27 Questions
What is the first enzyme involved in converting pyruvate to phosphoenolpyruvate in the bypass reaction?
Pyruvate carboxylase
Where does the conversion of pyruvate to oxaloacetate occur in the first step of the bypass reaction?
Mitochondria
Under what conditions does pyruvate serve as the precursor in the bypass reaction instead of lactate?
[Pyruvate] is high and NADH is needed in the cytosol
Why does oxaloacetate need to be transported outside mitochondria in the first step of the bypass reaction?
Because of lack of oxaloacetate transporters within mitochondria
Which enzyme catalyzes the conversion of oxaloacetate to PEP in the second step of the bypass reaction?
Phosphoenolpyruvate carboxykinase
Which of the following amino acids can be converted to pyruvate or oxaloacetate during gluconeogenesis?
Alanine and aspartate
Which of the following statements about glycerol is true?
It is a three-carbon molecule from triacylglycerols that enters gluconeogenesis at the level of glyceraldehyde-3-phosphate.
Which of the following organisms can convert fatty acids to carbohydrates?
Both b and c
What is the product of fatty acid degradation in mammals?
Acetyl-CoA
Which of the following metabolic pathways is involved in the conversion of carbon dioxide to carbohydrates?
Calvin cycle
What is the enzyme responsible for converting fructose 1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis?
Fructose 1,6-bisphosphatase-1
Which molecule is the starting substrate for the enzyme glucose 6-phosphatase in gluconeogenesis?
Glucose 6-phosphate
Which molecule is produced from the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis?
Pi (inorganic phosphate)
Which molecule is generated from the reaction catalyzed by glucose 6-phosphatase in the process of gluconeogenesis?
Glucose
Which of the following statements is true about the relationship between glycolysis and gluconeogenesis?
They are opposing pathways that operate in opposite directions, with the end product of one being the starting compound of the other.
Which of the following statements is correct regarding the regulation of glycolysis and gluconeogenesis?
They are reciprocally regulated to prevent a futile cycle.
Which of the following statements is true about the irreversible reactions in glycolysis?
The irreversible reactions in glycolysis are bypassed in gluconeogenesis using different enzymes.
In which cellular compartments do glycolysis and gluconeogenesis primarily occur?
Glycolysis occurs mainly in the muscle and brain (cytosol), and gluconeogenesis occurs mainly in the liver (mitochondria and cytosol).
Which of the following accurately describes the role of biotin in the pyruvate carboxylase reaction?
Biotin serves as a temporary carrier of CO2, shuttling it between two catalytic sites on the enzyme.
In which cellular compartment does the pyruvate carboxylase reaction occur?
Mitochondria
Which of the following enzymes also utilizes the biotin-dependent carboxylation mechanism?
Acetyl-CoA carboxylase
What is the ultimate fate of the CO2 incorporated into oxaloacetate by the pyruvate carboxylase reaction?
It is released as CO2 when oxaloacetate is converted to phosphoenolpyruvate.
Which of the following statements accurately describes the conversion of oxaloacetate to phosphoenolpyruvate?
It can occur in both the cytosol and mitochondria, catalyzed by their respective PEP carboxykinase enzymes.
In the bypass reaction of gluconeogenesis, which enzyme catalyzes the conversion of pyruvate to oxaloacetate?
Pyruvate carboxylase
Which enzyme catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate in the gluconeogenic pathway?
Fructose 1,6-bisphosphatase
In the second step of the bypass reaction, which enzyme catalyzes the conversion of oxaloacetate to phosphoenolpyruvate (PEP)?
PEP carboxykinase
Which of the following statements accurately describes the role of biotin in the pyruvate carboxylase reaction?
Biotin serves as a cofactor for the carboxylation of pyruvate to oxaloacetate.
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