TCA Cycle Flashcards Preview

DEMS: Unit II > TCA Cycle > Flashcards

Flashcards in TCA Cycle Deck (12):
1

Substrates for TCA Cycle

  • main substrate = acetyl CoA
  • carbon skeletons of sugars, fatty acids and several amino acids enter the citric acid cycle as acetyl CoA
  • acetyl CoA is not the only site where amino acids can enter the cycle

2

Key intermediates of TCA cycle

  • Citrate
  • α keto-glutarate
  • Succinyl CoA
  • Fumarate
  • Oxaloacetate (and to a lesser extent malate)

3

Importance of citrate intermediate in TCA cycle

this is the point @ which fatty acid synthesis takes off

4

Importance of alpha keto-glutarate intermediate in TCA cycle

α keto-glutarate: because this is an important entrance point for a number of amino acids that contribute to gluconeogenesis.

 

5

Importance of succinyl CoA intermediate in TCA cycle

Succinyl CoA: because this is an important entrance point for a number of amino acids and for products of the breakdown of fatty acids with an odd number of carbons that contribute to gluconeogenesis.

6

Importance of fumarate intermediate in TCA cycle

Fumarate: because this is an entrance point for amino acids and because it is a byproduct of the urea cycle.

7

Importance of oxaloacetate intermediate in TCA cycle

 

Oxaloacetate (and to a lesser extent malate): because these are involved in the gluconeogenic pathway from pyruvate.

8

Entry points into TCA for amino acids

  • AA ==> pyrubate ==> Oxaloacetate
  • AA ==> oxaloacetate
  • AA ==> fumarate
  • AA ==> Succinyl CoA
  • AA ==> alpha-ketoglutarate

A image thumb
9

Main products of TCA cycle

  • The TCA cycle generates NADH, FADH2, GTP.
  • The GTP produced can be used to generate ATP
  • NADH and FADH2 enter the electron transport pathway to also generate ATP

10

Metabolic role of TCA

  • Oxidation of glucose to pyruvate has not harnessed the energy stored in glucose completely.  
    • TCAC creates more energy from glucose.
  • It also makes biosynthetic precursors (AA’s, nucleotides).  
    • intermediates are continuously channeled into the pathways of amino acid synthesis, fatty acid synthesis, etc.
    • involved in gluconeogenesis @ liver 

11

TCA ==> gluconeogenesis @ liver

  • In the liver, during fasting, gluconeogenic precursors are converted to malate
  • malate leaves the mitochondria to enter the pathway of gluconeogenesis in the cytosol. 

12

Key TCA steps for production of NADH, FADH2, & CO2

  • Isocitrate + NAD ==> alpha-ketoglutarate + CO2 + NADH
  • alpha-ketoglutarate + NAD+ ==> Succinyl CoA + CO2 + NADH
  • Succinate + FAD2+ ==> Fumarate + FADH2
  • Malate + NAD+ ==> Oxaloacetate + NADH