Biochem - Metabolism (Part 1) Flashcards Preview

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Flashcards in Biochem - Metabolism (Part 1) Deck (200)
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1
Q

Fatty acid oxidation occurs in the _____ (mitochondria/cytoplasm), whereas fatty acid synthesis occurs in the _____ (mitochondria/cytoplasm).

A

Mitochondria; cytoplasm

2
Q

Glycolysis occurs in the _____ (mitochondria/cytoplasm), whereas the Krebs cycle occurs in the _____ (mitochondria/cytoplasm).

A

Cytoplasm; mitochondria

3
Q

Where in the cell are the enzymes of the hexose monophosphate shunt located?

A

In the cytoplasm

4
Q

Where in the cell does acetyl coenzyme A production occur?

A

In the mitochondria

5
Q

Protein synthesis occurs on the _____ (rough/smooth) endoplasmic reticulum, whereas steroid synthesis occurs on the _____ (rough/smooth) endoplasmic reticulum.

A

Rough; smooth

6
Q

Name the three pathways that occur in both the cytoplasm and the mitochondria.

A

Heme synthesis, the Urea cycle, and Gluconeogenesis; remember the mnemonic: HUGs take two

7
Q

Name four pathways that occur exclusively in the mitochondria.

A

Fatty acid oxidation, acetyl-CoA production, Krebs cycle, and oxidative phosphorylation

8
Q

Describe the function of a kinase.

A

An enzyme that utilizes adenosine triphosphate to add high-energy phosphate group onto substrate

9
Q

Describe the function of a phosphorylase.

A

An enzyme that adds inorganic phosphate onto substrate without utilizing adenosine triphosphate

10
Q

Describe the function of a phosphatase.

A

An enzyme that removes phosphate group from substrate

11
Q

Describe the function of a dehydrogenase.

A

An enzyme that oxidizes substrate

12
Q

Describe the function of a carboxylase.

A

An enzyme that adds one carbon with biotin as a cofactor

13
Q

What is the rate-determining enzyme of de novo pyrimidine synthesis?

A

Carbamoyl phosphate synthetase II

14
Q

Carbamoyl phosphate synthetase II is the rate-limiting enzyme of which metabolic process?

A

De novo pyrimidine synthesis

15
Q

What is the rate-determining enzyme of de novo purine synthesis?

A

Glutamine-phosphoribosyl pyrophosphate amidotransferase

16
Q

Glutamine-phosphoribosyl pyrophosphate amidotransferase is the rate-limiting enzyme of which metabolic process?

A

De novo purine synthesis

17
Q

What is the rate-determining enzyme of glycolysis?

A

Phosphofructokinase-1

18
Q

Phosphofructokinase-1 is the rate-limiting enzyme of which metabolic process?

A

Glycolysis

19
Q

What is the rate-determining enzyme of gluconeogenesis?

A

Fructose-1,6- bisphosphatase

20
Q

Fructose-1,6- bisphosphatase is the rate-limiting enzyme of which metabolic process?

A

Gluconeogenesis

21
Q

What is the rate-determining enzyme of the tricarboxylic acid cycle?

A

Isocitrate dehydrogenase

22
Q

Isocitrate dehydrogenase is the rate-limiting enzyme of which metabolic process?

A

The tricarboxylic acid cycle

23
Q

What is the rate-determining enzyme of glycogen synthesis?

A

Glycogen synthase

24
Q

Glycogen synthase is the rate-limiting enzyme of which metabolic process?

A

Glycogen synthesis

25
Q

What is the rate-determining enzyme of glycogenolysis?

A

Glycogen phosphorylase

26
Q

Glycogen phosphorylase is the rate-limiting enzyme of which metabolic process?

A

Glycogenolysis

27
Q

What is the rate-determining enzyme of the hexose monophosphate shunt?

A

Glucose-6-phosphate dehydrogenase

28
Q

Glucose-6-phosphate dehydrogenase is the rate-limiting enzyme of which metabolic process?

A

The hexose monophosphate shunt

29
Q

What is the rate-determining enzyme of fatty acid synthesis?

A

Acetyl-CoA carboxylase

30
Q

Acetyl-CoA carboxylase is the rate-limiting enzyme of which metabolic process?

A

Fatty acid synthesis

31
Q

What is the rate-determining enzyme of fatty acid oxidation?

A

Carnitine acetyltransferase I

32
Q

Carnitine acyltransferase I is the rate-limiting enzyme of which metabolic process?

A

Fatty acid oxidation

33
Q

What is the rate-determining enzyme of ketogenesis?

A

HMG-CoA synthase

34
Q

HMG-CoA synthase is the rate-limiting enzyme of which metabolic process?

A

Ketogenesis

35
Q

What is the rate-determining enzyme of cholesterol synthesis?

A

HMG-CoA reductase

36
Q

HMG-CoA reductase is the rate-limiting enzyme of which metabolic process?

A

Cholesterol synthesis

37
Q

What is the rate-determining enzyme of the urea cycle?

A

Carbamoyl phosphate synthetase I

38
Q

Carbamoyl phosphate synthetase I is the rate-limiting enzyme of which metabolic process?

A

The urea cycle

39
Q

What is the name of the molecule that contains adenine, ribose, three phosphoryl groups, and two phosphoanhydride bonds?

A

Adenosine triphosphate

40
Q

In which two organs is adenosine triphosphate produced from the aerobic metabolism of glucose via the malate-aspartate shuttle?

A

Heart and liver

41
Q

How many adenosine triphosphate molecules are produced from the aerobic metabolism of glucose via the malate-aspartate shuttle?

A

32

42
Q

How many adenosine triphosphate molecules are produced from the aerobic metabolism of glucose via the glyceraldehyde-3-phosphate shuttle?

A

30; this occurs in the muscle

43
Q

Where does the energy come from in order to proceed from substrate to product in energetically unfavorable reactions?

A

The hydrolysis of adenosine triphosphate can be coupled with energetically unfavorable reactions to produce enough net energy

44
Q

What is the net gain of adenosine triphosphate molecules after a molecule of glucose has participated in anaerobic glycolysis?

A

Two; the NADH created cannot be used to generate energy without oxygen

45
Q

A glucose molecule is metabolized to the level of pyruvate and lactate; is this process an anaerobic or aerobic process?

A

An anaerobic process; no oxygen has been used in this reaction

46
Q

Name the three activated carriers of electrons.

A

NADH, NADPH, FADH2

47
Q

What is the activated carrier for phosphoryl groups?

A

Adenosine triphosphate

48
Q

What molecule donates methyl groups?

A

S-adenosylmethionine

49
Q

Which activated carrier molecule donates aldehyde groups?

A

Thiamin pyrophosphate

50
Q

Acyl groups are transported using which two activated carriers?

A

Coenzyme A and lipoamide

51
Q

What compounds are used as single-carbon donors in various reactions?

A

Tetrahydrofolates

52
Q

What vitamin is the donor of the carboxyl group used in many biochemical reactions in the body?

A

Biotin

53
Q

What pathway produces NADPH?

A

The hexose monophosphate shunt

54
Q

Which molecule is used in catabolic processes as an acceptor of reducing equivalents?

A

NAD+

55
Q

Catabolic processes generally use _____ (NAD+/NADPH) as an electron acceptor, whereas anabolic processes generally use _____ (NAD+/NADPH) as an electron donor.

A

NAD+; NADPH

56
Q

Name the three universal electron acceptors.

A

NAD+, NADP+, and FAD+

57
Q

In which four metabolic processes is NADPH consumed?

A

Anabolic processes, respiratory burst, P450, glutathione reductase

58
Q

What is the enzymatic reaction catalyzed by hexokinase and glucokinase?

A

Both enzymes phosphorylate glucose to form glucose-6-phosphate

59
Q

In the liver, formation of glucose-6-phosphate is the first step of which 2 reactions?

A

Glycolysis and glycogen synthesis

60
Q

Which two locations in the body contain high concentrations of glucokinase?

A

The liver and cells of the pancreas; hexokinase predominates in the rest of the body

61
Q

Which enzyme has a higher Km: glucokinase or hexokinase?

A

Glucokinase; this enzyme has no feedback-inhibition loop with glucose-6-phosphate, because its job is to store excess energy after a meal

62
Q

Which enzyme has a higher affinity for glucose: glucokinase or hexokinase?

A

Hexokinase; this enzyme has a feedback-inhibition loop with glucose-6-phosphate, because its job is just to keep the cells supplied with energy

63
Q

Which enzyme has a higher Vmax: glucokinase or hexokinase?

A

Glucokinase; this enzyme has no feedback-inhibition loop with glucose-6-phosphate, because its job is to store excess energy after a meal (remember: GLUcokinase is a GLUtton; it has a high Vmax because it cannot be satisfied)

64
Q

Which enzyme has a greater capacity to convert glucose to glucose-6-phosphate: glucokinase or hexokinase?

A

Glucokinase; this enzyme has no feedback-inhibition loop with glucose-6-phosphate, because its job is to store excess energy after a meal and buffer blood glucose

65
Q

By what process does glucokinase sequester glucose in the liver to prevent blood glucose spikes after meals?

A

Phosphorylation

66
Q

Which enzyme is induced by insulin: hexokinase or glucokinase?

A

Glucokinase

67
Q

What is the effect of glucokinase on the blood glucose level?

A

By storing excess glucose in the liver, the liver can act as a buffer to regulate the blood glucose level

68
Q

Where in the cell are the reactions that produce 2 pyruvate molecules from 1 glucose?

A

In the cytoplasm

69
Q

In glycolysis, what enzyme catalyzes the formation of fructose-1,6 bisphosphate?

A

Phosphofructokinase-1

70
Q

In glycolysis, what enzyme catalyzes the rate-limiting step?

A

Phosphofructokinase-1

71
Q

Which molecules inhibit phosphofructokinase-1?

A

Adenosine triphosphate and citrate inhibit phosphofructokinase-1 since glycolysis is unnecessary in an energy-replete cell

72
Q

In glycolysis, the reactions catalyzed by what five enzymes are irreversible?

A

Hexokinase, glucokinase, phosphofructokinase-1, pyruvate kinase, and pyruvate dehydrogenase

73
Q

Is citrate an activator or an inhibitor of the enzyme that catalyzes the rate-limiting step in glycolysis?

A

Inhibitor

74
Q

In glycolysis, fructose-2,6-bisphosphate _____ (increases/decreases) the production of fructose-1,6-bisphosphate from fructose-6-phosphate.

A

Increases

75
Q

In glycolysis, is adenosine monophosphate an activator or an inhibitor of phosphofructokinase-1?

A

Activator

76
Q

Name three compounds that decrease the activity of pyruvate dehydrogenase through negative feedback.

A

Adenosine triphosphate, NADH, and acetyl-CoA are inhibitors of pyruvate dehydrogenase; they are indicators that a cell is energy replete

77
Q

In glycolysis, fructose-1,6-bisphosphate _____ (increases/decreases) the activity of pyruvate kinase.

A

Increases

78
Q

What enzyme catalyzes the conversion of phosphoenolpyruvate to pyruvate during glycolysis?

A

Pyruvate kinase

79
Q

In glycolysis, the formation of acetyl-CoA from pyruvate is catalyzed by what enzyme?

A

Pyruvate dehydrogenase

80
Q

In the reaction that produces glucose-6-phosphate from D-glucose, is adenosine triphosphate produced or consumed?

A

Consumed

81
Q

In the reaction that produces fructose-1,6-bisphosphate from fructose-6-phosphate, is adenosine triphosphate produced or consumed?

A

Consumed

82
Q

In the reaction that produces 3-phosphoglycerate from 1,3-bisphosphoglycerate, is adenosine triphosphate produced or consumed?

A

Produced

83
Q

In the reaction that produces pyruvate from phosphoenolpyruvate, is adenosine triphosphate produced or consumed?

A

Produced

84
Q

In glycolysis, the formation of 3-phosphoglycerate from 1,3-bisphosphoglycerate is catalyzed by which enzyme?

A

Phosphoglycerate kinase

85
Q

True of False? In glycolysis, the reaction catalyzed by phosphoglycerate kinase is reversible.

A

TRUE

86
Q

What is the most potent activator of phosphofructokinase-1?

A

Fructose-2,6-bisphosphate

87
Q

The enzyme phosphofructokinase 2 catalyzes which reaction?

A

The conversion of fructose-6-phosphate to fructose-2,6-bisphosphate

88
Q

What enzyme converts fructose-1,6-bisphosphate (F1,6BP) into fructose-6-phosphate during gluconeogenesis?

A

Fructose bisphosphatase-1 (FB Pase-1)

89
Q

Fructose bisphosphatase-2 catalyzes which reaction?

A

Conversion of fructose-2,6-bisphosphate into fructose-6-phosphate

90
Q

What function do FBP-1 and FBP-2 have in common?

A

Both remove a phosphate group from their target; FBP-1 removes that from the 1 carbon of F1,6BP, while FBP-2 removes that from the 2 carbon of F2,6BP

91
Q

What function do PFK-1 and PFK-2 have in common?

A

Both add a phosphate group to either the 1 carbon (in PFK-1) or the 2 carbon (in PFK-2) of fructose-6-phosphate

92
Q

Which enzyme regulating the level of F2,6BP is active in the fed state?

A

Phosphofructokinase 2, increasing glycolysis and thus adenosine triphosphate creation for anabolic processes

93
Q

Which enzyme regulating the level of F2,6BP is active in the fasting state?

A

Fructose bisphosphatase-2, increasing gluconeogenesis when glucose is needed for catabolic processes

94
Q

In the fed state, does the cell perform glycolysis or gluconeogenesis? What enzyme is responsible?

A

When glucose is available, the body will perform glycolysis because PFK-2 is active and will increase the amount of F2,6BP

95
Q

In the fasting state, does the cell perform glycolysis or gluconeogenesis? What enzyme is responsible?

A

The liver cell will perform gluconeogenesis because FB Pase-2 is active and will decrease the amount of F2,6BP

96
Q

Glucagon has what effect on F26BP levels? By what mechanism?

A

Increases; increased protein kinase A

97
Q

Insulin has what effect on F26BP levels? By what mechanism?

A

Decreases; decreased protein kinase A

98
Q

A patient with a genetic mutation in their glycolysis pathway is anemic; what is the likely etiology?

A

This is likely hemolytic anemia due to red blood cell swelling and lysis

99
Q

Why does inhibition of the erythrocyte Na+/K+ adenosine triphosphatase cause hemolytic anemia?

A

Inability to transfer ions results in cell swelling and lysis

100
Q

True or False? Red blood cells are able to metabolize glucose through oxidative phosphorylation.

A

False; red blood cells have no mitochondria, which are the site of oxidative phosphorylation

101
Q

True or False? Red blood cells depend solely on glycolysis to produce adenosine triphosphate from glucose.

A

TRUE

102
Q

What is the most common glycolytic enzyme deficiency?

A

Pyruvate kinase

103
Q

How many enzymes make up the pyruvate dehydrogenase complex?

A

Three

104
Q

How many cofactors are required for pyruvate dehydrogenase complex activity?

A

Five

105
Q

A sick patient has rice water stools, vomiting, and garlic breath; what is the diagnosis?

A

Arsenic poisoning

106
Q

How does arsenic interfere with pyruvate dehydrogenase?

A

Arsenic inhibits lipoic acid

107
Q

What enzyme catalyzes the conversion of pyruvate to acetyl-CoA?

A

Pyruvate dehydrogenase complex

108
Q

A(n) _____ (increase/decrease) in the NAD+/NADH ratio in a cell leads to increased activity of the pyruvate dehydrogenase complex.

A

Increase

109
Q

A(n) _____ (increase/decrease) in the concentration of calcium in a cell leads to increased activity of the pyruvate dehydrogenase complex.

A

Increase

110
Q

Which enzyme in the citric acid cycle has a similar structure to the pyruvate dehydrogenase complex and uses the same cofactors?

A

The -ketoglutarate dehydrogenase complex

111
Q

Which cofactors are required for the activity of the pyruvate dehydrogenase complex?

A

Pyrophosphate (B1 [thiamine]), FAD (B2 [riboflavin]), NAD (B3 [niacin]), CoA (B5 [pantothenate]), and lipoic acid

112
Q

What types of stimuli activate the pyruvate dehydrogenase complex?

A

Stimuli that indicate a deficit of energy (or adenosine triphosphate)

113
Q

A(n) _____ (increase/decrease) in adenosine diphosphate in a cell leads to increased activity of the pyruvate dehydrogenase complex.

A

Increase; increased adenosine diphosphate indicates that the cell requires more adenosine triphosphate production in the tricarboxylic acid cycle

114
Q

What substance causes the acid-base imbalance in patients with pyruvate dehydrogenase deficiency?

A

Lactic acid; patients have a lactic acidosis

115
Q

Which substrates of the pyruvate dehydrogenase complex build up if the enzyme complex is deficient?

A

Pyruvate and alanine

116
Q

How does pyruvate dehydrogenase deficiency present clinically?

A

With neurologic deficits such as lethargy, ataxia, and developmental delay

117
Q

A patient with pyruvate dehydrogenase deficiency should have what type of diet?

A

Ketogenic; it will allow for energy generation with development of lactic acidosis

118
Q

What are the only two purely ketogenic amino acids?

A

Lysine and leucine

119
Q

Why is pyruvate dehydrogenase deficiency seen in alcoholics?

A

These individuals have a vitamin B1 deficiency, which is necessary to create active pyruvate dehydrogenase

120
Q

In pyruvate metabolism, which enzyme catalyzes the conversion of pyruvate to alanine?

A

Alanine transaminase

121
Q

In pyruvate metabolism, which enzyme converts pyruvate to lactate?

A

Lactate dehydrogenase

122
Q

What enzyme converts pyruvate to acetyl-CoA?

A

Pyruvate dehydrogenase complex

123
Q

In pyruvate metabolism, which enzyme catalyzes the conversion of pyruvate to oxaloacetate?

A

Pyruvate carboxylase

124
Q

Which amino acid serves as a carrier of amino groups from muscle to liver?

A

Alanine

125
Q

What four compounds can be formed from pyruvate in a single step?

A

Acetyl-CoA, lactate, alanine, and oxaloacetate

126
Q

The conversion of pyruvate to lactate is the final step of which pathway?

A

Anaerobic glycolysis

127
Q

Which cells in the body use anaerobic glycolysis as a major source of adenosine triphosphate?

A

Red blood cells, leukocytes, kidney medulla, testes, lens, and cornea

128
Q

Pyruvate can be converted to what substance used to replenish intermediates during the citric acid cycle?

A

Oxaloacetate; can also be used for gluconeogenesis

129
Q

Pyruvate is converted into which two molecules that can enter the tricarboxylic acid cycle?

A

Acetyl-CoA and oxaloacetate

130
Q

What is the purpose of the Cori cycle?

A

Allows lactate formed in muscles to be used for gluconeogenesis in the liver

131
Q

Which tissues create adenosine triphosphate in the Cori cycle? Which tissues consume adenosine triphosphate?

A

Muscles and red blood cells; liver

132
Q

Does the Cori cycle facilitate aerobic or anaerobic glycolysis?

A

Anaerobic; the Cori cycle facilitates the metabolism of lactate

133
Q

What is the net gain or loss of adenosine triphosphate molecules during the Cori cycle?

A

There is a net loss of four adenosine triphosphate molecules

134
Q

A runner is found to be producing large amounts of lactate in his leg muscles during training; what process is likely occurring in the liver at the same time?

A

Gluconeogenesis; he is performing anaerobic glycolysis in his legs and replenishing the glucose supply in his liver via the Cori cycle

135
Q

During the Cori cycle, ______ (pyruvate/lactate) returns to the liver to undergo gluconeogenesis.

A

Lactate

136
Q

The Cori cycle preferentially supplies energy to the ______ (muscles/liver) in spite of energetically unfavorable reactions in the ______ (muscles/liver).

A

Muscles; liver

137
Q

How many NADH molecules are produced during one turn of the citric acid cycle?

A

Three

138
Q

How many FADH2 molecules are produced during one turn of the citric acid cycle?

A

One

139
Q

How many carbon dioxide molecules are produced during one turn of the citric acid cycle?

A

Two

140
Q

In the citric acid cycle, adenosine triphosphate _____ (activates/inhibits) citrate synthase.

A

Inhibits; this is a negative feedback mechanism for when the cell is energy replete

141
Q

How many guanosine triphosphate molecules are produced during one turn of the citric acid cycle?

A

One

142
Q

In the citric acid cycle, adenosine triphosphate is an _____ (activator/inhibitor) of isocitrate dehydrogenase, whereas adenosine diphosphate is an _____ (activator/inhibitor).

A

Inhibitor; activator; the mechanism ensures that the cell produces adenosine triphosphate only when required

143
Q

How many adenosine triphosphate molecules are produced during one turn of the citric acid cycle?

A

12

144
Q

How many adenosine triphosphate molecules are produced from one molecule of glucose by the citric acid cycle?

A

24

145
Q

How many FADH2 molecules are produced from one molecule of glucose by the citric acid cycle?

A

Two

146
Q

How many carbon dioxide molecules are produced from one molecule of glucose by the citric acid cycle?

A

Four

147
Q

How many guanosine triphosphate molecules are produced from one molecule of glucose by the citric acid cycle?

A

Two

148
Q

In the citric acid cycle, -ketoglutarate dehydrogenase is _____ (inhibited/activated) by the high-energy compounds NADH and adenosine triphosphate.

A

Inhibited

149
Q

In the citric acid cycle, adenosine triphosphate, acetyl-CoA, and NADH are _____ (inhibitors/activators) of pyruvate dehydrogenase.

A

Inhibitors

150
Q

What intermediate of the tricarboxylic acid cycle provides negative feedback to -ketoglutarate dehydrogenase to inhibit its function?

A

Succinyl-CoA

151
Q

In the citric acid cycle, the production of -ketoglutarate, succinyl-CoA, and oxaloacetate from their precursors produces which high-energy molecule?

A

NADH

152
Q

Where in the cell does the tricarboxylic acid cycle take place?

A

The mitochondria

153
Q

In the citric acid cycle, the conversion of oxaloacetate to citrate is catalyzed by what enzyme?

A

Citrate synthase

154
Q

In the citric acid cycle, the conversion of isocitrate to -ketoglutarate is catalyzed by what enzyme?

A

Isocitrate dehydrogenase

155
Q

In the citric acid cycle, which enzyme catalyzes the conversion of -ketoglutarate to succinyl-CoA?

A

The -ketoglutarate dehydrogenase complex

156
Q

Name the intermediates of the citric acid cycle.

A

Citrate, Isocitrate, a-Ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, and Oxaloacetate (remember: Citrate Is Kreb's Starting Substrate F or Making Oxaloacetate)

157
Q

The formation what two substances during the citric acid cycle involve the release of carbon dioxide?

A

-Ketoglutarate and succinyl-CoA

158
Q

What step of the citric acid cycle produces guanosine triphosphate?

A

The conversion of succinyl-CoA into succinate

159
Q

What step of the citric acid cycle produces FADH2?

A

The conversion of succinate into fumarate

160
Q

True or False? The enzymes of the citric acid cycle are generally inhibited by high-energy compounds such as adenosine triphosphate or NADH.

A

TRUE

161
Q

Name four enzymes in the tricarboxylic acid cycle whose actions are irreversible.

A

Pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, and -ketoglutarate dehydrogenase

162
Q

Electrons carried by NADH created in glycolysis and the tricarboxylic acid cycle may enter the mitochondria via which two shuttles?

A

Malate-aspartate shuttle or glycerol-3-phosphate shuttle

163
Q

How many adenosine triphosphate molecules can be produced from one NADH molecule during oxidative phosphorylation?

A

Three

164
Q

How many adenosine triphosphate molecules can be produced from one FADH2 molecule during oxidative phosphorylation?

A

Two

165
Q

Which complex in the electron transfer chain receives electrons carried by NADH?

A

Complex I

166
Q

Which complex in the electron transfer chain receives electrons carried by FADH2?

A

Complex II (succinate dehydrogenase)

167
Q

Why does FADH2 produce fewer molecules of adenosine triphosphate than NADH?

A

It enters the electron transport chain at a lower energy level than NADH on complex II rather than I

168
Q

How is the energy of the electron transport chain converted into adenosine triphosphate?

A

By creation of a proton gradient

169
Q

What molecule ultimately accepts electrons from the electron transport chain?

A

Oxygen

170
Q

What is the mechanism by which oligomycin interrupts adenosine triphosphate production?

A

Oligomycin directly inhibits mitochondrial adenosine triphosphate synthase

171
Q

How does the pesticide rotenone block adenosine triphosphate synthesis?

A

Via direct inhibition of electron transport

172
Q

What happens to the proton gradient in the mitochondria when adenosine triphosphate synthase is inhibited by oligomycin?

A

It increases, but protons cannot be released, causing the electron transport chain to halt and decreased adenosine triphosphate formation

173
Q

How does the poison cyanide block adenosine triphosphate synthesis?

A

Via direct inhibition of electron transport

174
Q

How does the gas carbon monoxide block adenosine triphosphate synthesis?

A

Via direct inhibition of electron transport

175
Q

Poisons that directly inhibit the electron transport chain lead to a(n) _____ (increased/decreased) proton gradient in the mitochondria.

A

Decreased

176
Q

Regarding oxidative phosphorylation, name three examples of uncoupling agents that will block adenosine triphosphate production.

A

2,4-Dinitrophenylhydrazine (2,4-DNP), aspirin, thermogenin

177
Q

Regarding oxidative phosphorylation, 2,4-dinitrophenylhydrazine _____ (increases/decreases) the permeability of the mitochondrial membrane.

A

Increases

178
Q

Regarding oxidative phosphorylation, electron transport inhibitors _____ (increase/decrease) the proton gradient.

A

Decrease

179
Q

When acting as an uncoupling agent, aspirin _____ (increases/decreases) the proton gradient in the mitochondria.

A

Decreases; because of increased membrane permeability, protons are not forced through adenosine triphosphate synthase

180
Q

What is the effect of thermogenin on oxygen use, adenosine triphosphate production, and heat generation?

A

Increase

181
Q

Why does adenosine triphosphate production decrease when the mitochondrial membrane is disturbed?

A

The loss of the proton gradient means that there is no energy to drive adenosine triphosphate synthase

182
Q

What is the action of an uncoupling agent on the mitochondrial membrane?

A

These increase the permeability of the membrane, decreasing the proton gradient

183
Q

Does disruption of the proton gradient by an uncoupling agent cause electron transport to stop?

A

No; electron transport continues, but the protons moved across the membrane are free to return down the gradient without producing adenosine triphosphate

184
Q

What is the result of an uncoupling agent on mitochondrial oxygen consumption?

A

There is increased oxygen consumption, because electron transport continues in an attempt to maintain the proton gradient

185
Q

To produce adenosine triphosphate, protons must flow down their gradient from the _____ across the inner mitochondrial membrane to the _____.

A

Intermembranous space; mitochondrial matrix

186
Q

In gluconeogenesis, what reaction is catalyzed by pyruvate carboxylase?

A

The conversion of pyruvate into oxaloacetate

187
Q

Is pyruvate carboxylase found in the mitochondria or in the cytosol?

A

The mitochondria

188
Q

Is phosphoenolpyruvate carboxykinase found in the mitochondria or in the cytosol?

A

The cytosol

189
Q

In gluconeogenesis, what enzyme catalyzes the conversion of oxaloacetate into phosphoenolpyruvate?

A

Phosphoenolpyruvate carboxykinase

190
Q

In gluconeogenesis, what is the name of the enzyme that catalyzes the reaction of fructose-1,6-bisphosphate to fructose-6-phosphate?

A

Fructose-1,6-bisphosphatase

191
Q

In gluconeogenesis, does phosphoenolpyruvate carboxykinase require adenosine triphosphate or guanosine triphosphate?

A

Guanosine triphosphate

192
Q

True or False? Gluconeogenesis occurs in skeletal muscle.

A

False; muscle does not contain the enzymes needed for gluconeogenesis

193
Q

_____ (Odd/Even)-chain fatty acids yield propionyl-CoA during metabolism, which can produce new glucose; while _____ (odd/even)-chain fatty acids only yield acetyl-CoA equivalents.

A

Odd; even

194
Q

In gluconeogenesis, what reaction is catalyzed by glucose-6-phosphatase?

A

The conversion of glucose-6-phosphate into glucose

195
Q

A deficiency of gluconeogenic enzymes leads to what condition?

A

Hypoglycemia

196
Q

Which cofactors are required by the enzyme pyruvate carboxylase?

A

Biotin and adenosine triphosphate

197
Q

Name four enzymes in gluconeogenesis whose actions are irreversible.

A

Pyruvate carboxylase, PEP carboxykinase, Fructose-1,6-bisphosphatase, Glucose-6-phosphatase (remember: Pathway Produces Fresh Glucose)

198
Q

What is the expected presenting sign of von Gierke's disease, which is a deficiency of glucose-6-phosphatase in the liver?

A

Hypoglycemia due to inability to perform gluconeogenesis

199
Q

What is the primary location of gluconeogenesis in the body?

A

This process occurs mostly in the liver

200
Q

Which small molecule can produce glucose after fatty acid metabolism: acetyl-CoA or propionyl-CoA?

A

Propionyl-CoA; acetyl-CoA cannot undergo gluconeogenesis