The pentose phosphate pathway occurs in which organelle(s)? Choose one:
A. cytoplasm
B. mitochondria
C. nucleus
D. throughout the cell and cellular compartments
A. cytoplasm
The pentose phosphate pathway is an alternative branch off of glycolysis that produces sugars to make nucleotides. It occurs in the cytoplasm, as does glycolysis.
Which of the following pentose phosphate pathway enzymes produce NADPH? Choose one or more:
A. 6-phosphogluconate dehydrogenase
B. lactonase
C. transaldolase
D. glucose-6-phosphate dehydrogenase
A. 6-phosphogluconate dehydrogenase
D. glucose-6-phosphate dehydrogenase
Reduction of NADP+ to NADPH is part of two reactions found in the pentose phosphate pathway. These are the reactions catalyzed by glucose-6-phosphate dehydrogenase and 6-phosphogluco
Put the following enzymes in the order they appear in the pentose phosphate pathway, starting with glucose-6-P and ending with erythrose-4-P.
Ribulose -5-P Isomerase
Transketolase
Transaldolase
Glucose-6-Phosphate-Dehygrodenase
Glucose-6-Phosphate-Dehygrodenase --> Ribulose -5-P Isomerase --> Transketolase --> Transaldolase
The reaction of which enzyme is part of the oxidative phase of the pentose phosphate pathway? Choose one:
A. ribulose-5-P isomerase
B. transketolase
C. phosphoglucose isomerase
D. glucose-6-phosphate dehydrogenase
E. transaldolase
D. glucose-6-phosphate dehydrogenase
Deficiency of glucose-6-phosphate dehydrogenase would leave cells vulnerable to reactive oxygen species because the production of ______ would be reduced. Choose one:
A. NADH
B. ATP
C. NADPH
D. NAD+
E. NADP+
C. NADPH
Glucose-6-phosphate dehydrogenase catalyzes the oxidation of glucose-6-P to 6-phosphogluconolactone. NADP+ is reduced to NADPH as part of the reaction. The redox active product NADPH is then capable of neutralizing, or oxidizing, reactive oxygen
Given that glucose-6-phosphate is a substrate for both glycolysis and the pentose phosphate pathway, determine which pathway will have the highest metabolic flux of glucose-6-P under the following conditions.
o Low cellular ATP
o Elevated Levels of ADP an
To Glycolysis
o Low cellular ATP
o Elevated Levels of ADP and AMP
To Pentose Phosphate Pathway
o High NADP+ to NADPH ration in the cell
o High levels of ROS in a cell
Correct; the energy demand for ATP overrides glucose-6-P entry into the pentose phosphat
Which of the following is a product of the oxidative phase of the pentose phosphate pathway? Choose one:
A. 6 Ribulose-5-phosphate
B. 6 Glucose-6-phosphate
C. 6 H2O
D. 12 NADP
A. 6 Ribulose-5-phosphate
Which of the following is an effect of high NADPH? Choose one:
A. Glycolysis is reduced.
B. Glucose-6-phosphate enters the pentose phosphate pathway.
C. Glucose-6-phosphate dehydrogenase is inhibited.
D. Glucose-6-phosphate dehydrogenase is activated.
C. Glucose-6-phosphate dehydrogenase is inhibited.
The ratio of NADP+ to NADPH allosterically regulates glucose-6-phosphate dehydrogenase and controls the fate of glucose-6-phosphate. When NADP+ is high, the enzyme is activated and glucose-6-phosphate ent
For animals, identify the major sources of carbon for gluconeogenesis. Choose one or more:
A. acetate
B. ribose
C. amino acids
D. lactate
C. amino acids
D. lactate
In gluconeogenesis, how many molecules of pyruvate are required to synthesize three molecules of glucose?
6 molecules of pyruvate
Sort the following enzymes into those specific to gluconeogenesis and those specific to glycolysis.
o Hexokinase
o Glucose-6-Phosphatase
o Phosphoenolpyruvate Carboxylase
o Fructose-1,6-bisphophaspatase-1
o Pyruvate Carboxylase
o Phosphofructokinase-1
o P
Only Glycolysis
o Hexokinase
o Phosphofructokinase-1
o Pyruvate Kinase
Only Gluconeogenesis
o Glucose-6-Phosphatase
o Phosphoenolpyruvate Carboxylase
o Fructose-1,6-bisphophaspatase-1
o Pyruvate Carboxylase
Which of the following enzymes is shared by gluconeogenesis and glycolysis? Choose one:
A. Phosphoenolpyruvate carboxykinase
B. Pyruvate carboxylase
C. Aldolase
D. Fructose-1,6-bisphosphatase-1
C. Aldolase
Gluconeogenesis uses four enzymes that are not used in glycolysis. These enzymes catalyze bypass reactions, which are catalyzed by essentially irreversible enzymes in glycolysis. The enzymes are pyruvate carboxylase, phosphoenolpyruvate carbox
Which glycolytic enzymes are bypassed and which are utilized by gluconeogenesis?
o Hexokinase
o Phosphofructokinase-1
o GAP dehydrogenase
o Phosphohexose isomerase
o Phosphoglycerate mutase
o Pyruvate Kinase
Bypassed
o Hexokinase
o Phosphofructokinase-1
o Pyruvate Kinase
Utilized
o GAP dehydrogenase
o Phosphohexose isomerase
o Phosphoglycerate mutase
To help separate anabolic and catabolic pathways and prevent futile cycling, enzymes in anabolic pathways have evolved to use _________ as the primary reductant, whereas enzymes in catabolic pathways use NAD+ as the primary _________
o NADPH, Oxidant
Correct; anabolic pathways, those that produce complex molecules, generally utilize NADPH as a reductant.
Correct; for many catabolic processes, NAD+ is the primary oxidant, or oxidizing agent.
The Cori cycle involves the transport of what molecule, produced under anaerobic conditions, from the muscles to the liver? Choose one:
A. valine
B. lactate
C. cholesterol
D. pyruvate
E. ATP
B. lactate
Correct; lactate is produced from pyruvate to regenerate NAD+. Lactate is then transported to the liver as part of the Cori cycle for utilization in gluconeogenesis.
In humans, to maintain flux through the glyceraldehyde-3-phosphate dehydrogenase reaction in the gluconeogenic pathway, NADH
A. exosome to the cytosol
B. cytosol to the extracellular space.
C. mitochondrial matrix to the cytosol.
D. cytosol to the mitocho
C. mitochondrial matrix to the cytosol.
Correct; NADH must be moved from the matrix to the cytosol since the mitochondria are still producing NADH. Glycolysis, a primary source of NADH in the cytosol, does not function when gluconeogenesis is active.
Molecules of NADH are not moved across the mitochondrial membrane. Instead, __________ is the molecule transported to move reducing equivalents of NADH out of the mitochondrial matrix. Choose one:
A. oxaloacetate
B. malate
C. FADH2
D. glyceraldehyde-3-pho
B. malate
Correct; malate is transported out of the mitochondria where, in the cytosol, it is converted to oxaloacetate, producing NAD+
For lactate transported to the liver, which of the following conversions reduces NAD+ to form the NADH required for generation of glyceraldehyde-3-phosphate by GAP dehydrogenase? Choose one:
A. lactate to pyruvate
B. DHAP to GAP
C. pyruvate to oxaloacetat
A. lactate to pyruvate
Correct; conversion of lactate to pyruvate is coupled to conversion of NAD+ to NADH by the enzyme lactate dehydrogenase.
If energy levels in the cell are low, the level of AMP is _______ compared to normal when energy is abundant. Thus, it makes sense that AMP regulates FBPase-1 since gluconeogenesis is _________ when a cell is in need of energy. Complementing effects on gl
o elevated, downregulated, activator
Correct; if ATP levels are low, consumed by energy demands, then AMP levels increase. Thus, the level of AMP is elevated compared to normal when energy is abundant.
Correct; if energy levels in the cell are low, glycol
What is the regulatory means by which hexokinase and glucose-6-phosphatase are kept from forming a futile cycle? Choose one:
A. transcriptional regulation
B. separation into different cellular compartments
C. allosteric inhibition
D. phosphorylation of ac
B. separation into different cellular compartments
Correct; keeping hexokinase (cytoplasm) and glucose-6-phosphatase activity (ER lumen) spatially separated prevents a futile cycle.
High levels of fructose-2,6-BP reciprocally regulate glycolysis and gluconeogenesis. Fructose-2,6-BP_____ flux through the glycolytic pathway by increasing the activity of _______. Flux through the gluconeogenic pathway is inhibited by fructose-2,6-BP, wh
o stimulates, phosphofructokinase-1, fructose-1,6-bisphosphatase-1
o Correct; high levels of fructose-2,6-BP signal an abundance of glucose. Elevated levels stimulate glycolysis.
o Correct; fructose-2,6-BP activates phosphofructokinase-1, the enzyme that
Which of the following activates FBPase-1? Choose one:
A. AMP
B. Fructose-2,6-BP
C. Citrate
D. ATP
C. Citrate
The conversion between fructose-6-phosphate and fructose-1,6-bisphosphate is important for glycolysis and gluconeogenesis. Thus, the enzymes that catalyze these conversions are highly regulated in opposite manners. The glycolysis enzyme, PFK-1,
Which of the following is correct concerning the Cori cycle? Choose one:
A. Glycolysis occurs in liver while gluconeogenesis is occurring in muscles.
B. Pyruvate is converted to glucose in muscle.
C. Glycolysis is occurring under anaerobic conditions.
D.
C. Glycolysis is occurring under anaerobic conditions.
The Cori cycle represents a division of labor between two tissues, where actively working muscle is performing glycolysis under anaerobic conditions and producing lactate that is transported by the bl
What is the cofactor that functions as an acid-base catalyst that donates a proton to inorganic phosphate as part of the glycogen phosphorylase reaction? Choose one:
A. thiamine pyrophosphate
B. flavin adenine dinucleotide
C. pyridoxal phosphate
D. pyroph
C. pyridoxal phosphate
Correct; pyridoxal phosphate adds additional function beyond that found in amino acids. In glycogen phosphorylase, it is essential for catalyzing the removal of glucose-1-P from the nonreducing ends of glycogen.
Given that ?G�� for the glycogen phosphorylase reaction is +3.1 kJ/mol, what factors in the cell make the actual free energy change (??G) favorable?Choose one:
A. Pi being much greater than glucose-1-P
B. highly reducing environment of the cytoplasm
C. hi
A. Pi being much greater than glucose-1-P
Correct; by having a high concentration of a reactant in the cell, Pi, the reaction is driven forward (and the subsequent change in free energy is reduced from nonstandard conditions).
For glycogen synthesis, glucose is activated by what molecule being attached at the C-1 position? Choose one:
A. ATP
B. uridine
C. UDP
D. pyrophosphate
C. UDP
Correct; UDP is added to activate glucose in the process of glycogen synthesis.
Which form of glucose is required by UDP-glucose pyrophosphorylase?Choose one:
A. glucose
B. glucose-1-P
C. glucose-6-P
D. glucose-2,6-BP
B. glucose-1-P
Correct; UMP is added to the phosphate of glucose-1-P to form UDP-glucose.
Glucose is added to which end of a growing glycogen chain? Choose one:
A. neither reducing nor nonreducing ends
B. nonreducing ends
C. both nonreducing and reducing ends
D. reducing end
B. nonreducing ends
Correct; in a growing glycogen chain, glucose is added to the nonreducing end, or C-4 of the last attached glucose. The reducing end of the glycogen chain is at the center of the glycogen granule, protected from further reactions.
Sort the following into activators or inhibitors of glycogen synthase.
Insulin
Glucagon
Protein phosphatase 1
Protein Kinase A (PKA)
Glycogen synthase kinase 3
Epinephrine
Activators
1. Insulin
2. Protein phosphatase 1
Inhibitors
1. Glucagon
2. Protein Kinase A (PKA)
3. Glycogen synthase kinase 3
4. Epinephrine
oCorrect; whenever energy consumption is elevated, glycogen synthase is inhibited.
Sort the following enzymes according to those required for glycogen synthesis and those required for glycogen breakdown.
Glycogen Debranching Enzyme
Glycogen Synthase
Glycogen Phosphorylase
Glycogen Branching Enzyme
UDP-glucose pyrophosphorylase
Glycogen Synthase
1. Glycogen synthase
2. Glycogen Branching Enzyme
3. UDP-glucose pyrophosphorylase
Glycogen Breakdown
1. Glycogen Phosphorylase
2. Glycogen Debranching Enzyme
o Correct; glycogen synthesis involves three enzymes that: (1) prepare or prim
What symptoms would be observed in the following diseases?
Von Glerke Disease
Cori Disease
Anderson Disease
McArdle Disease
Von Glerke Disease: build up of glycogen in liver due to G-6-P accumulation and activation of glycogen synthase
Cori Disease: Glycogen containing short outer chains in the glycogen particle that cannot be removed
Anderson Disease: Synthesis of large, unbr
Glycogen __________ uses UDP-glucose as a substrate. Choose one:
A. branching enzyme
B. synthase
C. phosphorylase
D. debranching enzyme
B. synthase
o Glycogen, the storage form of glucose in animals, is degraded by a combination of debranching enzyme (to release branches) and glycogen phosphorylase, which removes one glucose unit at a time from the nonreducing end of glycogen. Glycogen is
Starting from a molecule of glucose imported from the blood, what is the energy cost for adding that molecule of glucose to a growing glycogen chain? Choose one:
A. 1 ATP
B. 1 ATP, 1 UTP
C. 1 UTP
D. 2 ATP
D. 2 ATP
When glucose first enters the cell, it is phosphorylated by hexokinase, at the expense of one ATP molecule. Ultimately, it is attached to UDP to form UDP-glucose, the substrate for glycogen synthase. A second molecule of ATP is used to regenerate
Which of the following is FALSE concerning glycogen degradation? Choose one:
A. Glycogen phosphorylase produces glucose-1-P.
B. Debranching enzyme cleaves ?-1,6 bonds to release glucose.
C. Glycogen phosphorylase cleaves fewer than four residues from a br
C. Glycogen phosphorylase cleaves fewer than four residues from a branch point.
Glycogen phosphorylase cleaves glucose units one at a time from the non-reducing end and releases glucose-1-P. It cannot cleave fewer than four residues from a branch point, s
Which of the following describes the role of glycogenin in glycogen synthesis? Choose one:
A. Glycogenin catalyzes the formation of ?-1,6 glycosidic bonds.
B. Glycogenin anchors the growing glycogen chain.
C. Glycogenin adds the first three glucose units
B. Glycogenin anchors the growing glycogen chain.
Glycogenin plays two roles in glycogen synthesis. It serves as an anchor protein and then catalyzes glycosyltransferase and synthase activity using UDP-glucose to generate the first seven glucose unit chai
Which of the following is correct concerning the regulation of glycogen metabolism by hormones? Choose one:
A. Insulin activates protein kinase A, which inactivates glycogen synthase.
B. Glycogen phosphorylase is active when phosphorylated, which occurs i
D. Glucagon activates protein kinase A, which inactivates glycogen synthase.
Glucagon and epinephrine have a similar effect in that both signal low blood glucose levels and stimulate glycogen degradation and glucose release. This requires activation of gl
How does glycogen metabolism regulation differ between liver cells and muscle cells? Choose one:
A. Glucose is not exported from muscle cells because it remains as glucose-6-P.
B. Muscle cells are not sensitive to insulin.
C. The active state of glycogen
A. Glucose is not exported from muscle cells because it remains as glucose-6-P.
o Liver and muscle cells have the same general pattern of regulation by glucagon and insulin. The activation via phosphorylation or dephosphorylation for glycogen phosphorylas
Which of the following is the correct net reaction for the complete oxidation of palmitate? Choose one:
A. Palmitate + 7 NAD+ + 7 FAD + 8 CoA + 7 H2O + 7 ATP ? 8 Acetyl-CoA + 7 NADH + 7 FADH2 + 7 AMP + 14 Pi + 14 H+
B. Palmitate + 7 NAD+ + 7 FAD + 8 CoA +
B. Palmitate + 7 NAD+ + 7 FAD + 8 CoA + 7 H2O + ATP ? 8 Acetyl-CoA + 7 NADH + 7 FADH2 + AMP + 2 Pi + 7 H+
o Correct; palmitate goes through seven rounds of ? oxidation to produce 8 acetyl-CoA. In each round, FAD and NAD+ are reduced to FADH2 and NADH, res