TCA Cycle Flashcards
Four fates of pyruvate
1) lactate (under anaerobic conditions)
2) alanine (amino acid synthesis)
3) acetyl CoA (citric acid cycle)
4) oxaloacetate (anaplerotic reaction to replenish TCA intermediates)
What is acetyl-coA oxidized to in the citric acid cycle
CO2
Enzyme responsible for conversion of pyruvate to acetyl-CoA
pyruvate dehydrogenase
Five coenzymes used by pyruvate dehydrogenase complex
1) Thiamine pyrophosphate
2) lipoyllysine
3) FAD
4) NAD+
5) CoA-SH
Riboflavin (Vit B2) deficiency can cause what condition with chapped/fissured lips
Cheilosis
Pellagra is a deficiency in…
Niacin (B3)
Net Inputs into the Citric Acid Cycle (6)
1) Acetyl-Coa
2) 3 NAD+
3) FAD
4) GDP
5) Pi
6) 2 H2O
Net Outputs from the Citric Acid Cycle (6)
1) 2 CO2
2) 3 NADH
3) FADH2
4) GTP
5) CoA
6) 3 H+
In this anaplerotic reaction, pyruvate forms oxaloacetate via which enzyme
pyruvate carboxylase
Enzyme responsible for pyruvate to malate conversion
Malic enzyme
Converts PEP to oxaloacetate.
PEP carboxykinase
Besides glycolysis products, what else can be a source for TCA cycle intermediates?
glucogenic amino acids
Tissue specificity of pyruvate carboxylase
Liver and kidney
Tissue specificity of PEP carboxykinase
Heart and skeletal muscle
Tissue specificity of PEP carboxylase
Higher plants, yeast, bacteria (we aint got it?)
Tissue specificity of malic enzyme
Trick question, it’s pretty widespread
Three highly thermodynamically favorable and irreversible steps of the TCA cycle
1) pyruvate dehydrogenase
2) isocitrate dehydrogenase
3) alpha-ketoglutarate dehydrogenase
When these three ratios are high, the citric acid cycle is allosterically inhibited. Indicates an energy-sufficient metabolic state.
1) ATP/ADP
2) NADH/NAD+
3) Acetyl-CoA/CoA
The rate of flow through the citric acid cycle can be limited by the availability of citrate synthase substrates. What are they?
oxaloacetate and acetyl-CoA
Feedback inhibition is done by what three molecules in the citric acid cycle
succinyl-CoA, citrate, and ATP
What stimulates energy-yielding metabolism of the TCA cycle in muscle tissue
Ca2+ (its levels increase during muscle contraction… right…)
Positive regulators of pyruvate dehydrogenase (4)
AMP, CoA, NAD+, Ca2+
Negative regulators of pyruvate dehydrogenase (4)
ATP, acetyl-CoA, NADH, fatty acids
Positive regulators of citrate synthase (1)
ADP
