Upgrade to remove ads
Only $35.99/year

Ch 14: Carbohydrate Metabolism

Terms in this set (75)

The pentose phosphate pathway occurs in the
a. cytoplasm.
b. nucleus.
c. Golgi apparatus.
d. mitochondria.
a
The main function of the pentose phosphate pathway is to provide
a. the cell with backup capability when glycolysis is inhibited.
b. energy and reducing power.
c. a mechanism for the utilization of the carbon skeletons of excess amino acids.
d. a source of ribose and NADPH.
d
The pentose phosphate pathway
a. resembles the TCA cycle in that it couples the loss of CO2 with the formation
of NADH.
b. allows 5C sugars to converge with or diverge from the glycolysis pathway.
c. contains 2C, 3C, 4C, 5C, 6C, and 7C sugar molecules.
d. enables the production of ATP from glucose.
b
The pentose phosphate pathway
a. can be used to make seduheptulose-7-phosphate for use in RNA and DNA synthesis.
b. is linked at its start and at its end to the glycolysis pathway.
c. converges glycolysis intermediates with TCA cycle intermediates.
d. occurs in the mitochondrial matrix of cells.
b
Which of the following is NOT a role played by the pentose phosphate pathway?
a. converting pyruvate into TCA cycle intermediates
b. making NADPH for other metabolic pathways
c. converting 6C glucose into 5C ribose
d. converting DNA backbone sugars into glycolysis intermediates
a
The products of the oxidative portion of the pentose phosphate pathway are carbon
dioxide and
a. 2 NADH + 1 hexose phosphate.
b. 2 NADP+ + 1 pentose phosphate.
c. 2 NADPH + 1 hexose phosphate.
d. 2 NADPH + 1 pentose phosphate.
d
Which is the substrate or product of the reactions that comprise the oxidative branch of the
pentose phosphate pathway?
a. sedoheptulose-7-phosphate
b. glyceraldehyde-3-phosphate
c. ribulose-5-phosphate
d. ribose-5-phosphate
c
Which enzyme class catalyzes the following pentose phosphate pathway reaction?
b: Oxidoreductase
Which of the following molecules is found in the nonoxidative phase of the pentose
phosphate pathway?
c
What enzyme class in the nonoxidative phase of the pentose phosphate pathway allows
for the reaction of ribose-5-phosphate and xylulose-5-phosphate to produce
glyceraldehyde-3-phosphate and seduheptulose-7-phosphate?
c
Which of the following molecules is found in the nonoxidative phase of the pentose
phosphate pathway?
a. glucose-6-phosphate
b. sedoheptulose-7-phosphate
c. phosphoenolpyruvate
b
Which enzyme class catalyzes the following pentose phosphate pathway reaction (note that
there may be some missing reactants and products)?
a. lyase
b. isomerase
c. transferase
d. oxidoreductase
d
Starting from the oxidative phase of the pentose phosphate pathway, how many ATP and
high-energy reduced molecules, respectively, are made in going from one glucose molecule to
glyceraldehyde-3-phosphate and fructose-6-phosphate?
a. 0; 0
b. 0; 2
c. 2; 0
d. 2; 2
b
Which enzyme in the pentose phosphate pathway catalyzes the following reaction?
a. glucose-6-phosphate dehydrogenase
b. transaldolase
c. 6-phosphogluconate dehydrogenase
d. ribulose-5-phosphate epimerase
c
Which enzyme in the pentose phosphate pathway is regulated to control flux through the
pathway?
a. glucose-6-phosphate dehydrogenase
b. transaldolase
c. 6-phosphogluconate dehydrogenase
d. ribulose-5-phosphate epimerase
a
What molecule activates the pentose phosphate pathway?
a. NADP+
b. ribulose-5-phosphate
c. ADP
d. NADH
a
If the ratio of NADP+ to NADPH were high, the
a. net production of ATP would occur.
b. pentose phosphate pathway oxidative phase would be activated.
c. cellular levels of nucleotides would have to increase from an activated pentose
phosphate pathway.
d. pentose phosphate pathway would be inhibited.
b
Which enzyme uses cellular NADPH to regenerate reduced glutathione?
a. glucose-6-phosphate dehydrogenase
b. glutathione peroxidase
c. glutathione reductase
d. hemoglobin
c
How would individuals with decreased levels of the pentose phosphate enzyme
glucose-6-phosphate dehydrogenase respond to oxidative stress?
a. Higher than normal levels of NADPH would accumulate.
b. They would not have the ability to regenerate reduced glutathione as rapidly.
c. They would rapidly neutralize cellular levels of H2O2 and other reactive oxygen
species.
d. They would compensate with higher than normal levels of pentose phosphate
pathway activity.
b
Which of the following metabolites is NOT a gluconeogenesis substrate in humans?
a. pyruvate
b. lactate
c. oxaloacetate
d. acetate
d
Which of the following metabolites has carbon atoms that can end up in glucose via the
gluconeogenesis pathway in humans?
a. CO2
b. glycerol
c. ATP
d. NADH
b
Two moles of pyruvate molecules running through the gluconeogenesis pathway to give
1 mole of glucose requires the hydrolysis of __________ moles of ATP equivalents.
a. 0
b. 2
c. 4
d. 6
d
How many moles of NADH are required in gluconeogenesis to convert 2 moles of pyruvate
molecules into 1 mole of glucose?
a. 0
b. 1
c. 2
d. 4
c
Which pathway is opposite to gluconeogenesis?
a. TCA cycle
b. glycogen synthesis pathway
c. pentose phosphate pathway
d. glycolysis pathway
d
The gluconeogenesis pathway
a. converts NADH into NAD+ so that glycolysis can continue.
b. provides energy for the cell.
c. increases the ratio of ATP to ADP in the cell.
d. converts two 3C sugars into a 6C sugar.
d
In the reaction catalyzed by pyruvate carboxylase (the first reaction in gluconeogenesis),
CO2 is
a. lost from oxaloacetate.
b. activated by ATP energy.
c. activated by the cofactor NADH.
d. added to the phosphoenolpyruvate product
b
The conversion of pyruvate to phosphoenolpyruvate (PEP) in gluconeogenesis
a. requires the net input of two equivalents of NADH.
b. occurs in two steps and is catalyzed by the enzymes pyruvate carboxylase and
phosphoenolpyruvate carboxykinase.
c. is a thermodynamically spontaneous reaction that gives rise to a stable product.
d. requires lactate as a precursor.
b
The gluconeogenesis reaction shown below is missing some reactants and products. What class
of enzyme catalyzes this reaction?
a. lyase
b. hydrolase
c. transferase
d. oxidoreductase
b
The first two reactions of gluconeogenesis are required to reverse reaction 10 (or the last
reaction) of glycolysis. How many ATP equivalents are used by these first two reactions of
gluconeogenesis?
a. 1
b. 2
c. 3
d. 4
b
What molecules are missing from boxes in the gluconeogenesis reaction shown below?
a. Ser-Pi; Ser-Pi
b. H2O; Pi
c. ADP; ATP
d. ATP; ADP
b
In the gluconeogenesis pathway, the enzyme glucose-6-phosphatase reverses which step in
glycolysis?
a. the formation of glucose
b. the reaction catalyzed by pyruvate dehydrogenase
c. the reaction catalyzed by hexokinase
d. the formation of fructose-1,6-bisphosphate
c
How many of the 10 glycolysis reactions use the same enzyme in the gluconeogenesis
pathway?
a. 10
b. 7
c. 5
d. 3
b
Which enzyme in the glycolysis pathway catalyzes a reaction that requires two enzymes to
reverse in the gluconeogenesis pathway?
a. pyruvate kinase
b. phosphofructokinase I
c. pyruvate dehydrogenase
d. glycogen phosphorylase
a
Cytoplasmic levels of NADH must be maintained in order for gluconeogenesis to occur. What
generates NADH for this pathway?
a. the glycolysis pathway
b. the TCA cycle
c. the mitochondrial electron transport chain
d. the movement of NADH equivalents from inside the mitochondria via malate
transport
d
Which correctly describes the role of the transport system shown below?
a. It provides an alternate fate for pyruvate degradation.
b. It provides a source of NADH for gluconeogenesis via malate transport.
c. It converts NADH equivalents into reduced forms of carbon.
d. It allows for pyruvate transport into and out of the mitochondria.
b
Of the four molecules listed below, three of them reciprocally regulate phosphofructokinase 1
(PFK1) and fructose-1,6-bisphosphatase. Which molecule does NOT fit?
a. pyruvate
b. fructose-2,6-bisphosphate
c. citrate
d. AMP
a
Gluconeogenesis is favored when citrate levels are __________, when AMP levels are
__________, and when ATP levels are __________.
a. low; low; high
b. high; low; high
c. low; high; low
d. high; high; low
b
Gluconeogenesis would most likely be allosterically activated simultaneously along with which
other metabolic process?
a. glycolysis
b. pentose phosphate pathway
c. glycogen synthesis
d. TCA cycle
c
The regulated reactions of gluconeogenesis have/are
a. large positive ΔG values.
b. those that are counter to regulated reactions in glycolysis.
c. reversible reactions.
d. activated by molecules indicating a low energy charge in the cell.
b
The hormone insulin activates phosphofructokinase 2 (2PFK2). This leads to a(n)
__________ in concentration of fructose 2,6 bisphosphate, which favors the __________
pathway.
a. increase; glycolysis
b. increase; gluconeogenesis
c. decrease; glycolysis
d. decrease; gluconeogenesis
a
Which hormone slows down glycolysis while stimulating gluconeogenesis through the
phosphorylation of phosphofructokinase 2 (PFK2) and fructose-2,6-bisphosphatase?
a. insulin
b. protein kinase
c. ATP
d. glucagon
d
Which pair of opposite enzymes in the glycolysis and gluconeogenesis pathway are not
allosterically regulated but rather regulated by compartmentalization?
a. pyruvate kinase/PEP carboxykinase
b. phosphofructokinase 1/fructose-1,6-bisphosphatase
c. phosphofructokinase 2/fructose-2,6-bisphosphatase
d. hexokinase/glucose-6-phosphatase
d
What controls the activity of the opposing enzymes hexokinase and glucose-6-phosphatase
from the glycolysis and gluconeogenesis pathways?
a. levels of ATP
b. cellular compartmentalization and separation of the two enzymes
c. fructose-2,6-bisphosphate concentration
d. phosphorylation of the enzymes
b
Which molecule allosterically activates pyruvate carboxylase?
a. AMP
b. NAD+
c. epinephrine
d. acetyl-CoA
d
Which of the following molecules would inhibit the regulated steps in gluconeogenesis?
a. ATP
b. ADP
c. pyruvate
d. NADH
b
The enzymes that catalyze the regulated steps in glycolysis are
a. phosphofructokinase, pyruvate dehydrogenase, and lactate dehydrogenase.
b. hexokinase, phosphofructokinase, and pyruvate dehydrogenase.
c. aldolase, phosphofructokinase, and pyruvate kinase.
d. hexokinase, phosphofructokinase, and pyruvate kinase.
d
Which of the following molecules might inhibit the regulated enzymes in glycolysis?
a. NAD+
b. ATP
c. AMP
d. fructose-2,6-bisphosphate
b
Which of the following molecules would activate phosphofructokinase 1 (PFK1)?
a. NADH
b. AMP
c. ATP
d. pyruvate
b
Which of the following molecules would inhibit the last reaction of glycolysis?
a. ATP
b. glucose
c. AMP
d. NAD+
a
The Cori cycle
a. transports pyruvate from working muscles to the liver, where it is converted back to
glucose.
b. is important in organisms respiring aerobically.
c. involves the conversion of muscle pyruvate to alanine followed by transport to the
liver.
d. relies on functioning lactate dehydrogenase in both muscle and liver tissues.
d
What triggers the Cori cycle?
a. a buildup of cellular NAD+
b. oxygen-limited working muscle cells
c. low levels of glucose in the muscle cells
d. elevated glucagon levels
b
The Cori cycle
a. requires both glycolysis and gluconeogenesis pathways.
b. removes lactic acid from liver cells and delivers it to muscle cells.
c. involves the regeneration of NADH equivalents for the working muscles.
d. converts glucose into lactic acid.
a
The branching enzyme of glycogen synthesis is involved in
a. making the α(1,6) branch points.
b. making α(1,4) linkages at the branch points.
c. breaking the α(1,6) branches and smoothing out the glycogen chain.
d. transferring ∼3 glucose units from a branch point to the end of a growing glycogen
chain.
a
Which one of the following is involved in the breakdown of glycogen?
a. inorganic phosphate
b. ATP
c. branching enzyme
d. hexokinase
a
The glycogen phosphorylase enzyme
a. makes α(1,4) links at the nonreducing end of glycogen.
b. uses Pi (phosphate) as a nucleophile in the cleavage of glucose units off of the
glycogen chain.
c. cleaves the α(1,6) linkages of glucose units in the glycogen polymer.
d. releases free glucose units as its immediate product.
b
How many high-energy NTP molecules are hydrolyzed for each glucose monomer added to a
growing glycogen polymer?
a. 0
b. 1
c. 2
d. 3
c
In the elongation of glycogen, activated glucose units are attached to which hydroxyl of the
terminal residue of the growing glycogen chain?
a. C-1
b. C-3
c. C-4
d. C-6
c
In the elongation of glycogen, activated glucose units are attached to which hydroxyl of the
terminal residue of the growing glycogen chain?
a. C-1
b. C-3
c. C-4
d. C-6
d
In the glycogenesis pathway, which enzyme catalyzes the formation of α(1,6) linkages?
a. debranching enzyme
b. glycogen synthase
c. glycogen phosphorylase
d. branching enzyme
d
In the breakdown of glycogen by glycogen phosphorylase, the immediate predominant
product is
a. glucose.
b. glucose-1-phosphate.
c. UDP-glucose.
d. glucose-6-phosphate.
b
The branching enzyme
a. couples the formation of glycogen with UDP loss from UDP-glucose.
b. makes α(1,4) linkages with the transfer of seven glucose units.
c. breaks α(1,6) branch points and remakes α(1,4) linkages.
d. catalyzes the cleavage of α(1,4) links and the formation of α(1,6) links.
d
In the glycogenesis pathway, the role of the glucose-6-phosphate isomerization reaction is to
a. create a more stable intermediate for the subsequent reaction.
b. decrease the concentration of glucose-6-phosphate, thereby driving the pathway
forward.
c. ensure that the charged molecule stays in the cell.
d. prepare the anomeric carbon for nucleophilic attack.
d
In the breakdown of glycogen, the debranching enzyme catalyzes the formation of
a. glucose-1-phosphate.
b. glucose.
c. α(1,6) branched glycogen.
d. glucose-6-phosphate.
b
Which enzyme catalyzes the following reaction? (there is a picture that i can't add)
a. debranching enzyme
b. glycogen phosphorylase
c. branching enzyme
d. glycogen synthase
a
The debranching enzyme does NOT catalyze the
a. formation of α(1,6) linkages.
b. cleavage of α(1,6) linkages.
c. formation of α(1,4) linkages.
d. cleavage of α(1,4) linkages.
a
Which statement of the debranching enzyme is true?
a. It catalyzes the addition of free glucose to a nonreducing end of glycogen.
b. Its product is glucose-1-phosphate.
c. It evenly distributes branch points across the glycogen polymer.
d. It is one enzyme with three unique catalytic activities.
d
The role of glycogenin is to
a. catalyze the formation of UDP-glucose.
b. act as a hormone to regulate glucose levels.
c. serve as the origin of the glycogen polymer.
d. enable glycogen to fold properly.
c
What class of biomolecule is glycogenin?
a. hormone
b. carbohydrate
c. enzyme
d. lipid
c
The activation of glycogen phosphorylase will lead to a(n) __________ in blood glucose
concentrations and is stimulated by the hormone __________.
a. decrease; insulin
b. decrease; glucagon
c. increase; insulin
d. increase; glucagon
d
The hormone insulin stimulates __________ and inhibits __________, leading to a(n)
__________ in the glucose levels.
a. glycogen synthase; glycogen phosphorylase; decrease
b. glycogen phosphorylase; glycogen synthase; decrease
c. glycogen synthase; glycogen phosphorylase; increase
d. glycogen phosphorylase; glycogen synthase; increase
a
What is the name of the enzyme that removes phosphate groups from the regulated glycogen
metabolism enzymes to reverse their activity?
a. phosphorylase kinase
b. protein phosphatase 1
c. insulin
d. protein kinase A
b
Because muscles lack receptors for glucagon, what hormone activates muscle glycogen
phosphorylase?
a. insulin
b. adrenaline
c. glycogenin
d. UDP-glucose
b
Why is it important that muscle cells are unresponsive to glucagon?
a. Muscle cells store glycogen for its own energy needs and not the needs of other
tissues.
b. The muscles do not store glycogen.
c. The muscles release glucose to other tissues in need.
d. Muscle cells respond to insulin instead.
a
McArdle disease is due to a deficiency in muscle glycogen phosphorylase activity. The result
of this deficiency is an inability to
a. form α(1,4) linkages in glycogen.
b. form glucose-1-phosphate during the breakdown of glycogen.
c. store glycogen.
d. cleave α(1,6) linkages.
b
A patient is found to have a mutated enzyme that results in fewer branch points in glycogen.
Which one of the following would best characterize the way in which the patient's glycogen is
altered relative to normal glycogen?
a. an increase in the proportion of α(1,6) linkages relative to α(1,4) linkages
b. a change in the stereochemical configuration at the reducing end
c. some β(1,4) linkages in place of α(1,4) linkages
d. a decreased ratio of nonreducing to reducing ends
d
Students also viewed