Name: _______________________ Chem 351 Exam 3

1

Multiple Choice – For Problems 1-15, pick the BEST answer. Write the letter corresponding to your choice in the box. *1) Which of the following is a correct match of enzyme with its direct substrate/product (you may assume the reaction can run in either direction)?

A) Enolase: pyruvate. B) Pyruvate carboxylase: phosphoenolpyruvate. C) Argininosuccinate lyase (aka argininosuccinase): fumarate. D) Glycogen phosphorylase: glucose. E) Lactonase: glucose-6-phosphate. F) More than one of the above is correct. G) None of the above is correct.

*2) The molecule shown at the right plays a key role in fatty acid metabolism. What is its primary role/function?

A) It primarily serves to carry fats through the bloodstream. B) It is a shared intermediate that links β-oxidation with the urea cycle. C) It allosterically activates enzymes like CAT-I and CAT-II. D) It is attached to fatty acids that are destined to enter the mitochondrial matrix. E) None of the above.

*3) Glycogen production is a fairly straightforward process in which

A) glycogenin catalyzes the necessary branch point linkages for optimal glycogen storage. B) activated sugar residues are added to the reducing ends of a growing polymer. C) initiation of a glycogen granule begins with a glucosylated tyrosine residue. D) UDP-sugar phosphorylase produces glucose-1-diphosphate activated sugars. E) liver glycogen synthase activity is stimulated by phosphoprotein phosphatase (PP1). F) More than one of the above is true. G) None of the above is true.

F (c and e) *4) Which of the following statements about oxidative phosphorylation is false?

A) Reduction of various electron carriers during metabolic chemical events leads ultimately to phosphorylation of ADP.

B) Changes in pH are a direct result of the oxidative phosphorylation reactions. C) Oxidation of ATP is coupled to the phosphorylation of various organic substrates in this

process. D) F1-Fo-ATPase activity runs in reverse as a result of electron flow. E) None of the above is false.

*5) Which of the following protein transporters plays a key role in shuttling reducing equivalents in/out of the mitochondrial matrix?

A) Malate/aspartate antiporter B) NADH/NAD+ exchanger C) Glycerol-3-phosphate/glycerol antiporter D) Adenine nucleotide translocase E) none of the above

D

E

C

OHO-

ON+

F

C

Name: _______________________ Chem 351 Exam 3

2

*6) The oxidative branch of the pentose phosphate pathway

A) utilizes oxidative decarboxylation as a means of producing pentoses. B) involves the phosphorylation and activation of pentose sugars. C) is a feeder pathway for pentoses entering the glycolytic pathway. D) is essential in the regeneration of oxidized nicotinamide cofactor(s). E) None of the above.

*7) Which of the following statements regarding the coordination of liver activity with muscle activity is true?

A) Glutamate is the major carrier of ammonia from the muscle to the liver. B) An epinephrine/glucagon signal cascade has a very different effect on glycolysis in muscle vs.

liver. C) Lactic acid is shipped to the muscle from the liver to provide carbon skeletons for quick energy

needs. D) Transamination can only occur in the liver or in the muscle when nitrogen is being carried. E) None of the above is true.

*8) Reversing the phosphoenolpyruvate à pyruvate reaction when shifting from glycolysis to gluconeogenesis

A) always leads to the production of PEP within the mitochondrial matrix. B) requires the net use of carbon dioxide that is only replaced by TCA cycle byproducts. C) is not impacted at all by lactic acid buildup. D) requires PEP carboxykinase activities in both the cytosol and mitochondrial matrix. E) None of the above is accurate.

*9) Which of the following statements about the coordinated regulation of hexokinase and glucose-6-phosphatase is false?

A) Hexokinase enzymes within liver cells are likely to be contained within the nucleus when blood glucose is low.

B) Glucose-6-phosphatase is a membrane bound protein, and compartmentalization always plays a role in its regulation.

C) Insulin signals are likely to enhance the activity of hexokinase. D) Phosphate is removed from glucose-6-phosphate in the lumen of the endoplasmic reticulum. E) Hexokinase is located only in supplier tissues so that release of glucose into the blood can be

controlled. F) More than one of the above is false. G) None of the above is false.

*10) Glucose labeled with 14C in C-6 is completely converted to acetyl-CoA. What atom will carry the label in acetyl-CoA, and how much of the acetyl-CoA will be labeled?

A) the carbonyl carbon; 50% labeled. B) the carbonyl carbon; 100% labeled. C) the methyl carbon; 50% labeled. D) the methyl carbon; 100% lableled. E) none of the carbons are labeled

E

D

B

C

A

Name: _______________________ Chem 351 Exam 3

3

*10) Which of the following reversible reactions would be favored in the direction shown after the start of an epinephrine signal cascade?

A) ATP + creatine à creatine-phosphate + ADP B) Glycogenn + Pi à Glucose-1-phosphate + glycogenn-1 C) Glyceraldehyde-3-phosphate à dihydroxyacetone phosphate D) Pyruvate + NADH + H+ à lactate + NAD+ E) More than one of the above F) None of the above E (B and D )

*11) Which of the following statements accurately describes the mitochondrial cytochrome P450 proteins?

A) P450 refers to the phosphorylation of these proteins during their activity. B) These proteins catalyze the reduction of oxidized glutathiones. C) They are simply binding proteins, holding oxygen for use in the mitochondria. D) These proteins are particularly important in the hydroxylation of steroids. E) None of the above is true.

*12) Which of the following statements about the regulation of gluconeogenesis is true? A) FBPase-2 activity is enhanced under insulin control. B) Pyruvate kinase is phosphorylated and active under a glucagon signal. C) Fructose-1,6-bisphosphate inhibits pyruvate kinase activity. D) Fructose-1,6-bisphosphate allosterically inhibits FBPase-2. E) More than one of the above is true F) None of the above is true.

*14) What of the following statements about the connections that exist between various catabolic and anabolic processes is false?

A) The Cori Cycle connects sugar production in the liver with sugar breakdown in the muscle. B) Citrate is an intermediate in the TCA cycle that inhibits glycolysis. C) The pyruvate dehydrogenase complex catalyzes several reactions that connect glycolysis

with gluconeogenesis. D) The Urea Cycle and the TCA cycle are connected by the carbon skeletons of aspartate and

α-ketoglutarate . E) All of the above are false. F) None of the above is false.

15) Which of the following is a proper match of an enzyme with a natural inhibitor?

A) Citrate synthase/ADP B) CAT-I/Malonyl-CoA C) Pyruvate carboxylase/Acetyl-CoA D) Phosphoprotein phosphatase-1/Glucose E) None of the above.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

C

D F C E A B D E C E D F C B

E

D

B

C

F

Name: _______________________ Chem 351 Exam 3

4

Short Answer *1) The following picture depicts the regulation/production of ketone bodies. Please identify enzymes (1 and 2), draw in the missing ketone body chemical structures, and answer the question. (9 points)

Enzyme 1) HMG-CoA lyase Enzyme 2) b-hydroxybutyrate dehydrogenase E) Of the compounds shown (A-D), which is considered the main storage form of ketone bodies in

the liver? A *2) Complete each reaction in the b-oxidation process required to digest each fat. Fill in the missing product(s) or substrate(s) and name the enzyme and other cofactors required next to the reaction number.

1) acyl-CoA dehydrogenase; FAD is required (à FADH2, but that is not necessary)

2) enoyl-CoA hydratase; water is needed

1) D3-D2-enoylCoA isomerase NOTE ABOVE CoASH was given in exam: no points for that

O

SCoA

HOO

O

O

SCoA

+OO

O acetoacetate decarboxylase

O

OHO

O1 2

A

B

C

D

O

SCoA

O

SCoA

O

SCoA

HO

1 2

A

OSCoA

O

SCoAO

SCoA

O thiolase

1

O

SCoA

B

SHCoA

Name: _______________________ Chem 351 Exam 3

5

3) Fats again True/False (1 point each) a) Succinyl-CoA can be a final product in the complete oxidation of fatty acids. T

b) Fats absorbed in the intestinal tract are mainly shipped via the bloodstream as free fats. F

c) WAT cells contain fat droplets of low SA/Vol ratio compared to other adipocytes. T

d) CAT I is a transporter that facilitates passive, non-electrogenic, antiport activity. T

e) An insulin hormonal signal stimulates fatty acid breakdown in the cell. F

4) and again: This picture depicts the regulation of some metabolic process. Please identify proteins (A-C) and answer the other questions (6 points)

A: Perilipin

B: Hormone-sensitive lipase

C: Albumin 1) Name the second messenger most

directly responsible for this cascade: cAMP

2) Name the cell: adipocyte

3) What is depicted by the circles identified as 1? Phosphorylation as a regulation

5) Energy Calculations!

Reaction E’˚ (volts) Dehydroascorbic acid + 2e- à ascorbic acid + 0.06 Glutathione(ox) + 2e- à glutathione(red) - 0.23 For the following reaction: glutathione(red) + dehydroascorbic acid à glutathione(ox) + ascorbic acid

1) Calculate ΔE’˚, ΔG’˚ and Keq for the reaction (3 pts). ΔE’˚=.29 V ΔG’˚= -2 (96.5) (.29) = - 55.97 kJ -55.97 = -8.3(298) ln Keq

Keq = e22 6.7x109 HIGH FAVORABILITY 2) If the actual concentrations of the substrates and products inside a compartment were maintained as follows, how would this affect the ΔGrxn? Calculate Q in your answer. (3 pts)

[Glutathione(ox)] = 2 x 10-3M [Dehydroascorbic acid] = 2 x 10-9 M [glutathione(red)] = 4 x10-8 M [ascorbic acid] = mM = 3 x 10-3 M

Q = 7.5x1010 - Higher than Keq - so reaction is always shifted left toward Keq˚ - it is a less favorable reaction under cellular conditions (depends on 1 above) 3 a) Circle the better oxidizing agent: glutathione(ox) dehydroascorbic acid

b) Which is more likely to be oxidized? glutathione(red) ascorbic acid

R = 8.3 J/molK T = 298K F =96,500 J/Vmol

B

C

A

1

Name: _______________________ Chem 351 Exam 3

6

6) This picture shows a section of the inner mitochondrial membrane containing some of the machinery for the electron transport chain. (11 pts)

Name the proteins: A) Protein 1: Succinate Dehydrogenase (or II for .5 pt)

B) Protein 2: Cytochrome C oxidase (or IV)

C) Draw directly in the figure (showing position clearly/describing it clearly): N and P sides

Ubiquinone (Q)

Cytochrome C

F1-F0 (label each protein subunit carefully)

D) Write Reaction A (initial reaction delivering electrons):

NADH + H+ à NAD+ + 2 e-

E) What is the solute indicated by B? H+

F) Write Reaction C (terminal reaction delivering electrons to final acceptor):

4H+ + O2 à 2H2O (balance)

G) Write the reaction catalyzed by F1-F0: ADP + Pi à ATP

H) Considering only the contribution of the proton as far as concentration and electrical differences

(i.e. pmf), what is the ΔG of proton transport when the membrane potential is 54 mV and the difference in pH is 0.29 units. (2pts)

G=2.3X2.48(0.29) + 1F(.054) = 1.65 + 5.21 = 6.86 kJ (sign does not matter, watch for rounding)

Note that the chemical and electrical have to be going in the same direction

1 2

Reaction A B Reaction C

F1 F0 N side

P side Q (in membrane)

Cyt C outside inner membrane

Name: _______________________ Chem 351 Exam 3

7

7) The following figures represent the activity of intact mitochondria exposed to all reactants and ingredients required for oxidative phosphorylation. After establishing an equilibrium rate of O2 consumption and ATP production, various disruptors were added to the system (the event is indicated by the arrow). For each of the compounds listed below, pick the results you would expect to see; if none of the graphs apply, state “none” and give a reason.

A) Sodium amytal: A

B) Atractyloside: B

C) Dinitrophenol: C

D) Cyanide: A

8) Oxidative phosphorylation True/False (1 point each)

a) The adenine nucleotide exchanger helps to create the chemiosmotic gradient that drives ATP production. F

b) The malate-aspartate shuttle system requires the 1:1 exchange of glutamate and aspartate. T

c) Glycerol-3-phosphate dehydrogenase activity reduces Q and oxidizes FADH2 in the matrix. F

*10) You might remember the protonated Schiff product from your first exam. After cyanogen bromide treatment leads to this product, a typical “reverse Schiff” hydrolysis occurs. This process can be shown mechanistically using curved arrows, water, and a general HB/:B- pair. Generally, it is accomplished in two mechanistic steps, with neutral final products forming. Show the steps, and show the product(s). (12 points total)

HN

C CH2C

HN

OCH2

H

C

H

R

C

O

R

R

H B

B

H OH

Product from cyanogen bromide treatment of polypeptide in exam 1

time

Rat

e A

TP p

rodu

ctio

n

Rat

e of

con

sum

ptio

n of

O2

A

time

Rat

e A

TP p

rodu

ctio

n

Rat

e of

con

sum

ptio

n of

O2

B

time

Rat

e A

TP p

rodu

ctio

n

Rat

e of

con

sum

ptio

n of

O2

C

HN

C CH2C

HN

OCH2

H

C

H

R

C

O

R

RH B

B

H OH

HN

C CH2C

HN

OCH2

H

C

H

R

C

O

R

R O

H

H B

B

H B

HN

C CH2C

H2NOCH2

HC

H

R

C

O

R

R

O

Name: _______________________ Chem 351 Exam 3

8

*10) Krebs Complete the following reactions (all occurring in rapidly catabolizing muscle cells). Provide all missing substrate(s), product(s), important cofactor(s), and the names of enzyme(s). (3 points each)

E) Meanwhile, over in the liver, a different reaction yields a familiar Krebs intermediate; complete the reaction by drawing in missing substrate(s) and listing other essential cofactor(s).

a) The pyruvate carboxylase reaction is part of the third bypass in gluconeogenesis. F

b) [Creatine-phosphate] is likely to be high in the muscles under these conditions. F

c) A glucagon hormonal signal would be consistent with reaction E above. T

d) Glycogen phosphorylase is likely to be highly activated in both liver and muscle. T

O

O

O O O

O

O

O

O OO

OOH

H2O forms as wellaconitase

O

OO

OO

OO

O

succinate dehydrogenaseFADH2 formed also

O

O

O

OOisocitrate dehydrogenase

produces CO2 as wellOH

O

O

O OO

O

A)

B)

C)

D)

OH

O

OO

O

malate dehydrogenase O

O

OO

O

NADH forms too

O

O

O

O

O

OO

O

pyruvate carboxylaseO

OHO

+ ATP + biotin

Name: _______________________ Chem 351 Exam 3

9

*11) Urea Cycle

The following metabolites play some role in the functioning of the Urea Cycle. Answer the questions below; provide letters for corresponding intermediate(s) when needed or, if none of the compounds apply, write NONE.

A) Name the enzyme that catalyzes the production of (1 pt):

1) C: arginase (1) 2) F: ornithine transcarbamoylase (1)

B) Which of the compounds shown above (A-E in the illustration above) (1 pt)

1) is/are directly broken down or fomed in the Urea Cycle? BCDEF (1)

2) is/are formed as product(s) in a reaction that also uses ATP? D (1)

3) is/are common amino acid(s)? B E (1)

C) Name the compound, and briefly describe its role(s) in the urea cycle: 1) A: N-acetylglutamate, allosteric activator of CPSI (2)

2) B: arginine, allosteric activator of N-acetylGlu production(A) and direct carrier of urea (2)

3) E: aspartate: N carrier transport from Mito to cytosol, substrate of argininosuccinate

synthetase reaction (2)

D)

1) Write the reaction that is most favorably occurring when the compounds listed in the table above are mixed; give the name of the enzyme that catalyzes this reaction in liver cells:

α-ketoglutarate + NH4+ + NADPH à Glutamate + NADP+ + H+

Glutamate dehydrogenase (3 pts) 2) Calculate ΔE’˚ for the reaction (2 pts). (.32+-.14) = 0.18V 3) Calculate ΔG’˚ and Keq for the reaction (2 pts). -2 (96.5) (.18) = -34.74kJ (using the E from above - dependent on 1) =-RTlnKeq 34.74/RT = lnKeq Keq = e^14 or 2.3x10^6 highly favorable

NH3NH

NH2

H2N

O

ONH3

H3N

O

O

NH3NH

O

H2N

O

OP

O

OO

OH2N

O

NH3O

OO

O

A B C

DE F

NH O

OOOO

Reaction (E’˚) (volts) NADP+ + H+ + 2e- à NADPH - 0.320 α-ketoglutarate + 2e- + NH4

+à glutamate - 0.14

R = 8.3 J/molK T = 298K F =96,500 J/Vmol

Name: _______________________ Chem 351 Exam 3

10

*12) Glycolysis - assume only catabolic events are occurring in muscle cells that are only importing free glucose from the bloodstream (do not worry about stereochemistry).

Provide the letter(s) of the structure(s) that fulfill the descriptions given. If none apply, write “none.” (2 points each) A) Which of the above:

1) Is/are substrate(s) in the same step(s) in which NAD+is reduced? C

2) Is/are substrate(s) in reaction(s) that require hydrolysis of ATP? E (C uses Pi)

3) Is/are substrate(s) in reaction(s) that release CO2? None

4) Is/are substrate(s) in reaction(s) that produce ATP? A

5) Is/are also substrate(s) in the oxidative branch of the pentose phosphate pathway? B

B) Name the enzyme that catalyzes the reaction in which 1) A is used as a substrate: Pyruvate kinase (1)

2) B is formed as a product: hexokinase (1)

3) D is used as a substrate: enolase (1)

C) If the glucose being imported into these cells carried a radiolabel, in what order would the label appear in these intermediates? (simply give the order in which these metabolites are formed). BECDA (2) D) Pyruvate is quickly turned into lactic acid in these cells; draw lactic acid and suggest a reason for this reaction’s favorability.

need to regenerate NAD+ so glycolysis can continue, they are in user mode so

they have used up all they have (2 pts)

MC /30 Page 5 /19 Page 7 /19

Page 9 /18 (155 possible)

Page 4 /20 Page 6 /13 Page 8 /19

Page 10 /17 Total /150

PO

OO O

O

OOH

OH

OH

OHO P

O

OOO

OH

OP

O

OO

O

PO

OO O

O

O

OH

OOH

OHHO

OH

OP

O

OO

A B C

ED

OH

O

O