Mitochondrial Bioenergetics Flashcards

Flashcards about Mitochondrial Bioenergetics

Mitochondria

The powerhouse of the cell

Mitochondria

Plays a unique role in the generation of energy under aerobic conditions.

Pyruvate Dehydrogenase Complex (PDC)

Links the production of pyruvate in cytoplasm with the TCA in the mitochondrial matrix.

Pyruvate Dehydrogenase Complex (PDC)

A large complex of multiple copies of 3 different subunits.

Prosthetic groups required by PDC

Thiamine pyrophosphate (TPP), lipoamide, and FAD

Co-substrates for PDC

Coenzyme A and NAD+

ΔGº´ of PDC reaction

• 33 kJ/mol

E1 subunit of PDC

Pyruvate dehydrogenase

E2 subunit of PDC

Dihydrolipoyl transacetylase

E3 subunit of PDC

Dihydrolipoamide dehydrogenase

Pyruvate Dehydrogenase Complex (PDC)

A soluble complex of 3 enzymatic subunits and 5 different cofactors found in the mitochondrial matrix.

Pyruvate

Oxidized and activated to form Acetyl CoA.

PDC Reaction

A redox decarboxylation reaction, producing CO2 and NADH.

Regulation of PDC

Important for control due to the large, negative standard free energy change.

PDC regulation

Inhibit by rising levels of Acetyl CoA and NADH.

PDC regulation

Stimulated by rising levels of Pyruvate, ADP and Calcium.

NADH and Acetyl CoA in muscles at rest

Stimulates the kinase to inhibit the complex by phosphorylation.

Mediators of covalent modification of PDC

PD kinase and PD phosphatase

Phosphorylation of E1 by PD kinase

Leads to complex inactivation.

Dephosphorylation by PD phosphatase

Restores activity.

Allosteric control of PDC

Feedback inhibition by Acetyl CoA and NADH.

Ca2+

Stimulates PD phosphatase and PDC activity.

Citric Acid Cycle

Links the breakdown of fuel molecules to ATP production in oxidative phosphorylation.

First stage of TCA cycle

Incoming acetyl group joins with oxaloacetate for 2 oxidative decarboxylation reactions that release CO2 and 2 NADH.

Second stage of TCA cycle

Regeneration of oxaloacetate producing 1 FADH2, 1 NADH and 1 GTP.

Succinate dehydrogenase

A membrane-bound protein linking the citric acid cycle to oxidative phosphorylation.

Pathways

May couple unfavourable and favourable reactions to help drive product formation.

Regulation of TCA

Occurs at favourable reactions (negative ∆G) to control the cycle.

Amphibolic pathway

Linking anabolic and catabolic pathways via Acetyl CoA and CAC intermediates.

Control of TCA

Low energy, calcium and upstream substrates stimulate the cycle, high energy, reduced coenzymes or products inhibit the cycle.