCA cycle

Answer 35

- Restore TCA intermediates to maintain cycle function

Question 36

Name the 2 key regulatroy enzymes in TCA cycle

Answer 36

- Pyruvate dehydrogenase -Isocitrate dehydrogenase