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MCAT > Biochem: Ch 9, 10 > Flashcards

Biochem: Ch 9, 10 Flashcards

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1
Q

GLUT2 is found in ___ for ___

A

liver for glucose storage

pancreatic beta islet cells as part of the glucose sensor

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2
Q

GLUT2 has a ___ Km

A

high

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3
Q

GLUT4 is found in ___

A

adipose tissue and muscle

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4
Q

GLUT4 is stimulated by ___

A

insulin

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5
Q

GLUT4 has a ___ Km

A

low

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6
Q

glycolysis occurs in

A

cytoplasm of all cells

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7
Q

glycolysis does not require

A

oxygen

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8
Q

glycolysis yields

A

2 ATP per molecule of glucose

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9
Q

glucokinase

A

irreverible

converts glucose to glucose 6-phosphate in pancreatic beta-islet. ells as part of glucose sensor

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10
Q

glucokinase is present in

A

pancreatic beta-islet cells as part of the glucose sensor

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11
Q

glucokinase is repsonsive to

A

insulin in the liver

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12
Q

hexokinase

A

irreversible

converts glucose to glucose 6-phosphate in peripheral tissues

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13
Q

posphofructokinase-1 (PFK-1)

A

irreversible

phosphorylates fructose 6-phosphate to fructose 1,6-biphosphate in the rate-limiting step of glycolysis

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14
Q

PFK-1 is activated by

A

AMP and fructose 2,6-biphosphate (F2,6-BP)

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15
Q

PFK-1 is inhibited by

A

ATP and citrate

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16
Q

phosphofructokinase-2 (PFK-2)

A

produces the F2,6-BP that activates PFK-1

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17
Q

PFK-2 is activated by

A

insulin

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18
Q

PFK-2 is inhibited by

A

glucagon

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19
Q

glyceraldehyde-3-phosphate dehydrogenase

A

produces NADH, which can feed into the electron transfer chain

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20
Q

3-phosphoglycerate kinase

A

perform substrate level phosphorylation

place inorganic phosphate (Pi) onto ADP to form ATP

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21
Q

pyruvate kinase

A

irreversible

perform substrate level phosphorylation

place inorganic phosphate (Pi) onto ADP to form ATP

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22
Q

enzymes that catalyze irreversible reactions

A

glucokinase, hexokinase, PFK-1, pyruvate kinase

(How Glycolysis Pushes Forward the Process: Kinases)

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23
Q

what happens to the NADH produced in glycolysis when oxygen is present

A

oxidized by the mitochondrial electron transport chain when oxygen

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24
Q

what happens to the NADH produced in glycolysis when oxygen is not present

+ex

A

if oxygen or mitochondria are absent, NADH is oxidized by cytoplasmic lactate dehydrogenase

ex: red blood cells, skeletal muscle (during short, intense bursts of exercise), any cell deprived of oxygen

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25
Q

glycolysis in liver

A

part of the process by which excess glucose is converted to fatty acids for storage

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26
Q

hexokinase is inhibited by

A

its product G 6-P

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27
Q

glycolysis rxn rq

A
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28
Q

substrate level phosphorylation

A

ADP is directly phosphorylated to ATP using high energy intermediate

not dependent on oxygen

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29
Q

feed forward activation

A

product of an earlier rxn of glycolysis stimulates or prepares a later reaction in glycolysis

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30
Q

in the absence of oxygen, ___ will occur

A

fermentation

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31
Q

lactate dehydrogenase

A

oxidized NADH to NAD+

important during fermentation

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32
Q

fermentaion

A

reduces pyruvate to lactate and oxidizes NADH to NAD+

so that all the available NAD+ isn’t used up if glycolysis continues

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33
Q

dihydroxyaceton phosphate (DHAP)

A

used in hepatic and adipose tissue for triacylglycerol synthesis

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34
Q

1,3-BPG and phosphoenolpyruvate (PEP)

A

high energy intermediates used to generate ATP by substrate level phosphorylation

the only ATP gained in anaerobic respiration

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35
Q

why must pyruvate undergo fermentation for glycolysis to continue?

A

fermentation must occur to regenerate NAD+, which is limited in supply in cells

fermentation generates no ATP or energy carriers, it merely regenerates the coenzymes needed in glycolysis

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36
Q

galactose comes from

A

lactose in milk

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37
Q

galactose metabolism

A
  1. trapped in cell by galactose kinase
  2. converted to glucose 1-phosphate via galactose-1-phosphate uridyltransferase and an epimerase
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38
Q

fructose comes from

A

honey, fruit, and sucrose (common table sugar)

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39
Q

fructose metabolism

A
  1. trapped in cell by fructokinase
  2. cleaved by aldolase B to form glyceraldehyde and DHAP
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40
Q

in well fed state, galactose can enter…

A

glycolysis or contribute to glycogen storage

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41
Q

epimerases

A

enzymes that catalyze the conversion of one sugar epimer to another

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42
Q

primary lactose intolerance is caused by

A

hereditary deficiency of lactase

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43
Q

pyruvate dehydrogenase complex (PDH)

A

irreversible

complex of enzymes that oxiidizes pyruvate to acetyl-CoA

requires multiple cofactors and coenzyme (vitamin B1, TPP, Mg2+)

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44
Q

pyruvate dehydrogenase is found in

A

the liver

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45
Q

high insulin levels signal to the liver that individual is in…

thus…

A

a well fed state

the liver should burn glucose for energy and shift fatty acid equilibrium toward production and storage rather than oxidation

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46
Q

possible fates of pyruvate

A
  1. conversion to acetyl CoA by PDH
  2. conversion to lactate by lactate dehydrogenase
  3. conversion to oxaloacetate by pyruvate carboxylase
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47
Q

how does caetyl CoA affect PDH complex? why?

A
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48
Q

glycogenesis

A

glycogen synthesis

production of glycogen using two main enzymes: glycogen synthase, branching enzyme

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49
Q

glycogen synthase

A

rate limiting enzyme of glycogenesis

creates alpha-1,4 glycosidic links between glucose molecules

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50
Q

branching enzyme

A

glycogenesis

moves a block of oligoglucose from one chain and adds it to the growing glycogen as a new branch using an alpha-1,6 glycosidic link

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51
Q

glycogenolysis

A

breakdown of glycogen using two main enzymes: glycogen phosphorylase, debranching enzyme

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52
Q

glycogen phosphorylase

A

glycogenolysis

removes single glucose 1-phosphate molecules by breaking alpha-1,4 glycosidic links

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53
Q

debranching enzyme

A

glycogenolysis

moves a block of oligoglucose from one branch and connects it to the chain using an alpha-1,4 glycosidic link

also removes the branchpoint, releasing a free glucose molecule

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54
Q

glycogen is stored in

A

cytoplasm in granules

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55
Q

isoforms

A

slightly different versions of the same protein

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56
Q

glycogen storage diseases

A

accumulation or lack of glycogen in one or more tissues due to glycogen enzyme isoforms

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57
Q

what types of glycosidic links exist in a glycogen granule?

A
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58
Q

gluconeogenesis occurs in

A

cytoplasm and mitochondria, predominantly in the liver

small contribution from the kidneys

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59
Q

gluconeogenesis

A

opposite of glycolysis (with same enzymes)

production of glucose

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60
Q

gluconeogenesis steps thru enzymes

A

three irreversible steps

  1. pyruvate carboxylase and phosphoenolpyruvate carboxykinase (PEPCK)
  2. fructose-1,6-biphosphatase –> rate limiting step
  3. glucose-6-phosphatase
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61
Q

pyruvate carboxylase

A

gluconeogenesis

converts pyruvate into oxaloacetate

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62
Q

phosphoenolpyruvate carboxykinase (PEPCK)

A

gluconeogenesis

converts oxaloacetate into phosphoenolpyruvate

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63
Q

fructose-1,6-biphosphatase

A

gluconeogenesis

converts fructose 1,6-biphosphate to fructose-6-phosphate

rate limiting step of gluconeogensis

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64
Q

glucose-6-phosphatase

A

gluconeogenesis

converts glucose 6-phosphate to free glucose

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65
Q

glucose-6-phosphatase is found in

A

endoplasmic reticulum of liver only

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66
Q

glucogenic amino acids

A

all except leucine and lysine

can be converted into intermediates that feed into gluconeogenesis

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67
Q

ketogenic amino acids

A

can be converted into ketone bodies, which can be used as an alternative fuel, particularly during periods of prolonged starvation

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68
Q

to produce glucose in liver during gluconeogenesis, fatty acids…

A

must be burned to provide this energy and stop the forward flow of the citric acid cycle

69
Q

under what physiological conditions should the body carry out gluconeogenesis?

A

when an individual has been fasting for >12 hours

hepatic and renal cells must have enough energy to drive the process of glucose creation, which requires sufficient fat stores to undergo beta oxidation

70
Q

pentose phosphate pathway (PPP)

A

aka hexose monophosphate (HMP) shunt

glucose 6-phosphate enters the pathways and the products are NADPH, sugars for biosynthesis, and glycolysis intermediates

71
Q

pentose phosphate pathway (PPP) occurs in

A

cytoplasm of most cells

72
Q

glucose-6-phosphate dehydrogenase (G6PD)

A

PPP

rate limiting enzyme

73
Q

NAD+

A

high energy electron acceptor (in many biochemical rxns)

potent oxidizing agent - helps produce NADH

74
Q

NADPH

A

primarily acts as electron donor

potent reducing agent

used in biosynthesis, in the immune system, and to help prevent oxidative damage

75
Q

NADH produced from

A

reduction of NAD+

76
Q

NADH

A

feeds in ETC to indirectly produce ATP

77
Q

glutathione

A

reducing agent that helps reverse radical formation before damage is done to cell

78
Q

what are the major metabolic products of the PPP?

A

NADPH and ribose-5-phosphate

79
Q

acetyl-CoA

A

contains high energy thioester bond that can be used to drive other reactions when hydrolysis occurs

80
Q

acetyl coa can be formed from

A
  1. pyruvate via pyruvate dehydrogenase complex (PDH)
  2. fatty acids that enter the mitochondria using carrier
  3. carbon skeletons of ketogenic amino acids, ketone bodies, and alcohol
81
Q

pyruvate dehydrogenase kinase

A

phosphorylates PDH when ATP or acetyl CoA levels are high, turning it off

82
Q

pyruvate dehydrogenase phosphatase

A

dephosphorylates PDH when ADP levels are high, turning it on

83
Q

acetyl coA formation from fatty acids

A
  1. fatty acids couple with CoA in cytosol to form fatty acyl CoA, which moves to intermembrane space
  2. acyl (fatty acid) group is transferred to carnitine to form acyl-carnitine which crosses the inner membrane
  3. acycl group is transferred to a mitochondrial CoA to reform fatty acyl CoA, which can undergo beta oxidation to form acteyl CoA
84
Q

citric acid cycle/krebs cycle/TCA cycle occurs in

A

mitochondrial matrix

85
Q

citric acid cycle/krebs cycle/TCA cycle main function

A

oxidation of acteyl COA to CO2 and H2O

produces high energy electron carrying molecules (NADH and FADH2) and GTP

86
Q

citric acid cycle steps

A
  1. citrate formation
  2. citrate isomerized to isocitrate
  3. alpha-ketoglutarate and CO2 formation –> rate limiting enzyme: isocitrate dehydrogenase
  4. succinyl-CoA and CO2 formation
  5. succinate formation
  6. fumarate formation
  7. malate formation
  8. oxaloacetate formed anew
87
Q

citric acid cycle

citrate formation

A
88
Q

citric acid cycle

citrate isomerized to isocitrate

A
89
Q

citric acid cycle

alpha-ketoglutarate and CO2 formation

A
90
Q

citric acid cycle

succinyl-coA and CO2 formation

A
91
Q

citric acid cycle

succinate formation

A
92
Q

citric acid cycle

fumarate formation

A
93
Q

citric acid cycle

malate formation

A
94
Q

citric acid cycle

oxaloacetate formed anew

A
95
Q

citrate synthase

A

citric acid cycle: 1 citrate formation

96
Q

citrate synthase inhibitors

A

ATP, NADH, succinyl-CoA, citrate

97
Q

aconitase

A

citric acid cycle step 2: 2 citrate isomerized to isocitrate

98
Q

isocitrate dehydrogenase

A

citric acid cycle: 3 alpha ketoglutarate and CO2 formation

99
Q

isocitrate dehydrogenase

activators

A

ADP, NAD+

100
Q

isocitrate dehydrogenase inhibitors

A

ATP, NADH

101
Q

alpha-ketoglutarate dehydrogenase complex

A

citric acid cycle: 4 succinyl-CoA and CO2 formation

102
Q

alpha-ketoglutarate dehydrogenase complex activators

A

ADP, Ca2+

103
Q

alpha-ketoglutarate dehydrogenase complex inhibitors

A

ATP, NADH, succinyl-CoA

104
Q

succinyl-CoA synthetase

A

citric acid cycle: 5 succinate formation

105
Q

succinate dehydrogenase

A

citric acid cycle: 6 fumarate formation

106
Q

fumarase

A

citric acid cycle: 7 malate formation

107
Q

malate dehydrogenase

A

citric acid cycle: 8 oxaloacetate formed anew

108
Q

dehydrogenases

A

subtype of oxidoreductases

transfer hydride ion to electron acceptor (NAD+ or FAD)

109
Q

synthases

A

create new covalent bonds without energy input

110
Q

synthetases

A

create new covalent bonds with energy input

111
Q

flavoprotein

A

covalently bonded to FAD

112
Q

control points of citric acid cycle

A
  • citrate synthase
  • isocitrate dehydrogenase
  • alpha-ketoglutarate dehydrogenase complex
113
Q

what enzyme catalyzes the rate limiting step of the citric acid cycle?

A

isocitrate dehydrogenase

114
Q

electron transport chain occurs in

A

matrix facing surface of inner mitochondrial membrane

115
Q

electron transport chain

A
  • NADH donates electrons to the chain, which are passed from one complex to another
  • as ETC progresses, reduction potentials increase until oxygen receives the electrons
  • 4 complexes
116
Q

complex I

A
117
Q

complex II

A
118
Q

complex III

A
119
Q

complex IV

A
120
Q

NADH shuttles (why?)

A

NADH cannot cross intermembrane –> two shuttle mechanisms to transfer electrons

glycerol 3-phosphate, malate-aspartate

121
Q

glycerol 3-phosphate shuttle

A

NADH shuttle

122
Q

malate-aspartate

A

NADH shuttle

123
Q

aerobic components of respiration occur in the

A

mitochondria

124
Q

anaerobic components of respiration occur in

A

cytosol

125
Q

anaerobic components of respiration include

A

glycolysis and fermentation

126
Q

proton-motive force

A

electrochemical proton gradient generated by the complexes of the ETC

As [H+] increases in intermembrane space: pH drops, voltage difference between intermembrane space and matrix inc due to proton pumping

127
Q

cytochromes

A

proteins with heme groups in which iron is reduced to Fe2+ and reoxidized to Fe3+

128
Q

Q cycle

A

increases the gradient of proton motive force across inner mitochondrial membrane

129
Q

ATP Synthase

A
130
Q
A
131
Q

ATP synthase

F0

A

ion channel that allows protons to travel along their gradient into the matrix

132
Q

chemiosmotic coupling

A

allows the chemical energy of the gradient to be harnessed as a means of phosphorylated ADP, forming ATP

133
Q

ATP synthase

F1

A

utilizes the energy released from electrochemical gradient to phosphorylate ADP to ATP

134
Q

key regulators of oxidative phosphorylation

A

O2 and ATP

135
Q

respiratory control

O2 dec

A

O2 is limited –> rate of oxidative phosphorylation decreases –> conc of NADH and FADH2 inc –> inhibits citric acid cycle

136
Q

oxidative phosphorylation

A

ATP synthase generates ATP by harnessing the proton gradient

137
Q

glycolysis produces

A

2 NADH + 2 ATP

138
Q

citric acid cycle produces

A

3 NADH, 1 FADH2, 1 GTP

(6 NADH, 2 FADH2, 2 GTP / molecule of glucose)

139
Q

each NADH yields ____ ATP

A

2.5

140
Q

each FADH2 yields ____ ATP

A

1.5

141
Q

pyruvate dehydrogenase produces

A

1 NADH/molecule of glucose

142
Q

carbohydrate metabolism produces ____

A

30-32 ATP/molecule of glucose

143
Q

respiratory control

ADP inc

A

ADP conc inc –> decrease in ATP –> ADP allosterically activates isocitrate dehydrogenase –> inc rate of citric acid cycle –> produces NADH and FADH2 –> inc rate of ETC and ATP synthesis

144
Q

What is the correct order in which cellular respiration takes place?

I. Krebs Cycle
II. Glycolysis
III. Electron Transport Chain

(A) I, III, and II
(B) II, III, and I
(C) II, I, and III
(D) I, II, and III

A

(C) II, I, and III

Glycolysis takes place first then goes into the Krebs cycle, then finally into the electron transport chain.

145
Q

What is the net ATP produced in each step of cellular respiration and where does each step occur in the cell?

(1) Glycolysis
(2) Krebs Cycle
(3) ETC

A

Glycolysis produces a net of 2 ATP molecules and occurs in the cytoplasm of the cell.

Krebs Cycle produces a net of 2 ATP and occurs in the outer lumen of the mitochondria.

Electron Transport Chain (ETC) produces a net of about 34 ATP and occurs in the inner membrane (lumen) of the mitochondria.

146
Q

Which of the following processes are conducted during aerobic AND anaerobic respiration?

(A) Glycolysis
(B) The Linking Step
(C) Electron Transport Chain
(D) Kreb’s Cycle

A

(A) Glycolysis

Glycolysis is conducted during aerobic respiration and anaerobic respiration. The linking step (pyruvate dehydrogenase (PDH) step), Kreb’s cycle and electron transport chain are only conducted during aerobic respiration when O2 is available.

147
Q

Anaerobic respiration in humans results in the production of _____________ while in anaerobic respiration in yeast (known as fermentation) results in the production of ____________.

(A) lactic acid, ethanol
(B) lactic acid, ethane
(C) ethanol, lactic acid
(D) ethane, lactic acid

A

(A) lactic acid, ethanol

Anaerobic respiration in humans results in the production of lactic acid while in anaerobic respiration in yeast (known as fermentation) results in the production of ethanol (an alcohol).

148
Q

Glycolysis requires __ ATP and produces __ ATP; thus, this process yields a net total of __ ATP.

(A) 4, 6; 2
(B) 2, 6; 4
(C) 2, 4; 2
(D) 0, 4; 4

A

(C) 2, 4; 2

Glycolysis requires 2 ATP and produces 4 ATP; thus, this process yields a net total of 2 ATP.

149
Q

During the fasted state, which of the following mechanisms does the body utilize to maintain its blood glucose level?

I. Glycogenolysis
II. Glycolysis
III. Gluconeogenesis

(A) II only
(B) I and II only
(C) I and III only
(D) I, II and III

A

(C) I and III only

In a fasted state, blood glucose levels are maintained through glycogenolysis (the breakdown of glycogen) and gluconeogenesis (the formation of glucose).

150
Q

Before you can breakdown glycogen in Glycogenolysis, you have to create Glycogen. Which of the following statements about Glycogenesis is FALSE?

(A) Glucose-1-Phosphate is used to synthesize glycogen.
(B) Glucose needs to be activated by coupling to UTP.
(C) Glycogen Synthase is the rate-limiting enzyme and forms α-1,4-glycosidic bonds.
(D) A separate branching enzyme must be used to form the α-1,6-glycosidic bonds at branch points.

A

(B) Glucose needs to be activated by coupling to UTP.

UDP is used for coupling, not UTP.

151
Q

According to Le Chatlier’s principle, if the concentration of glucose increased within a cell, what would happen to the rate of glycolysis and gluconeogenesis?

A

If the concentration of glucose increased within a cell, the rate of glycolysis would increase and the rate of gluconeogenesis would decrease.

152
Q

According to Le Chatlier’s principle, if the concentration of oxaloacetate increased within a cell, what would happen to the rate of glycolysis and gluconeogenesis?

A

If the concentration of oxaloacetate increased within a cell, the rate of glycolysis would decrease and the rate of gluconeogenesis would increase.

153
Q

If the concentration of ATP increased within a cell, what would happen to the rate of glycolysis and gluconeogenesis? Why?

A

If the concentration of ATP increased within a cell, the rate of glycolysis would decrease and the rate of gluconeogenesis would increase. This is because ATP is an allosteric inhibitor of some of the enzymes involved in glycolysis and an allosteric activator of some of the enzymes involved in gluconeogenesis.

154
Q

CRB Write out a table of the amino acids that are Glucogenic (can be used as intermediates in gluconeogenesis), Ketogenic (can be converted into ketone bodies), or both.

A

I like to remember that the two “L” amino acids are the Ketogenic-only ones!

155
Q

When someone has hyperglycemia, their body will produce insulin or glucagon? Why?

When someone has hypoglycemia, their body will produce insulin or glucagon? Why?

A

When someone has hyperglycemia, their body will produce insulin since insulin promotes the storage of glucose via pathways such as glycogenesis.

When someone has hypoglycemia, their body will produce glucagon since glucagon activates pathways such as gluconeogenesis and glycogenolysis that will increase one’s blood glucose levels.

156
Q

Why is the production of Ribose-5-phosphate important?

A

Ribose-5-phosphate is a key component of DNA and RNA.

157
Q

During each stage of cellular respiration, state how many net ATP/GTP, NADH, and FADH2 molecules are produced per molecule of glucose?

(1) Glycolysis
(2) The Linking Step (Pyruvate Dehydrogenase)
(3) Kreb’s Cycle

A

(1) Glycolysis - 2 ATP, and 2 NADH
(2) The Linking Step (Pyruvate Dehydrogenase) - 2 NADH
(3) Kreb’s Cycle - 2 GTP [similar to ATP], 6 NADH, and 2 FADH2

In total: 4 ATP/GTP, 10 NADH, 2 FADH2

158
Q

Where is the majority of the Kreb’s cycle carried out in the mitochondria of eukaroytic cells?

(A) Outer Membrane
(B) Inner Membrane
(C) Intermembrane Space
(D) Mitochondrial Matrix

A

(D) Mitochondrial Matrix

The majority of the Kreb’s cycle is carried out in the mitochondrial matrix of eukaroytic cells.

159
Q

During the linking step (pyruvate dehydrogenase), pyruvate is _______________ and becomes ______________.

(A) oxidized, oxaloacetate
(B) oxidized, acetyl-CoA
(C) reduced, oxaloacetate
(D) reduced, acetyl-CoA

A

(B) oxidized, acetyl-CoA

During the linking step (pyruvate dehydrogenase), pyruvate is oxidized and becomes acetyl-CoA.

160
Q

If ATP levels are high, why would it be in the cell’s best interest to inhibit pyruvate dehydrogenase?

A

If ATP levels are high, that indicates that the cell already has enough energy; thus, it should slow down the production of that energy by inhibiting pyruvate dehydrogenase, which will in turn slow down the citric acid cycle since acetyl-CoA is required for it to run.

161
Q

Which of the following molecules would Pyruvate be directly converted to in order to enter Gluconeogenesis?

(A) Glycerol
(B) Citrate
(C) Acetyl CoA
(D) Oxaloacetate

A

(D) Oxaloacetate

Pyruvate is converted to Oxaloacetate to enter Gluconeogenesis.

162
Q

If calcium levels are high, why would it be in the cell’s best interest to activate pyruvate dehydrogenase?

A

High levels of calcium result from muscle contraction, which is a process that requires energy. To get more energy, the cell will want to ramp up the linking step and the Kreb’s cycle by activating pyruvate dehydrogenase.

163
Q

Why is it that glycolysis can be completely turned off while Kreb’s cycle is usually turned on to one degree or another?

A

Glycolysis is only needed when you are using glucose for energy. The Kreb’s cycle on the other hand is needed for the utilization of sugars, fats, or amino acids for energy. Because cells need energy basically all the time, they will at least want the Kreb’s cycle turned on to some degree or another.

164
Q

What will happen to the activity of the citric acid cycle when citrate is shuttled out of the mitochondrial matrix in an effort to carry acetyl-CoA to the site for fatty acid synthesis?

A

The citric acid cycle will slow down since the substrates of acetyl-CoA and citrate are not as available anymore.

165
Q

Which of the following statements about forming Citrate are true?

I. The Thioester bond in Acetyl-CoA is hydrolyzed, providing the energy to drive Citrate Synthesis.
II. The two carbons from the Acetyl-CoA are incorporated into Citrate’s 5 Carbons.
III. The two carbons Citrate acquired from Acetyl-CoA will leave the TCA cycle as Carbon Dioxide.

(A) I only
(B) I and III only
(C) II and III only
(D) I, II and III

A

(B) I and III only

Each of the following statements about Citrate are true:

I. The Thioester bond in Acetyl-CoA is hydrolyzed, providing the energy to drive Citrate Synthesis.
II. The two carbons from the Acetyl-CoA are incorporated into Citrate’s 6 Carbons.
III. The two carbons Citrate acquired from Acetyl-CoA will leave the TCA cycle as Carbon Dioxide.

166
Q

During the electron transport chain, NADH is oxidized to NAD+, resulting in the formation of electrons. Those electrons are then used to convert O2 into:

(A) CO2
(B) ROS
(C) H2O
(D) CO

A

(C) H2O

O2 is reduced into H2O via the following reaction during the electron transport chain:

2e- + 2H+ + 1/2O2 –> H2O

167
Q

Fill in the blanks: The electrons from Complexes I and II are transferred to _______________, which are later transfered to _______________.

(A) Ubiquinone, Coenzyme Q
(B) Coenzyme Q, Cytochrome C
(C) Cytochrome C, Coenzyme Q
(D) None of the above.

A

(B) Coenzyme Q, Cytochrome C

The electrons from Complexes I and II are transferred to Coenzyme Q, which are later transfered to Cytochrome C.

Note that Coenzyme Q is synonymous with Ubiquinone.

168
Q

Compare oxidative phosphorylation versus substrate-level phosphorylation.

A

Oxidative phosphorylation is a very specific name for what occurs during the electron transport chain. It entails the oxidation of electron carrier molecules and the phosphorylation of ADP to form ATP (via ATP synthase).

Substrate phosphorylation is when ATP is generated via a generic enzyme (i.e. pyruvate kinase).

MCAT (26 decks)

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