citric acid cycle Flashcards
TCA cycle - a biochemical hub of the intermediary metabolism:
- oxdizing carbons fuels for harvesting:
- it is ____ (e.g. catabolism and anabolism)
- source of precursors for
- takes place inside ____
- high energy electrons
- amphibolic
- biosynthesis
- mitochondria
other names of TCA cycle
Tricarboxylic acid cycle (TCA)
citric acid cycle
krebs cycle
precursor stage 1 of TCA
fats, polysaccharides, and proteins are reduced to fatty acids and glycerol, glucose and other sugars, and amino acids
precursor stage 2 of TCA
fatty acids and glycerols, glucose and other sugars, and amino acids are all converted to Acetyl CoA (common currency)
1 mol of NADH =
2.5 moles ATP
1 mol of FADH2 =
1.5 moles ATP
1 mol of GTP =
1 mol ATP
TCA cycle overview: oxidation of 2-carbon units to produce:
2 CO2 molecules
1 GTP
High energy electrons (3 NADH and 1 FADH2)
how is glucose converted into acetyl CoA?
glucose (6C) –oxidation–> 2 pryuvate (3C) –decarboxylation–> 2 Acetyl CoA (2C)
how are lipids converted into acetyl CoA?
TAG –> fatty acids –betaoxidation–> acetyl CoA (2C)
how are proteins converted to Acetyl CoA?
breakdown into various amino acids –> acetyl CoA
how is pyruvate converted to acetyl CoA?
- decarboxylation
- oxidation
- transfer acetyl group to CoA (by coupling with NAD+ –> NADH rxn)
aerobic glycolysis coupled with oxidative phosphorylation:
- pyruvate must enter:
- pyruvate utilizes:
- ______ catalyzes the decarboxylation of pyruvate
- the mitochondira
- mitochondrial pyruvate carrier (MPC)
- pyruvate dehydrogenase complex (PDC) or (PDH)
pyruvate dehydrogenase reaction:
- requires 3 enzymes:
- requires 5 coenzymes: catalytic cofactors and stoichiometric cofactors
- E1 (TPP), E2(Lipoic acid), E3(FAD)
2.
catalytic cofactors:
- thiamine pyrophosphate (TPP/Vitamin B1)
- lipoic acid
- FAD
stoichiometric cofactor:
- CoA
- NAD+
phosphorylated version of PDC/PDH is
inactive
dephosphorylated version of PDC/PDH is
active
overall reaction of pyruvate –> Acetyl CoA
pyruvate + NAD+ + CoA → Acetyl CoA + CO2 + NADH + H+
high [aceytl CoA] directly inhibits
E2
accumulation of ADP and pyruvate activates phosphatases which dephosphorylates ____
PDH/PDC (making it active)
increased levels of acetyl CoA will inhibit
PDH/PDC
the TCA cycle occurs under
aerobic conditions and procuces more energy from glucose than glycolysis
the TCA cycle takes place in the
mitochondria
what enzyme links glycolyis to the TCA cycle
pryuvate dehydrogenase (PDH/PDC)
first step of TCA cycle
4-carbon oxaloacetate + 2-carbon acetyl CoA +H2O → citrate
catalyzed by citrate synthase