Lecture 16b

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What is the first enzyme involved in converting pyruvate to phosphoenolpyruvate in the bypass reaction?

Malate dehydrogenase

Pyruvate carboxylase (correct)

Pyruvate kinase

Lactate dehydrogenase

Where does the conversion of pyruvate to oxaloacetate occur in the first step of the bypass reaction?

Golgi apparatus

Endoplasmic reticulum

Cytosol

Mitochondria (correct)

Under what conditions does pyruvate serve as the precursor in the bypass reaction instead of lactate?

[Lysine] is high and NADH is needed in the cytosol

[Glucose] is high and NADH is needed in the cytosol

[Pyruvate] is high and NADH is needed in the cytosol (correct)

[Lactate] 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 Signup and view all the answers

Which enzyme catalyzes the conversion of oxaloacetate to PEP in the second step of the bypass reaction?

Phosphoenolpyruvate carboxykinase Signup and view all the answers

Which of the following amino acids can be converted to pyruvate or oxaloacetate during gluconeogenesis?

Alanine and aspartate Signup and view all the answers

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. Signup and view all the answers

Which of the following organisms can convert fatty acids to carbohydrates?

Both b and c Signup and view all the answers

What is the product of fatty acid degradation in mammals?

Acetyl-CoA Signup and view all the answers

Which of the following metabolic pathways is involved in the conversion of carbon dioxide to carbohydrates?

Calvin cycle Signup and view all the answers

What is the enzyme responsible for converting fructose 1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis?

Fructose 1,6-bisphosphatase-1 Signup and view all the answers

Which molecule is the starting substrate for the enzyme glucose 6-phosphatase in gluconeogenesis?

Glucose 6-phosphate Signup and view all the answers

Which molecule is produced from the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis?

Pi (inorganic phosphate) Signup and view all the answers

Which molecule is generated from the reaction catalyzed by glucose 6-phosphatase in the process of gluconeogenesis?

Glucose Signup and view all the answers

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. Signup and view all the answers

Which of the following statements is correct regarding the regulation of glycolysis and gluconeogenesis?

They are reciprocally regulated to prevent a futile cycle. Signup and view all the answers

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. Signup and view all the answers

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). Signup and view all the answers

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. Signup and view all the answers

In which cellular compartment does the pyruvate carboxylase reaction occur?

Mitochondria Signup and view all the answers

Which of the following enzymes also utilizes the biotin-dependent carboxylation mechanism?

Acetyl-CoA carboxylase Signup and view all the answers

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. Signup and view all the answers

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. Signup and view all the answers

In the bypass reaction of gluconeogenesis, which enzyme catalyzes the conversion of pyruvate to oxaloacetate?

Pyruvate carboxylase Signup and view all the answers

Which enzyme catalyzes the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate in the gluconeogenic pathway?

Fructose 1,6-bisphosphatase Signup and view all the answers

In the second step of the bypass reaction, which enzyme catalyzes the conversion of oxaloacetate to phosphoenolpyruvate (PEP)?

PEP carboxykinase Signup and view all the answers

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. Signup and view all the answers