Chapter 17 Gluconeogenesis

Flashcards for reviewing the gluconeogenesis lecture notes.

What is gluconeogenesis?

The synthesis of glucose from pyruvate.

Where does gluconeogenesis primarily occur?

The liver, though it can also occur in the kidney.

When is gluconeogenesis especially important?

During fasting or starvation.

What are the prevalent hormones during fasting/stress that affect gluconeogenesis?

Glucagon

What are the prevalent hormones during fed/rested states that affects gluconeogenesis?

Insulin

How does energy charge (Low/High) affect Glycolysis/Gluconeogenesis?

Low energy charge increases Gluconeogenesis, and decreases Glycolysis

How does energy charge (Low/High) affect Glycolysis/Gluconeogenesis?

High energy charge increases Glycolysis, and decreases Gluconeogenesis

What is the key allosteric effector that inhibits gluconeogenesis?

Fructose 2,6-bisphosphate

What is the key allosteric effector that activates glycolysis?

Fructose 2,6-bisphosphate

What precursors can pyruvate be formed from in the liver?

Muscle-derived lactate.

By what enzyme in the liver can muscle-derived lactate form pyruvate?

Lactate dehydrogenase.

What can the carbon skeletons of some amino acids be converted into?

Gluconeogenic intermediates.

Glycerol is derived from what molecule?

Triacylglycerols.

Glycerol can be converted into what molecule for gluconeogenesis or glycolysis?

Dihydroxyacetone phosphate.

Are the enzymes for gluconeogenesis primarily located in the cytoplasm or mitochondria?

Cytoplasm, except for pyruvate carboxylase (mitochondria) and glucose 6-phosphatase (endoplasmic reticulum).

What three irreversible steps in glycolysis must be bypassed in gluconeogenesis?

Hexokinase/glucokinase, phosphofructokinase, and pyruvate kinase.

What two enzymes are required for the formation of phosphoenolpyruvate from pyruvate?

Pyruvate carboxylase and phosphoenolpyruvate carboxykinase.

What vitamin does pyruvate carboxylase require as a cofactor?

Biotin.

In what cellular compartment does the formation of oxaloacetate by pyruvate carboxylase occur?

Mitochondria.

Oxaloacetate is reduced to what molecule for transport into the cytoplasm?

Malate.

By what enzyme is PEP synthesized in the cytoplasm from oxaloacetate?

Phosphoenolpyruvate carboxykinase.

What enzyme catalyzes the hydrolysis of fructose 1,6-bisphosphate in gluconeogenesis?

Fructose 1,6-bisphosphatase.

Where does the generation of free glucose primarily occur?

The liver.

Where is glucose 6-phosphate transported for the final step in gluconeogenesis?

Lumen of the endoplasmic reticulum.

What enzyme catalyzes the formation of glucose from glucose 6-phosphate?

Glucose 6-phosphatase.

How are gluconeogenesis and glycolysis reciprocally regulated?

Within a cell, one pathway is relatively inactive while the other is highly active.

When does glycolysis predominate?

When glucose is abundant.

When is gluconeogenesis highly active?

When glucose is scarce.

What is the key regulatory site regarding glycolysis and gluconeogenesis?

The interconversion of fructose 1,6-bisphosphate and fructose 6-phosphate.

What happens if ATP is needed?

Glycolysis predominates.

What happens if glucose is needed?

Gluconeogenesis is favored.

What is the key regulator of glucose metabolism in the liver?

Fructose 2,6-bisphosphate.

What does fructose 2,6-bisphosphate do?

Stimulates phosphofructokinase and inhibits fructose 1,6-bisphosphatase.

What is a bifunctional enzyme?

The kinase that synthesizes fructose 2,6-bisphosphate (phosphofructokinase 2) and the phosphatase that hydrolyzes this molecule (fructose bisphosphatase 2) are located on the same polypeptide chain.

What hormone is secreted when blood glucose levels are low?

Glucagon.

In type 2 diabetes, what condition affects insulin's role in gluconeogenesis?

Insulin resistance.

What is the Cori cycle?

Muscle and liver display interorgan cooperation in a series of reactions.

What is the role of the liver in the Cori cycle?

Removes lactate and converts it into glucose.

What are the two key chacateristics of Pyruvate carboxylase deficiency (PCD)?

Hypoglycemia and lactic acidosis

What is the metabolic role of the liver?

The release of glucose into the blood for use by other tissues such as muscle, brain, and red blood cells.