Chapter 7 Flashcards
(14 cards)
What is generated from the citric acid cycle?
2 CO2
1 GTP or ATP
3 NADH/H+
1 FADH2
One turn of the citric acid cycle generates
2 CO2
1 GTP or ATP
3 NADH/H+
1 FADH2
Acetyl-CoA is a product of:
Beta-Oxidation
Glucose
Lipids
Amino acids
1 Citrate Synthase
Condensation of Acetyl-CoA with oxaloacetate
produces citrate
2 Aconitase
Isomerization of citrate to isocitrate
Reversible
Produces isocitrate
3 Isocitrate Dehydrogenase
Oxidation of isocitrate to alpha-ketoglutarate
NAD+ is reduced to NADH/H+
Produces alpha-ketoglutarate
1 CO2 generated
4 Alpha-ketoglutarate Dehydrogenase
Alpha-ketoglutarate is oxidized to succinyl-CoA
Rate determining step
NAD+ is reduced to NADH/H+
1 CO2 generated
5 Succinyl-CoA Synthetase
Substrate - level phosphorylation
Reversible
Produces succinate
Produces 1 GTP or ATP
6 Succinate Dehydrogenase
Oxidation of Succinate
FAD is reduced to FADH2
Produces fumarate, a trans dioic acid
7 Fumarase
Hydration reaction
Reversible
Energy is neither consumed nor produced
8 Malate dehydrogenase
Malate is oxidized
NAD+ is reduced to NADH/H+
Reversible
Regulation of Citric Acid Cycle
SUBSTRATE AVAILABILITY
- increase or decrease pathway activity
NADH inhibits 3 dehydrogenases
- NADH slows down or blocks those enzymes so the cycle doesn’t keep running full speed when the cell doesn’t need more energy carriers
- the 3 dehydrogenases: isocitrate, alpha-ketoglutarate, and Malate dehydrogenase are used to reduce NAD+ to NADH
ALLOSTERIC REGULATORS
- ATP, Ca2+, Succinyl-CoA
- can bind to enzymes allosteric site to either inhibit (slow down) or activate (speed up) the activity of the enzyme
-high levels of ATP signal the cycle to slow down
Note: Modes or Regulation
- Allosteric regulation
- Substrate availability
- Covalent modification: phosphorylation. Enzymes can be turned on or off by adding or removing chemical groups like phosphate
Pyruvate is … by ….. to form …..
Oxidized
Pyruvate dehydrogenase
Acetyl-CoA
