Shuttles of NAD Flashcards
Why are shuttles of NADH Required?
There is only a finite amount of NAD+ So unless its regenerated glycolysis would stop.
NAD needs to enter the mitochondrial matrix in order for Oxidative Phosphorylation to occur
Describe what happens in the shuttles
High energy electrons of NADH cross from the cytosol into the matrix of the mitochondria
Name the two shuttles, and where they may be located within the body
Glycerate phosphate shuttle - skeletal muscle/brain
Malate-aspartate shuttle - Liver kidney heart
Name the enzyme found in the glycerol phosphate shuttle, and where its located
Glycerol-3-phosphate dehydrogenase
Found in the cytosol and In a membrane found form
What does the cytosolic Glycerol 3 phosphate dehydrogenase do?
Converts DHAP To glycerol 3 phosphate Oxidising NADH to NAD
What does the membrane-bound glycerol three phosphate dehydrogenase do?
Converts glycerol 3 phosphate to DHAP reducing enzymatic FAD to FADH2.
The electrons are then transferred to coenzyme Q which is part of the electron transport chain.
Name the two membrane transporters involved in the malate-aspartate shuttle
Alpha ketoglutarate transporter (Exchanges alpha ketoglutarate for malate)
Glutamate/aspartate transporter
What is the H+ added to in the cytoplasm, and by which enzyme?
Oxaloacetate forming malate, By cytosolic malate dehydrogenase
What is the purpose of the malate-aspartate shuttle?
To regenerate cytosolic NAD+, and transfer NADH into the mitochondria to be used in oxidative phosphorylation
What happens once Malate is transferred into the mitochondria?
It is rapidly reoxidised by NAD+ to oxaloacetate by Mitochondrial Malate dehydrogenase
What type of reaction is used to convert the different compounds so they can pass through the transporters?
Describe it.
Transamination.
Glutamate + Oxaloacetate –> Alpha-Ketoguterate + Aspartate
What happens to the oxaloacetate in the mitochondrial matrix to get it back to the cytoplasm?
It is transaminated with the glutamate brought in by the glutamate/aspartate transporter, Producing alpha ketoglutarate and aspartate that can travel through the transporters back into the cytoplasm.
