Question 1

The breakdown of glycogen produces G1P.Which of the following is FALSE regarding G1P?

Accepted Answer

The answer of The breakdown of glycogen produces G1P.Which of...

Question 2

Increased levels of epinephrine in the blood will
(I)activate adenylate cyclase in liver and muscle cells.
(II)stimulate glycogen synthesis.
(III)inhibit glycolysis in the muscle cell.
(IV)stimulate gluconeogenesis in the muscle cell.

Accepted Answer

Epinephrine, a hormone released during stress or excitement, activates adenylate cyclase in liver and muscle cells, leading to increased levels of cyclic AMP. This activation promotes glycogen breakdown and inhibits glycogen synthesis, contrary to option II. It also stimulates glycolysis in muscle cells, making option III incorrect. Muscle cells cannot perform gluconeogenesis, which makes option IV incorrect. Therefore, only option I is correct.

Question 3

Which statement is TRUE concerning the metabolic reaction shown below?

Accepted Answer

The answer of Which statement is TRUE concerning the metabolic...

Question 4

The diagram represents a "substrate cycle" in glucose metabolism.Which of the following statements about the cycle is true?

Accepted Answer

The answer of The diagram represents a "substrate cycle" in...

Question 5

What molecules correspond to correspond to X and Y in the following gluconeogenic reaction?
Fructose-1,6-bisphosphotase + X $\to$ Fructose-6-phosphate + Y

Accepted Answer

In the gluconeogenic reaction catalyzed by fructose-1,6-bisphosphatase, water (H2O) is used to hydrolyze fructose-1,6-bisphosphate, releasing inorganic phosphate (Pi) and forming fructose-6-phosphate.

Question 6

Which of the following is correct concerning the metabolic reaction shown below? Pyruvate + CO₂ + ATP SYMBOL 174 \f "Symbol" oxaloacetate + ADP + P_i (I)This metabolic reaction is catalyzed by pyruvate carboxykinase. (II)The enzyme that catalyzes this reaction is activated by high concentrations of acetyl-CoA . (III)The enzyme that catalyzes this reaction is covalently bonded to the coenzyme pyridoxal-5ꞌ-phosphate. (IV)The enzyme that catalyzes this reaction is located in the endoplasmic reticulum of the cell .

Accepted Answer

The reaction described is catalyzed by pyruvate carboxylase, not pyruvate carboxykinase. Pyruvate carboxylase is activated by high concentrations of acetyl-CoA, making statement II correct. It does not require pyridoxal-5' phosphate as a coenzyme, nor is it located in the endoplasmic reticulum; it is found in the mitochondria.

Question 7

Which of the following is true regarding the reaction shown below? Pyruvate + HCO₃⁻ + ATP $\to$ oxaloacetate + ADP + P_i (I)It requires the direct transport of oxaloacetate across the membrane. (II)It utilizes the malate-aspartate shuttle in some species. (III)It is essential for gluconeogenesis. (IV)Its reactants require the function of enzymes which are only found in the cytosol.

Accepted Answer

The reaction described is the conversion of pyruvate to oxaloacetate, a step in gluconeogenesis, making statement (III) correct. The malate-aspartate shuttle is used in some species to transport intermediates like oxaloacetate across the mitochondrial membrane, validating statement (II). There's no direct transport of oxaloacetate across the membrane as implied in (I), and the enzymes involved are not exclusively found in the cytosol, as the reaction occurs in the mitochondria, making (IV) incorrect.

Question 8

Avidin,a protein intact in raw egg whites,prevents the absorption of biotin in the intestine resulting in biotin deficiency.Which of the following is affected in individuals who consume large amounts of raw egg?

Accepted Answer

Biotin is a coenzyme for carboxylase enzymes, which are involved in the synthesis of fatty acids, isoleucine, and valine, and in gluconeogenesis. The conversion of pyruvate to oxaloacetate by pyruvate carboxylase is a biotin-dependent process, thus biotin deficiency affects this conversion.

Question 9

Which of the following metabolic conversions does not occur in gluconeogenesis?

Accepted Answer

In gluconeogenesis, 1,3-bisphosphoglycerate is converted to glyceraldehyde-3-phosphate, not 3-phosphoglycerate. The conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate occurs in glycolysis, not gluconeogenesis.

Question 10

Which statement is true regarding the activation of pyruvate carboxylase by acetyl-CoA?

Accepted Answer

Acetyl-CoA activates pyruvate carboxylase to convert pyruvate to oxaloacetate, promoting gluconeogenesis when energy levels are high, rather than converting pyruvate to acetyl-CoA for the TCA cycle.

Question 11

Which of the following best describes the role of fructose-2,6-bisphosphate (FBP)in liver cells?

Accepted Answer

Fructose-2,6-bisphosphate (FBP) is not an intermediate in glycolysis or gluconeogenesis but acts as a potent allosteric activator of phosphofructokinase, which is a key enzyme in glycolysis, and as an inhibitor of fructose bisphosphatase, which is a key enzyme in gluconeogenesis. This regulatory role helps balance the rates of glycolysis and gluconeogenesis in liver cells.

Question 12

Which enzyme has an intermediate of the form presented below?

Accepted Answer

The intermediate presented is a glucose-6-phosphate molecule, which is formed during the conversion of glucose-1-phosphate to glucose-6-phosphate by the enzyme phosphoglucomutase. None of the other enzymes listed in the options has a glucose-6-phosphate intermediate.

Question 13

Which of the following metabolic conversions involved in glucose synthesis requires the direct expenditure of ATP?
(I)3-Phosphoglycerate $\to$ 1,3-bisphosphoglycerate
(II)Glyceraldehyde-3-phosphate + dihydroxyacetone phosphate $\to$ fructose-1,6-bisphosphate
(III)Fructose-1,6-bisphosphate $\to$ fructose-6-phosphate
(IV)1,3-Bisphosphoglycerate $\to$ glyceraldehyde-3-phosphate

Accepted Answer

The conversion of 3-phosphoglycerate to 1,3-bisphosphoglycerate requires the direct expenditure of ATP, whereas the other three conversions do not require ATP. Therefore, only option (I) involves the direct expenditure of ATP.

Question 14

Hexokinase does not catalyze the final step in gluconeogenesis as written below because
Glucose-6-phosphate + ADP $\to$ glucose + ATP

Accepted Answer

The phosphate bond in glucose-6-phosphate does not have a high enough free energy to form ATP, which is why hexokinase cannot catalyze this reaction.

Question 15

Which of the following best explains the energetically favorable formation of UDP-glucose in the liver and muscle?

Accepted Answer

The hydrolysis of pyrophosphate (PPi) to two inorganic phosphates (2Pi) is highly exergonic, driving the formation of UDP-glucose.

Question 16

The synthesis of N-linked oligosaccharides occur in the _____ while O-linked oligosaccharides are synthesized in the ______.

Accepted Answer

N-linked oligosaccharides are synthesized in the endoplasmic reticulum (ER), while O-linked oligosaccharides are synthesized in the Golgi apparatus.

Question 17

Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?

Accepted Answer

The glycogen debranching enzyme has two activities: it transfers a trisaccharide unit to another branch and then cleaves the α(1→6) bond at the branch point, releasing free glucose.

Question 18

What is the net ATP yield for a muscle cell that stores one dietary glucose molecule as glycogen and then releases it and sends it through glycolysis?

Accepted Answer

One glucose molecule yields 2 ATP through glycolysis. However, since the glucose was stored as glycogen, it requires one ATP to activate glycogen phosphorylase to release the glucose from glycogen. Therefore, the net ATP yield is 2 ATP - 1 ATP = 1 ATP.

Question 19

Levels of glucose-6-phosphate (G6P)are affected by which of the following?
(I)glycogen breakdown
(II)activity of the pentose phosphate pathway
(III)galactose preparation for entry into glycolysis

Accepted Answer

G6P is involved in all three processes mentioned: 
(I) it is a precursor for glycogen synthesis and is produced during glycogen breakdown, 
(II) it is the initial substrate for the pentose phosphate pathway, and 
(III) it is a key intermediate in the conversion of galactose to glucose-1-phosphate for entry into glycolysis. Therefore, the levels of G6P are affected by all three processes, making choice B the best answer.

Question 20

If cAMP levels are high
(I)Glycogenolysis will occur in muscle cells but not liver cells.
(II)Glucose released from muscle glycogen will enter glycolysis.
(III)Glucose released from liver glycogen will exit liver cells via the GLUT4 transporter.
(IV)Glucose will enter liver cells resulting in glycogen synthesis.

Accepted Answer

If cAMP levels are high, it will activate protein kinase A which will phosphorylate and activate enzymes involved in glycogenolysis in both muscle and liver cells. Therefore, (I) is true for both muscle and liver cells. However, (III) is incorrect as glucose released from liver glycogen will enter into the bloodstream and not through GLUT4 transporter. (IV) is also incorrect as high cAMP levels stimulate glycogen breakdown rather than glycogen synthesis. (II) is the only true statement as glucose released from muscle glycogen will enter glycolysis to provide energy for the muscle cell.

Quiz 16: Glycogen Metabolism and Gluconeogenesis

The breakdown of glycogen produces G1P.Which of the following is FALSE regarding G1P?

Increased levels of epinephrine in the blood will (I) activate adenylate cyclase in liver and muscle cells. (II) stimulate glycogen synthesis. (III) inhibit glycolysis in the muscle cell. (IV) stimulate gluconeogenesis in the muscle cell.

Which statement is TRUE concerning the metabolic reaction shown below?

The diagram represents a "substrate cycle" in glucose metabolism.Which of the following statements about the cycle is true?

What molecules correspond to correspond to X and Y in the following gluconeogenic reaction? Fructose-1,6-bisphosphotase + X $\to$ Fructose-6-phosphate + Y

Avidin,a protein intact in raw egg whites,prevents the absorption of biotin in the intestine resulting in biotin deficiency.Which of the following is affected in individuals who consume large amounts of raw egg?

Which of the following metabolic conversions does not occur in gluconeogenesis?

Which statement is true regarding the activation of pyruvate carboxylase by acetyl-CoA?

Which of the following best describes the role of fructose-2,6-bisphosphate (FBP) in liver cells?

Which enzyme has an intermediate of the form presented below?

Hexokinase does not catalyze the final step in gluconeogenesis as written below because Glucose-6-phosphate + ADP $\to$ glucose + ATP

Which of the following best explains the energetically favorable formation of UDP-glucose in the liver and muscle?

The synthesis of N-linked oligosaccharides occur in the _ while O-linked oligosaccharides are synthesized in the __.

Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?

What is the net ATP yield for a muscle cell that stores one dietary glucose molecule as glycogen and then releases it and sends it through glycolysis?

Levels of glucose-6-phosphate (G6P) are affected by which of the following? (I) glycogen breakdown (II) activity of the pentose phosphate pathway (III) galactose preparation for entry into glycolysis

Quiz 16: Glycogen Metabolism and Gluconeogenesis

The breakdown of glycogen produces G1P.Which of the following is FALSE regarding G1P?

Increased levels of epinephrine in the blood will (I) activate adenylate cyclase in liver and muscle cells. (II) stimulate glycogen synthesis. (III) inhibit glycolysis in the muscle cell. (IV) stimulate gluconeogenesis in the muscle cell.

Which statement is TRUE concerning the metabolic reaction shown below?

The diagram represents a "substrate cycle" in glucose metabolism.Which of the following statements about the cycle is true?

What molecules correspond to correspond to X and Y in the following gluconeogenic reaction? Fructose-1,6-bisphosphotase + X →\to→ Fructose-6-phosphate + Y

Avidin,a protein intact in raw egg whites,prevents the absorption of biotin in the intestine resulting in biotin deficiency.Which of the following is affected in individuals who consume large amounts of raw egg?

Which of the following metabolic conversions does not occur in gluconeogenesis?

Which statement is true regarding the activation of pyruvate carboxylase by acetyl-CoA?

Which of the following best describes the role of fructose-2,6-bisphosphate (FBP) in liver cells?

Which enzyme has an intermediate of the form presented below?

Hexokinase does not catalyze the final step in gluconeogenesis as written below because Glucose-6-phosphate + ADP →\to→ glucose + ATP

Which of the following best explains the energetically favorable formation of UDP-glucose in the liver and muscle?

The synthesis of N-linked oligosaccharides occur in the _____ while O-linked oligosaccharides are synthesized in the ______.

Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?

What is the net ATP yield for a muscle cell that stores one dietary glucose molecule as glycogen and then releases it and sends it through glycolysis?

Levels of glucose-6-phosphate (G6P) are affected by which of the following? (I) glycogen breakdown (II) activity of the pentose phosphate pathway (III) galactose preparation for entry into glycolysis

What molecules correspond to correspond to X and Y in the following gluconeogenic reaction? Fructose-1,6-bisphosphotase + X $\to$ Fructose-6-phosphate + Y

Hexokinase does not catalyze the final step in gluconeogenesis as written below because Glucose-6-phosphate + ADP $\to$ glucose + ATP

The synthesis of N-linked oligosaccharides occur in the _ while O-linked oligosaccharides are synthesized in the __.