Name: _______________________ Chem 351 Exam 3

1

Multiple Choice: Pick the BEST answer and write it in the box at the end of the section. 1) The TCA (Krebs) Cycle depends on oxygen availability, though it does not directly use it. How can you best explain oxygen’s role?

A) Oxygen activates several dehydrogenation reactions in the cycle. B) Oxygen accepts electrons in the electron transport chain, reoxidizing reduced

cofactors C) Oxygen is necessary for producing water, which is necessary for everything in

living cells. D) Oxygen removes toxic byproducts of the TCA cycle and the electron transport

chain E) Oxygen does none of the above

2) Which of the following is true about β-oxidation of fatty acids?

A) In one round of oxidation, one FADH2 and one NADPH are produced. B) It happens the same way, with the same energy yield, for saturated and unsaturated fatty acids. C) In each round, the fatty acid is oxidized at C-3 (the β-carbon) to remove a two-carbon unit. D) It occurs in the intermembrane space of the mitochondria. E) Lipoprotein lipase catalyzes the first step in oxidation.

3) The carbon atoms from a fatty acid with an odd number of carbons will enter the citric acid cycle as acetyl-CoA and:

A) butyrate. B) citrate. C) malate. D) succinyl-CoA. E) α-ketoglutarate.

4) Glucose labeled with 14C in C-1 is completely converted to pyruvate. What atom will carry the label in pyruvate when the first radioactive pyruvate is formed?

A) the carboxylate carbon. B) the carbonyl carbon (in the middle). C) both A and B. D) the methyl carbon E) none of the carbons

5) The citric acid cycle and the urea cycle overlap. Which of these statements best describes this overlap?

A) Aspartate can be converted to oxaloacetate. B) Aspartate combines with citrulline. C) Fumarate is a citric acid cycle intermediate. D) Fumarate is formed in the urea cycle. E) All of the above are true

Name: _______________________ Chem 351 Exam 3

2

6) Which of the following statements is true about the variation in mitochondria isolated from different tissue?

A) Mitochondria isolated from different tissues have vastly different structures because they perform completely different functions in their cells.

B) Structural differences between mitochondria do relate to cell/tissue energy requirements and can best be seen in the cristae.

C) The most obvious difference between mitochondria isolated from different tissues can be seen in the surface structure of the outer mitochondrial membrane.

D) While the mitochondria coming from different tissues have basically the same structure, their protein and lipid compositions vary widely as a result of tissue requirements.

E) There is no real difference in mitochondria structure, since its function is universal.

7) The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following, except?

A) ATP synthesis. B) catalysis by phosphoglycerate kinase. C) oxidation of NADH to NAD+. D) the formation of 1,3-bisphosphoglycerate. E) utilization of Pi.

8) In humans, all of the pathways that pyruvate can take:

A) are aerobic and require oxygen. B) ultimately reduce NAD+ to NADH. C) lead to the reoxidation of NADH to NAD+. D) yield equal amounts of ATP to the cell. E) lower the pH (increase acidity) of the cell.

9) Which of the following statements about the pentose phosphate pathway is false:

A) The reactions occur in the cytosol. B) It produces sugars for biosynthetic reactions. C) It generate NADH for reductive biosynthesis. D) It occurs in many types of cells. E) None of the above are false.

10) Which of the following has the effect of increasing glycogen breakdown in a cell?

A) increased levels of cAMP B) increased AMP/ATP ratio C) increased blood levels of glucagon D) A and C only E) A, B, C

Name: _______________________ Chem 351 Exam 3

3

11) An enzyme used in both glycolysis and gluconeogenesis is: A) glucose 6-phophatase. B) 3-phosphoglycerate kinase. C) hexokinase. D) phosphofructokinase-1. E) pyruvate kinase.

12) Ketone bodies are formed in the liver and transported to the extrahepatic tissues mainly as:

A) acetoacetyl-CoA. B) acetone. C) β-hydroxybutyric acid. D) β-hydroxybutyryl-CoA. E) lactic acid.

13) In normal mitochondria, the rate of NADH consumption (oxidation) will:

A) be increased in active muscle, decreased in inactive muscle. B) be very low if the ATP synthase is inhibited, but increase when an uncoupler

is added. C) decrease if mitochondrial ADP is depleted. D) decrease when cyanide is used to prevent electron transfer through the

cytochrome a + a3 complex. E) All of the above are true.

14) Which of the following is not true regarding phosphofructokinase-1 (PFK-1)? A) It is inhibited by fructose-2,6-bisphosphate B) It is inhibited by citrate C) It is inhibited by ATP D) It is activated by a high AMP/ATP ratio in the cell E) It is a main regulatory enzyme in the glycolytic pathway.

15) When glutamate is converted to α-ketoglutarate, releasing free NH4

+, the reaction is best described as:

A) Amidation B) Hydrolysis C) Oxidative deamination D) Reductive deamination E) Transamination

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

Name: _______________________ Chem 351 Exam 3

4

1) Short Answer: True or False

Regarding glycogenin:

Glycogenin regulates glycogen synthase activity Glycogenin is covalently bound to the end of a growing glycogen chain

during synthesis. Glycogenin forms branches in glycogen

Regarding glycogen regulation:

Glycogen synthase uses glucose as a substrate. Glycogen phosphorylase is only active in the liver. Glycogen synthase is phosphorylated when it is adding glucose

monomers to the glycogen chain. Glycogen phosphorylase is a substrate for a kinase.

2) Fat Digestion: For each of the following short fats: 1) give the name of the enzyme that

would directly use the fat as its substrate during breakdown, 2) draw the resulting product, and 3) indicate whether anything else forms. (4 points each)

1) A)

2) 3)

B)

1) 2) 3)

C) 1) 2) 3)

CO

SCoA

OH

CO

SCoA

CO

SCoA

Name: _______________________ Chem 351 Exam 3

5

3) The following picture represents the regulation of glycogen phosphorylase in the liver. Please provide the missing information (6 points)

4) For boxes A-E, indicate (using an arrow) the direction of the equilibrium that would be observed under the hormonal influences indicated (5 points)

For each of the liver enzymes/activities listed below, circle whether the glucagon signal will increase, decrease, or have no effect on the level of its activity (kcat).

F) Fructose 2,6-bisphosphatase increase decrease no effect G) UDP-Glucose pyrophosphorylase increase decrease no effect

C)  What  does  this  represent?

A)  What  atom  or  group  is  attached  to  the  CH2  in  Form  II?  

B)  What  atom  or  group  is  attached  to  the  CH2    in  Form  III?

D)  What  is  IN  this  site?

insulin Form  I Form  II Form  III

E)  Which  form  above  is  most  active,  and  what  is  it  called?  

D)

E) C)

B) A)

Name: _______________________ Chem 351 Exam 3

6

5) Energy Calculations! R = 8.3 J/molK T= 298K F (Faraday constant) = 96,500 J/V.mol

Reaction Standard reduction potential (E’˚) (volts)

Fumarate + 2H+ + 2 e- succinate + 0.031 FAD + 2H+ + 2e- FADH2 - 0.219 NAD+ + H+ + 2e- NADH - 0.32 Dihydroxyacetone-phosphate + 2H+ + 2 e- glycerol-3-phosphate - 0.29 A) For the following reaction:

Glycerol-3-phosphate + NAD+ NADH + H+ + dihydroxyacetone phosphate 1) Calculate ΔE’˚ for the reaction. 2) Calculate ΔG’˚ for the reaction.

B) If all of the ingredients listed in the table were mixed together in equal concentrations (with enzymes available to carry electrons), which compound would be reduced? (circle one) NAD+ FAD fumarate dihydroxyacetone-phosphate none of these

Reaction Standard ΔG˚’ (kJ/mol) Fructose-1,6-bisphosphate fructose-6-phosphate + Pi -16.0 ATP ADP -30.5 C) Consider the following reaction:

Fructose-6-phosphate + ATP fructose-1,6-bisphosphate + ADP

1) Using the information in the table above, calculate ΔG˚’ for the reaction: 2) Calculate the Keq for this reaction at 25˚ C (298K). 3) 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.

[fructose-1,6-bisphosphate] = 2 mM Fructose-6-phosphate] = 0.1 mM [ADP] = 2.4 mM [ATP] = 0.02 mM

Name: _______________________ Chem 351 Exam 3

7

6) Transport R = 8.3 J/molK T= 298K F (Faraday constant) = 96,500 J/V.mol

A) Proton-motive force

1) Calculate the proton-motive force across a biological membrane. Vm = 0.190 V, and the difference in pH is 1.43 units.

B) For each of the following transporters, choose the letter that best describes the transport event that occurs, then provide the solute(s) moved by the transporter (1 pt. each)

1) inorganic phosphate translocase during active oxidative phosphorylation activity. Type of transport (circle one): Uniport Antiport Symport Solute(s) moved:

2) carnitine shuttle transporter while fats are being consumed at a high rate. Type of transport (circle one): Uniport Antiport Symport Solute(s) moved:

7) Bypass 1: (2 points each) A) Complete the reaction by providing the curved arrows necessary for this one-step mechanism in which oxaloacetate is converted to phosphoenolpyruvate. B)What enzyme catalyzes this reaction? C) If this reaction is happening in the matrix, what can you say about the NADH/NAD+ ratio in the cytosol of the cell?

Name: _______________________ Chem 351 Exam 3

8

8A) Give the names of the structures indicated with letters and give the substrates and products for each reaction (1, 2) in the electron transport chain shown. Also label the space on the side of the bilayer shown (be specific).

A: B: C:

Reaction 1: Reaction 2: Space a:

B) Which form (i.e. how many electrons is it carrying) of Q is shown?

9) Inhibitors/poisons and other effectors have been used to study the coupling of ATP production and electron transport. For each of the treatments listed below, describe the target of the effector and consider the most likely overall long-term effect on the mitochondria compared to the natural, unaltered rate. Note: all necessary ingredients are present in sufficient levels for the mitochondria to function.

A) Atractyloside treatment. Specific target:

1) O2 consumption (circle one): increases decreases remains the same 2) ATP production (circle one): increases decreases remains the same

B) DNP treatment. Specific target: 1) O2 consumption (circle one): increases decreases remains the same 2) ATP production (circle one): increases decreases remains the same

Reaction 1

Reaction 2

A

B

C

space  a:

Name: _______________________ Chem 351 Exam 3

9

10) Glycogen breakdown and glycolysis Under intense catabolic conditions, a muscle cell is actively working to break down its glycogen and produce ATP as quickly as possible. Analyze the following metabolites that form during this entire process.

A) Provide the letter(s) of the structure(s) that fulfill the descriptions given. If none apply, write “none.” Consider only the catabolic processes that occur in glycogen breakdown and glycolysis. Which of the above:

1) is/are produced in a reaction that also produces NADH? 2) is/are used as a substrate in a reaction that also uses ATP? 3) is/are used as a substrate in a reaction that produces ATP directly? 4) is/are formed sometime during the payoff phase of glycolysis?

B) Name C: C) Name D: D) Name the enzyme that produces C as a product: E) Because the muscle is using ATP as quickly as it is produced, lactic acid is building up in the cells. Provide the entire reaction (draw structures, name enzyme and other cofactors) in which lactic acid is produced from pyruvate (4 points).

O

HOH

OHH

OHH

CH2OPO3-2

CH2OH OH

OH

H

OPO3-2

H

OHH

HO

CH2OH

H

A BD

C

C OH

C

OPO3-2

OOPO3-2

H

C

HH

CH2OH

C O

CH2OPO3-2

Name: _______________________ Chem 351 Exam 3

10

11) Urea Cycle The compounds listed at the right were found in elevated concentrations in the liver cells of mice that were fed large amounts of protein for an extended period of time. After studying the urea cycle in these animals, a few questions were posed.

A) arginine B) citrulline C) ornithine D) argininosuccinate E) aspartate

A) Which of the compounds (A-E) above (write “none” if none apply) (2 pts each):

1) move(s) freely between the cytosol and the mitochondrial matrix during the urea cycle? 2) is/are produced in a urea cycle reaction that utilizes ATP?

B) Name the urea cycle enzyme that uses D as its substrate: C) Name the urea cycle enzyme that uses C as its substrate. D) Draw B (citrulline) (3 points). E) Draw the products that would result when aspartate (E above) and pyruvate undergo a successful transamination reaction (4 points).

Name: _______________________ Chem 351 Exam 3

11

12) Krebs.

The Krebs cycle was examined in cells that were actively respiring. Provide the letter(s) of the structure(s) that fulfill the descriptions given. If none apply, write “none.” A) Which of the above:

1) Is/are produced in the same step that produces a reduced flavin dinucleotide? 2) Is/are produced in the same step that produces CO2? 3) Is/are produced in the same step that reduces a nicotinamide dinucleotide? 4) Is/are produced in a dehydration reaction?

B) At some point, radiolabeled acetyl-CoA was introduced to the system (labeled on both acetyl carbon atoms). Place the intermediates above in order based on when each will incorporate the radiolabel (from first to last). C) Name the enzyme that catalyzes the reaction in which

1) A is used as a substrate?

1) D is used as a substrate? D) Write the entire reaction (draw substrates and products, but you can abbreviate cofactors, etc.) catalyzed by citrate synthase (3 points):

COOCH2CH2COO

B

COO

CHHC

COO

A

COO

H2CC

C COO

COO

H

C DCOO

CH2CH2C

COO

O

Multiple Choice: 30

Page 8 19

Page 4 19

Page 9 18

Page 5 13

Page 10 15

Page 6 12

Page 11 17

Page 7 12

Total: 150 (+5)