462 - 553 Carbohydrate metabolism Flashcards
The branches in glycogen consist of glucose molecules linked by
Select one:
a. alpha-1,5 linkages
b. alpha-1,4 linkages
c. alpha-1,6 linkages
d. alpha-1,2 linkages
c. alpha-1,6 linkages
The straight glucose chains of glycogen molecules are broken down initially to
Select one:
a. glucose
b. glucose- 6- phosphate c. glucose-1- phosphate d. fructose diphosphate e. UDP-glucose
The straight glucose chains of glycogen molecules are broken down initially to
Select one:
a. glucose
b. glucose- 6- phosphate
c. glucose-1- phosphate
d. fructose diphosphate
e. UDP-glucose
c. glucose-1- phosphate
The straight glucose chains of glycogen molecules are broken down initially to
Select one:
a. glucose
b. glucose- 6- phosphate
c. glucose-1- phosphate
d. fructose diphosphate
e. UDP-glucose
c. glucose-1- phosphate
The branch points of glycogen are broken down to
Select one:
a. fructose diphosphate
b. glucose
c. glucose- 1- phosphate
d. glucose -6- phosphate
e. UDP-glucose
b. glucose
(release 1 free glucose)
The branch points of glycogen are broken down to
Select one:
a. fructose diphosphate
b. glucose
c. glucose- 1- phosphate
d. glucose -6- phosphate
e. UDP-glucose
b. glucose
The straight chains of glycogen molecules are broken down by
Select one:
a. adenylate cyclase
b. glycogen glicosidase
c. glycogen phosphorylase
d. glycogen-glycosidase
e. protein kinase
c. glycogen phosphorylase
The debranching enzyme possesses the following activity(ies)
Select one:
a. A transferase activity
b. Both debranching and a transferase activity
c. Debranching activity
d. Elongase activity
e. Neither a debranching and a transferase activity
b. Both debranching and a transferase activity
Glucagon
Select one:
a. inhibits the formation of glycogen and stimulates the breakdown of glycogen
b. simultaneously inhibits the formation of glycogen and glycogen breakdown
c. simultaneously stimulates the formation of glycogen and glycogen breakdown
d. simultaneously stimulates the formation of glycogen and ketone bodies
e. stimulates the formation of glycogen and inhibits the breakdown of glycogen
a. inhibits the formation of glycogen and stimulates the breakdown of glycogen
Epinephrine
Select one:
a. stimulates the formation of glycogen and inhibits the breakdown of glycogen
b. simultaneously stimulates the formation of glycogen and ketone bodies
c. simultaneously stimulates the formation of glycogen and glycogen breakdown
d. simultaneously inhibits the formation of glycogen and glycogen breakdown
e. inhibits the formation of glycogen and stimulates the breakdown of glycogen
e. inhibits the formation of glycogen and stimulates the breakdown of glycogen
Insulin
Select one:
a. stimulates the formation of glycogen and inhibits the breakdown of glycogen
b. simultaneously stimulates the formation of glycogen and ketone bodies
c. simultaneously stimulates the formation of glycogen and glycogen breakdown
d. simultaneously inhibits the formation of glycogen and glycogen breakdown
e. inhibits the formation of glycogen and stimulates the breakdown of glycogen
a. stimulates the formation of glycogen and inhibits the breakdown of glycogen
Glucagon
Select one:
a. activates glycogen phosphorylase and increases the rate of glycogen synthesis
b. activates glycogen phosphorylase and increases the rate of glycogen breakdown
c. activates phosphofruktokinase 1 and increases the rate of gluconeogenesis
d. deactivates glycogen phosphorylase and decreases the rate of glycogen synthesis
e. deactivates glycogen phosphorylase and increases the rate of glycogen synthesis
b. activates glycogen phosphorylase and increases the rate of glycogen breakdown
Insulin
Select one:
a. activates phosphofruktokinase 2 and increases the rate of gluconeogenesis
b. decreases the activity of glycogen synthase and decreases the rate of glycogen synthesis
c. decreases the activity of glycogen synthase and increases the rate of glycogen synthesis
d. increases the activity of glycogen synthase and decreases the rate of glycogen synthesis
e. increases the activity of glycogen synthase and increases the rate of glycogen synthesis
e. increases the activity of glycogen synthase and increases the rate of glycogen synthesis
The binding of epinephrine to a receptor
Select one:
a. deactivates protein kinase A
b. deactivates adenylate cyclase
c. causes the breakdown of cyclic AMP to ATP
d. activates phosphodiesterase
e. activates adenylate cyclase
b. deactivates adenylate cyclase
The binding of glucagon to its receptor
Select one:
a. deactivates protein kinase
b. deactivates adenylate cyclase
c. causes the breakdown of cyclic AMP to ATP
d. activates adenylate cyclase
e. activates phosphodiesterase
d. activates adenylate cyclase
(same effect with epinephrine)
The binding of glucagon to its receptor will lead to
Select one:
a. the deactivation of adenylate cyclase
b. the deactivation of protein kinase A
c. the deactivation of glycogen phosphorylase
d. the activation of phosphorylase kinase
a. the deactivation of adenylate cyclase
Which of the following statements are true?
Select one:
a. Fructose-1-phosphate activates glucokinase
b. Fructose-6-phosphate activates glucokinase
c. Glucokinase is inhibited by glucose-6-phosphate
d. Glucokinase is inhibited by high glucose level
e. Glucokinase is sequestered in the nucleus when glucose level is high.
a. Fructose-1-phosphate activates glucokinase
Protein kinase A
Select one:
a. removes a phosphate molecule from glycogen synthase
b. removes a phosphate molecule from cAMP
c. adds a phosphate to fructose-6-phosphate
d. adds a phosphate molecule to glycogen synthase
e. adds a phosphate molecule to cAMP
d. adds a phosphate molecule to glycogen synthase
Protein kinase A
Select one:
a. adds a phosphate molecule to phosphorylase kinase
b. adds a phosphate molecule to glycogen phosphorylase
c. adds a phosphate to glucokinase
d. removes a phosphate molecule from glycogen phosphorylase
e. removes a phosphate molecule from phosphorylase kinase
adds a phosphate molecule to phosphorylase kinase
Protein kinase A
Select one:
a. adds a phosphate molecule to phosphorylase kinase
b. adds a phosphate molecule to glycogen phosphorylase
c. adds a phosphate to glucokinase
d. removes a phosphate molecule from glycogen phosphorylase
e. removes a phosphate molecule from phosphorylase kinase
a. adds a phosphate molecule to phosphorylase kinase
Protein kinase A
Select one:
a. Directly activates glycogen phosphorilase
b. activates glycogen synthase
c. converts ATP to cAMP
d. converts cAMP to ATP
e. deactivates glycogen synthase
e. deactivates glycogen synthase
Protein kinase A directly
Select one:
a. deactivates glucokinase
b. deactivates glycogen phosphorylase c. activates glycogen phosphorylase
d. deactivates phosphorylase kinase
e. activates phosphorylase kinase
e. activates phosphorylase kinase
(which then activate glycogen phosphorylase)
In glycogenesis, the enzyme (i)________ uses a molecule of (ii)_________ to lengthen the glycogen chain
Select one:
a. (i) glycogen synthase (ii) glucose
b. (i)glycogen phosphorylase (ii) glucose
c. (i) glycogen phosphorylase (ii) UDP-glucose
d. (i) glycogen synthase (ii) UDP-glucose
e. (i) glycogenin (ii) glucose-1-phosphate
d. (i) glycogen synthase (ii) UDP-glucose
Patients suffering from Von Gierke’s disease
Select one:
a. cannot convert glucose-6-phosphate to glucose
b. have enlarged livers
c. cannot convert glycogen to glucose
d. have high plasma levels of lactate
e. all of them are correct
a. cannot convert glucose-6-phosphate to glucose
Patients suffering from Von Gierke’s disease
Select one:
a. have a faulty glucose-6-phosphatase
b. cannot perform gluconeogenesis
c. tend to suffer from hypoglycemia between meals. d. have high plasma levels of lactate
e. All of them are correct
e. All of them are correct
A person is suffering from a disease which is caused by a defective glucose-6-phosphatase. Such a person
Select one:
a. can breakdown glycogen completely to glucose
b. can convert pyruvate to glucose
c. can dephosphorylate glucose-6-phosphate
d. can convert glycogen to pyruvate
e. can convert acetyl-CoA to glucose
d. can convert glycogen to pyruvate
A person is suffering from a disease in which is caused by a defective glucose-6-phosphatase. Such a person
Select one:
a. can convert acetyl-CoA to glucose
b. cannot breakdown glycogen completely to glucose
c. cannot convert acetyl-CoA to citric acid
d. cannot convert glycogen to pyruvate
e. would suffer no ill-effects from this defect
b. cannot breakdown glycogen completely to glucose
In glycogenolysis, the enzyme (i)________ breaks an (ii) _______ bond to release a molecule of (iii)_________.
Select one:
a. (i) glycogen synthase (ii) alpha 1-4 (iii) glucose
b. (i) glycogen synthase (ii) alpha 1-4 (iii) UDP-glucose
c. (i) glycogen phosphorylase (ii) alpha 1-4 (iii) glucose-1-phosphate
d. (i) glycogen phosphorylase (ii) alpha 1-6 (iii) glucose-6-phosphate
e. (i) debranching enzyme (ii) alpha 1-6 (iii) glucose-1-phosphate
c. (i) glycogen phosphorylase (ii) alpha 1-4 (iii) glucose-1-phosphate
What is true concerning glucose-6-phosphatase enzyme system?
Select one or more:
a. responsible for dephosphorylation of glucose-6-phosphate
b. expressed in the endoplasmic reticulum of hepatocytes
c. an enzyme system in gluconeogenic pathway
d. is involved in pentose-phosphate pathway
a. responsible for dephosphorylation of glucose-6-phosphate
b. expressed in the endoplasmic reticulum of hepatocytes
c. an enzyme system in gluconeogenic pathway
Activity of phosphofructokinase1 is inhibited by
Select one or more:
a. ATP
b. citrate
c. fructose 2,6 bisphosphate
d. AMP
b. citrate
c. fructose 2,6 bisphosphate
Lactate dehydrogenase
Select one or more:
a. requires NAD as hydrogen acceptor
b. requires NADP as hydrogen acceptor
c. catalyzes a reversible process
d. requires molecular oxygen
a. requires NAD as hydrogen acceptor
c. catalyzes a reversible process
Which enzyme catalyzes the first ATP producing step of glycolysis?
Select one:
a. phosphofructokinase 1
b. hexokinase
c. pyruvate kinase
d. phosphoglycerate mutase
e. phosphoglycerate kinase
e. phosphoglycerate kinase
Which enzyme catalyzes the second ATP producing step of glycolysis?
Select one:
a. phosphofructokinase 1
b. hexokinase
c. pyruvate kinase
d. phosphoglycerate mutase
e. phosphoglycerate kinase
c. pyruvate kinase
Which are the ATP producing steps of glycolysis?
Select one or more:
a. phosphofructokinase 1
b. lactate-dehydrogenase
c. pyruvate kinase
d. glyceraldehyde 3-phosphate dehydrogenase
e. phosphoglycerate kinase
c. pyruvate kinase
e. phosphoglycerate kinase
Which are the ATP consuming steps of glycolysis?
Select one or more:
a. phosphofructokinase 1
b. lactate dehydrogenase
c. pyruvate kinase
d. hexokinase
e. phosphoglycerate kinase
c. pyruvate kinase
d. hexokinase
Upon phosphorylation of phosphofructokinase 2 by protein kinase A in liver:
Select one:
a. it becomes active.
b. it becomes inactive.
c. phosphatase function is activated, kinase function is inactivated.
d. kinase function is activated, phosphatase function is inactivated.
e. phosphofructokinase 2 is not covalently regulated.
c. phosphatase function is activated, kinase function is inactivated.
Which of the following amino acids are only ketogenic?
Select one or more:
a. Ser
b. Trp
c. Lys
d. Pro
e. Leu
c. Lys
e. Leu
Which enzyme deficiency may result in lactic acidosis?
Select one or more:
a. Pyruvate kinase
b. Pyruvate dehydrogenase
c. Pyruvate carboxylase
d. Lactate dehydrogenase
b. Pyruvate dehydrogenase
c. Pyruvate carboxylase
Which condition is not found in pyruvate carboxylase deficiency?
Select one:
a. Demyelination
b. Hyperammonemia
c. Hyperglycemia
d. Hypoglycemia
e. Lactic acidosis
c. Hyperglycemia
(High blood sugar (hyperglycaemia) is where the level of sugar in your blood is too high. )
Which statements are true for hereditary fructose intolerance?
Select one or more:
a. It is caused by the inadequate function of aldolase B
b. It is accompanied by hypoglycemia
c. It results in liver damage
d. Glycogenolysis is increased
e. It results in the accumulation of fructose 1-phosphate
a. It is caused by the inadequate function of aldolase B
b. It is accompanied by hypoglycemia
c. It results in liver damage
e. It results in the accumulation of fructose 1-phosphate
The allosteric activator of pyruvate carboxylase is:
Select one:
a. oxaloacetate
b. NADH
c. CoA
d. ATP
e. acetyl-coA
e. acetyl-coA
Lactose can be formed in a single step from:
Select one or more:
a. glucose
b. UDP-galactose
c. glucosamin 6-phosphate
d. glucosamin 1-phosphate
e. glucose 1-phosphate
a. glucose
b. UDP-galactose
Hypoglycemia develops when:
Select one:
a. glucagon secretion increases
b. glucokinase is defective
c. epinephrine level rises
d. insulin level is low.
e. there is an overproduction of insulin.
e. there is an overproduction of insulin.
When is the glycogen pool of the liver depleted during fasting?
Select one:
a. in 6 hours
b. in 1 hour
c. in 24 hours
d. in 3 days
e. in a week
c. in 24 hours
Choose the enzyme, the lack of which leads to fructose intolerance
Select one:
a. aldolase A (fructose 1,6-bisphosphate aldolase)
b. aldolase B (fructose 1-phosphate aldolase)
c. fructokinase
d. hexokinase
e. phosphofructokinase
b. aldolase B (fructose 1-phosphate aldolase)
Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:
Select one:
a. CO2.
b. lactate.
c. glucose.
d. hemoglobin.
e. ethanol.
b. lactate.
Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:
Select one:
a. CO2.
b. lactate.
c. glucose.
d. hemoglobin.
e. ethanol.
b. lactate.
The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a compound whose hydrolysis has a highly negative DG’°) is catalyzed by:
Select one:
a. glyceraldehyde 3-phosphate dehydrogenase.
b. hexokinase.
c. phosphofructokinase-1.
d. phosphoglycerate kinase.
e. triose phosphate isomerase.
a. glyceraldehyde 3-phosphate dehydrogenase.
The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of:
Select one:
a. 2 mol of NADH and 4 mol of ATP.
b. 2 mol of NADH and 2 mol of ATP.
c. 2 mol of NAD+ and 4 mol of ATP.
d. 1 mol of NADH and 1 mol of ATP.
e. 1 mol of NAD+ and 2 mol of ATP.
a. 2 mol of NADH and 4 mol of ATP.
The anaerobic conversion of 1 mol of glucose to 2 mol of lactate is accompanied by a net gain of:
Select one:
a. 1 mol of ATP.
b. 1 mol of NADH.
c. 2 mol of ATP.
d. 2 mol of NADH.
e. none of the above.
c. 2 mol of ATP.
Which of these cofactors participates directly in the oxidation-reduction reactions in the conversion of glucose to lactate?
Select one:
a. FAD/FADH2
b. NAD+/NADH
c. glyceraldehyde 3-phosphate
d. ATP
e. ADP
b. NAD+/NADH
Glycogen is converted to monosaccharide units by:
Select one:
a. glycogenase.
b. glycogen synthase.
c. glycogen phosphorylase.
d. glucokinase.
c. glycogen phosphorylase.
Classic galactosemia is a genetic error of metabolism associated with:
Select one:
a. excessive ingestion of galactose.
b. inability to digest lactose.
c. deficiency of galactokinase.
d. deficiency of galactose 1-phosphate uridylyltransferase.
e. deficiency of UDP-glucose.
d. deficiency of galactose 1-phosphate uridylyltransferase.
The rate-limiting reaction in glycolysis is:
Select one:
a. the phosphorylation of glucose.
b. the phosphorylation of fructose 6-phosphate.
c. the isomerization of glucose 6-phosphate to fructose 6-phosphate.
d. the breakdown of glycogen.
e. some step in the conversion of fructose 1,6-bisphosphate to pyruvate.
b. the phosphorylation of fructose 6-phosphate.
Glucokinase:
Select one:
a. is found in all mammalian tissues.
b. is a hexokinase isozyme found in liver hepatocytes and ß-cells.
c. converts glucose 6-phosphate to fructose 6-phosphate.
d. acts in the conversion of liver glycogen to glucose 1-phosphate
b. is a hexokinase isozyme found in liver hepatocytes and ß-cells.
Epinephrine triggers an increased rate of glycogen breakdown in muscle by causing:
Select one:
a. activation of hexokinase.
b. activation of phosphofructokinase-1.
c. conversion of glycogen phosphorylase b to glycogen phosphorylase a.
d. the Pasteur effect.
e. Activation of protein phosphatase-1
c. conversion of glycogen phosphorylase b to glycogen phosphorylase a.
The main function of the pentose phosphate pathway is to:
Select one:
a. supply energy.
b. give the cell an alternative pathway should glycolysis fail.
c. supply NADH.
d. provide a mechanism for the utilization of the carbon skeletons of excess amino acids.
e. supply pentoses and NADPH.
e. supply pentoses and NADPH.
The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:
Select one:
a. 3 mol of pentose, 4 mol of NADPH, and 3 mol of CO2.
b. 2 mol of pentose, 4 mol of NADPH, and 8 mol of CO2.
c. 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.
d. 4 mol of pentose, 6 mol of NADPH, and 6 mol of CO2.
c. 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.
(In the oxidative phase of PPP pathway,
G6P + 2 NADP+ + H2O -> Ribulose-5-P + 2 NADPH + 2H+ + CO2)
Which of the following statements about the pentose phosphate pathway is correct?
Select one:
a. It provides precursors for the synthesis of nucleotides.
b. It is a reductive pathway; it consumes NADH.
c. It generates 36 mol of ATP per mole of glucose consumed.
d. It is present in plants, but not in animals.
a. It provides precursors for the synthesis of nucleotides.
Which of the following enzymes acts in the pentose phosphate pathway?
Select one:
a. pyruvate kinase
b. phosphofructokinase-1
c. glycogen phosphorylase
d. aldolase
e. 6-phosphogluconate dehydrogenase
e. 6-phosphogluconate dehydrogenase
The metabolic function of the pentose phosphate pathway is:
Select one:
a. to act as a source of ADP biosynthesis.
b. to generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
c. to participate in oxidation-reduction reactions during the formation of H2O.
d. to provide intermediates for the citric acid cycle.
e. none of the above.
b. to generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
All of the following enzymes involved in glycolysis are also involved in gluconeogenesis except:
Select one:
a. 3-phosphoglycerate kinase.
b. aldolase.
c. enolase.
d. phosphofructokinase-1.
e. phosphoglucoisomerase.
d. phosphofructokinase-1.
An enzyme used in both glycolysis and gluconeogenesis is:
Select one:
a. 3-phosphoglycerate kinase.
b. glucose 6-phosphatase.
c. hexokinase.
d. phosphofructokinase-1.
e. pyruvate kinase.
a. 3-phosphoglycerate kinase.
Which one of the following statements about gluconeogenesis is false?
Select one:
a. For starting materials, it can use carbon skeletons derived from certain amino acids.
b. It requires metabolic energy (ATP or GTP).
c. It is one of the ways that mammals maintain normal blood glucose levels between meals.
d. It employs the enzyme glucose 6-phosphatase.
e. It consists entirely of the reactions of glycolysis, operating in the reverse direction.
e. It consists entirely of the reactions of glycolysis, operating in the reverse direction.
A person who cannot synthesize liver fructose 1,6-bisphosphatase would probably not be able to:
Select one:
a. synthesize fats when the diet contained excess carbohydrate.
b. metabolize fructose.
c. convert fructose 1,6-bisphosphate into triose phosphates.
d. resynthesize glucose from lactate produced during exercise.
e. none of the above is correct.
d. resynthesize glucose from lactate produced during exercise.
The glycogen-branching enzyme catalyzes:
Select one:
a. formation of (alpha 1-6) linkages during glycogen synthesis.
b. formation of (alpha 1-4) linkages in glycogen.
c. glycogen degradation in tree branches.
d. removal of glucose residues at the ends of branches.
a. formation of (alpha 1-6) linkages during glycogen synthesis.
Glycogenin:
Select one:
a. catalyzes the conversion of starch into glycogen.
b. is the enzyme responsible for forming branches in glycogen.
c. is the gene that encodes glycogen synthase.
d. is the primer on which new glycogen chains are initiated.
e. regulates the synthesis of glycogen.
d. is the primer on which new glycogen chains are initiated.
Which of the following is true of glycogen synthase?
Select one:
a. The enzyme has measurable activity only in liver.
b. The conversion of an active to an inactive form of the enzyme is directly controlled by the concentration of cAMP.
c. It catalyzes addition of glucose residues to the non-reducing end of a glycogen chain by formation of (alpha 1-4) bonds.
d. Activation of the enzyme involves a phosphorylation.
c. It catalyzes addition of glucose residues to the non-reducing end of a glycogen chain by formation of (alpha 1-4) bonds.
Which of the following is true of glycogen synthesis and breakdown?
Select one:
a. Under normal circumstances glycogen synthesis and glycogen breakdown occur simultaneously and at high rates.
b. The immediate product of glycogen breakdown is free glucose.
c. The glycogen molecule ``grows’’ at its reducing end.
d. Synthesis is catalyzed by the same enzyme that catalyzes breakdown.
e. Phosphorylation activates the enzyme responsible for breakdown, and inactivates the synthetic enzyme.
e. Phosphorylation activates the enzyme responsible for breakdown, and inactivates the synthetic enzyme.
Transketolase requires the coenzyme:
Select one:
a. thiamine pyrophosphate.
b. tetrahydrofolic acid.
c. pyridoxal phosphate.
d. cobalamin (vitamin B12).
a. thiamine pyrophosphate.
Which of the following conversions requires more than one step?
Select one:
a. alanine →pyruvate
b. glutamate → alpha-ketoglutarate
c. aspartate →oxaloacetate
d. glutamin → alpha-ketoglutarate
d. glutamin → alpha-ketoglutarate
(glutamine -> glutamate catalyzed by glutaminase
- Glutamate is formed directly from glutamine by deamidation via phosphate activated glutaminase a reaction that also yields ammonia.)
