citric acid cycle

which steps of the citric acid cycle are regulated

pyruvate dehydrogenase (if starting with pyruvate)

citrate synthase

isocitrate dehydrogenase

alpha-ketoglutarate dehydrogenase

what are the regulators for pyruvate dehydrogenase

(+) = Ca²⁺

(-) = acetyl-CoA, NADH

what are the regulators for citrate synthetase

(-) = succinyl-CoA, NADH, ATP

what are the regulators for isocitrate dehydrogenase

(+) = ADP

(-) = NADH, ATP

what are the regulators of alpha-ketoglutarate dehydrogenase

(-) = succinyl-CoA, NADH, ATP

what are the three enzyme components of the pyruvate dehydrogenase complex

E1 = pyruvate dehydrogenase

E2 = dihydrolipoamide transacetylase

E3 = dihydrolipoamide dehydrogenase

coenzymes of E1 (pyruvate dehydrogenase)

thiamine pyrophosphate

coenzymes of E2 (dihydrolipoamide transacetylase)

lipoic acid, coenzyme A

coenzymes of E3 (dihydrolipoamide dehydrogenase)

FAD, NAD+

what five reactions does pyruvate dehydrogenase catalyze

pyruvate + TPP → hydroxyethyl TPP via E1

hydroxyethyl TPP + lipoamide group → acetyl-dihydrolipoamide via E1

acetyl-dihydrolipoamide + CoA → acetyl CoA + dihydrolipoamide via E2

dihydrolipoamide + FAD → lipoamide + FADH₂ via E3

FADH₂ + NAD+ → FAD + NADH + H+ via E3

regulators of pyruvate dehydrogenase kinase

(+) = NADH, acetyl CoA

(-) = pyruvate

how does pyruvate dehydrogenase KINASE regulate pyruvate dehydrogenase

it phosphorylate PDH, inactivating it

regulators of pyruvate dehydrogenase phosphatase

(+) = insulin, Ca²⁺

(-) = NADH, acetyl CoA, pyruvate

how does pyruvate dehydrogenase PHOSPHATASE regulate pyruvate dehydrogenase

it reactivates PDH by hydrolyzing the phosphorylated serine

what is the function of lipoic acid

it accepts the hydroxyethyl carbanion from TPP as an acetyl group

what does citrate synthase regulate

flux of intermediates

which stereoisomer of citrate does aconitase prefer?

the Pro-R conformation of citrate

what does aconitase use to activate stereospecificity

an iron-sulfur cluster

what are the five coenzymes of alpha-ketoglutarate dehydrogenase

TPP, CoASH, lipoic acid, NAD+, FAD

what are the three enzymes in the alpha-ketoglutarate dehydrogenase complex

E1 = alpha-ketoglutarate dehydrogenase

E2 = dihydrolipoyl transsuccinylase

E3 = dihydrolipoyl dehydrogenase

what are the five reactions catalyzed by alpha-ketoglutarate dehydrogenase

a-k glutarate + TPP → hydroxyl-succinyl TPP via E1

hydroxy-succinyl TPP + lipoamide group → succinyl-dihydrolipoamide via E1

succinyl-dihydrolipoamide + CoASH → succinyl-CoA + dihydrolipoamide via E2

dihydrolipoamide + FAD → lipoamide + FADH₂ via E3

FADH₂ + NAD+ → FAD + NADH + H+ via E3

coenzymes of E1 (alpha-ketoglutarate dehydrogenase)

thiamine pyrophosphate

coenzymes of E2 (dihydrolipoyl transsuccinylase)

lipoic acid, CoASH

coenzymes of E3 (dihydrolipoyl dehydrogenase)

NAD+, FAD

what is an anaplerotic reaction

the reactions that replenish the intermediates of citric acid cycle

what is the anaplerotic reaction involving pyruvate carboxylase

pyruvate + CO₂ + ATP + H₂O → oxaloacetate + ADP + P_i

what special molecule does pyruvate carboxylase contain

biotin

what is the anaplerotic reaction involving malic enzyme

malate + NADP⁺ → pyruvate + NADPH + CO₂

what is the malic enzyme dependent on?

NADP⁺

why can’t we thrive using acetate or ethanol as our sole carbon source?

this would require use of the glyoxylate cycle, which we do not do, only plants and certain bacteria

this cycle also produces intermediates that are used in the citric acid cycle

How does the glyoxylate cycle enable plants and microorganisms to thrive using acetate or ethanol as the sole carbon source?

it allows the conversion of two acetyl CoA → succinate

plays a role in germination of seeds and producing carbohydrate precursors in pathogens

which steps from the citric acid cycle are missing in the glyoxylate cycle?

all oxidative decarboxylation steps, including the use of isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, and succinyl CoA synthetase

what are the two unique enzymes of the glyoxylate cycle

isocitrate lyase and malate synthase