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BLG 143 Chapter 1 > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Metabolic pathways harvest energy from high- energy molecules, such as

A

Glucose

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2
Q

The energy released is used to add a phosphate group to ADP to make

A

ATP

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3
Q

Cells generally contain enough ATP to sustain

A

from 30 seconds to a few minutes of activity
– ATP is unstable
– Most cells are making it all the time

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4
Q

Cells obtain glucose to make

A

ATP
– Plants produce glucose during photosynthesis
– Other organisms obtain glucose from food

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5
Q

Organisms store glucose as

A

glycogen or starch

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6
Q

When glucose is oxidized to carbon dioxide by burning

A

some energy is released as heat and light

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7
Q

Glucose + 6 oxygen –>

A

6Carbon dioxide+ 6 water+ heat and light

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8
Q

Oxygen atoms are reduced to form

A

water
– Oxygen acts as electron acceptor

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9
Q

In cells, glucose is oxidized through

A

a long series of carefully controlled redox reactions
– The released free energy is used to synthesize ATP
– These reactions comprise cellular respiration

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10
Q

Fermentation

A

also oxidizes glucose
– Does not oxidize it fully
– Small, reduced organic molecules are produced as waste

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11
Q

Does cellular respiration or fermentation produce more energy?

A

Cellular respiration

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12
Q

Cellular respiration is a set of four processes, they are

A

Glycolysis, pyruvate processing, citric acid cycle, electron transport & oxidative phosphorylation

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13
Q

Glycolysis is when

A

A six-carbon glucose is broken down into two three-carbon pyruvate

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14
Q

Pyruvate processing involves

A

Each pyruvate is oxidized to form acetyl CoA

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15
Q

The citric acid cycle is

A

Each acetyl CoA is oxidized to CO2

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16
Q

Electron transport and oxidative phosphorylation involve

A

Electrons move through a transport chain and their energy is used to set up a proton gradient, which is used to make ATP

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17
Q

Each of the four processes of cellular respiration produce

A

High-energy molecules in the form of nucleotides (ATP) and/or electron carriers (NADH or FADH2). Because the four processes are connected, cellular respiration is an integrated metabolic pathway. The first three processes oxidize glucose to produce NADH and FADH2, which then feed the electron transport chain.

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18
Q

cellular respiration is

A

Cellular respiration is any set of reactions that uses electrons from high-energy molecules to make ATP

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19
Q

Two fundamental requirements of cells are :

A
  1. Energy to generate ATP
  2. A source of carbon to use as raw materials for synthesizing macromolecules
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20
Q

Catabolic pathways

A

– Involve the breakdown of molecules
– Often harvest stored chemical energy to produce ATP

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21
Q

Anabolic pathways

A

– Result in the synthesis of larger molecules from smaller
components
– Often use energy in the form of ATP

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22
Q

Cellular respiration interacts with

A

other catabolic and anabolic pathways

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23
Q

For ATP production, cells use

A

– First use carbohydrates
– Then fats
– And finally proteins

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24
Q

Proteins, carbohydrates, and fats can all furnish what for cellular respiration

A

substrates

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25
Q

A variety of high-energy compounds from carbohydrates, fats, or proteins can be broken down in catabolic reactions and

A

used by cellular respiration for ATP production.

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26
Q

Several of the intermediates in cellular respiration serve as precursor molecules in anabolic reactions leading to

A

the synthesis of carbohydrates, nucleotides, lipids, and amino acids

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27
Q

Fats are broken down into

A

– Glycerol, which enters glycolysis
– Fatty acids, which are converted to acetyl CoA, which enters the citric acid cycle

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28
Q

Proteins are broken down into amino acids

A

– Amino groups are removed and excreted as waste
– The remaining carbon compounds are converted to
pyruvate, acetyl CoA, or other intermediates
– Used in glycolysis and the citric acid cycle

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29
Q

Molecules found in carbohydrate metabolism are used to synthesize

A

macromolecules

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30
Q

About half the required amino acids can be synthesized from

A

citric acid cycle molecules

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31
Q

Acetyl CoA is the starting point in

A

fatty acid synthesis
 Can be used to build phospholipids or fats

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32
Q

Glycolysis intermediates can be used to make

A

nucleotides for DNA and RNA synthesis

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33
Q

Pyruvate and lactate can be used to make

A

glucose

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34
Q

Metabolism comprises thousands of different

A

chemical reactions.
Organizing them into pathways allows them to be regulated

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35
Q

Maintaining a stable internal environment even under different environmental conditions is

A

Homeostasis

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36
Q

Glycolysis is

A

Oxidizing Glucose to Pyruvate

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37
Q

The enzymes responsible for glycolysis have been observed in

A

nearly every prokaryote and
eukaryotes
– Glycolysis is an ancient method to make ATP
– Process discovered by accident

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38
Q

How many chemical reactions occur in the cytosol during glycolysis

A

10

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39
Q

Three key points regarding glycolysis

A
  1. Glycolysis starts by using two ATP in the energy investment phase (reactions 1–5)
  2. During the energy payoff phase (reactions 6–10), NADH is made and ATP is produced by substrate- level phosphorylation
  3. The net yield is two NADH, two ATP, and two pyruvate
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40
Q

Substrate-level phosphorylation involves

A

An enzyme and a phosphorylated substrate. Substrate-level phosphorylation occurs when an enzyme catalyzes the transfer of a phosphate group from a phosphorylated substrate to ADP, forming ATP

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41
Q

Reaction 1 of glycolysis

A

Hexokinase uses ATP to phosphorylate glucose, increasing its potential energy

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42
Q

reaction 2 of glycolysis

A

Phosphoglucose isomerase: converts glucose-6-phosphate to fructose-6-phosphate; referred to as an isomer of glucose-6-phosphate

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43
Q

reaction 3 of glycolysis

A

Phosphofructokinase uses ATP to phosphorylate the opposite end of fructose-6-phosphate, increasing its potential energy

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44
Q

reaction 4 of glycolysis

A

Fructose-biphosphate aldolase: cleaves fructose-1,6-biphosphate into two different 3-carbon sugars

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45
Q

reaction 5 of glycolysis

A

Triose phosphate isomerase converts dihydrogen phosphate (daP) to glyceraldehyde-3-phosphate (G3P). Although the reaction is fully reversible, the DAP-to-GDP reaction is favoured because G3P is immediately used as a substrate for step 6

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46
Q

reaction 6 of glycolysis

A

Glyceraldehyde-3-phosphate dehydrogenase: a two-step reaction that first oxidizes G3P using the NAD+ coenzyme to produce NADH. Energy from this reaction is used to attach a Pi to the oxidized product to form 1,3-biphosphoglycerate

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47
Q

reaction 7 of glycolysis

A

Phosphoglycerate kinase transfers a phosphate from 1,3-biphosphoglycerate to ADP to make 3-phosphoglycerate and ATP

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48
Q

reaction 8 of glycolysis

A

Phosphoglycerate mutase: rearranges the phosphate in 3-phosphoglycerate to make 2-phosphoglycerate

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49
Q

reaction 9 of glycolysis

A

Enolase: removes a water molecule from 2-phosphoglycerate to form a C=C double bond and produce phosphoenolpyruvate

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50
Q

reaction 10 of glycolysis

A

Pyruvate kinase: transfers a phosphate from phosphoenolpyruvate to ADP to make pyruvate and ATP

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51
Q

Glycolysis is regulated by

A

feedback inhibition
High levels of ATP (a product of glycolysis) inhibit the third enzyme: phosphofructokinase

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52
Q

Phosphofructokinase has two binding sites for ATP

A
  1. When ATP binds to the active site, the enzyme catalyzes the third step in glycolysis. In the active site, ATP is used as a substrate to transfer one of its phosphate groups to fructose-6-phosphate
  2. When ATP levels are high, it binds to a regulatory site and inhibits the enzyme. In the regulatory site, ATP binding inhibits the reaction by changing the shape of the enzyme
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53
Q

Pyruvate produced during glycolysis is transported into

A

Mitochondria

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54
Q

Mitochondria have both inner and outer

A

Membranes that define the inter-membrane space and matrix

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55
Q

Cristae are extensions of the

A

inner membrane
– Layers of sac-like structures
– Fill the interior of the mitochondria
– Are connected to the inner membrane by short tubes

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56
Q

The mitochondrial matrix

A

is inside the inner membrane

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57
Q

Pyruvate processing occurs in the

A

mitochondrial matrix

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58
Q

Pyruvate processing takes place inside an enormous enzyme complex called

A

pyruvate dehydrogenase
– Located in the mitochondrial matrix in eukaryotes
– Located in the cytosol in prokaryotes

59
Q

Pyruvate undergoes a series of reactions

A

– One of its carbons is oxidized to CO2
– NADH is produced
– The remaining two-carbon unit is attached to coenzyme A, producing acetyl CoA

60
Q

During the reactions of pyruvate what goes in and comes out

A

– Pyruvate, NAD+, and CoA go in
– CO2, NADH, and acetyl CoA come out

61
Q

Pyruvate processing is also regulated by feedback inhibition

A

– When products of glycolysis and pyruvate processing are abundant
– Pyruvate dehydrogenase is phosphorylated
– Changes shape and is inhibited

62
Q

The Citric Acid Cycle

A

Oxidizes Acetyl CoA to CO2

63
Q

In the citric acid cycle, each acetyl CoA from pyruvate processing is oxidized into

A

two CO2

64
Q

The citric acid cycle is located in the

A

– Mitochondrial matrix in eukaryotes
– Cytosol in prokaryotes

65
Q

The reactions of citric acid cycle

A

– Starts by moving the acetyl group from acetyl CoA to
oxaloacetate to form citrate
– At the end, oxaloacetate is regenerated

66
Q

Some of the potential energy released in citric acid cycle is used to

A
  1. Reduce three NAD+ to NADH
  2. Reduce one FAD to FADH2
  3. Phosphorylate ADP (or GDP) to form ATP (or GTP)
67
Q

The cycle turns twice for each

A

glucose molecule,
since two pyruvate are produced by glycolysis

68
Q

What goes in and comes out of the citric acid cycle

A

Acetyle CoA goes into the citric acid cycle and carbon dioxide, NADH, FADH, and ATP or GTP come out. ATP or GTP is produced by substrate-level phosphorylation. If you follow individual carbon atoms around the cycle several times, you’ll come to an important conclusion. Each of the carbons in the cycle is eventually a “red carbon” that is released as CO2

69
Q

The citric acid cycle can be turned off at multiple points via several mechanisms of

A

feedback inhibition

70
Q

Reaction rates are high in citric acid cycle when

A

ATP and NADH are
scarce

71
Q

reaction rates are low in citric acid cycle when

A

ATP or NADH are
abundant

72
Q

How many reactions are there in the citric acid cycle

A

8

73
Q

reaction 1 of citric acid cycle

A

Citrate synthase: transfers the 2-carbon acetyl group from acetyl CoA to the 4-carbon oxaloacetate to produce the 6-carbon citrate

74
Q

reaction 2 of citric acid cycle

A

Aconitase: convert citrate to isocitrate by the removal of one water molecule and the addition of another water molecule

75
Q

reaction 3 of citric acid cycle

A

Isocitrate dehydrogenase: oxidizes isocitrate using the NAD+ coenzyme to produce NADH and releases one CO2, resulting in the formation of the 5-carbon molecule alpha-ketoglutarate

76
Q

reaction 4 of citric acid cycle

A

Alpha-ketoglutarate: oxidizes alpha-ketoglutarate using the NAD+ coenzyme to produce NADH and releases one CO2. the remaining 4-carbon molecules are added to coenzyme A (CoA) to form succinyl CoA

77
Q

reaction 5 of citric acid cycle

A

Succinyl CoA synthetase: CoA is removed, converting succinyl CoA to succinate., the energy released is used to transfer Pi to ADP to form ATP, or to GDP to form GTP, depending on the enzyme used

78
Q

reaction 6 of citric acid cycle

A

Succinate dehydrogenase: oxidizes succinate by transferring two hydrogens to the coenzyme FAD to produce FADH2, resulting in the formation of fumarate

79
Q

reaction 7 of citric acid cycle

A

Fumarase converts fumarate to malate by the addition of one water molecule

80
Q

reaction 8 of citric acid cycle

A

Malate dehydrogenase: oxidizes malate by using the NAD+ coenzyme to produce NADH, resulting in the regeneration of the oxaloacetate that will be used in step 1 of the cycle

81
Q

For each molecule of glucose that is oxidized, the cell produces

A

– 6 CO2—disposed of when you exhale
– 4 ATP—directly used as fuel
– 10 NADH
– 2 FADH2

82
Q

Free energy changes as

A

glucose is oxidized
About 2680 kj/mol of free energy is released from the oxidation of glucose
Much of the energy is harnessed in the form of ATP, NADH, and FADH2

83
Q

Most of glycose’s original energy is contained in the electrons transferred to

A

NADH and FADH2

84
Q

The electrons (and protons) are ultimately transferred to oxygen to form

A

water

85
Q

Researchers determined that NADH is oxidized when combined with

A

the inner membrane of
mitochondria

86
Q

In prokaryotes,NADH is oxidized by

A

The plasma
membrane

87
Q

Molecules in the inner mitochondrial membrane could cycle between

A

oxidized and reduced states

88
Q

The molecules that oxidize NADH and FADH2 are called the

A

electron transport chain (ETC)
– Most are proteins that are easily oxidized
– One is a lipid-soluble, non-protein called ubiquinone or coenzyme Q or “Q”
– They have different ability to accept electrons, called their redox potential
– Some accept only electrons; others accept electrons plus protons

89
Q

As electrons move from one molecule to another in the ETC

A

– They are held more and more tightly
– A small amount of energy is released in each reaction
– Each successive bond holds less potential energy

90
Q

The ETC is organized into four protein complexes

A

– Called complexes I–IV
– Cytochrome c transfers electrons between complexes

91
Q

At the end of the ETC

A

– Low-energy electrons are passed to oxygen, along with protons
– Water is formed

92
Q

Which reactions occur in the electron transport chain

A

oxidation and reduction reactions
- The potential energy in shared electrons steps down from the electron carriers NADH and FADH2 through an electron transport chian to a final electron acceptor
- In this electron transport chain, oxygen is the final electron acceptor and it forms water as a by-product
- The overall free-energy change of 222 KJ/mol (from NADH to oxygen) is borken into small steps

93
Q

What is the reaction of complex I in ETC

A

Complex I (NADH dehydrogenase): oxidizes NADH and transfers two electrons through proteins containing FMN prosthetic groups and Fe.S cofactors to reduce and oxidized from of the ubiquinone (Q). Four H+ are pumped out of the matrix to the inter-membrane space

94
Q

What is the reaction of complex II in ETC

A

Complex II (succinate dehydrogenase): oxidized FADH2 and transfers the two electrons through proteins containing Fe.S cofactors to reduce an oxidized form of Q. this complex is also used in step 6 of the citric acid cycle

95
Q

What is the reaction of Q in ETC

A

Q (ubiquinone): reduced by complexes I and II and moves throughout the hydrophobic interior of the ETC membrane, where it is oxidized by complex III

96
Q

what is the reaction of complex III in ETC

A

Complex III (cytochrome c reductase): oxidizes Q and transfers one electron at a time through proteins containing heme prosthetic groups and Fe.S cofactors to reduce an oxidized form of cytochrome c (cyt c). A total of four H+ for each pair of electrons is transported from the matrix to the intermembrane space

97
Q

What is the reaction of cyt c in the ETC

A

Cyt c (cytochrome c): reduced by accepting a single electron from complex III and moves along the surface of the ETC membrane, where it is oxidized by complex IV

98
Q

What is the reaction of complex IV in ETC

A

Complex IV ( cytochrome c oxidase): oxidizes cyt c and transfers each electron through protein containing heme prosthetic groups to reduce oxygen gas (O2) which picks up two H+ from the matrix to produce water. Two additional H+ are pumped out of the matrix to the inter-membrane space

99
Q

The reactions of the ETC comprise the

A

fourth pathway of cellular respiration

100
Q

The energy released as electrons moves through the ETC and

A

– Is used to pump protons across the mitochondrial inner membrane into the intermembrane space
– Forms a strong electrochemical gradient

101
Q

Most of the chemical energy from glucose is now accounted for by

A

a proton electrochemical
gradient

102
Q

How does the electron transport chain work

A
  • The individual components of the electron transport chain are found in the inner membrane of the mitochondria
  • Electrons are carried from one complex to another by Q and by cytochrome c; Q also shuttles protons across the membrane.
  • The orange arrow indicates Q moving back and forth
  • Complexes I and IV use the energy released by the redox reactions to pump protons from the mitochondrial matrix to the inter-membrane space
103
Q

ATP synthase is

A

the enzyme that synthesizes
ATP – “complex V

104
Q

Protons move through a proton channel in ATP synthase

A

– Driving the production of ATP from ADP and Pi
– Process is called chemiosmosis
– ATP production is dependent on a proton-motive force generated by the proton electrochemical gradient

105
Q

What is the chemiosmotic hypothesis

A

The linkage between the electron transport chain and ATP production is indirect.
The ETC creates a protein gradient and ATP synthase uses the gradient to synthesize ATP

106
Q

What is the alternate hypothesis to chemiosmotic hypothesis

A

Alternate hypothesis: the linkage is direct. Specific ETC proteins are required for ATP synthesis by ATP synthase

107
Q

What is the experimental setup for chemiosmotic hypothesis

A
  1. Produce venues from artificial membranes: add ATP synthase, an enzyme found in mitochondria
  2. Add bacteriorhodopsin, a protein that acts as a light-activated proton pump
  3. Illuminate the vesicle so that bacteriorhodopsin pumps protons out of the vesicle, creating a proton gradient
108
Q

Prediction of chemiosmotic hypothesis:

A

ATP will be produced within the vesicle

109
Q

Prediction of alternate hypothesis:

A

No ATP will be produced without the ETC

110
Q

results of chemiosmotic experiment

A

Results: ATP is produced within the vesicle, in the absence of the electron transport chain

111
Q

conclusion of chemiosmotic experiment

A

Conclusion: the linkage between electron transport and ATP production by ATP synthase is indirect, the synthesis of ATP only requires a proton gradient

112
Q

Oxidative Phosphorylation Involves

A

the ATP Synthase Motor and a Proton Gradient
- ATP synthase has two major components, designated F0 and F1, connected by a shaft
- The F0 unit spins as protons pass-through
- The shaft transmits the rotation to the F1 unit, causing it to make ATP from ADP and Pi

113
Q

The Proton-Motive Force Couples

A

Electron Transport to ATP Synthesis

114
Q

ATP synthase can reverse direction by

A

Hydrolyze ATP to build a proton gradient

115
Q

If the proton gradient dissipates

A

the spin is reversed and ATP is hydrolyzed to pump protons from the matrix to the inter-membrane space.

116
Q

Thus, the energy to produce ATP comes from a

A

proton gradient

117
Q

Approximate yield of ATP from glucose is

A

29
– 25 ATP from ATP synthase
– This process is called oxidative phosphorylation
– As opposed to substrate-level phosphorylation that
occurs during glycolysis and the citric acid cycle

118
Q

Most of the ATP made during cellular respiration is made by

A

oxidative phosphorylation

119
Q

The actual yield of ATP per glucose (29 ATP) is lower than

A

the theoretical calculation (38 ATP) because the proton gradient is used to drive other mitochondrial activities, such as the active transport of Pi into the mitochondrial matrix

120
Q

All eukaryotes and many prokaryotes

A

– Use oxygen as the final electron acceptor for the ETC
– This is called aerobic respiration

121
Q

Some prokaryotes

A

– Especially those in oxygen-poor environments
– Use other electron acceptors
– This is called anaerobic respiration

122
Q

Oxygen is the most effective electron acceptor because

A

– It is highly electronegative
– A large difference exists between the potential energy
of electrons in NADH and O2
– It allows the generation of a large proton-motive force

123
Q

Aerobic organisms

A

grow and reproduce faster

124
Q

What happens when there is no electron acceptor?

A

– The electrons have no place to go
– The ETC stops

125
Q

NADH builds up and there is no NAD+ available to accept electrons causing

A

– Glycolysis, pyruvate processing, and the citric acid cycle stop
– The situation is life threatening
– NAD+ must be regenerated

126
Q

Fermentation is

A

a metabolic pathway that
regenerates NAD+ from NADH
– Electrons from NADH are transferred to pyruvate
– Serves as an emergency backup in respiring cells

127
Q

Glycolysis can continue to produce ATP by

A

substrate-level phosphorylation in the absence of oxygen

128
Q

What are the alternative pathways for producing ATP

A

Cellular respiration and fermentation
- When oxygen or another final electron acceptor used by the ETC is present in a cell, the pyruvate produced by glycolysis enters the citric acid cycle and the electron transport system is active
- If no electron acceptor is available to keep the ETC running, then pyruvate undergoes reactions known as fermentation

129
Q

When our muscle cells cannot get enough oxygen, they convert to

A

lactic acid fermentation
– Pyruvate produced by glycolysis accepts electrons
from NADH
– Lactate and NAD+ are produced

130
Q

As muscle cells get more oxygen, lactate can be

A

converted back to pyruvate

131
Q

Fermentation regenerates

A

NAD+ so that glycolysis can continue
- Lactic acid fermentation occurs in humans
- No intermediate; pyruvate accepts electrons from NADH
- Alcohol fermentation occurs in yeast (bubbles in beer and champagne)

132
Q

Some yeast cells can perform

A

alcohol fermentation
– Pyruvate is converted to acetaldehyde and CO2
– Acetaldehyde accepts electrons from NADH
– Ethanol and NAD+ are produced

133
Q

Cells that perform other types of fermentation are used to make

A

soy sauce, tofu, yogurt, cheese, etc

134
Q

Prokaryotes that rely on fermentation are present in our

A

intestines

135
Q

Fermentation is much less efficient than

A

cellular respiration
- It produces 2 ATP per glucose, compared with
about 29 ATP per glucose in cellular respiration

136
Q

Some organisms can switch between fermentation and aerobic respiration called

A

facultative anaerobes
– They use fermentation only if an electron acceptor is
not available

137
Q

Our transportations systems are run on

A

petroleum
– Mixture of organic material from long dead creatures

138
Q

Biofuels can be produced

A

to power transportation
– Mixture of organic molecules produced by living organisms.
– Renewable

139
Q

Gasoline in Canada must contain an average renewable fuel content of

A

5 percent

140
Q

How to turn corn into the biofuel ethanol?

A

– remove the kernels from the cob.
– starch is broken down into glucose and then fermented into ethanol by the action of enzymes and yeast
– the water removed by distillation and dehydration.
– the pure ethanol is mixed with gasoline to serve as car fuel

141
Q

Biofuels can be controversial because

A

– Growing corn uses
 Fuel
 Water
 Land
 Fertilizer
 Less cropland for food
 Increase food costs in developing nations
 May not reduce greenhouse gas emissions

142
Q

Brazil as an example

A

– Has produced bio-ethanol from sugar cane for more than 30 years
– Brazil’s automobile fuel has a minimum of 25% ethanol
 Many vehicles use 100% ethanol
– Only 1% of Brazil’s land is used for growing this sugar cane.

143
Q

Anaerobic respiration of waste material is another alternative

A

– methane is produced
– then used as a fuel to produce electricity

BLG 143 Chapter 1 (5 decks)

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