4. Metabolic pathways and ATP production II Flashcards
What is the significance of the high energy thioester bond in Acetyl CoA?
Readily hydrolysed
Enables acetyl CoA to donate acetate (2C)
What is the Krebs cycle also known as?
The Tricarboxylic Acid Cycle (TCA)
The Citric acid cycle
What is produced in each turn of the TCA cycle?
2 x CO2
3 x NADH
1 x GTP
1 x FADH2
Where are the Krebs’ Cycle enzymes found?
Mitochondrial Matrix
Which Krebs’ Cycle enzyme is not found in the mitochondrial matrix and where is it?
Succinate Dehydrogenase
In inner mitochondrial membrane
What conditions are required for the TCA cycle?
Aerobic
As to regenerate NAD+ and FAD, oxidation is required
What occurs in degradation of amino acids?
Amino group removed, excreted as urea
Carbon skeleton used for production of glucose or fed into TCA cycle
What 7 molecules can be produced from degradation of amino acids?
Pyruvate Acetyl CoA Acetoacetyl CoA Alpha- Ketoglutarate Succinyl CoA Fumarate Oxaloacetate
What occurs in a transamination reaction?
Amine group is transferred from an amino acid to a keto acid
Produces a new pair of amino and keto acids
Give an example of transamination
alanine + alpha-ketoglutarate
->
pyruvate + glutamate
(enzyme = alanine aminotransferase)
Why does NADH produced in glycolysis need to enter the mitochondria?
To be used in oxidative phosphorylation, to regenerate NAD+
What are the 2 ways of electrons from NADH entering the mitochondrial matrix?
Where are these 2 transport mechanisms found?
Glycerol Phosphate Shuttle – skeletal muscle, brain
Malate-Aspartate Shuttle – liver, kidney, heart
Describe the glycerol phosphate shuttle.
Cytoplasmic glycerol-3-phosphate dehydrogenase transfers electrons from NADH to DHAP: converting it to glycerol-3-phosphate
Glycerol-3-phosphate is converted by mitochondrial glycerol-3-phosphate dehydrogenase back into DHAP and the electrons are passed via FAD to coenzyme Q
What does DHAP stand for?
Dihydroxyacetone phosphate
Describe the malate-aspartate shuttle.
H- transferred from cytoplasmic NADH to oxaloacetate, forms malate
Malate transported into mitochondria, rapidly re-oxidised by NAD+, forms oxaloacetate + NADH
