10.2 Citric Acid Cyle [HY] Flashcards
(12 cards)
What is the main purpose of the citric acid cycle?
Oxidize carbons into CO2 and generate high energy electron carriers (NADH, FADH2) and GTP.
Citric Acid Cycle Step 1
Citrate Synthase adds acetyl-CoA and Oxaloacetate and hydrolyzes to form citrate and CoA-SH
Enzyme regulated by negative feedback from ATP, NADH, succinyl-CoA and Citrate
Citric Acid Cycle Step 2
Aconitase isomerizes citrate to isocitrate
Citric Acid Cycle Step 3
Isocitrate Dehydrogenase oxidizes and decarboxylates isocitrate to form alphaketoglutarate.
generates the 1st CO2 and NADH of the cycle.
Inhibited by ATP and NADH; Activated by ADP and
NAD+
First of the 2 C is lost here
Citric Acid Cycle Step 4
α-Ketoglutarate dehydrogenase complex metabolizes α-ketoglutarate to form succinyl-CoA.
Generates 2nd CO2 and NADH of the cycle.
inhibited by ATP, NADH, and succinyl-CoA;
Activated by ADP and Ca2
Citric Acid Cycle Step 5
Succinyl-CoA synthetase hydrolyzes succinyl-CoA thioester bond forming succinate and CoA−SH.
Makes only GTP of Cycle
Citric Acid Cycle Step 6
Succinate dehydrogenase oxidizes succinate to fumarate. FAD is reduced to FADH2 and carries into ETC.
*Succinate is flavoprotein (bound to FAD)
Citric Acid Cycle Step 7
Fumarase hydrolyzes fumarate, forming malate.
Citric Acid Cycle Step 8
Malate dehydrogenase oxidizes malate to oxaloacetate.
Generates the third and final NADH of the cycle.
Citric Acid Cyle Mnemonic
Please, Can I Keep Selling Seashells For Money, Officer?
Pyruvate
Citrate
Isocitrate
α-Ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate
Oxaloacetate
Where does Citric Acid Cycle Take Place?
The mitochondrial matrix
Difference between Synthetases and Synthases?
Synthetases require energy to make covalent bonds
