10.2 Citric Acid Cyle [HY] Flashcards
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
