Glycogen Synthesis and Breakdown

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Questions and Answers

What role does adenylate cyclase play in the regulatory cascade?

It converts ATP to cyclic AMP. (correct)

It activates G proteins.

It degrades cyclic AMP.

It catalyzes protein kinase activation.

What is one effect of epinephrine on glycogen metabolism?

It promotes glycogen synthesis.

It enhances ATP production.

It activates phosphorylase a to break down glycogen. (correct)

It blocks the action of cyclic AMP.

How does the action of pyrophosphatase impact the adenylate cyclase reaction?

It stabilizes cyclic AMP.

It inhibits the conversion of ATP to cyclic AMP.

It drives the reaction towards product formation. (correct)

It allows inorganic pyrophosphate to accumulate.

What is the main purpose of the pentose phosphate pathway?

To provide NADPH for biosynthesis. Signup and view all the answers

Which enzyme is activated by cyclic AMP as part of the glycogen breakdown process?

Phosphorylase kinase. Signup and view all the answers

What is the consequence of the dual function of the epinephrine cascade?

It prevents futile cycling of energy. Signup and view all the answers

Where do all reactions of the pentose phosphate pathway take place?

In the cytosol. Signup and view all the answers

What is produced when ATP is converted by adenylate cyclase?

Cyclic AMP. Signup and view all the answers

What molecule is formed when glucose-1-P reacts with UTP?

UDP-glucose Signup and view all the answers

What is the role of inorganic pyrophosphatase in glycogen synthesis?

It hydrolyzes pyrophosphate to release energy. Signup and view all the answers

Which enzyme transfers a glucose unit from UDP-glucose to glycogen?

Glycogen synthetase Signup and view all the answers

Why is it necessary to use different enzymes for glycogen breakdown and synthesis?

To allow for efficient energy utilization. Signup and view all the answers

What is the consequence if both breakdown and synthesis of glycogen occurred simultaneously?

There would be a futile cycle that wastes energy. Signup and view all the answers

What defines hormones in the context of metabolism?

They are organic compounds synthesized in one tissue and transported to another. Signup and view all the answers

How does epinephrine affect glycogen metabolism?

It activates catabolic enzyme phosphorylase a. Signup and view all the answers

What is the net result of the hormonal regulation in glycogen metabolism?

Neither breakdown nor synthesis occurs simultaneously. Signup and view all the answers

What is the primary source of reducing power for anabolic pathways?

NADPH Signup and view all the answers

Which of the following anabolic pathways is specifically mentioned as utilizing NADPH?

Fatty acid biosynthesis Signup and view all the answers

In the oxidative phase of the pentose phosphate pathway, which substance is formed from glucose 6-phosphate?

Ribulose 5-phosphate Signup and view all the answers

What is the net reaction of the oxidative phase of the pentose phosphate pathway?

glucose 6-phosphate + 2 NADP+ + H2O → ribulose 5-phosphate + 2 NADPH + 2 H+ + CO2 Signup and view all the answers

What happens to the ribulose 5-phosphate after the oxidative phase if it is in excess?

It is converted to glucose 6-P. Signup and view all the answers

During the non-oxidative phase of the pentose phosphate pathway, which two five-carbon sugars are converted into fructose 6-P and glyceraldehyde 3-P?

Ribose 5-P and Xylulose 5-P Signup and view all the answers

What is a main characteristic of the anabolic pathways, as described?

They produce more reduced products than reactants. Signup and view all the answers

What type of reactions primarily take place in the oxidative phase of the pentose phosphate pathway?

Oxidative reactions Signup and view all the answers

What is the initial product formed from the oxidation of glucose 6-P in the oxidative phase?

6-phosphoglucano-δ-lactone Signup and view all the answers

What molecule is reduced during the first reaction of the oxidative phase?

NADP+ Signup and view all the answers

Why does the oxidative phase stop despite producing NADPH?

To avoid the toxicity of excess ribulose 5-P Signup and view all the answers

Which compound is produced directly after the decarboxylation of 6-P-gluconate?

Ribulose 5-P Signup and view all the answers

What is the primary purpose of the non-oxidative phase of the pentose pathway?

To produce useful intermediates for glycolysis Signup and view all the answers

Which enzyme catalyzes the conversion of ribulose 5-P into ribose 5-P?

Phosphopentose isomerase Signup and view all the answers

What are the final products formed from ribulose 5-P in the non-oxidative stage?

Glyceraldehyde 3-P and fructose 6-P Signup and view all the answers

What is the consequence of stopping the pathway after synthesizing NADPH?

Accumulation of ribulose 5-P Signup and view all the answers

Which coenzyme is utilized by transketolase in the reaction process?

Thiamine pyrophosphate Signup and view all the answers

In the transaldolase reaction, which fragments are being transferred?

A three-carbon fragment from sedoheptulose 7-phosphate Signup and view all the answers

What is the stereochemistry of sedoheptulose 7-phosphate derived from?

Ribose 5-phosphate Signup and view all the answers

How does the transketolase reaction function in relation to the pentose phosphate pathway?

It can function reversibly under certain conditions Signup and view all the answers

Which of the following represents the correct conversion in the transaldolase step?

C-7 + C-3 = C-6 + C-4 Signup and view all the answers

What is produced when erythrose 4-phosphate reacts with xylulose 5-phosphate in the final transketolase reaction?

Glyceraldehyde-3-phosphate and fructose 6-phosphate Signup and view all the answers

What is the role of the transketolase enzyme in the series of reactions described?

To transfer two-carbon fragments between sugar phosphates Signup and view all the answers

What is the immediate result of adenylate cyclase activity?

Conversion of ATP to cyclic AMP Signup and view all the answers

How does the inactivation of glycogen synthase by epinephrine primarily affect glycogen metabolism?

It prevents simultaneous synthesis and breakdown of glycogen Signup and view all the answers

Which feature characterizes the regulatory cascade triggered by hormone binding to its receptor?

Sequential activation of enzymes via phosphorylation Signup and view all the answers

What is the function of phosphorylase kinase within the glycogen breakdown cascade?

It phosphorylates phosphorylase b to phosphorylase a Signup and view all the answers

Which statement regarding second messengers like cyclic AMP is accurate?

They mediate signaling between extracellular hormones and intracytoplasmic reactions Signup and view all the answers

What consequence does the rapid degradation of inorganic pyrophosphate have on the adenylate cyclase reaction?

It enhances the formation of cyclic AMP Signup and view all the answers

In the context of the pentose phosphate pathway, what primary compound is generated from glucose-6-phosphate during its oxidative phase?

NADPH Signup and view all the answers

What distinguishes the dual function of the epinephrine cascade in terms of glycogen metabolism?

It activates breakdown while inhibiting synthesis Signup and view all the answers

Which compound is formed after the oxidation of glucose 6-P by glucose 6-P dehydrogenase?

6-phosphoglucano-δ-lactone Signup and view all the answers

What is the primary outcome of the oxidative phase of the pentose phosphate pathway?

Synthesis of NADPH Signup and view all the answers

How many reactions are involved in the conversion of ribulose 5-P to other useful intermediates during the non-oxidative phase?

Five reactions Signup and view all the answers

What type of compound is ribulose 5-P before being converted in the non-oxidative phase?

Pentose sugar Signup and view all the answers

Which enzyme is responsible for the conversion of the lactone product into an open chain carboxylic acid?

Lactonase Signup and view all the answers

What is a likely consequence of excess ribulose 5-P accumulation in the cell?

Energy waste Signup and view all the answers

What two five-carbon compounds result from the conversion of ribulose 5-P during the non-oxidative phase?

Ribose 5-P and xylulose 5-P Signup and view all the answers

Which molecule is produced during the decarboxylation of 6-P-gluconate?

Ribulose 5-P Signup and view all the answers

What is the significance of NADPH in anabolic pathways?

It acts as a reducing agent for biosynthetic processes. Signup and view all the answers

What occurs during the oxidative phase of the pentose phosphate pathway?

Production of NADPH from the oxidation of glucose 6-P. Signup and view all the answers

In mode 4 of the pentose phosphate pathway, when is this pathway primarily utilized?

When both NADPH and ATP are required without ribose 5-P. Signup and view all the answers

How does the pentose phosphate pathway manage excess ribulose 5-P?

It converts it back to glucose 6-P via gluconeogenesis. Signup and view all the answers

Which of the following correctly describes the non-oxidative phase of the pentose phosphate pathway?

It involves the conversion of five-carbon sugars to intermediates of glycolysis. Signup and view all the answers

What is the net reaction of the oxidative phase regarding outputs?

1 glucose 6-P + 2 NADP+ + H2O → 1 ribulose 5-P + 2 NADPH + 2 H+ + CO2. Signup and view all the answers

What type of molecules are formed during the conversion of xylulose 5-P and ribose 5-P in the non-oxidative phase?

Fructose 6-P and glyceraldehyde 3-P. Signup and view all the answers

Which statement best summarizes the anabolic nature of biosynthetic pathways?

They require reducing power to synthesize more complex molecules. Signup and view all the answers

What is the primary function of UDP-glucose pyrophosphorylase in glycogen synthesis?

To convert glucose-1-P and UTP into UDP-glucose Signup and view all the answers

What is an important outcome of the hydrolysis of pyrophosphate (PPi) in the context of glycogen synthesis?

It drives the reaction toward product formation Signup and view all the answers

Which enzyme is responsible for transferring a glucose unit from UDP-glucose to glycogen?

Glycogen synthetase Signup and view all the answers

Why is it important that different enzymes are used for glycogen breakdown and synthesis?

To allow hormonal regulation of each process separately Signup and view all the answers

What could occur if both glycogen breakdown and synthesis were to happen simultaneously?

A futile cycle that wastes energy Signup and view all the answers

What type of molecule is epinephrine classified as in metabolic processes?

A low molecular weight hormone Signup and view all the answers

What is the initial product formed when glucose-1-P reacts with UTP?

UDP-glucose Signup and view all the answers

Which enzyme is activated by epinephrine to promote glycogen breakdown?

Phosphorylase a Signup and view all the answers

What is the outcome of the transketolase reaction involving xylulose 5-phosphate and ribose 5-phosphate?

Glyceraldehyde-3-phosphate and sedoheptulose 7-phosphate Signup and view all the answers

Which product is generated from the transaldolase reaction using sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate?

Erythrose 4-phosphate and fructose 6-phosphate Signup and view all the answers

How does the stereochemistry of sedoheptulose 7-phosphate relate to ribose 5-phosphate?

It has a hydroxyl group on C-3 from the C-1 carbonyl carbon. Signup and view all the answers

What is the role of thiamine pyrophosphate in the transketolase reaction?

It facilitates the transfer of a two carbon fragment. Signup and view all the answers

What unique aspect distinguishes the second transketolase reaction from the first?

It involves different substrates and products. Signup and view all the answers

Which two compounds are produced from the final transketolase II reaction?

Glyceraldehyde-3-phosphate and fructose 6-phosphate Signup and view all the answers

What type of reaction do transketolase and transaldolase facilitate in the pentose phosphate pathway?

Transfers of carbon fragments between sugars. Signup and view all the answers

Which of the following best describes the products formed from the transketolase reaction?

A combination of three and seven carbon sugars. Signup and view all the answers

What is the primary role of phosphorylase a in glycogen metabolism?

To release 1,4-linked glucose units from glycogen Signup and view all the answers

Which structure primarily characterizes glycogen?

A polymer with 90% α-1,4 and 10% α-1,6 linked glucose units Signup and view all the answers

Why does phosphorylase a face limitations in glycogen degradation?

It cannot attack glucose units near α-1,6 branch points Signup and view all the answers

What enzyme facilitates the conversion of glucose-1-P to glucose-6-P?

Phosphoglucomutase Signup and view all the answers

What is the significance of the non-reducing ends in glycogen molecules?

They allow for rapid release of glucose units Signup and view all the answers

What type of reaction is involved in glycogen synthesis compared to glycogen breakdown?

Glycogen synthesis requires an energy input Signup and view all the answers

What is the activated sugar nucleotide intermediate used in glycogen synthesis?

UDP-glucose Signup and view all the answers

How does the structure of glycogen affect its enzyme interactions?

The configuration allows multiple enzymatic reactions at once Signup and view all the answers

What product is formed when glucose-1-P reacts with UTP during glycogen synthesis?

UDP-glucose Signup and view all the answers

What role does the hydrolysis of pyrophosphate (PPi) play in glycogen synthesis?

It drives the reaction toward product formation. Signup and view all the answers

Why are different enzyme systems necessary for glycogen synthesis and breakdown?

To allow for hormonal regulation of each process. Signup and view all the answers

What is the primary outcome of the hormonal regulation in glycogen metabolism?

It coordinates the activation and deactivation of metabolic pathways. Signup and view all the answers

What is released as a byproduct when a glucose unit is transferred to glycogen?

UDP Signup and view all the answers

What effect does the activation of phosphorylase a have on glycogen?

It degrades glycogen to release glucose. Signup and view all the answers

What is a characteristic of hormones in metabolic processes?

They are synthesized in one tissue and transported to another. Signup and view all the answers

Which statement is true regarding the enzyme systems in glycogen metabolism?

They employ specific enzymes for each process. Signup and view all the answers

What crucial role does the binding of a hormone play in the regulatory cascade?

It activates the extracellular receptor protein. Signup and view all the answers

Which statement best describes the effect of epinephrine on glycogen metabolism?

It activates glycogen breakdown while inhibiting synthesis. Signup and view all the answers

What is a consequence of the rapid degradation of inorganic pyrophosphate in the adenylate cyclase reaction?

It enhances the conversion of ATP to cyclic AMP. Signup and view all the answers

Which enzyme is responsible for converting ATP into cyclic AMP?

Adenylate cyclase Signup and view all the answers

During the regulatory cascade, what happens after cyclic AMP activates a protein kinase?

It activates phosphorylase kinase. Signup and view all the answers

Which factors characterize the pentose phosphate pathway?

It integrates with glycolysis and gluconeogenesis. Signup and view all the answers

Which part of the regulatory cascade is responsible for the cleavage of glycogen?

Phosphorylase a Signup and view all the answers

What is the main signal transduction effect of hormonal actions like that of epinephrine?

Concurrent activation of catabolic and inactivation of anabolic pathways. Signup and view all the answers

What is the primary function of NADPH in anabolic pathways?

To act as a reducing agent Signup and view all the answers

In which phase of the pentose phosphate pathway is NADPH generated?

Oxidative phase Signup and view all the answers

What occurs to ribulose 5-P when it is in excess after the oxidative phase?

It undergoes further reactions to produce intermediates of the TCA cycle Signup and view all the answers

Which of the following is a product of the oxidative phase of the pentose phosphate pathway?

Ribulose 5-P Signup and view all the answers

What defines the non-oxidative phase of the pentose phosphate pathway?

It involves the conversion of five-carbon sugars to glycolytic intermediates Signup and view all the answers

How does the cell's demand for NADPH influence the pentose phosphate pathway?

It directs the excess ribulose 5-P to gluconeogenesis Signup and view all the answers

What is a consequence of the anabolic nature of biosynthetic pathways?

They produce molecules with a higher reduction state Signup and view all the answers

Which of the following intermediates is NOT produced during the non-oxidative phase of the pentose phosphate pathway?

Glucose 6-P Signup and view all the answers

What is produced during the first reaction of the oxidative phase of the pentose phosphate pathway?

NADPH Signup and view all the answers

Why is the pathway unable to stop after the oxidative phase despite producing NADPH?

Ribulose 5-P would accumulate and become toxic. Signup and view all the answers

Which enzyme catalyzes the conversion of 6-P-gluconate to ribulose 5-P?

6-P-Gluconate Dehydrogenase Signup and view all the answers

What are the products formed from ribulose 5-P during the non-oxidative phase?

Fructose 6-P and Glyceraldehyde 3-P Signup and view all the answers

Which intermediate does glucose 6-P get oxidized to in the first reaction of the oxidative phase?

6-Phosphoglucono-δ-lactone Signup and view all the answers

What is the main role of lactonase in the pentose phosphate pathway?

To open the lactone structure and form 6-P-gluconate Signup and view all the answers

What happens to the five-carbon intermediate, ribulose 5-P, in the non-oxidative phase?

It is transformed into intermediates for glycolysis. Signup and view all the answers

Which reaction type primarily occurs in the oxidative phase of the pentose phosphate pathway?

Oxidation and reduction Signup and view all the answers

What is the predominant type of linkage in the glycogen polymer structure?

α-1,4 linked glucose units Signup and view all the answers

What role does NADPH play in anabolic pathways?

It is a source of reducing power. Signup and view all the answers

What is formed when phosphorylase a cleaves glycogen?

Glucose-1-P Signup and view all the answers

Which enzyme is responsible for converting glucose-1-P to glucose-6-P in glycogen metabolism?

Phosphoglucomutase Signup and view all the answers

In which phase of the pentose phosphate pathway is NADPH primarily produced?

Oxidative phase Signup and view all the answers

What is the significance of the non-oxidative phase of the pentose phosphate pathway?

It converts ribulose 5-P into intermediates of the TCA cycle. Signup and view all the answers

What is the energy implication of glycogen synthesis in contrast to its breakdown?

Glycogen synthesis requires energy input. Signup and view all the answers

What type of glucose units cannot be cleaved by phosphorylase a due to their proximity to branch points?

1,6-linked Signup and view all the answers

What reaction is catalyzed during the conversion of glucose 6-P in the oxidative phase?

Oxidation to pentose sugars. Signup and view all the answers

What intermediate is involved in the synthesis of glycogen from glucose?

UDP-glucose Signup and view all the answers

What occurs to excess ribulose 5-P produced in the oxidative phase?

It is converted back to glucose 6-P. Signup and view all the answers

Which feature of glycogen structure is primarily responsible for enabling rapid glucose mobilization?

Extensive branching Signup and view all the answers

Which statement accurately describes the anabolic pathways mentioned?

They are reductive and require reducing power. Signup and view all the answers

Which product is NOT formed during the oxidative phase of the pentose phosphate pathway?

Pyruvate Signup and view all the answers

What mechanism allows for the transformation of 1,6 branches in glycogen to linear forms for further degradation?

Transferase and α-1,6-glucosidase Signup and view all the answers

Which phase of the pentose phosphate pathway generates ATP?

None of the phases generate ATP Signup and view all the answers

What is the ultimate effect of the epinephrine cascade on glycogen metabolism?

It inactivates glycogen synthesis and activates glycogen breakdown. Signup and view all the answers

Which enzyme is responsible for the conversion of ATP to cyclic AMP?

Adenylate cyclase Signup and view all the answers

What happens to inorganic pyrophosphate in the adenylate cyclase reaction?

It is hydrolyzed rapidly by pyrophosphatase. Signup and view all the answers

What is a significant outcome of the pentose phosphate pathway?

It synthesizes NADPH for reductive biosynthesis. Signup and view all the answers

Which of the following correctly describes a feature of the regulatory cascade involved in activating glycogen catabolism?

It includes the interaction of activated receptors and G proteins. Signup and view all the answers

What is the primary role of cyclic AMP in cellular signaling?

It activates downstream kinases. Signup and view all the answers

Why does the action of epinephrine prevent a futile cycle in glycogen metabolism?

It regulates enzymatic activity, ensuring that only one pathway is active at a time. Signup and view all the answers

During the oxidative phase of the pentose phosphate pathway, which compound is primarily produced from glucose 6-phosphate?

Ribulose 5-phosphate Signup and view all the answers

What is the primary role of UDP-glucose pyrophosphorylase in glycogen synthesis?

To convert glucose-1-P and UTP into UDP-glucose and PPi Signup and view all the answers

What effect does the hydrolysis of inorganic pyrophosphate have on glycogen synthesis?

It drives the reaction towards product formation Signup and view all the answers

What is the outcome of the second step in glycogen synthesis?

Transfer of glucose from UDP-glucose to the non-reducing end of glycogen Signup and view all the answers

Why is it crucial to use different enzyme systems for glycogen breakdown and synthesis?

To ensure both processes can be hormonally regulated Signup and view all the answers

What would be the consequence of concurrent glycogen breakdown and synthesis?

No net product would be formed Signup and view all the answers

How does epinephrine influence glycogen metabolism?

It activates phosphorylase a to degrade glycogen Signup and view all the answers

What does the release of hormones like adrenaline achieve in metabolism?

Quick response to immediate energy needs Signup and view all the answers

What is the significance of the energy-hydrolysis of pyrophosphate during glycogen synthesis?

It drives the reaction toward forming glucose products Signup and view all the answers

What are the products formed when xylulose 5-phosphate reacts with ribose 5-phosphate in the transketolase reaction?

Glyceraldehyde-3-phosphate and sedoheptulose 7-phosphate Signup and view all the answers

Which type of fragment does transaldolase transfer in its reaction?

Three carbon fragment from C-7 to C-3 Signup and view all the answers

In the context of the pentose phosphate pathway, what is the role of thiamine pyrophosphate?

It serves as a coenzyme for transketolase. Signup and view all the answers

What stereochemical change occurs in the transketolase reaction to produce sedoheptulose 7-phosphate?

The C-1 carbonyl carbon of ribose 5-phosphate becomes a hydroxyl group on C-3. Signup and view all the answers

During which step does erythrose 4-phosphate react with xylulose 5-phosphate?

Final transketolase reaction Signup and view all the answers

What is the total number of carbon atoms produced from the reaction involving transaldolase?

8 carbon atoms Signup and view all the answers

Which key transformation occurs in the reversible transketolase reaction?

Conversion of C-5 to C-7 and C-3. Signup and view all the answers

Which intermediates are produced in the reaction between sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate?

Erythrose 4-phosphate and fructose 6-phosphate Signup and view all the answers

What product is formed when glucose-1-P reacts with UTP in glycogen synthesis?

UDP-glucose Signup and view all the answers

What is released as a result of pyrophosphate hydrolysis in the glycogen synthesis process?

Two Pi Signup and view all the answers

Which enzyme is responsible for transferring a glucose unit from UDP-glucose to glycogen?

Glycogen synthetase Signup and view all the answers

Why is it necessary for glycogen breakdown and synthesis to involve different enzyme systems?

To prevent futile cycling Signup and view all the answers

What role do hormones play in the regulation of glycogen metabolism?

They regulate the activity of enzyme systems Signup and view all the answers

What is the net result of hormonal regulation in glycogen metabolism?

Prevention of futile cycles Signup and view all the answers

What is the consequence of epinephrine activating phosphorylase a in glycogen metabolism?

Enhanced glycogen breakdown Signup and view all the answers

What percentage of glucose units in glycogen is linked by 1-6 bonds?

10% Signup and view all the answers

What is the initial step catalyzed by UDP-glucose pyrophosphorylase in glycogen synthesis?

Formation of UDP-glucose from glucose-1-P and UTP Signup and view all the answers

Which enzyme converts glucose-1-P to glucose-6-P during glycogen degradation?

Phosphoglucomutase Signup and view all the answers

What is the main disadvantage of phosphorylase a in glycogen breakdown?

It cannot act on glucose units near 1,6-branch points. Signup and view all the answers

What is the role of the activated sugar nucleotide in glycogen synthesis?

To serve as a substrate for glucose storage Signup and view all the answers

Which of the following correctly describes the structure of glycogen?

A polymer with α-1,4 linked units and α-1,6 branches Signup and view all the answers

What process is essential for the conversion of glycogen back into glucose?

Hydrolysis Signup and view all the answers

What is required to synthesize glycogen from glucose?

Energy input and specific anabolic enzymes Signup and view all the answers

Which statement best describes phosphorylase a's action in glycogen metabolism?

It releases glucose-1-P from non-reducing ends of glycogen. Signup and view all the answers

What is the primary effect of epinephrine on glycogen synthase?

Inhibits glycogen synthase Signup and view all the answers

Which enzyme directly converts ATP to cyclic AMP?

Adenylate cyclase Signup and view all the answers

What is a characteristic feature of the regulatory cascade triggered by hormone binding?

Sequential enzyme activation Signup and view all the answers

In the regulatory cascade involving epinephrine, what happens to phosphorylase kinase?

It is activated by cyclic AMP Signup and view all the answers

What role does inorganic pyrophosphate play in the reaction facilitated by adenylate cyclase?

Is rapidly degraded to force product formation Signup and view all the answers

Which process is primarily affected by the activation of phosphorylase a?

Glycogen breakdown Signup and view all the answers

What is the main reason for the phosphorylation of glycogen phosphorylase by phosphorylase kinase?

To activate it for glycogen degradation Signup and view all the answers

What's the role of the pentose phosphate pathway compared to glycolysis?

It provides NADPH and pentose sugars Signup and view all the answers

What is the first product formed in the oxidative phase of the pentose phosphate pathway?

6-phosphoglucano-δ-lactone Signup and view all the answers

Which enzyme is responsible for converting 6-P-gluconate to ribulose 5-P?

6-P-Gluconate dehydrogenase Signup and view all the answers

Why does the pentose phosphate pathway continue beyond the oxidative phase?

To prevent the accumulation of ribulose 5-P Signup and view all the answers

Which two five-carbon compounds are produced from ribulose 5-P during the non-oxidative phase?

Ribose 5-P and Xylulose 5-P Signup and view all the answers

What happens to NADP+ during the first reaction of the oxidative phase?

It is oxidized to NADPH Signup and view all the answers

What is the primary outcome of the non-oxidative phase?

Producing intermediates for glycolysis Signup and view all the answers

How is ribulose 5-P eventually utilized during the non-oxidative phase?

Changed into intermediates that enter glycolysis Signup and view all the answers

What is the potential consequence of an excessive accumulation of ribulose 5-P in the cell?

Toxicity to the cell Signup and view all the answers

What is the structure formed as an unstable intermediate during the isomerization of ribulose 5-P to ribose 5-P?

Enediol intermediate Signup and view all the answers

What are the products formed during Mode 2 of the pentose phosphate pathway?

Two NADPH, one CO2, and one ribose 5-P Signup and view all the answers

During the non-oxidative phase of the pentose phosphate pathway, what conversion occurs involving ribose 5-P?

It is converted to xylulose 5-P Signup and view all the answers

What is necessary for the continuation of the pentose phosphate pathway beyond Mode 2?

Different ratios of NADPH and ribose 5-P Signup and view all the answers

Which characteristic of the non-oxidative reactions in the pentose phosphate pathway is highlighted?

They follow a relatively linear sequence Signup and view all the answers

Which enzyme is responsible for catalyzing the conversion of ribulose 5-P to ribose 5-P?

Phosphopentose isomerase Signup and view all the answers

In which reaction does ribulose 5-P change its chirality?

In the epimerase reaction to produce xylulose 5-P Signup and view all the answers

What can be considered a consequence of the isomerization reaction involving ribulose 5-P?

It results in the decay of an unstable intermediate Signup and view all the answers

What is the end result of the regulatory cascade triggered by epinephrine in terms of glycogen metabolism?

Inactivation of glycogen synthase Signup and view all the answers

Which step in the regulatory cascade involves the conversion of ATP to cyclic AMP?

Activation of adenylate cyclase Signup and view all the answers

What is a key feature of second messengers like cyclic AMP in cellular signaling?

They act as intracellular signaling agents Signup and view all the answers

How does the action of pyrophosphatase impact the reaction involving adenylate cyclase?

It facilitates the breakdown of a product to drive the reaction forward Signup and view all the answers

What product is formed when glucose-1-P reacts with UTP in glycogen synthesis?

UDP-glucose Signup and view all the answers

What is one of the main reasons for inactivating glycogen synthase during the epinephrine signaling cascade?

To prevent energy waste from futile cycles Signup and view all the answers

Which substance is released along with UDP-glucose during the transfer of a glucose unit to glycogen?

UDP Signup and view all the answers

What is the role of inorganic pyrophosphatase in glycogen synthesis?

To hydrolyze pyrophosphate (PPi) Signup and view all the answers

During the pentose phosphate pathway, what type of sugars are primarily generated?

Pentose sugars Signup and view all the answers

What is a key reason for using different enzyme systems for glycogen synthesis and breakdown?

To prevent a futile cycle of enzyme activity Signup and view all the answers

What happens to the reaction of adenylate cyclase once cyclic AMP is produced?

It is driven forward by the degradation of inorganic pyrophosphate Signup and view all the answers

Which of the following is true regarding the activation of phosphorylase kinase?

It is activated by cyclic AMP through the activation of a kinase Signup and view all the answers

How does the hydrolysis of pyrophosphate (PPi) impact glycogen synthesis?

It drives the reaction toward product formation Signup and view all the answers

What is the net result of hormonal regulation in glycogen metabolism?

Only one pathway is active at a time Signup and view all the answers

What is the primary action of adrenaline (epinephrine) on glycogen metabolism?

It activates catabolic enzymes Signup and view all the answers

Which statement about hormones is accurate?

They are organic compounds that exert effects after being transported in blood. Signup and view all the answers

What is the main structural characteristic of glycogen?

It has both α-1,4 and α-1,6 linked glucose units. Signup and view all the answers

Which enzyme is responsible for the initial cleavage of glycogen at non-reducing ends?

Phosphorylase a Signup and view all the answers

What is the product formed when glucose-1-P is converted by phosphoglucomutase?

Glucose-6-P Signup and view all the answers

Why is energy input necessary for glycogen synthesis?

Synthesis requires the activation of sugar nucleotides. Signup and view all the answers

What differentiates the enzymes used for glycogen synthesis from those used for degradation?

Different enzymes are utilized for anabolic and catabolic processes. Signup and view all the answers

What is the role of branching in glycogen structure?

It provides multiple non-reducing ends for enzyme action. Signup and view all the answers

Which of the following enzymes converts 1,6-branches into linear glucose units?

Transferase Signup and view all the answers

What is the predominant type of bond linking glucose units in glycogen?

α-1,4 linkage Signup and view all the answers

What product is generated from glucose 6-P during the first reaction of the oxidative phase?

6-phosphoglucano-δ-lactone Signup and view all the answers

What is the immediate result of the decarboxylation of 6-P-gluconate?

Ribulose 5-P Signup and view all the answers

Why does the pentose phosphate pathway continue beyond the oxidative phase?

To prevent toxic accumulation of ribulose 5-P Signup and view all the answers

Which enzyme catalyzes the conversion of 6-P-gluconate to ribulose 5-P?

6-P-Gluconate Dehydrogenase Signup and view all the answers

What are the five carbon compounds produced from ribulose 5-P in the non-oxidative stage?

Ribose 5-P and xylulose 5-P Signup and view all the answers

What consequence would occur if ribulose 5-P accumulates excessively in the cell?

Toxic effects on the cell Signup and view all the answers

Which reaction is coupled to the reduction of NADP+ to NADPH during the oxidative phase?

Decarboxylation of 6-P-gluconate Signup and view all the answers

During the non-oxidative phase, ribose 5-P and xylulose 5-P are ultimately converted to which of the following?

Fructose 6-P and glyceraldehyde 3-P Signup and view all the answers

What are the products of the transketolase reaction involving xylulose 5-phosphate and ribose 5-phosphate?

Glyceraldehyde-3-phosphate and sedoheptulose 7-phosphate Signup and view all the answers

Which enzyme catalyzes the transfer of a three-carbon fragment from sedoheptulose 7-phosphate to glyceraldehyde 3-phosphate?

Transaldolase Signup and view all the answers

How does the stereochemistry of sedoheptulose 7-phosphate derive from ribose 5-phosphate?

From the carbonyl carbon of ribose becoming a hydroxyl group on C-3 of sedoheptulose Signup and view all the answers

What is the function of thiamine pyrophosphate in the transketolase reaction?

To transfer a two-carbon fragment Signup and view all the answers

What is synthesized when erythrose 4-phosphate reacts with xylulose 5-phosphate in the final transketolase reaction?

Fructose 6-phosphate and glyceraldehyde-3-phosphate Signup and view all the answers

Which statement is true regarding the reversibility of the transketolase reaction?

The reaction is reversible under certain conditions in the pentose phosphate pathway. Signup and view all the answers

What type of compounds are ultimately produced from the series of reactions involving transketolase and transaldolase?

Compounds that can be metabolized in core reaction pathways Signup and view all the answers

Which of the following best describes the overall purpose of the reactions mentioned?

To produce metabolites for core reaction pathways Signup and view all the answers

What component of glycogen metabolism allows for the continued breakdown of glucose units near branch points?

Transferase and α-1,6-glucosidase enzymes Signup and view all the answers

Which enzyme is responsible for converting glucose-1-P to glucose-6-P in glycogen metabolism?

Phosphoglucomutase Signup and view all the answers

What primary feature of glycogen contributes to its quick mobilization as an energy source?

Extensive branching of the glycogen molecule Signup and view all the answers

In glycogen synthesis, which process involves the formation of an activated sugar nucleotide intermediate?

Formation of UDP-glucose Signup and view all the answers

Why is energy input necessary for glycogen synthesis compared to its breakdown?

Breakdown of glycogen is an energy-releasing reaction Signup and view all the answers

What type of linkage predominates in the structure of glycogen?

α-1,4 glycosidic linkages Signup and view all the answers

What is the main function of the pentose pathway related to NADPH?

To provide reducing power for anabolic reactions Signup and view all the answers

Which of the following correctly describes the enzymatic action of phosphorylase a in glycogen metabolism?

It cleaves non-reducing ends to release glucose-1-P Signup and view all the answers

What is the effect of cyclic AMP on phosphorylase kinase during glycogen breakdown?

It activates its activity. Signup and view all the answers

How does the inactivation of glycogen synthase by epinephrine prevent futile cycles?

By simultaneously promoting glycogen breakdown. Signup and view all the answers

Which of the following accurately describes the role of adenylate cyclase in the regulatory cascade?

It converts ATP to cyclic AMP. Signup and view all the answers

What is the significance of the rapid degradation of inorganic pyrophosphate in the adenylate cyclase reaction?

It drives the reaction toward product formation. Signup and view all the answers

Which enzyme directly catalyzes the conversion of phosphorylase b to phosphorylase a?

Phosphorylase kinase. Signup and view all the answers

Which feature distinguishes the pentose phosphate pathway from glycolysis?

It produces NADPH for reductive biosynthesis. Signup and view all the answers

What is the consequence of the simultaneous activation of glycogen breakdown and inactivation of glycogen synthesis during the epinephrine cascade?

Increased glucose availability for energy. Signup and view all the answers

In which cellular compartment does the pentose phosphate pathway occur?

Cytosol. Signup and view all the answers

What type of intermediate is formed during the isomerization of ribulose 5-P to ribose 5-P?

Enediol intermediate Signup and view all the answers

Which product is NOT typically generated from the oxidative phase of the pentose phosphate pathway?

Xylulose 5-phosphate Signup and view all the answers

What is the main reducing agent utilized in anabolic pathways?

NADPH Signup and view all the answers

What is the main enzymatic activity involved in the conversion of ribose 5-P to xylulose 5-P?

Phosphopentose epimerase Signup and view all the answers

What is the consequence of the cell's need for NADPH and ribose 5-P in different ratios?

Two separate pathways are necessary Signup and view all the answers

Which of the following best describes the first phase of the pentose phosphate pathway?

Includes oxidative reactions producing NADPH Signup and view all the answers

What happens to ribulose 5-P when produced in excess during the oxidative phase?

It is converted to glucose 6-P Signup and view all the answers

What characteristic feature do enediol intermediates share in both the pentose phosphate pathway and glycolysis?

Existence as unstable compounds Signup and view all the answers

Which products are directly formed from the non-oxidative phase of the pentose phosphate pathway?

Fructose 6-P and Glyceraldehyde 3-P Signup and view all the answers

Which reaction marks the completion of the oxidative phase of the pentose phosphate pathway?

Formation of ribose 5-P Signup and view all the answers

Which enzyme catalyzes the reaction that converts ribulose 5-phosphate to ribose 5-phosphate?

Phosphopentose isomerase Signup and view all the answers

The oxidative phase of the pentose phosphate pathway results in the reduction of which cofactor?

NADP+ Signup and view all the answers

In what phase of the pentose phosphate pathway is xylulose 5-P produced?

Non-oxidative phase Signup and view all the answers

Which of the following intermediates is NOT produced during the non-oxidative phase of the pentose phosphate pathway?

Pyruvate Signup and view all the answers

What is the net reaction of the oxidative phase of the pentose phosphate pathway?

Glucose 6-P + 2 NADP+ + H2O -> Ribulose 5-P + 2 NADPH + 2 H+ + CO2 Signup and view all the answers

During the non-oxidative phase, which two five-carbon sugars are primarily interconverted?

Xylulose 5-P and Ribose 5-P Signup and view all the answers

What is the first product formed when glucose 6-P is oxidized in the oxidative phase?

6-phosphoglucano-δ-lactone Signup and view all the answers

Which enzyme catalyzes the conversion of 6-phosphoglucano-δ-lactone to 6-P-gluconate?

Lactonase Signup and view all the answers

Why does the oxidative phase of the pentose phosphate pathway stop after synthesizing NADPH?

There is an accumulation of ribulose 5-P Signup and view all the answers

What is the main purpose of the non-oxidative phase of the pentose phosphate pathway?

To convert ribulose 5-P into glycolytic intermediates Signup and view all the answers

After the oxidative phase, which compound is decarboxylated and oxidized to form ribulose 5-P?

6-P-gluconate Signup and view all the answers

Which two five-carbon compounds are produced during the conversion of ribulose 5-P in the non-oxidative stage?

Ribose 5-P and Xylulose 5-P Signup and view all the answers

In the non-oxidative phase, what is the outcome of the series of three reactions involving ribose 5-P and xylulose 5-P?

Formation of Fructose 6-P and Glyceraldehyde 3-P Signup and view all the answers

Which of the following accurately describes the function of glucose 6-P dehydrogenase in the oxidative phase?

It catalyzes the coupling of NADP+ reduction to glucose oxidation Signup and view all the answers

What is the primary role of phosphorylase a in glycogen metabolism?

It releases glucose-1-P from non-reducing ends of glycogen. Signup and view all the answers

What is the structure of glycogen primarily composed of?

α-1,4 linked glucose units with α-1,6 branches. Signup and view all the answers

What transformation allows phosphorylase a to continue breaking down glycogen?

Conversion of 1,6 branches into linear 1,4-linked glucose. Signup and view all the answers

Which process is essential for the synthesis of glycogen from glucose?

Formation of UDP-glucose as an activated precursor. Signup and view all the answers

How does the enzymatic structure of glycogen enable its rapid mobilization?

The numerous branching points create many non-reducing ends. Signup and view all the answers

What percentage of the glycogen polymer is composed of 1-4 linked glucose units?

90% Signup and view all the answers

What type of enzymatic reaction does phosphoglucomutase catalyze?

Conversion of glucose-6-P to glucose-1-P. Signup and view all the answers

Which statement about glycogen synthesis compared to glycogen degradation is accurate?

Glycogen synthesis requires energy input, while degradation is energy releasing. Signup and view all the answers

What is the primary purpose of the regulatory cascade involving epinephrine in glycogen metabolism?

To activate glycogen breakdown while inhibiting glycogen synthesis Signup and view all the answers

What role does cyclic AMP play in the regulatory cascade?

It acts as a second messenger activating protein kinases Signup and view all the answers

Which of the following statements accurately describes the action of adenylate cyclase?

It catalyzes the conversion of ATP to cyclic AMP and is irreversible due to pyrophosphate degradation Signup and view all the answers

In the context of glycogen metabolism, what is the result of phosphorylase a activity?

Cleavage of glycogen to release glucose-1-phosphate Signup and view all the answers

Which component of the regulatory cascade is responsible for phosphorylating phosphorylase b to phosphorylase a?

Cyclic AMP-sensitive kinase Signup and view all the answers

What is a consequence of the dual functionality of epinephrine in glycogen metabolism?

It prevents futile cycles by activating breakdown and inhibiting synthesis Signup and view all the answers

During the oxidative phase of the pentose phosphate pathway, what is primarily produced from glucose-6-phosphate?

NADPH and ribulose-5-phosphate Signup and view all the answers

What distinguishes the pentose phosphate pathway from glycolysis?

It generates NADPH for reductive biosynthesis Signup and view all the answers

What characterizes the unstable endiol intermediate in the isomerization reaction of ribulose 5-P?

It features two adjacent carbon-atom-carrying hydroxyl groups linked by a double bond. Signup and view all the answers

What does the non-oxidative phase of the pentose phosphate pathway primarily achieve?

Interconversion of sugar phosphates to meet various cellular needs. Signup and view all the answers

What is the primary function of phosphopentose epimerase in the non-oxidative phase?

To catalyze the conversion of ribose 5-P to xylulose 5-P. Signup and view all the answers

How does the need for NADPH and ribose 5-P typically vary in a cell?

They are often required in different ratios depending on the metabolic context. Signup and view all the answers

What reaction is essential for the isomerization of ribulose 5-P to ribose 5-P?

Enediol formation. Signup and view all the answers

Which interaction is similar in the mechanisms of isomerase reactions seen in both the pentose phosphate pathway and glycolysis?

They both involve enediol intermediates. Signup and view all the answers

What role does transketolase play in the non-oxidative phase of the pentose phosphate pathway?

Facilitates the transfer of carbon units between sugar phosphates. Signup and view all the answers

In the context of the pentose phosphate pathway, what is one limitation of stopping the process after the oxidative phase?

Lack of necessary reducing power for anabolic reactions. Signup and view all the answers

What compound is produced directly after the action of glucose 6-P dehydrogenase in the oxidative phase?

6-phosphoglucano-δ-lactone Signup and view all the answers

Which enzyme is responsible for converting the lactone form to the open chain carboxylic acid during the oxidative phase?

Lactonase Signup and view all the answers

Why does the oxidative phase of the pentose pathway conclude after the synthesis of NADPH?

Accumulation of ribulose 5-P becomes toxic for the cell. Signup and view all the answers

What is the final product of the decarboxylation of 6-P-gluconate?

Ribulose 5-P Signup and view all the answers

Which of the following best describes the main function of the non-oxidative stage of the pentose pathway?

To convert ribulose 5-P into various glycolysis intermediates. Signup and view all the answers

During the non-oxidative phase, which two compounds are produced from ribulose 5-P?

Ribose 5-P and xylulose 5-P Signup and view all the answers

What series of transformations occur after ribulose 5-P is converted into its five-carbon compounds?

They are further processed to glyceraldehyde 3-P and fructose 6-P. Signup and view all the answers

In the context of the pentose phosphate pathway, what typically happens if there is an excess of ribulose 5-P?

It might lead to toxic levels within the cell. Signup and view all the answers

What is the significance of the hydrolysis of pyrophosphate (PPi) in glycogen synthesis?

It provides energy that drives the reaction toward product formation. Signup and view all the answers

Which statement about the roles of enzymes in glycogen breakdown and synthesis is accurate?

Different enzymes allow for independent regulation of both processes. Signup and view all the answers

Why is it necessary for the breakdown and synthesis of glycogen to be energy-releasing processes?

To drive the reactions toward product formation effectively. Signup and view all the answers

Which of the following statements best describes the role of adrenaline in glycogen metabolism?

It activates enzymes responsible for glycogen breakdown. Signup and view all the answers

During glycogen synthesis, what compound is produced along with UDP-glucose when glucose-1-P reacts with UTP?

Pyrophosphate (PPi) Signup and view all the answers

What could be a potential consequence of simultaneous activity of glycogen synthesis and breakdown?

A futile cycle leading to energy wastage. Signup and view all the answers

Which enzyme facilitates the transfer of glucose from UDP-glucose to the growing glycogen chain?

Glycogen synthase Signup and view all the answers

What is the primary effect of hormonal regulation on glycogen metabolism?

To ensure that only one pathway is active at any given time. Signup and view all the answers

What starting material is primarily oxidized in the oxidative phase of the pentose phosphate pathway?

Glucose 6-P Signup and view all the answers

Which product is synthesized from glucose 6-phosphate during the oxidative phase of the pentose phosphate pathway?

Ribulose 5-phosphate Signup and view all the answers

What main product results from the non-oxidative phase after converting excess ribulose 5-phosphate?

Pyruvate Signup and view all the answers

Which cofactors are generated during the oxidative part of the pentose phosphate pathway?

NADPH and carbon dioxide Signup and view all the answers

In mode 4 of the pentose phosphate pathway, what primary need does the cell have?

NADPH and ATP without ribose-5-phosphate Signup and view all the answers

Which of the following correctly describes the outcome of the oxidative reactions in the pentose phosphate pathway?

It generates reducing power in the form of NADPH. Signup and view all the answers

During which phase of the pentose phosphate pathway does the conversion of five-carbon sugars occur?

Non-oxidative phase Signup and view all the answers

What happens when ribulose 5-phosphate is in excess after the oxidative phase?

It gets converted back to glucose 6-P. Signup and view all the answers

What is the initial substrate for the reaction catalyzed by glucose 6-P dehydrogenase?

Glucose 6-P Signup and view all the answers

What type of compound is formed by the action of lactonase on 6-phosphoglucono-δ-lactone?

6-P-gluconate Signup and view all the answers

What is produced directly after the decarboxylation of 6-P-gluconate?

Ribulose 5-P Signup and view all the answers

Which enzyme is responsible for the conversion of ribulose 5-P into ribose 5-P?

Phosphopentose isomerase Signup and view all the answers

What happens to ribulose 5-P if the pentose phosphate pathway stops after the oxidative phase?

It accumulates, potentially becoming toxic to the cell. Signup and view all the answers

Which statement correctly describes the purpose of the non-oxidative phase of the pentose phosphate pathway?

To convert ribulose 5-P into other useful metabolites. Signup and view all the answers

What is the end result of the series of five reactions in the non-oxidative phase?

Formation of glyceraldehyde 3-P and fructose 6-P. Signup and view all the answers

Which of the following compounds is a product of the oxidative phase of the pentose phosphate pathway?

NADPH Signup and view all the answers

Which of the following accurately describes the function of adenylate cyclase in the regulatory cascade?

It catalyzes the conversion of ATP to cyclic AMP. Signup and view all the answers

What role does the cleavage of glycogen by phosphorylase a play in glycogen metabolism?

It releases glucose-1-P for energy production. Signup and view all the answers

Which statement about the dual function of the epinephrine cascade in glycogen metabolism is incorrect?

It promotes glycogen synthesis. Signup and view all the answers

What impact does the rapid degradation of inorganic pyrophosphate have on the adenylate cyclase reaction?

It drives the reaction toward product formation. Signup and view all the answers

Which of the following correctly characterizes the location of the reactions involved in the pentose phosphate pathway?

The reactions occur in the cytosol. Signup and view all the answers

Which enzyme is responsible for converting phosphorylase b to phosphorylase a?

Phosphorylase kinase. Signup and view all the answers

Which feature is essential for preventing a futile cycle during the activation of glycogen catabolism?

Inactivation of glycogen synthase alongside the activation of glycogen phosphorylase. Signup and view all the answers

What is a significant outcome of cyclic AMP activation of protein kinase?

It leads to the breakdown of glycogen through downstream signaling. Signup and view all the answers

What is the unstable intermediate formed during the isomerization of ribulose 5-P to ribose 5-P?

Endiol Signup and view all the answers

What characterizes the conversion of ribose 5-P to xylulose 5-P in the non-oxidative phase?

It involves an epimerase reaction. Signup and view all the answers

Why can the pentose phosphate pathway have different modes beyond Mode 2?

Different cellular conditions may alter the requirement for NADPH and ribose 5-P. Signup and view all the answers

What type of reaction facilitates the transition from ribulose 5-P to ribose 5-P?

Isomerization Signup and view all the answers

Which step is NOT associated with the oxidative phase of the pentose phosphate pathway?

Production of xylulose 5-P Signup and view all the answers

Which of the following statements best describes the mechanism of phosphopentose isomerase?

It uses a similar mechanism to phosphoglucose isomerase. Signup and view all the answers

Which product results from the isomerization of ribulose 5-P to ribose 5-P?

Ribose 5-P Signup and view all the answers

Which intermediate is generated during the isomerization reaction involving ribulose 5-P?

Enediol Signup and view all the answers

What are the products formed when transketolase transfers a two carbon fragment from xylulose 5-phosphate to ribose 5-phosphate?

Glyceraldehyde-3-phosphate and Sedoheptulose 7-phosphate Signup and view all the answers

What structural feature of sedoheptulose 7-phosphate is derived from ribose 5-phosphate?

C-1 carbonyl carbon becomes a hydroxyl group on C-3 with left orientation Signup and view all the answers

During the transaldolase reaction, what is transferred from sedoheptulose 7-phosphate to glyceraldehyde 3-phosphate?

A three-carbon fragment Signup and view all the answers

What products are yielded when erythrose 4-phosphate reacts with xylulose 5-phosphate in the final transketolase reaction?

Fructose 6-phosphate and Glyceraldehyde-3-phosphate Signup and view all the answers

Which coenzyme is essential for transketolase to facilitate the transfer of carbon fragments?

Thiamine pyrophosphate (TPP) Signup and view all the answers

In the context of the pentose phosphate pathway, why is the transketolase reaction considered reversible?

It can switch direction depending on metabolic needs. Signup and view all the answers

Which of the following correctly describes the conversion occurring in the transaldolase step?

One C-7 and one C-3 compound to one C-4 and one C-6 compound Signup and view all the answers

What is the main purpose of the unusual reactions in the pentose phosphate pathway?

To produce intermediates for core metabolic pathways. Signup and view all the answers

What is the effect of hydrolyzing pyrophosphate (PPi) in glycogen synthesis?

It provides energy that drives the overall reaction toward product formation. Signup and view all the answers

Which enzyme is responsible for transferring a glucose unit during glycogen synthesis?

Glycogen synthetase Signup and view all the answers

What happens if the breakdown and synthesis of glycogen occur simultaneously?

It results in a futile cycle of enzyme activity. Signup and view all the answers

How is hormonal regulation significant to glycogen metabolism?

It ensures only one pathway operates at a time. Signup and view all the answers

What is the role of adrenaline (epinephrine) in glycogen metabolism?

It stimulates the activation of glycogen degradation enzymes. Signup and view all the answers

What is produced when glucose-1-P reacts with UTP in the first step of glycogen synthesis?

UDP-glucose Signup and view all the answers

What defines hormones in the context of metabolic processes?

They are organic compounds synthesized in one tissue and transported to another. Signup and view all the answers

Which process is characterized by the release of inorganic phosphate (Pi) from pyrophosphate (PPi)?

Glycogen synthesis Signup and view all the answers

Which event occurs directly after the activation of adenylate cyclase in the regulatory cascade?

The conversion of ATP to Cyclic AMP Signup and view all the answers

What is the primary function of the cyclic AMP-sensitive kinase in the glycogen breakdown process?

To phosphorylate phosphorylase kinase Signup and view all the answers

What role does inorganic pyrophosphate play in the reactions catalyzed by adenylate cyclase?

It promotes the breakdown of the reaction products Signup and view all the answers

Which statement accurately reflects the outcome of the epinephrine cascade on glycogen metabolism?

It prevents glycogen synthesis while promoting breakdown Signup and view all the answers

Which process describes the conversion of phosphorylase b to phosphorylase a?

Phosphorylation by phosphorylase kinase Signup and view all the answers

Which stage of the pentose phosphate pathway generates NADPH?

Oxidative phase Signup and view all the answers

Which compound primarily determines the direction of the reaction catalyzed by adenylate cyclase?

Inorganic pyrophosphate Signup and view all the answers

What is suggested by the term 'futile cycle' in the context of metabolic pathways like glycogen metabolism?

Simultaneous activation of both synthesis and breakdown pathways Signup and view all the answers

Which enzyme catalyzes the conversion of glucose 6-P to 6-phosphoglucano-δ-lactone?

Glucose 6-P Dehydrogenase Signup and view all the answers

What product is formed from the decarboxylation and oxidation of 6-P-gluconate?

Ribulose 5-P Signup and view all the answers

Why would the pathway not stop after the synthesis of NADPH?

Accumulation of ribulose 5-P could become toxic. Signup and view all the answers

What is primarily produced during the oxidative phase of the pentose phosphate pathway?

NADPH Signup and view all the answers

What happens to ribulose 5-P during the non-oxidative phase?

It is converted into useful intermediates like glyceraldehyde 3-P. Signup and view all the answers

Which form of the pentose phosphate pathway is active when a cell needs both NADPH and ATP?

Mode 4 Signup and view all the answers

Which of the following accurately describes the non-oxidative phase of the pentose phosphate pathway?

It involves the conversion of five-carbon sugars into intermediates of the TCA cycle. Signup and view all the answers

Which two five-carbon compounds are directly formed from ribulose 5-P?

Ribose 5-P and Xylulose 5-P Signup and view all the answers

What are the final products produced in the non-oxidative stage of the pentose pathway?

Fructose 6-P and Glyceraldehyde 3-P Signup and view all the answers

What happens to ribulose 5-phosphate after reaching excess amounts post-oxidative phase?

It is converted back into its precursor, glucose-6-phosphate. Signup and view all the answers

Which enzyme is responsible for converting the lactone to the open chain carboxylic acid during the oxidative phase?

Lactonase Signup and view all the answers

In the oxidative phase of the pentose phosphate pathway, which enzyme catalyzes the conversion of glucose-6-phosphate to ribulose-5-phosphate?

Glucose-6-phosphate dehydrogenase Signup and view all the answers

What is the function of NADP+ in the oxidative phase of the pentose pathway?

It is reduced to NADPH during the process. Signup and view all the answers

What is the fate of the reducing power provided by NADPH in anabolic pathways?

It is utilized in biosynthetic reactions. Signup and view all the answers

During which phase of the pentose phosphate pathway is the net reaction of converting glucose-6-phosphate resultantly producing NADPH?

Oxidative phase Signup and view all the answers

Which two five-carbon sugars are primarily converted into fructose 6-P and glyceraldehyde 3-P during the non-oxidative phase?

Xylulose 5-P and ribose 5-P Signup and view all the answers

What type of intermediate is formed during the isomerization of ribulose 5-P to ribose 5-P?

Enediol Signup and view all the answers

Which molecule is produced during the oxidative phase of the pentose phosphate pathway along with NADPH?

Ribose 5-phosphate Signup and view all the answers

What is the primary function of phosphopentose epimerase in the non-oxidative phase?

Convert ribose 5-P to xylulose 5-P Signup and view all the answers

Which reaction involves the decay of an unstable intermediate into a stable aldehyde?

Isomerization of ribulose 5-P Signup and view all the answers

In the context of the pentose phosphate pathway, what is the significance of non-oxidative reactions?

They allow for the production of sugars in different ratios Signup and view all the answers

Which of the following best describes the sequence of reactions before the non-oxidative phase of the pentose phosphate pathway?

Linear and more-or-less easy to follow Signup and view all the answers

What common feature is shared by the isomerization reactions discussed, including that of ribulose 5-P?

Presence of enediol intermediates Signup and view all the answers

What change occurs to the ribose 5-P during the epimerization process?

Changing the chirality of the hydroxyl group at carbon 3 Signup and view all the answers

What is the product of the reaction catalyzed by UDP-glucose pyrophosphorylase?

UDP-glucose Signup and view all the answers

What role does the hydrolysis of pyrophosphate (PPi) play in the glycogen synthesis process?

It helps in driving the reaction towards substrate formation. Signup and view all the answers

Which statement accurately describes the relationship between glycogen synthesis and breakdown?

Different enzyme systems prevent a futile cycle of activity. Signup and view all the answers

What is the primary function of hormones in metabolic processes?

They exert effects on other tissues after being synthesized in one tissue. Signup and view all the answers

What structural feature of glycogen allows for rapid mobilization of glucose units during metabolism?

Extensive branching and many non-reducing ends Signup and view all the answers

During glycogen degradation, which type of glucose linkage poses a challenge for phosphorylase a?

α-1,6 linkage Signup and view all the answers

What is the immediate effect of epinephrine on glycogen metabolism?

It activates the catabolic enzyme phosphorylase a. Signup and view all the answers

What is the main purpose of the enzyme phosphoglucomutase in glycogen metabolism?

To convert glucose-1-P to glucose-6-P Signup and view all the answers

What can be inferred about the net hydrolysis during one cycle of glycogen metabolism?

It represents a net consumption of one ATP equivalent. Signup and view all the answers

What is the consequence of the dual function of hormone signaling on glycogen metabolism?

It ensures coordinated regulation of both breakdown and synthesis. Signup and view all the answers

What must occur for the synthesis of glycogen to proceed after its breakdown?

Involvement of a sugar nucleotide intermediate Signup and view all the answers

How does the synthesis of UDP-glucose relate to glycogen storage?

It provides a glucose donor for the synthesis of glycogen. Signup and view all the answers

Which of these statements regarding glycogen structure is true?

About 90% of its structure consists of 1-4 linked glucose units Signup and view all the answers

What is the result of enzymatic action at the non-reducing ends of glycogen by phosphorylase a?

Formation of glucose-1-P from α-1,4 links Signup and view all the answers

Why does glycogen synthesis require energy input, despite being the reverse of glycogen breakdown?

The breakdown is an exergonic process Signup and view all the answers

Which type of enzyme is responsible for converting the 1,6-branches of glycogen into linear 1,4-linked glucose units?

Transferase enzyme Signup and view all the answers

What is the ultimate effect of the regulatory cascade initiated by the binding of epinephrine?

Inactivates glycogen synthase while activating glycogen breakdown Signup and view all the answers

Which key feature differentiates the action of adenylate cyclase in the regulatory cascade?

It produces a second messenger that activates protein kinases Signup and view all the answers

What is the significance of the irreversible nature of the adenylate cyclase reaction?

It ensures sustained levels of cyclic AMP after hormone binding Signup and view all the answers

During which specific phase of the pentose phosphate pathway is NADPH primarily generated?

Oxidative phase Signup and view all the answers

What distinguishes phosphorylase a from phosphorylase b in the context of glycogen metabolism?

Phosphorylase a is active and promotes glycogen breakdown Signup and view all the answers

Which statement accurately describes the consequences of the regulatory cascade involving glycogen synthase?

It triggers the inactivation of glycogen synthase Signup and view all the answers

In the pentose phosphate pathway, what role do pentose sugars play in relation to glycolysis?

They act as intermediates that link with glycolysis and gluconeogenesis Signup and view all the answers

What intermediate forms during the isomerization of ribulose 5-P to ribose 5-P?

Enediol Signup and view all the answers

Which explanation best describes the function of second messengers in hormonal signaling?

They amplify the hormone binding signal within the cell Signup and view all the answers

Which two products are generated during the oxidative phase of the pentose phosphate pathway?

NADPH and carbon dioxide Signup and view all the answers

What is the main purpose of the non-oxidative phase of the pentose phosphate pathway?

Convert sugar phosphate intermediates into glycolytic pathway intermediates Signup and view all the answers

What is the role of the epimerase enzyme in the pentose phosphate pathway?

Alteration of chirality at the carbon 3 position Signup and view all the answers

What type of reactions are primarily involved in the oxidative phase of the pentose phosphate pathway?

Reduction and oxidation reactions Signup and view all the answers

How does the isomerase reaction in the pentose phosphate pathway compare to similar reactions in glycolysis?

It is exactly analogous, involving enediol intermediates Signup and view all the answers

What is the outcome if the pentose phosphate pathway stops after synthesizing NADPH?

Accumulation of ribose 5-phosphate Signup and view all the answers

In the context of the pentose phosphate pathway, what is ribulose 5-P's fate after the oxidative phase if it is in excess?

It is metabolized through the non-oxidative phase Signup and view all the answers

What are the products formed from the transketolase reaction involving xylulose 5-phosphate and ribose 5-phosphate?

Glyceraldehyde-3-phosphate and sedoheptulose 7-phosphate Signup and view all the answers

Which statement accurately describes the transformation of ribose 5-phosphate in synthesizing sedoheptulose 7-phosphate?

C-1 carbonyl carbon becomes a hydroxyl group on C-3 with left orientation Signup and view all the answers

What functional role does thiamine pyrophosphate play in the transketolase reaction?

It acts as a coenzyme for carbon transfer Signup and view all the answers

In the transaldolase reaction, which two compounds are transformed into erythrose 4-phosphate and fructose 6-phosphate?

Sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate Signup and view all the answers

How many carbons does the newly formed sedoheptulose 7-phosphate have after its synthesis?

Seven carbons Signup and view all the answers

What unique aspect characterizes the reverse function of transketolase in the pentose phosphate pathway?

It produces different end products than initial reactants Signup and view all the answers

Which of the following correctly describes the final reaction of transketolase involving erythrose 4-phosphate and a second xylulose 5-phosphate?

It leads to the formation of glyceraldehyde-3-phosphate and fructose 6-phosphate Signup and view all the answers

What is the importance of the conversions happening in the pentose phosphate pathway as described?

They create intermediates for core metabolic pathways Signup and view all the answers

What is the primary enzyme that converts ATP to cyclic AMP in the regulatory cascade?

Adenylate cyclase Signup and view all the answers

Which feature of the regulatory cascade prevents the energy wastage associated with simultaneous glycogen breakdown and synthesis?

Inactivation of glycogen synthase Signup and view all the answers

What is the effect of the enzymatic action of cyclic AMP-sensitive kinases on phosphorylase b?

Conversion to phosphorylase a Signup and view all the answers

Which compound serves as a second messenger synthesized in response to hormone activation?

Cyclic AMP Signup and view all the answers

During which phase of the pentose phosphate pathway is NADPH primarily generated?

Oxidative phase Signup and view all the answers

What role does inorganic pyrophosphate play in the adenylate cyclase reaction?

Facilitates the irreversible reaction Signup and view all the answers

How does the pentose phosphate pathway contribute to cellular metabolism?

By providing NADPH for biosynthetic reactions Signup and view all the answers

Which enzyme initiates the cleavage of glycogen in the regulatory cascade?

Phosphorylase a Signup and view all the answers

What is the composition of glycogen in terms of glucose linkages?

90% 1-4 linked and 10% 1-6 linked Signup and view all the answers

What is the primary function of the enzyme phosphorylase a in glycogen metabolism?

It cleaves glycogen releasing glucose-1-P from non-reducing ends Signup and view all the answers

How does glycogen synthesis differ from glycogen degradation?

Synthesis requires energy, while degradation is energy releasing Signup and view all the answers

What intermediate is formed during glycogen synthesis?

UDP-glucose Signup and view all the answers

What occurs to glucose-1-P after it is cleaved from glycogen?

It is converted to glucose-6-P by phosphoglucomutase Signup and view all the answers

What is the enzyme responsible for converting the 1,6 branches of glycogen into linear glucose units?

α-1,6-glucosidase Signup and view all the answers

Why is the branching structure of glycogen important for its function?

It provides multiple non-reducing ends for rapid glucose release Signup and view all the answers

What happens to the glucose units that are cleaved by phosphorylase a when they reach a 1,6 branch?

They can no longer be processed further by phosphorylase a Signup and view all the answers

What is the unstable intermediate formed during the isomerization of ribulose 5-P to ribose 5-P?

Enediol Signup and view all the answers

What is produced during the oxidative phase of the pentose phosphate pathway?

Two molecules of NADPH, one molecule of carbon dioxide, and one molecule of ribose 5-phosphate Signup and view all the answers

Which enzyme catalyzes the conversion of ribose 5-P to xylulose 5-P during the non-oxidative phase?

Phosphopentose epimerase Signup and view all the answers

What factor influences the need for different modes of the pentose phosphate pathway?

Variable ratios of NADPH and ribose 5-phosphate usage Signup and view all the answers

Which isomerization mechanism is directly analogous to that of the phosphopentose isomerase?

Triose phosphate isomerase mechanism Signup and view all the answers

What happens to the enediol intermediate formed during the isomerization reaction?

It converts into an aldehyde Signup and view all the answers

How does the conversion of ribulose 5-phosphate to xylulose 5-phosphate specifically change its structure?

Changes the chirality of a hydroxyl group Signup and view all the answers

What defines the non-oxidative phase of the pentose phosphate pathway?

It involves the transformation of five-carbon sugars into intermediates Signup and view all the answers

What is the product of the first reaction catalyzed by glucose 6-P dehydrogenase?

6-Phosphoglucano-δ-lactone Signup and view all the answers

Which molecule is reduced during the oxidative phase of the pentose phosphate pathway?

NADP+ Signup and view all the answers

What is the consequence of stopping the pathway after the synthesis of NADPH?

Accumulation of ribulose 5-P Signup and view all the answers

What is the primary function of the non-oxidative stage of the pentose phosphate pathway?

To convert five carbon intermediates into glycolytic precursors Signup and view all the answers

What is 6-P-gluconate converted into during the oxidative phase?

Ribulose 5-P Signup and view all the answers

What characteristic defines anabolic pathways?

They result in products that are more reduced than the starting materials. Signup and view all the answers

Which two five-carbon compounds are formed from ribulose 5-P in the non-oxidative phase?

Ribose 5-P and Xylulose 5-P Signup and view all the answers

What is the primary source of NADPH in anabolic pathways?

Pentose phosphate pathway Signup and view all the answers

How many reactions are involved in converting ribulose 5-P to other useful intermediates in the non-oxidative phase?

5 reactions Signup and view all the answers

In the oxidative phase of the pentose phosphate pathway, which product is formed from glucose 6-phosphate?

Ribulose 5-P Signup and view all the answers

What occurs if ribulose 5-P is produced in excess after the oxidative phase?

It is converted back to glucose 6-P. Signup and view all the answers

What type of molecule is NADPH in relation to its role in the pentose phosphate pathway?

A reducing agent Signup and view all the answers

During the non-oxidative phase of the pentose pathway, which two five-carbon sugars are converted into fructose 6-P and glyceraldehyde 3-P?

Xylulose 5-P and ribose 5-P Signup and view all the answers

Which series of reactions primarily occurs during the non-oxidative phase of the pentose phosphate pathway?

Interconversion of sugars to TCA cycle intermediates. Signup and view all the answers

What is the net reaction of the oxidative phase of the pentose phosphate pathway?

Glucose 6-phosphate + NADP+ + H2O -> Ribulose 5-phosphate + NADPH + CO2 Signup and view all the answers

Which metabolic byproduct is generated during the oxidative phase along with NADPH?

Carbon dioxide Signup and view all the answers

Study Notes