Carbohydrates Metabolism II: Citric Acid Cycle and Oxidative Phosphorylation

cellular respiration

the complete combustion of biological fuels to carbon dioxide and water, producing ATP

composed of two phases: citric acid cycle and oxidative phosphorylation

90

cellular respiration produces over _____% of ATP required by humans

aerobic

is cellular respiration an aerobic or anaerobic process?

mitochondria

Where does cellular respiration occur?

pyruvate dehydrogenase

enzyme involved in the decarboxylation of pyruvate, converting it from pyruvate to acetyl-CoA

PDH, protein kinase

ATP, NADH, and acetyl-CoA are involved in the feedback inhibition of _____________ and stimulate ____________ (resting muscle)

protein kinase

enzyme activated by ATP, NADH, or acetyl-CoA that phosphorylates PDH, inactivating it

Ca 2+

stimulates phosphoprotein phosphatase, which dephosphorylates PDH, activating it (active muscle)

enzymes complexes

_______________ involved in the decarboxylation of pyruvate: pyruvate kinase, dihydrolipoyl transacetylase, dihydrolipoyl dehydrogenase

coenzymes

______________ involved in the decarboxylation of pyruvate: TTP, lipoic acid, FAD, CoA, NAD+

citrate synthase

synthesizes citrate from acetyl-CoA and oxaloacetate

oxaloacetate

causes an induced fit in citrate synthase that allows the reaction to proceed and prevents acetyl-CoA hydrolysis before citryl-CoA is produced

aconitase

catalyzes the isomerization of citrate into isocitrate; repositions hydroxyl group in preparation for the following reaction

fluoroacetate

inhibits aconitase

isocitrate dehydrogenase

catalyzes the oxidative decarboxylation of isocitrate to alpha-ketoglutarate; the first of four redox reactions in the citric acid cycle and generates NADH as the first high-transfer-potential carrier

a-ketogluterate dehydrogenase complex

catalyzes the oxidative decarboxylation of alpha-ketogluterate to succinyl CoA; similar to pyruvate dehydrogenase but not inhibited by phosphorylation; second of four redox reactions

arsenic

inhibits alpha-ketogluterate dehydrogenase

Succinate thiokinase

catalyzes the cleavage of succinyl CoA into succinate; only reaction in citric acid cycle that generate a high-phosphoryl-transfer potential compound: GTP

succinate dehydrogenase

catalyzes the oxidation of succinate to fumarate; FAD is employed instead of NAD+ because the reducing power of succinate isn't sufficient to reduce NAD+

malonate

inhibits succinate dehydrogenase

fumerase

catalyzes the hydration of fumarate, forming malate

malate dehydrogenase

catalyzes the oxidation of malate back to oxaloacetate

4

_______ pairs of electrons are transferred during one turn of the citric acid cycle

enters

___________ the citric acid cycle:

1 Acetyl CoA

3 NAD+

1 FAD

1 GDP

1 Pi

2 H2O

leaves

____________ the citric acid cycle:

1 CoA

3 NADH

1 FADH2

1 GTP

2 CO2

2 H+

10

total number of ATP produced per acetyl-CoA molecule by the end of phase II of cellular respiration

PDH, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase

three primary control points for regulation of the citric acid cycle, including prep phase

vitamin B2

riboflavin - in the form of FAD, a cofactor for succinate dehydrogenase

vitamin B3

niacin - form of NAD+, which is an electron acceptor in steps 3, 4, and 8 of the citric acid cycle

vitamin B1

thiamin - as thiamin diphosphate, a coenzyme for PDH and alpha-ketoglutarate dehydrogenase reactions

vitamin B5

pantothenic acid - part of coenzyme A

beriberi

disease caused by a thiamin (vitamin B1) deficiency

pellagra

disease caused by a niacin (vitamin B3) deficiency

inner membrane

part of the mitochondria that is impermeable to most small ions, small and large molecules; where the electron transport chain and ATP synthase are located

ATP synthase

enzyme in the inner membrane of mitochondria that catalyze the synthesis of ATP

matrix

part of the mitochondria that contain TCA cycle enzymes, fatty acid oxidation enzymes, mtDNA, mtRNA, and mitochondrial ribosomes

erythrocytes

mature ________________ do not have mitochondria because it allows them to function as oxygen carriers rather than consumers; glycolysis is sufficient for energy production

reduction potential

magnitude of ___________________________ is the driving force of the electron transport chain (makes movements of electrons favorable)

I

enzyme complex _____ = NADH-Q reductase

II

enzyme complex _____ = succinate dehydrogenase

III

enzyme complex _____ = cytochrome c reductase

IV

enzyme complex _____ = cytochrome c oxidase

respiratory poisons

amobarbital (amitol), rotenone (pesticide), antimycin A (fish poison), cyanide, carbon monoxide, sodium azide, and hydrogen sulfide are _____________________

uncouplers

chemicals that uncouple the electron transport chain from ATP synthesis, causing the energy generated by proton influx to not be captured as ATP and is lost as heat (DNP and high doses of aspirin can do this)

thermogenin

uncoupling protein produced in brown adipose tissue of newborn and hibernating mammals - they can be warm at the expense of high oxygen consumption

PMF( proton-motive force)

effective store of free energy; powers variety of energy requiring processes