BCH210H1 Lecture Notes - Lecture 32: Inner Mitochondrial Membrane, Acetyl-Coa, Enzyme Inhibitor

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BCH210 Lecture 26 Mitochondrial bioenergetics
Mitochondria
- It is the powerhouse where most energy is made in a cell ~95%
- Exception: Red blood cells
o They lack mitochondria so produce most of their energy in the cytoplasm via
glycolysis
- Outer mitochondrial membrane porous
o Many membrane proteins
- Inner mitochondrial membrane true barrier
o Impermeable to molecules
o Regulated what goes in and out
o Membrane transporters
- Cristae
o Increase the surface area for membrane proteins
Pyruvate Dehydrogenase Complex
- Pyruvate acetyl CoA
- + CoA + CO2
- + NAD+ + NADH
- G’ = -33 kJ/mol
o This reaction is highly favorable because carbon dioxide is released
- PDC is made up by multiple polypeptide chains
- Three subunits
- Each subunit catalyzes a reaction
- Different cofactors within the complex that help with the reactions
- Enzymes can function on their own or can have multiple subunits with different active
sites
o E1
CO2 is released
o E2
CoA added on
o E3
NADH is produced
- Control by feedback inhibition
o Buildup of products can slow down the reaction
o Does not inhibit the complex
o High acetyl CoA negatively regulates E2
o High NADH negatively regulates E3
PDC covalent modification
- Inactive PDC E1 is phosphorylated (inactive form)
- PD Phosphatase dephosphorylates E1 thus reactivating the complex
- PD Kinase adds pyrophosphate onto E1 thus inhibiting the complex
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