Krebs cycle Flashcards
summary of krebs cycle
central driver of cellular respiration
takes acetyl coa (produced by oxidation of pyruvate) as its starting material, and in redox reactions it harvests bond energy in form of NADH, FAD(2H) & ATP molecules
what happens to the reduced electron carriers generated?
pass electrons into electron transport chain and produce ATP through oxidative phosphorylation
where does krebs occur in eukaryotes and prokaryotes?
eukaryotes - matrix of mitochondria
prokaryotes - cytoplasm
closed loop
last part of pathway reforms molecule used in first step
overall molecules produced in krebs
releases 2 co2s, 3 nadh, 1 fad(2h), 1 atp or gtp
goes around twice for each molecule of glucose entering cellular respiration
step 1
acetyl CoA joins with 4 carbon molecule - oxaloacetate.
releases CoA group and forms 6 carbon molecule - citrate
citrate synthase
step 2
citrate converted to isomer isocitrate
first, removal and then an addition of a water molecule
aconitase
step 3
isocitrate oxidised - releases co2, leaving behind 5 carbon molecule - alpha-ketoglutarate.
NAD+ reduced to form NADH
isocitrate dehydrogenase
step 4
alpha-ketoglutarate is oxidised, reducing NAD+ to NADH and releasing CO2.
remaining 4 carbon molecule picks up CoA, forming unstable compound succinyl CoA
alpha-ketoglutarate dehydrogenase
step 5
CoA of succinyl CoA is replaced by a phosphate group, which is then transferred to ADP to make ATP. in some cells, guanosine diphosphate is used instead of ADP.
succinate (4C) produced
succinyl-CoA synthetase
step 6
succinate oxidised, forming a 4C molecule fumarate.
FAD(2H) produced
succinate dehydrogenase (embedded in inner membrane - FAD(2H) transfers electrons directly into ETC)
step 7
water added to fumarate, converting it into malate
fumarase
step 8
malate oxidised. NAD+ reduced to NADH. oxaloacetate produced
malate dehydrogenase.
