TCA Cycle Flashcards
Where does TCA cycle take place?
Mitochondrial matrix
How does pyruvate enter mitochondrion?
Pyruvate, hydroxide anti-transporter
How do fatty acids enter mitochondrion?
FACoA transporter
What are net products of TCA cycle?
6 NADH, 4 CO2, 2 FADH2, 2 ATP
What enzyme converts pyruvate to acetyl CoA?
Pyruvate dehydrogenase
What molecules inhibit pyruvate dehydrogenase complex?
Acetyl CoA, NADH (feedback inhibition)
How do carbohydrates, fatty acids, and proteins enter the TCA cycle?
Carbs - through glycolysis
Fatty acids - exclusively through acetyl CoA
Proteins - directly enter into TCA cycle
What are anaplerotic reactions?
Reactions that produce intermediates for TCA cycle
What vitamin is needed to make acetyl CoA? What kind of vitamin is it? What is its deficiency?
Pantatheine - B vitamin - no known deficiency
Where is pyruvate converted to acetyl-CoA?
Mitochondrial matrix (pyruvate transporter moves it from cytoplasm into matrix)
How is ATP generated in mitochondria exported to cytoplasm?
Specific ATP-ADP exchanger that ensures ADP is brought into mitochondrial matrix and ATP is exported out
What’s the pyruvate dehydrogenase complex do?
Oxidizes pyruvate to acetyl-CoA resulting in loss of CO2 and large negative free energy, making it irreversible
What cofactors are involved in pyruvate dehydrogenase complex?
NAD, TPP, Lipoic acid, FAD
Which cofactor is involved in pyruvate decarboxylase part of PDC? What kind of vitamin is it?
TPP (thiamine pyrophosphate)
B1 vitamin
What would a deficiency in TPP cause?
Beriberi, GI symptoms, neurological findings
What three enzymes make up PDC?
pyruvate decarboxylase, dihydrolipyl transacetylase, dihydrolipyl dehydrogenase
Which enzyme and its cofactor are involved in acetyl group transfer to CoASH and transfer of electrons to riboflavin?
Dihydrolipoyl acetyl transferase and Lipoic Acid
Which cofactor accepts electrons from lipoic acid?
FAD
What kind of vitamin is NAD? What would a deficiency in niacin or nicotinamide (NAD) cause?
Vitamin B3 - Pellagra skin disease, diarrhea, dementia, ultimately death (in dogs - black tongue)
What kind of vitamin is riboflavin? What does a deficiency in riboflavin cause?
B2 vitamin - Fissures in corners of mouth, inflammation of tongue, skin disease, sever irritation of eye
What’s the order of cofactors used during PDC rxns?
TPP, lipoic acid, FAD, NAD
What enzyme in TCA catalyzes the reaction of oxaloacetate with acetyl-CoA?
Citrate synthase
What enzyme in TCA catalyzes the reaction of isocitrate to alpha-ketoglutarate?
What molecules are given off?
isocitrate dehydrogenase; NADH and CO2
What enzyme is involved in substrate-level phosphorylation in TCA? It turns ______ into _________ and a ______.
Succinyl-CoA synthetase; it turns succinyl CoA into succinate and a GTP
How is TCA cycle regulated by phosphorylation?
Phosphorylated PDH complex is inactive. Dephosphorylated PDH complex is active.
If there is low energy in the cell, Ca2+ will activate phosphatase and PDH activity will increase.
If there is high energy in the cell, ATP-like signals decrease PDH complex activity.
Which enzyme generates FADH? Where does the FADH go?
Succinate dehydrogenase
Goes directly to CoQ
How much ATP does a single NADH and FADH2 molecule generate?
NADH - 2.5
FADH2 - 1.5
How many ATP does one acetyl-CoA generate?
About 12.5 through oxidative phosphorylation including the NADH from PDC
What does pyruvate carboylase do? What cofactor is needed for this reaction?
Carboxylation of pyruvate to yield oxaloacetate; requires biotin
What pathology is associated with biotin deficiency?
Dermatitis, GI symptoms
What low energy signals regulate TCA enzymes?
AMP-like signals
AMP, ADP, NAD, Ca2+, cAMP, CoASH
What high energy signals regulate TCA enzymes?
ATP-like signals
ATP, NADH, citrate, acetyl CoA, malonyl-CoA
