Answer:
i) In thee mitochondrion, pyruvate carboxylase converts pyruvate to oxloacetate.
ii) Malate dehydrogenase in the mitochondrion reduces oxaloacete to to malate.
iii) Malate dehydrogenase in the cytoplasm oxidizes malate to oxaloacetate.
iv) Phosphoenolpyruvate carboxykinase decarboxylates and phosphorylates oxaloacetate.forming phosphoenolpyruvate.
Explanation:
Gluconeogenesis is the synthesis of glucose from non - carbohydrate compounds. The substrates for gluconeogenesis are lactate, pyruvate, amino acids, propionate and glycerol.
Gluconeogenesis occurs only in cytosol but the precursor is produced in mitochondria. In the conversion of pyruvte to phosphoenolpyruvate occur in mitochondria and cytosol.
Step -1:
Pyruvate carboxylase is a biotin dependent enzyme located in mitochondria. It converts pyruvate to oxlaoacetate and carbondioxide in the presence of ATP.Oxlaocetate synthesized in mitochondrial matrix has to be transported to cytosol for gluconeogenesis. Oxaloacetate is impermeble, cannot be sent out of mitochondria. So it has to be converted to malate.
Step -2:
Malate dehydrogenase in mitochondria converts oxaloacetate synthesized in mitochondrial matrix to malate. And then it is transported to cytosol.
Step 3:
Malate dehydrogenase responsible for reversible reaction in cytosol converts malate to oxaloacetate.
Step -4
Phosphoenolpyruvate carboxy-kinase in cytosol converts oxaloacetate to PEP. The enzyme transfer high energy phosphate bond from GTP to oxaloacetate to from PEP and liberated carbondioxide.
Therefore, the steps of glycolysis converts phosphoenolpyruvate to pyruvate are as follows.
i) In thee mitochondrion, pyruvate carboxylase converts pyruvate to oxloacetate.
ii) Malate dehydrogenase in the mitochondrion reduces oxaloacete to to malate.
iii) Malate dehydrogenase in the cytoplasm oxidizes malate to oxaloacetate.
iv) Phosphoenolpyruvate carboxykinase decarboxylates and phosphorylates oxaloacetate.forming phosphoenolpyruvate.
Explanation:
