BICH Exam 1 Study Guide

What is the role of hexokinase in glycolysis?

Hexokinase phosphorylates glucose to glucose-6-phosphate, consuming 1 ATP.

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

Phosphofructokinase-1 (PFK-1) catalyzes this reaction and consumes 1 ATP.

What does phosphoglycerate kinase (PGK) do in glycolysis?

It catalyzes the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, yielding 1 ATP.

What is the function of pyruvate kinase (PK) in glycolysis?

Pyruvate kinase converts phosphoenolpyruvate (PEP) to pyruvate, yielding 1 ATP.

Which reactions in glycolysis yield non-ATP energy products?

The reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase (GAPDH) generates NADH.

Name two enzymes that operate near equilibrium in glycolysis.

Hexokinase and phosphoglycerate kinase operate near equilibrium.

Which enzymes operate far from equilibrium in glycolysis?

Phosphofructokinase-1 (PFK-1), pyruvate kinase, and hexokinase operate far from equilibrium.

What is the cofactor required for phosphoglucoisomerase?

Phosphoglucoisomerase requires Mg²⁺ as a cofactor.

What is the active site residue for triose phosphate isomerase (TIM)?

The active site of TIM contains histidine for proton transfer.

How does aldolase function in glycolysis?

Aldolase catalyzes the cleavage of fructose-1,6-bisphosphate into two triose sugars.

What is the role of GAPDH in glycolysis?

GAPDH catalyzes the oxidation of glyceraldehyde-3-phosphate to form 1,3-bisphosphoglycerate and NADH.

What pathway does galactose enter when metabolized?

Galactose is converted to glucose-6-phosphate via the Leloir pathway.

How is fructose metabolized in muscle tissue?

Fructose is phosphorylated by hexokinase to fructose-6-phosphate without ATP consumption.

What is the product of mannose conversion in glycolysis?

Mannose is converted to mannose-6-phosphate, which is isomerized to fructose-6-phosphate.

Describe how fructose is processed in the liver.

Fructose is converted to fructose-1-phosphate by fructokinase, yielding DHAP and G3P.

What does ribulose-5-phosphate become in glycolysis?

Ribulose-5-phosphate is converted into intermediates like fructose-6-phosphate through the pentose phosphate pathway.

Which pathway utilizes glucose-6-phosphate when both R5P and NADPH are needed?

The Pentose phosphate pathway (PPP) is used.

What happens to ATP yield when glucose-6-phosphate enters PPP?

ATP generation will be reduced because the PPP bypasses direct ATP production.

What are the activators of phosphofructokinase-1 (PFK-1)?

AMP and fructose-2,6-bisphosphate are activators of PFK-1.

Identify inhibitors of fructose-1,6-bisphosphatase (FBPase-1).

AMP and fructose-2,6-bisphosphate are inhibitors of FBPase-1.

What is the primary regulatory step in glycolysis?

PFK-1 and pyruvate kinase are the key regulatory enzymes in glycolysis.

Which enzyme is crucial for maintaining blood glucose levels in the liver?

Glucose-6-phosphatase is crucial for this function.

What effect do insulin and glucagon have on liver glycogen?

Insulin stimulates glycogen synthesis, while glucagon stimulates glycogen degradation.

What is the function of the Cori Cycle?

It transports lactate from muscles to the liver for conversion back to glucose.

What happens to glycogen phosphorylase during insulin stimulation?

Insulin inhibits glycogen phosphorylase by promoting dephosphorylation.

How does glucagon affect glycogen synthase?

Glucagon inhibits glycogen synthase through phosphorylation.

Explain how PFK-2 and FBPase-2 are regulated by glucagon.

Glucagon leads to phosphorylation of the enzyme, activating FBPase-2 and inactivating PFK-2.

What is the role of NAD⁺ in GAPDH activity?

NAD⁺ acts as a cofactor for GAPDH in the oxidation and phosphorylation reaction.

Which cofactor is required by pyruvate carboxylase?

Pyruvate carboxylase requires biotin as a cofactor.

What is produced from the conversion of pyruvate to oxaloacetate?

This reaction consumes 1 ATP.

What does glucagon induce in the liver during fasting?

Glucagon stimulates gluconeogenesis and glycogen degradation.

What enables the liver's release of glucose into the bloodstream?

The presence of glucose-6-phosphatase allows the liver to dephosphorylate glucose-6-phosphate.

How does the effect of insulin on gluconeogenesis manifest?

Insulin inhibits gluconeogenesis by inhibiting glycogen phosphorylase.

What happens to fructose-2,6-bisphosphate levels during insulin activation?

Insulin results in higher levels of fructose-2,6-bisphosphate.

Characterize the effect of AMP on phosphofructokinase-1 (PFK-1).

AMP activates PFK-1, promoting glycolysis.

Which chemical reaction does enolase catalyze?

Enolase catalyzes the dehydration of 2-phosphoglycerate to phosphoenolpyruvate (PEP).

Which reaction in gluconeogenesis consumes GTP?

PEP carboxykinase uses GTP to form PEP from oxaloacetate.

What does the oxidative phase of the PPP produce?

The oxidative phase of the PPP produces NADPH.

What happens to pyruvate in anaerobic conditions?

Pyruvate is converted to lactate during anaerobic glycolysis.

What is the significance of muscle tissue in carbohydrate metabolism?

Muscle tissue primarily uses glucose for energy production during exercise.

Which tissue is responsible for gluconeogenesis primarily?

The liver is primarily responsible for gluconeogenesis.

Identify the key pathways where glucose is stored in the body.

Glucose is stored as glycogen in the liver and muscles.

What are the effects of high blood glucose on glycogen synthesis?

High blood glucose levels stimulate glycogen synthesis.

Explain how phosphofructokinase-1 (PFK-1) is inhibited.

PFK-1 is inhibited by ATP and citrate.

What does lactate dehydrogenase require as a cofactor?

Lactate dehydrogenase requires NAD⁺ as a cofactor.

What role does phosphoglucomutase play in metabolism?

Phosphoglucomutase requires a phosphorylated serine residue in the active site.

How is glucose-1-phosphate formed from glycogen?

Glycogen phosphorylase catalyzes the breakdown of glycogen to release glucose-1-phosphate.

What is a common characteristic of isomerases in metabolism?

Isomerases rearrange atoms within a molecule.

What type of reaction does a decarboxylase catalyze?

Decarboxylases remove a carboxyl group, typically releasing CO₂.

Identify a key regulatory enzyme in gluconeogenesis.

Fructose-1,6-bisphosphatase (FBPase-1) is a key regulatory enzyme.

What regulates the activity of glycogen phosphorylase in the liver?

Glycogen phosphorylase activity is regulated by blood glucose levels.

Describe the role of glucose-6-phosphate dehydrogenase in the PPP.

Glucose-6-phosphate dehydrogenase is essential for the oxidative phase of the pentose phosphate pathway.

What is the end product of glycolysis?

The end product of glycolysis is pyruvate.

How does fructose enter glycolysis in muscle tissue?

Fructose is phosphorylated to fructose-6-phosphate by hexokinase.

What triggers a phosphorylation cascade in response to stress or fasting?

Epinephrine and glucagon trigger a phosphorylation cascade.

What happens to glycogen storage when insulin levels rise?

Insulin promotes glycogen storage in the liver and muscle.

What is the function of UDP-glucose pyrophosphorylase?

It converts glucose-1-phosphate into UDP-glucose for glycogen synthesis.

Which enzyme is responsible for converting pyruvate to acetyl-CoA?

Pyruvate dehydrogenase complex catalyzes this transformation.

How does AMP act on glycogen phosphorylase?

AMP activates glycogen phosphorylase, promoting glycogen breakdown.

What substrate does phosphoglycerate mutase convert?

It converts 3-phosphoglycerate to 2-phosphoglycerate.