Deck 21: Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Question 1

Which enzyme catalyzes bicarbonate "activation" by attachment to the g-phosphate of ATP to form carbonyl phosphate?

A)glucokinase
B)glucose-6-phosphatase
C)PEP carboxykinase
D)pyruvate carboxylase

Answer 1

D

Question 2

Which of the following is absolutely essential for the activation of pyruvate carboxylase?

A)high concentrations of acetyl-CoA
B)high levels of oxaloacetate
C)high levels of TCA cycle intermediates
D)high levels of citrate

Answer 2

A

Question 3

Which of the following enzymes is NOT unique to gluconeogenesis?

A)phosphoglucoisomerase
B)glucose-6-phosphatase
C)fructose-1,6-bisphosphatase
D)PEP carboxykinase

Answer 3

A

Question 4

In the Cori cycle,the liver shares the load of exercising muscle.What is this a result of?

A)high acetate levels
B)high galactose levels
C)a high NAD⁺/NADH ratio
D)a high FAD/FADH ratio

Question 5

The pentose phosphate pathway is an important source of NADPH and for ribose-5-phosphate.Which of the following is NOT made from ribose-5-phosphate?

A)ATP
B)NAD⁺
C)fatty acids
D)CoA

Question 6

What is the endoplasmic reticulum-bound enzyme that hydrolyzes glucose-6-phosphate to glucose in liver?

A)glucose-6-phosphatase
B)glucose oxidase
C)hexokinase
D)phosphoglucomutase

Question 7

How many ATP and GTP combined are required in gluconeogenesis for 2 pyruvate glucose?

A)4
B)5
C)6
D)7

Question 8

Glucose monitoring devices use the reaction,glucose + O₂ + 2 H₂O à gluconate + 2 H₂O₂.Which enzyme catalyzes this reaction?

A)gluconate synthase
B)glucose oxidase
C)peroxidase
D)glucose oxidase

Question 9

What is the primary regulatory point of gluconeogenesis?

A)glucose-6-phosphatase
B)fructose-1,6-bisphosphatase
C)fructose-2,6-bisphosphatase
D)pyruvate carboxylase
E)PEP carboxykinase

Question 10

Which conditions trigger the conversion of pyruvate into OAA for gluconeogenesis?

A)high levels of NADH and ATP
B)high levels of NAD⁺ and acetyl CoA
C)high levels of ATP and acetyl CoA
D)high levels of ATP and NAD⁺

Question 11

What is synthesized in gluconeogenesis?

A)glucose from non-carbohydrate precursors
B)glycogen from glucose
C)pyruvate from glucose
D)fatty acids from glucose

Question 12

Which enzyme of gluconeogenesis is NOT found in the cytosol?

A)PEP carboxykinase
B)pyruvate carboxylase
C)fructose-1,6-bisphosphatase
D)glucose-6-phosphatase

Question 13

Which of these reactions represents the gluconeogenic reversal of PFK-1 in glycolysis?

A)fructose-6-P + ADP fructose + ATP
B)fructose-6-P + H₂O fructose + Pi
C)fructose-1,6-bisphosphate + ADP fructose-6-P + ATP
D)fructose-1,6-bisphosphate + H₂O fructose-6-P + Pi

Question 14

Which of these steps is NOT a component of the pyruvate carboxylase-catalyzed reaction?

A)formation of N-carbonyl biotin
B)attack of H₂CO3 on ATP
C)formation of carbonyl phosphate
D)C-3 carbanion of pyruvate attack on N-carbonyl biotin

Question 15

Which of the following is NOT a substrate for gluconeogenesis?

A)glycerol
B)lactate
C)acetate
D)pyruvate

Question 16

Which 3 enzyme-regulated reactions of glycolysis are replaced by alternative reactions in the gluconeogenic pathway?

A)glucokinase;PFK-1;pyruvate kinase
B)phosphoglucoisomerase;PFK-1;pyruvate kinase
C)PFK-1;triose phosphate isomerase;pyruvate kinase
D)pyruvate carboxylase;PFK-1;glyceraldehyde-3-phosphate dehydrogenase

Question 17

Which of the following is NOT required for pyruvate carboxylase?

A)biotin covalently linked to the enzyme
B)thiamine pyrophosphate (TPP)
C)acetyl-CoA as an allosteric activator
D)tetrameric enzyme in the mitochondria

Question 18

Which major tissues carry out gluconeogenesis?

A)brain and muscles
B)muscles and kidneys
C)liver and kidneys
D)red blood cells and brain

Question 19

Which molecule does pyruvate carboxylase consume in order to drive a carboxylation so that PEP carboxykinase could use the energy from decarboxylation to facilitate formation of PEP?

A)NADH
B)NADPH
C)GTP
D)ATP

Question 20

Glucose-6-phosphatase is located in the endoplasmic reticulum.What does the enzyme produce in vesicles that diffuse to the plasma membrane,releasing their contents into the blood stream?

A)lactate
B)glucose-6-phosphate
C)sucrose
D)glucose

Question 21

Which of the following results can a blood test for "glycated hemoglobin" determine?

A)present blood glucose concentration
B)average glucose concentration in the blood over the past several months
C)level of AGEs in the blood stream
D)blood glucose concentration over the past month

Question 22

Which of the following is NOT a physiological effect of insulin?

A)inhibition of glycogen phosphorylase
B)inducement of synthesis of glucokinase,PFK-1,and pyruvate kinase
C)stimulation of active transport of glucose and amino acids into muscle and adipose tissues
D)stimulation of fructose-1,6-bisphosphatase

Question 23

Which of the following is NOT a characteristic of glucose-6-phosphate dehydrogenase?

A)located in the mitochondria
B)strongly inhibited by [NADPH]
C)inhibited by fatty acid-CoA
D)uses NADP+ as a coenzyme

Question 24

An individual with von Gierke's disease lacks the enzyme glucose-6-phosphatase,which is a liver enzyme used to maintain blood glucose.Which clinical feature is seen in patients with this disease?

A)overweight
B)weakness
C)headache
D)hypoglycemia

Question 25

Insulin in the bloodstream is a response to increased blood glucose.What does insulin do as a result of this?

A)stimulates gluconeogenesis
B)inhibits glycolysis
C)stimulates glycogen synthesis in muscle and liver
D)inhibits phosphoprotein phosphatase-1

Question 26

Which of the following is NOT correct for a-amylase?

A)Its activity is reduced in highly branched regions of polysaccharides and stops 4 residues from any branch point.
B)It is an important component of saliva and pancreatic juice.
C)It catalyzes hydrolysis of ? (1?6)linkages in amylopectin.
D)It catalyzes hydrolysis of ? (1?4)linkages in glycogen.

Question 27

Where is glucose from UDP-glucose transferred to so that the initiation of glycogen synthesis occurs?

A)to the tyrosine-OH group of glycogenin
B)to the 4-position of free glucose
C)to the 2-position of fructose
D)to the serine-OH group of glycogen synthase

Question 28

cAMP-dependent protein kinase phosphorylates and thus inhibits PFK-2.Which enzyme is simultaneously activated as a result of this inhibition?

A)fructokinase
B)glucose-6-phosphatase
C)hexokinase
D)F-2,6-BPase

Question 29

Which of the following is NOT a characteristic of AGEs?

A)AGEs means advanced glycation end products.
B)AGEs generated by elevated blood glucose contribute to circulation,joint,and vision problems of diabetics.
C)AGEs alter the function of the protein to which they are attached.
D)AGEs form by enzyme-catalyzed Schiff base formation between sugars and proteins.

Question 30

Which tandem enzyme controls the cellular levels of fructose-2,6-bisphosphate F-2,6-BP?

A)fructokinase and F-2,6-BPase
B)F-2,6-BPase and PFK-2
C)PFK-1 and F-2,6-BPase
D)PFK-2 and fructokinase

Question 31

The ratio of NADP⁺/NADPH in liver runs about 1/67.What does this mean?

A)Glucose-6-phosphate dehydrogenase activity is dependent upon use of some of the NADPH before activity increases.
B)Glucose-6-phosphate dehydrogenase will be turned on most of the time.
C)Glucose-6-phosphate is rate limiting for the pentose phosphate pathway.
D)Glucose-6-phosphate goes preferentially to the pentose phosphate pathway.

Question 32

Which 2 enzymes must be carefully controlled in glycogen synthesis and degradation in order to properly serve the metabolic needs of the organism?

A)glucokinase and hexokinase
B)hexokinase and glycogen synthase
C)glycogen synthase and glucokinase
D)glycogen phosphorylase and glycogen synthase

Question 33

Which of these effectors is required for glycogen synthase activity when the enzyme is phosphorylated?

A)glucose-1-phosphate
B)glucose-6-phosphate
C)fructose-1,6-bisphosphate
D)fructose-2,6-bisphosphate

Question 34

Epinephrine elicits many physiological changes such as the initiation of the adenylyl cyclase cascade.Which of these actions is NOT seen as a result of this initiation?

A)stimulation of glycogen synthase
B)activation of glycogenolysis in liver
C)stimulation of glycolysis by 2000-fold
D)activation of glycogenolysis in muscles

Question 35

Limit dextrins are degraded by the action of a debranching enzyme that has 2 distinct enzymatic activities.Which enzymatic activities does it carry out?

A)b-amylase;a(1à6)glucosidase
B)oligo(a1,4àa1,4)glucanotransferase;a(1à6)glucosidase
C)a-amylase;a(1à6)glucosidase
D)b-amylase;oligo(a1,4àa1,4)glucanotransferase

Question 36

Which of the following enzyme-catalyzed steps requires energy input for the synthesis of glycogen?

A)phosphoglucomutase
B)UDP-glucose pyrophosphorylase
C)glycogen synthase
D)amylo-(1,41,6)-transglycosylase

Question 37

Which process describes the 6-phosphogluconate dehydrogenase reaction?

A)substrate-level phosphorylation
B)oxidative decarboxylation
C)TPP-assisted decarboxylation
D)phosphate addition

Question 38

Which of the following is NOT a physiological change initiated by glucagon?

A)activation of glycogenolysis in liver
B)stimulation of liver gluconeogenesis
C)long-term maintenance of steady-state levels of glucose in the blood stream
D)activation of glycogenolysis in muscles

Question 39

Which of the following occurs in the muscle as a result of cortisol?

A)activation of gluconeogenesis
B)increased glycogen synthesis
C)activation of the urea cycle
D)increased degradation of muscle protein

Question 40

Which of the following is NOT an enzyme in the enzyme cascade for activation of glycogen phosphorylase?

A)adenylyl cyclase
B)protein kinase A
C)hormone-sensitive lipase
D)phosphorylase kinase

Question 41

What does the enzyme transketolase catalyze?

A)transfers of 3-carbon units from a ketose to an aldose
B)transfer of ketoses into aldoses
C)TPP-dependent transfer of 2-carbon units to the recipient aldose
D)keto-group transfer from C-2 to C-3

Question 42

What class of enzymes does transketolase belong to?

A)oxidoreductases
B)isomerases
C)transferases
D)ligases

Question 43

Which enzyme-catalyzed reaction is analogous to the phosphopentose isomerase reaction and mechanism?

A)UDP-glucose epimerase
B)phosphoglycerate isomerase
C)phosphopentose epimerase
D)phosphoglucoisomerase

Question 44

If NADPH is needed for biosynthetic reactions but ribose-5-P is not needed,which of the following best represents the net reaction of the pentose phosphate pathway?

A)4 fruc-6-P + 2 glyceraldehyde-3-P 6 ribose-5-P
B)3 gluc-6-P + 6 NADP+ 6 NADPH + 3 CO₂ + 2 fruc-6-P + 1 glyceraldehyde-3-P
C)gluc-6-P + 2 NADP+ 2 NADPH + CO₂ + ribose-5-P
D)gluc-6-P + 2 glyceraldehyde-3-P 3 ribose-5-P

Question 45

Which of these reactions is catalyzed by a transketolase in the pentose phosphate pathway?

A)erythrose-4-P + fructose-6-P Û sedoheptulose-7-P + glyceraldehyde-3-P
B)sedoheptulose-7-P + glyceraldehyde-3-P Û erythrose-4-P + fructose-6-P
C)fructose-6-P + glyceraldehyde-3-P Û xylulose-5-P + erythrose-4-P
D)glucose-6-P +2 NADP+ + H₂0 Û ribose-5-P +2 NADPH +2 H⁺

Question 46

Which of the following is NOT a part of the transketolase-catalyzed reaction?

A)formation of Schiff base intermediate of a new ketose
B)b-cleavage of Schiff base intermediate to release a ketose
C)active-site lysine formation of Schiff base with keto-carbonyl group
D)Schiff base hydrated to ketose and enzyme

Question 47

Which of the following CANNOT be used as a substrate for gluconeogenesis in the liver?

A)alanine
B)aspartic acid
C)glycerol
D)succinate

Question 48

Which process occurs when a cell with the pentose phosphate pathway has need for more pentose phosphates,but no additional NADPH?

A)Glucose-6-phosphate dehydrogenase is activated.
B)The oxidative and non-oxidative enzymes of the pentose phosphate pathway are active.
C)The non-oxidative enzymes produce pentose phosphates from fructose-6-phosphate and glyceraldehyde-3-phosphate.
D)All enzymes of glycolysis and pentose phosphate pathway are activated.

Question 49

Which of the following results when glucagon binds to its receptor?

A)Glycolysis is activated.
B)Protein synthesis is activated.
C)Glycogen synthesis is inhibited.
D)The citric acid cycle is inhibited.

Question 50

Which glycolytic enzyme is analogous to the transaldolase-catalyzed activity?

A)aldolase
B)phosphoglucomutase
C)enolase
D)PFK-1

Question 51

The polyol pathway is a suspected pathway for diabetes-induced cataract formation.Which enzyme does it involve?

A)aldose reductase
B)glucose-6-phosphate dehydrogenase
C)phosphopentose isomerase
D)transaldolase