Citric Acid Cycle Flashcards
Citric acid cycle produces reduced coenzymes
-NADH
- FADH2
- one ATP directly.
(1-8) Reactions in citric acid cyle
1: Condensation
2: Isomerization
3: Oxidative decarboxylation
4: Oxidative decarboxylation
5: hydrolysis
6: dehydration
7: hydration
8: dehydrogenation
Product in reaction 1
Citrate
Product in reaction 2
Isocitrate
Product in reaction 3
a-Ketoglutarate
Product in reaction 4
Succinyl CoA, NADH
Product in reaction 5
Succinate, GTP, CoA
Product in reaction 6
Fumarate
Product in reaction 7
Malate
Product in reaction 8
Oxaloacetate
Isomerizes to isocitrate.
Citrate
Has a tertiary —OH group converted to a secondary—OH in isocitrate that can be oxidized.
Citrate
Undergoes decarboxylation (carbon removed as CO2)
Isocitrate
▪ Undergoes decarboxylation to form succinyl CoA.
▪ Produces a 4-carbon compound that bonds to CoA.
▪ Provides H+ and 2e−
to reduce NAD+ to NADH.
(alpha)a-Ketoglutarate
Undergoes breaking of the thioester bond
Succinyl CoA
Provides energy to add phosphate to GDP and form GTP, a highenergy compound.
Succinyl CoA
▪ Undergoes dehydrogenation.
▪ Loses two H and forms a double bond.
▪ Provides 2H to reduce FAD to FADH2.
Succinate
▪ Undergoes hydration.
▪ Adds water to the double bond.
▪ Is converted to malate
Fumarate
▪ Undergoes dehydrogenation.
▪ Forms oxaloacetate with a C=O double bond.
▪ Provides 2H that reduce NAD+ to NADH + H+
Malate
Products formed in one turn of the citric acid cycle
- 2 CO2
- 3 NADH
- 1 FADH2
- 1 GTP
enzyme in reaction 1
Citrate synthase
enzyme in reaction 2
Aconitase
enzyme in reaction 3
Isocitrate dehydrogenase
enzyme in reaction 4
a-ketoglutarate dehydrogenase
enzyme in reaction 5
Succinyl-CoA synthetase
enzyme in reaction 6
Succinic dehydrogenase
enzyme in reaction 7
Fumarase
enzyme in reaction 8
Malate dehydrogenase
The reaction rate for citrict acid cycle:
Increases when low levels of ____ or ____ activate ______ ______.
- ATP or NAD+
- isocitrate
dehydrogenase.
Decreases when high levels of ___ __ ___ inhibit ____ _____ (first step in cycle).
- ATP or NADH
- citrate synthetase
