BIOC 212 Lecture Notes - Lecture 52: Pyruvate Dehydrogenase Complex, Beta Oxidation, Alkene
29 May 2018
School
Department
Course
Professor
Metabolism XIV
The Simplified Malate-Aspartate Shuttle
• Pyruvate has special transporters that pump it into the mt matrix
o Phosphates
o pH dependent transporters that pump it into the matrix
• ATP has other transporters that use the electrical gradient
• NADH is a special case
o Does not have protein transports that pump it across membranes
o Molecule that can never cross biological membranes
• For NAD+ and reduced NADH form
• Way to transfer NADH across the mitochondrial membrane is through a metabolic
system
o Transfer energy of NADH made in cytosol into the mitochondria through a
carbohydrate called malate
This is all need to know about shuttle:
• NADH & NAD+ cannot cross the inner membrane themselves
o Have reversible metabolic reaction in the IMS (continuous with cytosol)
• Cytosolic NADH diffuses into the IMS, where it is used to make malate
o Generate malate from oxaloacetate in the intermembrane space
o In the process, it uses up NADH
o Malate has a transporter in the inner membrane so able to cross
• Malate imported to the mt matrix, where it generates NADH
o Malate converted back to oxaloacetate, and re-generates NADH
o Get the reducing equivalent across the membrane
o Malate --> oxaloacetate is part of the citric acid cycle, so takes place
spontaneously
• Reaction products are recycled to the IMS
• Goal is to get the energy from NADH into the matrix without having the molecule
itself crossing
Carbon Oxidation - Glycolysis
• Use glycolysis to break glucose into two 3C molecules
o Carbohydrates called pyruvate
o Deprotonated version of pyruvic acid
• This generates a net total of:
o 2 ATP
o 2 NADH
• Turn all generated NADH into energy
