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CHM 432 > Exam Four > Flashcards

Exam Four Flashcards

1
Q

What step is the main control point for glycolysis?

A

step 3, phosphofructokinase

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2
Q

What can pyruvate be converted to after glycolysis?

A

lactate, acetyl coA, and oxaloacetate

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3
Q

What is the net reaction of glycolysis?

A

glucose + 2NAD+ + 2ADP + 2Pi –> 2 Pyruvate +2NADH + 2ATP + 4H+

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4
Q

What is the enzyme that converts glucose to glucose-6-phosphate?

A

hexokinase

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5
Q

How does hexokinase add a phosphate on the #6 carbon of glucose?

A

traps glucose inside the cell and lowers intracellular glucose concentration to allow further uptake
uses energy of ATP

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6
Q

Why does hexokinase require ATP coupling?

A

Without ATP, the overall reaction would be nonspontaneous

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7
Q

How does hexokinase “trap” glucose?

A

the addition of the negative charge by the phosphate group makes it difficult for glucose to escape the cell

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8
Q

What is the enzyme that converts glucose-6-phosphate into fructose-6-phosphate?

A

phosphoglucose isomerase

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9
Q

Why does glucose-6-phosphate need to be isomerized to fructose-6-phosphate?

A

this step makes the next steps easier/less energy required

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10
Q

What is the enzyme that converts fructose-6-phosphate into fructose-1,6-biphosphate?

A

phosphofructokinase (PFK)

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11
Q

What is/are the negative effector(s) of PFK?

A

PEP and ATP

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12
Q

What is/are the positive effector(s) of PFK?

A

ADP

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13
Q

What overall happens in the first 3 reaction of glycolysis?

A

sugar is activated via phosphorylation, 2 ATP requiring steps

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14
Q

What is the enzyme that converts fructose-1,6-biphosphate into dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP)

A

aldolase

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15
Q

What is the enzyme that converts DHAP to GAP?

A

triose phosphate isomerase

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16
Q

Why is DHAP converted to GAP?

A

only GAP is the substrate for the next enzyme, so DHAP is useless

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17
Q

How is the conversion of DHAP to GAP pulled forward?

A

GAP concentration is kept low

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18
Q

What is the enzyme that converts GAP to 1,3-biphosphoglycerate with the help of NAD+ oxidation?

A

glyceraldehyde-3-phosphate dehydrogenase

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19
Q

What are the 2 reactions that actually take place within the 6th reaction of glycolysis?

A
  1. oxidize GAP
  2. phosphorylate with Pi
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20
Q

How is the GAPDH step pulled forward with a positive delta g?

A

this reaction is coupled with the following reaction in the pathway

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21
Q

What is the enzyme that converts 1,3-BPG into 3-phosphoglycerate?

A

phosphoglycerate kinase

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22
Q

What is special about the 7th reaction in glycolysis?

A

1st ATP production in glycolysis!

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23
Q

What is the enzyme that converts 3-phosphoglycerate into 2-phosphoglycerate?

A

phosphoglycerate mutase

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24
Q

What is the enzyme that converts 2-phosphoglycerate into phosphoenolpyruvate?

A

enolase

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25
Q

What is the enzyme that converts phosphoenolpyruvate into pyruvate?

A

pyruvate kinase

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26
Q

What is special about the last reaction in glycolysis?

A

it is irreversible and is the second ATP generating step

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27
Q

What are the four reactions in glycolysis with large negative delta Gs?

A

hexokinase (1), phosphofructokinase (3), phosphoglycerate kinase (7), and pyruvate kinase (10)

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28
Q

What are the reactions in glycolysis that use ATP?

A

hexokinase (1) and phosphofructokinase (3)

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29
Q

What are the reactions in glycolysis that make ATP?

A

phosphoglycerate kinase (7) and pyruvate kinase (10)

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30
Q

What is the reaction in glycolysis with a large positive delta G?

A

aldolase (4)

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31
Q

How does PFK 2 affect glycolysis?

A

When it is dephosphorylated, it stimulates PFK and the glycolysis pathway

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32
Q

What dephosphorylates PFK 2?

A

phosphoprotein phosphatase

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33
Q

What activates phosphoprotein phosphatase?

A

insulin

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34
Q

How does PFK 2 work when it is phosphorylated?

A

it works as phosphatase 2 which breaks down F 2,6 BP which inhibits glycolysis

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35
Q

When is insulin released?

A

When well-fed/ high blood glucose levels

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36
Q

When is glucagon released?

A

When starving/low blood glucose levels

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37
Q

Why isn’t hexokinase the major regulatory step?

A

you can enter glycolysis without hexokinase by converting glycogen to glucose-6-phosphate using glycogen phosphorylase and phosphoglucose mutase

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38
Q

How do other carbohydrates generate energy?

A

they have to turn into one of the intermediates in glycolysis to generate pyruvate

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39
Q

How is mannose converted to generate energy?

A

mannose —-> fructose-6-phosphate

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40
Q

How is galactose converted to generate energy?

A

Galactose-1-P —> Glu-1-P —-> Glu-6-P

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41
Q

How is fructose (muscle and kidney) converted to generate energy?

A

—-> fructose-6-phosphate

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42
Q

How is fructose (liver) converted to generate energy?

A

—–> fructose-1-phosphate

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43
Q

Why is Fru-1-P a trouble maker?

A

it can enter glycolysis without being checked by PFK because it immediately converts to GAP

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44
Q

What is the purpose of the pentose phosphate pathway (oxidation of glucose-6-phosphate)?

A

produce NADPH from NADP

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45
Q

What is the net reaction of the pentose phosphate pathway?

A

G-6-P + 2NADP+ + H2O —> Ribose-5-Phosphate + 2NADPH + 2CO2 + 2H+

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46
Q

What does NADPH protect cells from?

A

free radicals

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47
Q

What is the degradation of glycogen to use glucose called?

A

glycogenolysis

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48
Q

What are the three enzymes important for glycogen breakdown?

A

glycogen phosphorylase, debranching enzyme, and phophoglucomutase

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49
Q

glycogen phosphorylase stops when it reaches to a point ________ glucose residues away from a branching point

A

four

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50
Q

What can you do with glu-1-phosphate?

A
  1. convert into g-6-p for glycolysis
  2. convert to free glucose to export
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51
Q

GLUT 1

A

most tissues

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52
Q

GLUT 2

A

liver, small intestine

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53
Q

GLUT 3

A

neurons

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54
Q

GLUT 4

A

muscle,fat - insulin activated

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55
Q

can G-6-P or G-1-P be transported in blood?

A

no

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56
Q

There is no glycogen formation or breakdown in the _______

A

brain

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57
Q

What is the first substrate for glycogen synthesis?

A

Glu-1-P

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58
Q

Primer protein that makes a minimum length (7) of glycogen before starting with glycogen synthase

A

glycogenin

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59
Q

How does phosphorylation affect glycogen synthesis?

A

it activates glycogen breakdown AND deactivates synthesis of glycogen

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60
Q

When is glycogen breakdown needed?

A

starving

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61
Q

What is the inhibitor of glycogen breakdown?

A

phosphoprotein phosphatase-1

62
Q

What is the activator of glycogen synthesis?

A

glycogen synthase

63
Q

What is on the active form of glycogen phosphorylase?

64
Q

What is on the inactive form of glycogen phosphorylase?

65
Q

What is on the active form of glycogen synthase?

66
Q

What is on the inactive form of glycogen synthase?

67
Q

What stimulates glycogen phosphorylase?

68
Q

What inhibits glycogen phosphorylase?

A

ATP and G-6-P

69
Q

What stimulate glycogen synthase?

A

G-6-P and ATP

70
Q

What inhibits glycogen synthase?

71
Q

What activates phosphatases?

72
Q

What activates cAMP production and kinases

73
Q

How does phosphorylation change the conformation of protein?

A

a phosphate group adds 2 negative charges and allows for 2-3 more hydrogen bonds to form

74
Q

Phosphorylation is tied to the concentration of _____ in the cell

75
Q

the cAMP cascade is triggered by _______

A

glucagon and epinephrine

76
Q

How do you stop the cAMP cascade?

A

Breaking cAMP/ decyclizing it

77
Q

What is the enzyme that decomposes cAMP and therefore stops the cascade?

A

phosphodiesterase

78
Q

What activates phosphodiesterase?

A

phosphorylation catalyzed by PKA

79
Q

What competitively inhibits phosphodiesterase so cAMP effect is prolonged?

80
Q

What is the term for glycolysis under anaerobic conditions?

A

fermentation

81
Q

What is the purpose of fermentation?

A

to produce NAD+

82
Q

How many ATP per glucose are produced in yeast aerobically vs. anaerobically

A

32 ATP/glucose aerobically
2 ATP/glucose anaerobically

83
Q

What is the purpose of lactate fermentation?

A

to produce NAD+, the lactate is not beneficial

84
Q

What does pyruvate decarboxylase do?

A

convert pyruvate into acetaldehyde

85
Q

Who has pyruvate decarboxylase in their bodies?

A

only yeast

86
Q

What does pyruvate decarboxylase need as a decarboxylation cofactor?

87
Q

What does alcohol dehydrogenase do?

A

convert acetaldehyde into ethanol

88
Q

What is the purpose of using alcohol dehydrogenase to convert acetaldehyde into ethanol?

A

produce NAD+

89
Q

What occurs if there is a shortage of NAD+?

A

ATP production in glycolysis is slowed down

90
Q

What happens if there is too much NADH?

A

trouble getting glucose to brain because there is not enough pyruvate for gluconeogenesis

91
Q

What is the goal of gluconeogenesis?

A

producing free glucose

92
Q

Where does gluconeogenesis occur?

A

mainly in the liver, but also in the kidney and small intestine

93
Q

Why is it necessary to produce free glucose?

A

to supply glucose to the brain and for transport in the blood stream

94
Q

What are the precursors of gluconeogenesis?

A

pyruvate, oxaloacetate, and glucogenic amino acids

95
Q

What 3 steps in glycolysis need to be replaced in gluconeogenesis?

A
  1. pyruvate kinase
  2. PFK
  3. hexokinase
96
Q

What replaces pyruvate kinase in gluconeogenesis?

A

pyruvate carboxylase and phosphoenolpyruvate carboxykinase

97
Q

What replaces phosphofructokinase in gluconeogensis?

A

fructose biphosphatase

98
Q

What replaces hexokinase in gluconeogenesis?

A

glucose-6-phosphatase

99
Q

What does pyruvate carboxylase use as a carrier for CO2

A

biotin (cofactor adding carbon)

100
Q

cofactor removing carbon

101
Q

What regulates the futile cycle/prevents waste?

A

fructose-2,6-biphosphate

102
Q

What is fructose-2,6-biphosphate?

A

positive allosteric effector for PFK and negative allosteric effector for FBPase

103
Q

Why is the citric acid cycle both catabolic and anabolic?

A

it is catabolic because it is breaking compounds apart and it is anabolic because the reduced cofactors produced may be helpful in other anabolic pathways

104
Q

What is the enzyme that converts pyruvate into acetyl CoA

A

pyruvate dehydrogenase

105
Q

What is the overall reaction of pyruvate dehydrogenase?

A

pyruvate + CoA-SH + NAD+ —> CO2 + Acetyl-CoA + NADH + H+

106
Q

How many steps are done and how many enzymes are used in the conversion of pyruvate into acetyl-coa

A

5 steps by 3 enzymes

107
Q

What does E1 do?

A

decarboxylate pyruvate using TPP

108
Q

What does E2 do?

A

oxidize the substrate using lipoamide cofactor

109
Q

What does E3 do?

A

oxidize lipoamide using FAD-S-S

110
Q

How is Beri-Beri disease caused?

A

thiamine deficiency that leads to limitations of pyruvate conversion to acetyl CoA which leads to loss of neural function

111
Q

What is the location of TPP?

A

bound to E1

112
Q

What is the function of TPP?

A

decarboxylates pyruvate yielding a hydroxyethyl-TPP carbanion

113
Q

What is the location of lipoic acid?

A

covalently linked to a Lys on E2

114
Q

What is the function of lipoic acid?

A

accepts the hydroxyethyl carbanion from TPP as an acetyl group

115
Q

What is the location for CoA?

A

substrate for E2

116
Q

What is the function of CoA?

A

accepts the acetyl group from lipoamide

117
Q

What is the location of FAD?

A

bound to E3

118
Q

What is the function of FAD?

A

reduced by lipoamide

119
Q

What is the location of NAD+?

A

Substrate for E3

120
Q

What is the function of NAD+?

A

reduced by FADH2

121
Q

What is step one in pyruvate to acetylcoa

A

decraboxylation of pyruvate

122
Q

what is step two in pyruvate to acetylcoa

A

oxidation of carbon by lipoamide

123
Q

what is step 3 in pyruvate to acetylcoa

A

formation of acetyl-coa

124
Q

what is step 4 in pyruvate to acetylcoa

A

reoxidation of the lipoamide by FAD

125
Q

what is step 5 in pyruvate to acetylcoa

A

reoxidation of FAD by NAD+ forming NADH

126
Q

Why is the citric acid cycle considered to be part of aerobic metabolism even though O2 does not explicitly appear in any reaction?

A

NADH and FADH2 produce lots of ATP when reoxidized by the electron transport chain

127
Q

What is the enzyme that converts oxaloacetate and acetyl-coa into citrate?

A

citrate synthase

128
Q

What is the enzyme that converts citrate into isocitrate?

129
Q

What is the enzyme that converts isocitrate and NAD+ into alpha-ketoglutarate, NADH, and CO2

A

isocitrate dehydrogenase

130
Q

What is the enzyme that converts alpha-ketoglutarate, NAD+, and CoASH into Succinyl-CoA, NADH, and CO2?

A

alpha-ketoglutarate dehydrogenase

131
Q

What is the enzyme that converts Succinyl-CoA, GDP, and Pi into Succinate, GTP, and CoASH?

A

succinyl-coA synthetase

132
Q

What is the enzyme that converts Succinate and Q into fumarate and QH2?

A

succinate dehydrogenase

133
Q

What is the enzyme that converts Fumarate and water into malate?

134
Q

What is the enzyme that converts malate and NAD+ into NADH and oxaloacetate?

A

malate dehydrogenase

135
Q

The following is a list of possible products of glycolysis. Assuming ONE molecule of glucose is used in glycolysis, fill the blanks with the correct coefficients.
pyruvate
ATP (net amount)
NAH+
NADH

A

2, 2, 0, 2

136
Q

Which 2 of the glycolysis intermediates contain a high-energy bond and are used to produce ATP by substrate-level phosphorylation in glycolysis?

A

phosphoenolpyruvate and 3-phosphoglycerate

137
Q

Fructose-2,6-biphosphate is a compound that prevents futile cycle, because it is an activator of _______ and an inhibitor of ______. What are the correct enzymes for the blanks?

A

phosphofructokinase, fructose-1,6-biphosphatase

138
Q

The phosphofructokinase (PFK) reaction is a major control point in glycolysis. It is the slowest reaction in glycolysis and is regulated by several molecules, but not by naturally changing concentrations of reactants and products. The molecules mentioned below allosterically regulate PFK activity. Indicate whether each condition described increases or reduces PFK activity (specifically in mammalian liver)
activation of PFK2, decreasing blood glucose concentration, increased pep concentration, increased levels of fructose 2,6 biphosphate, increased levels of ADP

A

activation of PFK2: increase PFK activity
decreasing blood glucose concentration: decrease PFK activity
Increased PEP concentration: decrease PFK activity
Increased levels of fructose 2,6 biphosphate: increase PFK activity
increased levels of ADP: increase PFK activity

139
Q

In animal cells, the pyruvate produced in glycolysis is converted lactate under anaerobic condition. What is the name of enzyme that catalyzes the reaction above?

A

lactate dehydrogenase

140
Q

What type of chemical change is made to the pyruvate in this reaction

A

pyruvate is reduced

141
Q

what is the important product of this reaction other than lactate?

142
Q

What are the unique enzymes in gluconeogenesis that are used to reverse the irreversible steps in glycolysis?

A

pyruvate carboxylase, fructose biphosphatase, glucose-6-phosphatase, PEP carboxykinase

143
Q

Which steps in gluconeogenesis consume or produce ATP?

A

pyruvate carboxylase, PEP carboxykinase, phosphoglycerate kinase

144
Q

aspartate can be converted by transamination reaction into oxaloacetate (OAA). OAA can then be converted to glucose through gluconeogenic pathway. What is the energy yield or cost (in ATP-equivalent) of converting two molecules of OAA to 1 molecule of glucose?

A

4 ATP (equivalent) consumed

145
Q

Glycogen synthesis requires formation of UDP-glucose. The process of UDP-glucose formation is thermodynamically driven by ______?

A

the hydrolysis of PPi

146
Q

Muscle cells are not able to supply glucose for other tissues because they do not contain which of the following enzymes?

A

glucose-6-phosphatase

147
Q

Glycogen phosphorylase catalyzes a _________ reaction that breaks __________ in glycogen. In the fasting state, the hormone glucagon _______ this enzyme, resulting in ________ blood glucose levels.

A

phosphorolysis, alpha 1,4 linkage, stimulates, increasing

148
Q

The pentose phosphate pathway leads to production of _______? (select a pair of correct answers)
1. NADPH for anabolic metabolism
2. NADH for anabolic metabolism
3. NAD+ for glycolysis
4. Ribose-1-P for glycogen synthesis
5. Ribose-5-P for nucleotide production

149
Q

What enzyme catalyzes the step between pyruvate to acetyl CoA and what is its cellular location?

A

pyruvate dehydrogenase in mitochondria

150
Q

Which of the enzymes in the citric acid cycle is regulated by the cellular level of NADH?

A

isocitrate dehydrogenase

CHM 432 (4 decks)

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