Gluconeogenesis and Glycolysis Review

These flashcards cover key concepts, processes, and enzymes related to gluconeogenesis and glycolysis.

What is gluconeogenesis?

The synthesis of glucose from non-carbohydrate precursors.

Where does gluconeogenesis primarily occur?

In the liver (70-90%) and kidneys.

What are the end products of glycolysis?

Pyruvate, lactate, and NADH.

Why is lactate produced during anaerobic conditions?

Lactate is produced when there is no oxygen for the electron transport chain (ETC), leading to a buildup of hydrogenated pyruvate.

What is the Cori cycle?

The cycle where lactate produced in muscles is transported to the liver to be converted back into glucose.

What effect does metabolic acidosis have on blood pH?

It lowers pH in the bloodstream.

What are the unique enzymes involved in gluconeogenesis?

Pyruvate carboxylase, PEP carboxykinase, fructose bisphosphatase, and glucose-6-phosphatase.

What is the first step of gluconeogenesis involving pyruvate carboxylase?

Pyruvate is converted into oxaloacetate (OAA) in the mitochondria.

What is the role of malate in gluconeogenesis?

Malate shuttles oxaloacetate from the mitochondria to the cytoplasm.

What is required for pyruvate carboxylase to function?

CO2, ATP, and biotin.

What is the significance of fructose bisphosphatase?

It catalyzes the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate in gluconeogenesis.

What does glucose-6-phosphatase do?

Converts glucose-6-phosphate to glucose, allowing glucose to leave cells into the bloodstream.

What is the role of acetyl CoA in gluconeogenesis?

It decreases the activity of pyruvate dehydrogenase and increases pyruvate carboxylase.

Which hormone stimulates gluconeogenesis?

Glucagon.

How does insulin affect gluconeogenesis?

It promotes glycogenesis and glycolysis while inhibiting gluconeogenesis.

What enzymes are inhibited by metformin?

Inhibits complex I of the electron transport chain and decreases liver glucose production.

What are the entry points for gluconeogenesis from lactate?

Lactate is converted to pyruvate by lactate dehydrogenase (LDH).

What process converts glycerol to DHAP in gluconeogenesis?

Glycerol is first converted to glycerol-3-phosphate by glycerol kinase, then to DHAP.

What is the intermediate formed in the conversion of OAA to PEP?

Phosphoenolpyruvate (PEP) is formed from OAA through the action of PEPCK.

What are the consequences of glycogen-storage diseases?

They can cause severe hypoglycemia, lactic acidemia, and hyperlipidemia.

What enzyme is deficient in von Gierke's disease?

Glucose-6-phosphatase (G-6-Pase).

What happens to glucose production in the liver during prolonged fasting?

Gluconeogenesis becomes a primary source of glucose as glycogen stores become depleted.

What initiates gluconeogenesis from alanine?

Alanine is converted to pyruvate by alanine aminotransferase (ALT).

In which part of the cell does PEP carboxykinase function primarily occur?

In the cytoplasm.

What is the purpose of using GTP in gluconeogenesis?

It provides energy needed for the conversion of OAA to PEP.

How does gluconeogenesis relate to the Cori cycle?

Lactate from the muscle is converted to glucose in the liver, preventing lactate buildup.

What role does fructose play in energy metabolism?

Fructose enters the glycolysis pathway at the triose phosphate step, bypassing PFK-1.

Which enzyme catalyzes the conversion of pyruvate to acetyl CoA?

Pyruvate dehydrogenase (not directly active in gluconeogenesis but mentioned in glucose metabolism).

What effect does lactate have on blood pH during lactic acidosis?

It decreases blood pH, resulting in metabolic acidosis.

What is the effect of metformin on lactate levels?

It reduces liver glucose production and alters lactate metabolism.

What is produced during the complete gluconeogenesis from one molecule of pyruvate?

One molecule of glucose.

What are the substrates that can be converted to glucose precursors during gluconeogenesis?

Lactate, amino acids, and glycerol.

Which specific phase of gluconeogenesis does phosphoglycerate kinase (PGK) participate in?

It is involved in the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate.