Biochem Test 4 Sample Questions Flashcards


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1

Which of the following regarding glycogen phosphorylase activity is true?

Phosphorylase yields glucose-1-phosphate

2

Which of the following regarding glycogen is not true?

Glycogen contains B-1,6 branch points
True:
Glycogen contains a-1,4 linkages of glucose units
Glycogen is found in the cytoplasm of liver cells
Glycogen is found in the cytoplasm of muscle cells

3

When glycogen synthase adds glucose units onto a glycogen granule, what molecule serves as the substrate and direct source of the glucose unit?

UDP-Glucose

4

Glycogen granules are limited in size to approximately 40 nm because:

Glycogen synthase is only active when bound to glycogenin

5

How does caffeine affect how epinephrine regulates both glycogen synthesis and glycogen breakdown.

Caffeine inhibits phosphodiesterase which breaks down cAMP. This keeps cAMP levels high and keeps PKA active.

6

The main function of the pentose phosphate pathway is to:

provide pentoses and NADPH

7

In a tissue that metabolizes glucose using the pentose phosphate pathway, C-1 (carbon #1) of glucose would end up primarily in:

carbon dioxide

8

Which of the following is not required for the formation of Acetyl CoA using pyruvate?

ATP

What is required:
NAD+
Lipoamide
Coenzyme A
FAD

9

They pyruvate dehydrogenase complex consists of multiple copies of three different proteis, E1, E2, and E3. For each, identify a coenzyme which is not free to dissociate from the protein and match each with one activity listed at right.

E1: Coenzyme- TPP Activity- decarboxylation of pyruvate
E2: Coenzyme- lipoamide Activity- formation of Acetyl CoA
E3: Coenzyme- FAD Activity- reduction of NAD+

10

Identify and name an enzyme in the citric acid cycle that is both positively and negatively regulated. Name one activator and one inhibitor of this enzyme.

Enzyme- IDH
Activator- NAD+, ADP
Inhibitor- ATP

11

Oxaloacetate uniformly labeled with 14C (i.e. equal amounts of 14C in each of its carbon atoms) is condensed with unlabeled Acetyl CoA. After a single pass through the citric acid cycle back to oxaloacetate, which fraction of the original radioactivity will be found in the oxaloacetate?

1/2

12

The standard reduction potentials for the following half reactions are given:
fumurate + 2H + 2e = succinate Eo = +.031 V
FAD + 2H + 2e = FADH2 Eo = -.219 V
If you mixed succinate, fumurate, FAD, and FADH2 together, each at 1 M concentration and in the presence of succinate dehydrogenase, which of the following would initially occur?

Fumurate would become reduced, FADH2 would become oxidized

13

Most of the molecular oxygen (O2) that you consume by breathing is converted to:

H20

14

In an animal cell, electron transport occurs primarily:

At the mitochondrial inner membrane

15

For each of the following complexes found in the Electron Transport System (ETS) provide the name of the electron donor, electron acceptor, and the number of protons pumped across the membrane for every 2 electrons that pass through each complex. Indicate the oxidation state of the e- donor and e- acceptor. Note that the complexes are not necessarily in order.

Complex #4
Initial e- Donor = Cyt(c(red))
Final e- Acceptor = O2
# of H pumped/2e- = 2H+/2e-

Complex #3
Iniitial e- Donor = QH2
Final e- Acceptor = Cyt(c(ox))
# of H+ pumped/2e- = 4H+/2e-

Complex #2
Initial e- Donor = succinate (FADH2)
Final e- Acceptor= Q
# of H+ pumped/2e- = None

Complex #1
Initial e- Donor = NADH
Final e- Acceptor = Q
# of H+ pumped/2e- = 4H+/2e-

16

In a cell that only metabolizes glucose using both the oxidative and nonoxidative branches of the pentose phosphate pathway, the C-1 (carbon #1) of the glucose would end up primarily in:

CO2

17

Two glucose molecules pass through the oxidative branch of the pentose phosphate pathway. Identify how many of the following are generated by this process.

0 ATP
0 GTP
0 NADH
2x2= 4 NADPH

18

The glycogen-branching enzyme catalyzes:

degradation of (a1-4) linkages during glycogen synthesis
formation of (a1-6) linkages during glycogen synthesis

19

Which of the following molecules is a substrate for the enzyme glycogen synthase?

UDP-glucose

20

Which of the following limits the size of glycogen particles in the liver?

The association of glycogen synthase with glycogenin

21

An increase in cellular (cAMP) in the liver would:

inactivate glycogen synthase and activate phsophorylase

22

Which of the following molecules is not required for the PDH-catalyzed oxidative decarboxylation of pyruvate to form Acetyl CoA?

ATP
Required:
CoA-SH
FAD
Lipoic acid (lipoamide)
NAD+

23

One of the coenzymes involved in the PDH reactions is not listed in the above problem. Which coenzyme is missing?

TPP, Thiamine Pyrophosphate

24

Identify the chronological order in which these 5 coenzymes participate in the PDH-catalyzed conversion of pyruvate to Acetyl CoA

1st. TPP
2nd. Lipoic Acid
3rd. CoA
4th. FAD
5th. NAD+

25

The methyl carbon of Acetyl CoA is labeled with 14C as it enters the citric acid cylce. After one complete pass of the cylce (back to oxaloacetate), what percentage of the original 14C is lost as CO2?

0%

26

In the next cycle (2nd pass), a 2nd, unlabeled Acetyl CoA (no 14C) enters and a second complete cycle is finished. What percentage of the orginal 14C is lost as CO2?

0%

27

The proton motive force results from the combination of which two potential energies?

1. Chemical (proton) gradient
2. charge gradient (electrical field)

28

For each of the following complexes found in the mitochondrial Electron Transport System (ETS), provide the name (or acronym) of the electron donor, electron acceptor and the number of protons pumped across the membrane for every 2 electrons that pass through each complex. Be sure to indicate the oxidation state of the electron donors and acceptors. Read carefully! note that the complexes are not necessarily in chronological order.

Complex #1
# of H+ pumped/2e- : 4
Electron Donor: NADH
Electron Acceptor: Ubiquinone, Q

Complex # 2
# of H+ pumped/2e-: 0
Electron Donor:Succinate (FADH2)
Electron Acceptor: Ubiquinone, Q

Complex # 3
# of H+ pumped/2e- : 4
Electron Donor: Ubiquinol, QH2
Electron Acceptor: Cytochrome c ox

Complex # 4
# of H+ pumped/2e- : 2
Electron Donor: Cytochrome c red
Electron Acceptor: O2

29

If proton channels were opened across the typical inner mitochondrial membrane, into which compartment would protons flow?

Mitochondrial Matrix

30

If proton channels were opened across the typical inner mitochondrial membrane, how much energy would be released per mole of protons that flowed across this membrane (down the protein gradient)?

23 kJ/mol

31

Which of the following ATP synthase subunits is known to spin?

y (gamma)

32

Sodium cyanide and sodium azide are effective poisons that block mitochondrial function. Which of the following protein complex activity is significantly inhibited in the presence of these two poisons?

All of the above
Because if you stop any of the complexes, you stop them all

33

How many protons flow through the F1F0 ATP synthase for every ATP synthesized and released?

4H+/ATP

34

How many ATP are synthesized for every full 360* spin/turn made by the ATP synthase?

3.0

35

How many ATP are synthesized for every NADH that passes electrons in the ETS?

2.5

36

We spent nearly a month describing the complete catabolism of glucose to the end products of CO2 and H20. Please fill in the blanks for the balanced equation given in class for the typical animal cell.

1 Glucose + 6 O2 + 30-32 ADP + 30-32 Pi -> 30-32 ATP + 6 CO2 + ~36 H2O

37

This compound is formed in the pentose phosphate pathway. According to the lecture, the next step would directly involve:

All answers were accepted

38

Six glucose molecules pass completely through both the oxidative and nonoxidative branches of the pentose phosphate pathway. Identify how many of the following are generated when this process is complete. Molecules that are generated and then consumed do not count.

0 ATP
6 CO2
0 NADH
12 NADPH
2 glyceraldehyde-3-P
4 fructose-6-P
0 ribulose-5-P

39

Circle all that apply. The glycogen debranching enzyme catalyzes:

formation of (a1->4) linkages during glycogen degradation
degradation of (a1->6) linkages during glycogen degradation

40

During glycogen degradation, glucose-1-phosphate is generated. Which of the following molecules participate directly in the conversion of glycogen to glucose-1-phosphate? Circle all that apply.

Inorganic Phosphate (Pi)

41

Explain briefly why glycogen particles in muscle and liver are limited in size.

Glycogen synthase must be bound to glycogenin, the core protein of each glycogen granule, in order to be active. Because of this, the synthase can only reach so far. Even with branching, glycogen synthase's reach limits the granule to ~55,000 glucose residues

42

Pyrophosphate plays a role during glycogen synthesis. The fate of pyrophosphate during this synthetic pathway is most likely:

to be hydrolyzed to form inorganic phosphate

43

Caffeine affects glycogen metabolism by binding to and directly:

inactivating phosphodiesterase

44

Illustrate the multi-step PDH-catalyzed oxidative decarboxylation of pyruvate.

card image

45

The carbonyl carbon of Acetyl CoA is labeled with 14C as it enters the citric acid cycle. After one complete pass of the cycle (back to oxaloacetate), what percentage of the original 14C remains in the oxaloacetate?

100%

46

In the next cycle (2nd pass), a 2nd, unlabeled Acetyl CoA (no 14C) enters and a second complete cycle is finished. What percentage of the original 14C remains in the resulting oxaloacetate?

0%

47

Name one citric acid cycle enzyme that is inactivated directly by Succinyl CoA.

Enzyme: Citrate Synthase or a-KGDH

48

Name on citric acid cycle enzyme that is actived directly by NAD+.

PDH or IDH

49

Name the two citric acid cycle intermediate that are used to synthesize most of the 20 amino acids.

1. a-Ketogluturate
2. Oxaloacetate

50

The following diagram represents the mitochrondrial Electron Transport System. Supply all the molecules that donate to or accept electrons from each of the complexes; fill in all 14 blanks. Be sure to indicate the oxidation state of the acceptors and donators.

card image

51

For every two electrons, how many protons are pumped into the mitochondrial matrix by each of the following electron transport complexes?

II : 0 H+
IV: 0 H+ ( complex IV pumps 2 H+/2e- out of the matrix and into the intermembrane space)

52

Identify the specific mitochondrial target of cyanide (CN-1)poisoning and explain why it shuts down operation of the mitochondria F1F0 and ATP synthase.

Specific Target: Complex IV of the ETS

Cyanide blocks function of complex IV which shuts down the entire ETS. With the ETS shut down, the proton gradient fails to be generated across the membrane. Since the ATP synthase requires the proton gradient to run, ATP synthesis is also blocked.

53

Which of the following F1 sphere subunits (found in the F1F0 ATP synthase) spin during normal operation of the enzyme?

y (gamma)

54

How many ATP are generated in the mitochondria for every glucose that is completely oxidized to CO2?

6 ATP (4 from complex III and 2 from complex IV)

55

How many protons flow through the ATP synthase for every ATP generated?

4

56

When protons flow through the ATP synthase, into which specific compartment of the cell or organelle do they flow?

mitochondrial matrix

57

Part of the gluconeogenic pathway in liver cell involves the production of cytosolic phosphoenolpyruvate (PEP) starting with cytosolic lactate. Illustrate this conversion by identifying all the intermediates by name. Include key small molecules such as ATP, CO2, NADPH, etc. Enzyme names and metabolite structures are not necessary.

card image

58

The molecule, AMP, is a reciprocal regulator of the glycolytic and gluconeogenic pathways. This means that:

AMP activates PFK-1 while inactivating fructose-1,6-bisphosphatase

59

For each hexose that feeds into the oxidative branch of the pentose phosphate pathway, there is a yield of one carbohydrate and two high energy molecules. Indentify these molecules:

Beginning hexose: Glucose-6-P
Carbohydrate product: Ribulose-5-Phosphate or Ribose-5-P
High energy molecules: 2 NADPH

60

The nonoxidative branch of the pentose phosphate pathway can convert pentoses into glycolytic intermediates. Identify these intermediates and indicate which and how many high energy compounds are consumed per pentose converted to these intermediates.

Glycolytic intermediates: Fructose-6-phosphate
Glyceraldehyde-3-P
High energy intermediates: No energy compounds are involved

61

a-1,6-Glucosidase is active during glycogen degradation. One substrate for this enzyme is the glycogen polymer. The second substrate is:

H20

62

Which molecule is a substrate for the enzyme glycogen synthase?

UDP-glucose

63

Circle all that apply. Phosphorylation of glycogen synthase by protein kinase A (PKA) will:

inactivate the synthase

64

Imagine that a mouse line has been genetically modified so that it can no longer produce the protein glycogenin. Without this protein you would expect the following to occur in the liver and muscle cells of the mutant mice. Circle all that apply.

Glycogen particles would fail to form
Glycogen synthase would be inactive

65

Insulin stimulation of a liver cell would be expected to have which of the following effects? Circle all that apply

Activation of protein phosphatase I (PPI)
Increased inactivation (hydrolysis) of cAMP
Activation of glycogen synthesis
Inactivation of glycogen degradation

66

The methyl carbon of Acetyl CoA is labeled with 14C as it enters the citric acid cycle. After one complete pass of the cycle (back to oxaloacetate), an unlabeled Acetyl CoA (no 14C) enters a second complete cycle is completed. What percentage of the original 14C remains in the oxaloacetate after the second cycle?

100%

67

In the next cycle (3rd pass), a 3rd, unlabeled Acetyl CoA (no 14C) enters and a third complete cycle is finished. What percetage of the original 14C remains in the resulting oxaloacetate?

50%

68

A number of citric acid cycle enzymes are regulated. Listed below are some allosteric effectors of some of these enzymes. Indicate whether or not the effector acts as an activator, inhibitor, or acts to activate one enzyme in the cycle while inactivating a 2nd enzyme in the same cycle.

AMP: Activate
NADH: Inactivate
Succinyl CoA: Inactivate

69

For every two electrons that pass through, how many protons are pumped across the membrane by each of the following electron transport complexes?

Complex II: 0
Complex III: 4
Complex IV: 2
Complex I: 4

70

If the pH on the matrix side of the inner mitochondrial membrane is pH 6.0, you would expect the pH on the intermembrane space side of the membrane would be closest to:

4.5

71

Identify the specific mitochondrial target of cyanide (CN-1) poisoning and explain why it shuts down operation of the mitochondrial F1FO ATP Synthase.

Specific Target: Complex IV of the ETS
Cyanide blocks function of complex IV which shuts down the entire ETS. With the ETS shut down, the proton gradient fails to be generated across the membrane. Since the ATP synthase requires the proton gradient to run, ATP synthesis is also blocked.

72

According to the lecture, how does fermentation differ from mitochondrial respiration?

The fermentation ETS terminal electron acceptor is an organic molecule.

73

Which of the following statements regarding the function of the mitochondrial F1F0 ATP synthase is/are correct? Circle all that apply.

Protons flowing through the synthase enter from the intermembrane space
ATP synthesis occurs in the mitochondrial matrix

74

Describe how spinning of the F1F0 ATP synthase is coupled to synthesis of ATP.

The spinning y-subunit turns inside of the F1 sphere which does not spin. As the y-subunit turns it changes the 3-D structure of the F1 sphere so that ATP can be released from one of the a-B dimers.

75

We spent a long time discussing how glucose can be completely oxidized to CO2 and how all the resulting high energy molecules can be transformed into ATP equivalents. Assuming that these events take place in a eukaryotic cell, balance the following equation.

1 Glucose + 6 O2 + 30-32 ADP + 30-32 Pi -> 6 CO2 +30-32 ATP + ~36 H20

76

In the final step of gluconeogenesis, glucose-6-phosphate is converted to glucose by the following enzyme in the appropriate cellular compartment.

Glucose-6-phosphatase in the endoplasmic reticulum

77

The molecule, citrate, is a reciprocal regulator of the glycolytic and gluconeogenic pathways. This means that:

citrate inactivates PFK-1 while activating fructose-1,6-bisphosphatase

78

All of the following molecules are associated with gluconeogenic metabolism within liver mitochondria. One or more of these molecules can not pass easily across the inner mitochondrial membrane due to lack of a specific transporter or translocase. Identify the molecule(s).

Oxaloacetate

79

The oxidative branch of the pentose phosphate pathway (PPP) generates which of the following molecules?

NADPH
CO2
ribose-6-phosphate

80

The nonoxidative branch of the pentose phosphate pathway can convert ribulose-5-phosphate into two glycolytic intermediates which in turn can enter the glycolytic or gluconeogenic pathways. Identify these two intermediates.

Fructose-6-phosphate
Glyceraldehyde-3-phosphate

81

One substrate for glycogen phosphorylase is the glycogen polymer. The second substrate is:

Pi

82

Which of the following would be expected to result in increased glycogen phosphorylase activity? Mark all that apply

Increased (glucagon)
Increase (cAMP)
Increased phosphorylase kinase activity
Increased (caffeine)

83

Which molecules function as substrate(s) for the enzyme glycogen synthase?

UDP-glucose

84

Each glycogen particle within the liver is limited in size to ~40 nm. This size restriction results directly from the:

inactivation of glycogen synthase when not bound to glycogenin

85

The enzymatic conversion of pyruvate to Acetyl CoA is a multi-step process. In which eukaryotic subcellular compartment does this process occur?

mitochondria

86

The enzymatic conversion of pyruvate to Acetyl CoA is a multi-step process. Which coenzyme visits (binds to) all three active sites (E1, E2, & E3)?

Lipoyl-lysine (lipoamide)

87

The enzymatic conversion of pyruvate to Acetyl CoA is a multi-step process. Which coenzyme serves as the terminal (final) electron acceptor?

Nicotinamide adenine dinucleotide

88

The carbonyl carbon of OAA (arrow) is labeled with 14C as it enters the citric acid cycle with unlabeled Acetyl CoA. After one complete pass of the cycle (back to oxaloacetate), what percentage of the original 14C remains in the oxaloacetate?

100%

89

After two more complete cycles using unlabeled Acetyl CoA, what percentage of the orginal 14C remains in the resulting oxaloacetate?

50%

90

Listed below are some allosteric effectors of some citric acid cycle enzymes. Indicate whether or not the molecule acts as an activator, inhibitor or acts to activate one enzyme in the cycle while inactivating a 2nd enzyme in the same cycle.

ATP: Inactivate
NAD+: Activate
CA2+: Activate

91

Which high energy molecule donates electrons to Complex I of the mitochondrial electron transport system?

NADH

92

Ubiquinone is routinely reduced by which mitochondrial electron transport complexes?

I and II

93

Mitochondrial cytochrome c(Fe+3) routinely accepts how many electrons at a time from which molecular species?

1 electron from complex III

94

For every two electrons that pass through, how many protons are pumped across the membrane by each of the following mitochondrial electron transport complexes?

Complex II: 0
Complex III: 4
Complex IV: 2
Complex I: 4

95

What is the indentiy of the mitochondrial terminal electron acceptor?

O2

96

If the pH of the intermembrane space side of an active mitochondrian is pH 6.0, you would expect the pH on the matrix side of the membrane would be closes to:

7.5

97

Identify the specific mitochondrial target of cyanide (CN-1) poisoning and explain why it shuts down operation of the mitochondrial F1F0 ATP synthase.

Specific Target: Complex IV of the ETS
Cyanide blocks function of complex IV which shuts down the entire ETS. With the ETS shut down, the proton gradient fails to be generated across the membrane. Since the ATP Synthase requires the proton gradient to run, ATP synthase is also blocked.

98

In class we calculated how many protons were required to generate ATP in mitochondrial oxidative phosphorylation based on the total number of 'c' subunits in the ATP synthase. If the total number of c subunits was modified to be 6 but all else remain the same, how many protons would flow through the machine for every ATP generate?

2

99

Spinning the y-subunit (gamma) of the intact F1F0 ATP Synthase results in:

conformational changes within the aB-dimers

100

Which of the following is true regarding lactate metabolism during strenuous exercise in an adult human?

Lactate production generate NAD+ that is consumed by glycolysis
Lactate production consumes protons (H+) generated by glycolysis

101

Shown to the right are three enzyme-catalyzed steps from the glycolytic pathway.
Glucose->Glc-6-P (1)
Glc-6-P -> Frc-6-P (2)
Frc-6-P -> Frc-1,6-BP (3)
Identify which of the glycolytic enzymes shown, if any, would be shared by the gluconeogenic pathway.

2

102

Identify which of the glycolytic enzymes shown, if any, would be reciprocally regulated with respect to the corresponding gluconeogenic enzyme. Identify one reciprocal regulator molecule that would inhibit gluconeogenesis.

3 : AMP or Frc-2,6-BP

103

During active use of the Cori Cycle, you would expect which of the following to best represent the early steps of gluconeogenesis in liver cells?

pyruvate enters mitochondria; phosphoenolpyruvate exits mitochondria

104

Using the oxidative branch of the pentose phosphate pathway (PPP), glucose -6-P undergoes conversion to 6-phosphogluconate. Which carbon(s) were oxidized in this conversion?

C-1

105

Using the oxidative branch of the pentose phosphate (PPP), glucose-6-P undergoes conversion to 6-phosphogluconate. Which of the six carbons will be further oxidized in the conversion of 6-phosphogluconate to ribulose-5-phosphate?

C-3

106

The nonoxidative branch of the pentose phosphate pathway can convert ribulose-5-phosphate into two glycolytic intermediates which in turn can enter the glycolytic or gluconeogenic pathways. Identify these two intermediates.

Fructose-6-phosphate
Glyceraldehyde-3-phosphate

107

Glycogen synthesis and degradation is strictly regulated within the cells of your liver. What effect do high levels of insulin have on glycogen degradation?

reduce degradation

108

Glycogen synthesis and degradation is strictly regulated within the cells of your liver. What regulates the total number of glycogen particles found in a particular cell?

The total number of glycogenin proteins

109

What limits the size of the glycogen particles to 40 nm?

Interaction between glycogen synthase and glycogenin

110

Which of the following would be expected to result in increased glycogen synthase activity?

Increased (insulin)
Increased protein phosphatase I activity

111

Which of the following is considered an inhibitory pseudosubstrate of the protein kinase A (PKA) catalytic subunit?

The regulatory subunit of PKA

112

The enzymatic conversion of pyruvate to Acetyl CoA is a multi-step process requiring multiple enzymes (E1, E2, and E3) and multiple coenzymes. Which coenzymes physically interact with or bond to the pyruvate and/or acetyl group?

Thiamine pyrophosphate
Lipoamide (lipoyl-lysine)
Coenzyme A (acetylation)

113

Which coenzyme, if any, visits (binds to) all three active sites (E1, E2, and E3)?

Lipoyl-lysine (lipoamide)

114

Which coenzyme serves as the terminal (final) electron acceptor for the PDH complex?

NAD+

115

Which of the above enzymes would be classified as a lyase?

Fumarase

116

The methyl carbon of acetyl CoA is labeled with 14C as it enters the citric acid cycle with unlabeled oxaloacetate. After one complete pass of the cycle (back to oxaloacetate), what percentage of the original 14C remains in the oxaloacetate?

100%

117

After one more complete cycle using unlabeled acetyl CoA, what percentage of the original 14C remains in the resulting oxaloacetate?

100%

118

Listed below are some potential allosteric effectors of some citric acid cycle enzymes. Indicate whether or not the molecule should act as an activator or inhibitor or acts to activate one enzyme in the cycle while inactivating a 2nd enzyme in the same cycle.

ADP: Activate
NADH: Inactivate
Succinate: Active 1 enzyme and Inhibit a 2nd enzyme

119

Which molecule donates electrons directly to Complex III of the mitochondrial electron transport system?

Ubiquinol

120

Which electron transport system (ETS) complex is also known as succinate dehydrogenase?

complex II

121

The reduced form of mitochondrial cytochrom c routinely donates how many electrons at a time to which molecular species?

1 electron to complex IV

122

For every single electron that passes through, how many protons are pumped across the membrane by each of the following mitochondrial electron transport complexes?

Complex III: 2
Complex IV: 1
Complex I: 2

123

What is the identity of the human mitochondrial terminal electron acceptor?

O2

124

If the pH of a mitochondrion's matrix was measured to be 7.0, you would expect the pH of the intermembrane space to be closest to:

5.5

125

Identify the specific mitochondrial target of cyanide (CN-1) poisoning and explain why it shuts down operation of the mitochondrial F1F0 ATp synthase.

Specific Target: Complex IV of the ETS
Cyanide blocks function of complex IV which shuts down the entire ETS. With the ETS shut down, the proton gradient fails to be generated across the membrane. Since the ATP Synthase requires the proton gradient to run, ATP synthesis is also blocked.

126

When operating normally, part of the F1F0 ATP synthase spins or turns. After one complete revolution of 360*, what are the expected quantities of each?

Number of protons to pass across the membrane: 12
Number of ATP generated per synthase: 3
Number of protons required to synthesize one ATP; 4

127

Spinning of the y-subunit (gamma) of the intact F1F0 ATP synthase results in:

release of ATP from the aB-dimers

128

An O2-free ATP generating pathway where carbon compounds are the electron donors and acceptors is known as:

Fermentation

129

Gluconeogenesis and glycolysis are reciprocally regulated pathways. As described in class, identify the one glycolytic enzyme and one gluconeogenic enzyme that are truly reciprocally regulated. Identify one allosteric effector that acts on both enzymes and indicate whether it activates or inhibits enzyme activity.

Reciprocally regulated enzymes:
Glycolytic- Phosphofructokinase-1
Gluconeogenic- Fructose-1,6-bisphosphatase

One common allosteric effecter:
Frc-2,6-BP; AMP; citrate

Effect on glycolytic enzyme:
Frc-2,6-BP; AMP -citrate
Effect on gluconeogenic enzyme:
-Frc-2,6-BP;AMP +citrate

130

During active use of the Cori cycle, lactate is moved from the muscle to the liver. Answer the following as they would apply to active use of the Cori Cycle in humans. Identify the metabolite that moves from the liver to the muscle:

Glucose

131

Identify the metabolite that enters the mitochondria of the liver:

Pyruvate

132

The conversion of one lactate to one oxaloacetate in the liver requires what cost in terms of high energy compounds?

ATP: 1
GTP: 0
NADH: 0
NADPH: 0

133

Which molecule served as the oxidant during the first step of PPP?

NADP+

134

The nonoxidative branch of the pentose phosphate pathway can convert ribulose-5-phosphate into two glycolytic intermediates. What is the cost in terms of high energy compounds consumed to convert three ribulose-5-P into the glycolytic intermediates?

ATP: 0
GTP: 0
NADH: 0
NADPH: 0

135

Glycogen synthesis and degradation is strictly regulated within liver and muscle. As described in class, which hormone(s) would act to activate glycogen degradation?

epinephrine
glucagon

136

Hormonal stimulation of glycogen breakdown requires the activation of which enzymes?

protein kinase A
phosphorylation kinase
phosphorylase

137

Normal glycogen granules are never bigger than ~40 nm across. What prevents the synthase enzyme from making the granule bigger than 40 nm?

Glycogen is physically attached to glycogenin core protein; the glycogen synthase is only active when bound to glycogenin. The size of the particle is limited by the synthase reach.

138

The carbonyl carbon of acetyl CoA is labeled with 14C as it enters the citric acid cycle with unlabeled oxaloacetate. After one complete pass of the cycle, the resulting oxaloacetate combines with unlabeled Acetyl CoA and continues to do so after every cycle. During which cycle is 100% of the 14 C loast as CO2?

2nd cycle

139

Which enzyme in the citric acid cycle catalyzes the specific step that results in a four or five carbon compound with only 50% of the original 14C remaining?

Isocitrate Dehydrogenase

140

Listed below are two potential allosteric effectors of some citric acid cycle enzymes. Indicate whether or not the molecule should act as an activator or inhibitor or acts to activate one enzyme in the cycle while inactivating a 2nd enzyme in the same cycle.

ATP: Inactivate
NAD+: Activate

141

When succinate dehydrogenase feeds two electrons directly into the mitochondrial electron transport chain and the electrons are ultimately picked up by the terminal electron acceptor, protons are pumped across a membrane. Where are the protons pumped? Identify which ETS complexes pump protons as a result of these two electrons reaching the terminal electron acceptor. Where are the protons pumped?

Intermembrane space of the mitochondria

Complex Protons Pumped
One 4
Two 0
Three 4
Four 2

142

Mitochondria use oxidative phosphorylation to synthesize ATP synthesis. Explain potions of this process in three distinct parts. Read carefully; it is possible to answer the 1st two questions succintly.
Part I: What is the direct energy source used to physically run the mitochondrial machine that makes ATP?

Proton and charge gradient across the inner mitochondrial membrane

143

Part II: What is the name of the mitochondrial machine that makes ATP?

F1F0 ATP synthase or F1F0 ATPase

144

Part III: How is the gamma (y) subunit of this machine used to force the machine to release newly synthesized ATP?

The y-subunit is spun along with the transmembrane c subunits. The y-subunit spins inside the aB sphere which forces a conformational change within the sphere that generates weak binding between the B-subunit and a molecule of ATP which allows the ATP to release.

145

When the Cori Cycle is operating in the human body, the biochemical conversion of lactate to pyruvate will be occurring in a specific tissue. This conversion to pyruvate requires the direct consumption of which of the following molecules?

NAD+

146

In which tissue is this conversion of lactate to pyruvate most likely to occur?

Liver

147

Gluconeogenesis and glycolysis share some of the same enzyme-catalyzed steps. Listed below are several glycolytic enzymes. Identify which, if any, also operate in the gluconeogenic pathway:

Aldolase
Glyceraldehyde-r-phosphate dehydrogenase

148

Gluconeogenesis in a liver cell (hepatocyte) occurs in multiple subcellular compartments. Identify where each of the following conversions would most likely occur during this pathway in a liver cell.

Glyc-2-P -> Glyc-3-P: Cytoplasm
Pyruvate-> OAA: Mitochondria
Glc-6-P -> glucose: Endoplasmic Reticulum

149

What is the full name of the glucoeogenic enzyme that catalyzes the conversion of Glc-6-P to glucose?

glucose-6-phosphatase

150

The third step of the oxidative branch of PPP would best be characterized as:

oxidative decarboxylation

151

The nonoxidative branch of the pentose phosphate pathway can convert 3 ribulose-5-phosphate molecules into glycolytic intermediates. Identify these glycolytic intermediates.

3 Ribulose-5-P -> 2 fructose-6-phosphate + 1 glyceraldehyde-3-P

152

As written, what is the cost in ATP (hydrolyzed to ADP) to complete this conversion?

ATP hydrolyzed: 0

153

Glycogen degradation is strictly regulated within liver and muscle. When active, glycogen phosphorylase results in the cleavage of what bond?

a-1,4 glycosidic bond

154

Which small molecule attacks this bond in this catalyzed reaction?

Pi

155

Hormonal stimulation of a liver cell by insulin (following a holiday feast) would be expected to inhibit which of the following enzymes?

Protein Kinase A
Phosphorylation Kinase
Phosphorylase

156

Normal glycogen granules are never bigger than ~40 nm across. What simple mechanism prevents the granules from becoming larger than 40 nm?

Glycogen is physically attached to glycogenin core protein; the glycogen synthase is only active when bound to glycogenin. The size of the particle is limited by the synthase reach.

157

The enzymatic conversion of pyruvate to Acetyl CoA is a multi-step process requiring multiple enzyme active sites and multiple coenzymes. What is the full name of the coenzyme that visits all three active sites?

Lipoic acid or lipoamide

158

When lipoic acid visit the E2 active site, what reaction is catalyzed?

The acetylated lipoyl group passes the acetyl group to CoA to make Acetyl CoA.

159

When lipoic acid visits the E3 active site, what reaction is catalyzed?

The dihydrolipoyl group is oxidized by FAD to regenerate the disulfide.

160

In two separate experiments, the #1 or #2 carbon of oxaloacetate is labeled with 14C as it enters the citric acid cycle with unlabeled Acetyl CoA. After one complete pass of the cycle, the resulting oxaloacetate combines with unlabeled Acetyl CoA and continues to do so after every cycle. During which cycle is 100% of the #1 carbon 14 C lost as CO2?

1st cycle

161

During which cycle is 100% of the #2 carbon 14C lost as CO2?

5th or later cycle

162

ATP and NADH are allosteric effectors of citrate synthase. You would expect these two effectors to act in the following manner on this enzyme:

both ATP and NADH would inactivate

163

One of the coenzymes described in lecture was ubiquinone. In a human cell, ubiquinone is confined to a very specific structure inside an organelle. Identify this structure.

Inner mitochondrial membrane

164

What chemical feature of ubiquinone ensures that it stays confined to the structure identified in the inner mitochondiral membrane?

Hydrophobic 40 carbon chain

165

One metabolite attacked by TPP in an enzyme-catalyzed reaction is:

pyruvate