Citric Acid Cycle Flashcards
What are the 3 components of Pyruvate Dehydrogenase?
E1: Pyruvate Dehydrogenase
E2: Dihydrolipoamide acetyltransferase
E3: Dihydrolipoamide dehydrogenase
What are the 5 cofactors used in PDH, and where do you get them nutritionally?
Thymine Pyrophosphate:derived from Vitamin B1 found in meats and whole grains (deficiency leads to muscle weakness and confusion, i.e. Buribere)
lipoic acid is found in spinach, broccoli, and potatoes
Coenzyme A is derived from vitamin B5 (Pantothenic Acid) found in whole grains and egg yolks
FAD+ is derived from vitamin B2 (riboflavin) found in milks and whole grains
NAD+ is derived from vitamin B3 (Niacin) found in meats, nuts, and legumes.
How is PDH allosterically regulated?
Pyruvate dehydrogenase can be allosterically regulated by increased levels of CoA and NAD+ (positive) or high levels of Acetyl CoA, NADH, and ATP (negative)
How is PDH covalently regulated?
The E1 subunit is phosphorylated (Inhibited) by a regulated kinase (Up by AcetylCoA and NADH, Down by ADP, CoA, pyruvate, and NAD+)
It is dephosphorylated (activated) by a regulated phosphatase (Up by Ca2++, pyruvate, insulin, low NADH/NAD+ ratio, and low AcetylCoA)
What is the second regulated step in the CAC, and how is it regulated?
Conversion of Acetyl CoA to Citrate by Citrate Synthase.
It is only down regulated by the presence of Succinyl CoA, NADH, and ATP
What is the third regulated step in the CAC and how is it regulated?
Conversion of Isocitrate to alpha-Ketoglutarate by isocitrate dehydrogenase
It is upregulated by ADP and NAD+, and downregulated by ATP
What is the fourth and final regulated step in the CAC and how is it regulated?
Conversion of alpha-Ketoglutarate to Succinyl CoA
It is Up regulated by AMP, and down regulated by Succinyl CoA and NADH
What energy molecules are generated in the Citric Acid cycle?
3 NADH, 1 FADH, one GTP (converted to ATP) for every one Acetyl CoA that enters the cycle
What are the energy producing steps in the Citric acid cycle?
Isocitrate -> alpha-Ketoglutarate = 1 NADH
alpha-Ketoglutarate -> Succinyl CoA = 1 NADH
Succinyl CoA -> Succinate = 1 GTP (->ATP by nucleotide diphosphate kinase)
Succinate -> Fumarate = 1 FADH2
Malate -> Oxaloacetate 1 NADH
Which CAC intermediates are involved in Anaplerotic reactions? Which reactions?
Pyruvate, alpha-Ketoglutarate, Succinyl CoA, Furmarate, and Oxaloacetate.
Pyruvate and be formed into Oxaloacetate by pyruvate carboxylase or malate by malic enzyme.
alpha-ketoglutarate in used in Glutamate synthesis
Fumarate and Oxaloacetate are used in Aspartate synthesis
Succinyl CoA is used in porphyrin synthesis
What is the function of Pyruvate Dehydrogenase?
to create the first NADH of the CAC and to convert Pyruvate into Acetyl CoA
