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Chapter 9 Cellular Respiration and Fermentation > Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels > Flashcards

Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels Flashcards

1
Q

Metabolic pathways that release stored energy by breaking down complex molecules are called

A

catabolic pathway

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2
Q

Organic compounds possess potential energy as a result of the arrangement of electrons in the bonds between their

A

atoms

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3
Q

Compounds that can participate in exergonic reactions can act as

A

fuels.

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4
Q

is a partial degradation of sugars or other organic fuel that occurs without the use of oxygen.

A

fermentation

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5
Q

most efficient catabolic pathway is ____________________ in which oxygen is consumed as a reactant along with the organic fuel

A

aerobic respiration

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6
Q

The cells of most eukaryotic and many prokaryotic organisms can carry out

A

aerobic respiration

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7
Q

Some prokaryotes use substances other than oxygen as reactants in a similar process that harvests chemical energy without oxygen; this process is called

A

anaerobic respiration

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8
Q

includes both aerobic and anaerobic processes.

A

cellular respiration

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9
Q

cellular respiration is often used to refer to the

A

aerobic process

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10
Q

Carbohydrates, fats, and protein molecules from food can all be processed and consumed as

A

fuel

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11
Q

In animal diets, a major source of carbohydrates is starch, a storage polysaccharide that can be broken down into

A

glucose subunits.

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12
Q

This breakdown of glucose is exergonic, having a free-energy change of

A

-686 kcal (2,870 kJ) per mole of glucose decomposed (∆G= -686 kcal/mol)

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13
Q

Recall that a negative ∆G ( ∆G<0) indicates that the products of the chemical process store less energy than the reactants and that the reaction can happen

A

spontaneously—in other words, without an input of energy.

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14
Q

Catabolic pathways do not directly move

A

flagella, pump solutes across membranes, polymerize monomers, or perform other cellular work.

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15
Q

to keep working, the cell must regenerate its supply of

A

ATP from ADP and ℗

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16
Q

The relocation of electrons releases energy stored in organic molecules, and this energy ultimately is used to

A

synthesize ATP.

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17
Q

In many chemical reactions, there is a transfer of one or more electrons (eˉ) from

A

one reactant to another.

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18
Q

These electron transfers are called

A

oxidation-reduction reactions, or redox reactions

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19
Q

In a redox reaction, the loss of electrons from one substance is called

A

oxidation

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20
Q

the addition of electrons to another substance is known as

A

reduction. (Note that adding electrons is called reduction; adding negatively charged electrons to an atom reduces the amount of positive charge of that atom.)

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21
Q

in the generalized reaction, substance Xeˉ, the electron donor, is called the

A

reducing agent; it reduces Y, which accepts the donated electron.

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22
Q

Substance Y, the electron acceptor, is the

A

oxidizing agent; it oxidizes Xeˉ by removing its electron.

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23
Q

Because an electron transfer requires both an electron donor and an acceptor, oxidation and reduction always

A

go hand in hand.

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24
Q

Not all redox reactions involve the complete transfer of electrons from one substance to another; some change

A

the degree of electron sharing in covalent bonds.

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25
Q

a reduction-oxidation (redox) reaction always involves two events:

A

one substance loses electron and is said to be oxidized, while another substance gains electrons and is said to be reduced

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26
Q

sodium chloride, or table salt offers an example of

A

atoms that have undergone oxidation and reduction to become ions

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27
Q

when sodium and chlorine react to form sodium chloride, one electron is completely transferred from the

A

sodium atom to the chlorine atom, the result is a sodium cation and a chloride anion

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28
Q

in this redox reaction, the sodium atom lost an electron- it was

A

oxidized

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29
Q

the new sodium ion is a

A

positively charged cation

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30
Q

the chlorine atom gained an electron- it was

A

reduced

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31
Q

the new chloride ion is a

A

negatively charged anion

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32
Q

in redox reactions, electrons can be transferred completely from one molecule or atom to another forming an

A

ionic bond, or they can simply shift positions in covalent bonds.

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33
Q

the combustion of methane is a good example of this second type of reaction. The electrons in the two reactants- methane and oxygen are shown as dots at equal distance from the atoms nuclei, indicating that

A

electrons are shared equally

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34
Q

when electrons are shared equally the bonds are

A

nonpolar

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35
Q

methane combustion involves the reaction of

A

two oxygen molecules with each methane molecule

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36
Q

the reaction yields

A

carbon dioxide and water as the products

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37
Q

the atoms in the products share electrons

A

unequally. meaning that the bonds are polar

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38
Q

in carbon dioxide, the nucleus of the

A

carbon atom holds the electrons less tightly

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39
Q

carbon has been

A

oxidized- it lost electrons

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40
Q

in water, the nucleus of the atom holds the electrons

A

more tightly

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41
Q

oxygen has been

A

reduced- it gained electrons

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42
Q

because the atomic nuclei of the product molecules hold the electrons more tightly than they were held in the reactant molecules the product have

A

lower potential energy

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43
Q

such reactions tend to be

A

spontaneous, or exergonic, and release free energy

44
Q

The two atoms of the oxygen molecule share their electrons

A

equally

45
Q

when oxygen reacts with the hydrogen from methane, forming water, the electrons of the covalent bonds spend more time near the

A

oxygen

46
Q

each oxygen atom has partially “gained” electrons, so the oxygen molecule has been

A

reduced.

47
Q

The more electronegative the atom (the stronger its pull on electrons), the more energy is required to take an

A

electron away from it

48
Q

An electron loses potential energy when it shifts from a less electronegative atom toward a more

A

electronegative one

49
Q

learn summary equation for cellular respiration

A

look under oxidation of organic fuel molecules during cellular respiration

50
Q

organic molecules that have an abundance of hydrogen are excellent fuels because their bonds are a source of ____________________whose energy may be released as these electrons ______ down an energy gradient during their transfer to oxygen.

A

“hilltop” electrons, “fall”

51
Q

energy state of the electron changes as hydrogen (with its electron) is transferred to

A

oxygen.

52
Q

In respiration, the oxidation of glucose transfers electrons to a lower energy state, liberating energy that becomes available for

A

ATP synthesis.

53
Q

we see fuels with multiple C—H bonds oxidized into products with multiple

A

C—O bonds.

54
Q

The main energy-yielding foods—carbohydrates and fats—are reservoirs of electrons associated with

A

hydrogen, often in the form of C—H bonds

55
Q

Only the barrier of activation energy holds back the

A

flood of electrons to a lower energy state

56
Q

glucose is broken down in a series of steps, each one catalyzed by an

A

enzyme.

57
Q

At key steps, electrons are stripped from the

A

glucose.

58
Q

As is often the case in oxidation reactions, each electron travels with a proton—thus, as a

A

hydrogen atom.

59
Q

The hydrogen atoms are not transferred directly to oxygen, but instead are usually passed first to an electron carrier, a coenzyme called

A

nicotinamide adenine dinucleotide, a derivative of the vitamin niacin

60
Q

This coenzyme is well suited as an electron carrier because it can cycle easily between its oxidized form

A

,NAD+ , and its reduced form, NADH

61
Q

As an electron acceptor, NAD+ functions as an

A

oxidizing agent during respiration.

62
Q

How does trap electrons from glucose and the other organic molecules in food? Enzymes called ___________________ remove a pair of hydrogen atoms (2 electrons and 2 protons) from the substrate (glucose, in the preceding example), thereby oxidizing it

A

dehydrogenases

63
Q

The enzyme delivers the 2 electrons along with 1 proton to its coenzyme,

A

NAD+ , forming NADH

64
Q

The other proton is released as a hydrogen ion (H+) into the

A

surrounding solution

65
Q

Learn surrounding solution above figure 9.4

A
66
Q

By receiving 2 negatively charged electrons but only 1 positively charged proton, the nicotinamide portion of NAD+ has its charge neutralized when

A

NAD+ is reduced to NADH.

67
Q

The name NADH shows the hydrogen that has been received in the reaction. NAD+ is the most versatile electron acceptor in cellular respiration and functions in several of the

A

redox steps during the breakdown of glucose.

68
Q

Electrons lose very little of their potential energy when they are transferred from

A

glucose to NAD+.

69
Q

Each NADH molecule formed during respiration represents

A

stored energy.

70
Q

Cellular respiration also brings hydrogen and oxygen together to form water, but there are two important differences. First, in cellular respiration, the hydrogen that reacts with oxygen is derived from

A

organic molecules rather than .

71
Q

Second, instead of occurring in one explosive reaction, respiration uses an electron transport chain to break the fall of electrons to oxygen into

A

several energy-releasing steps

72
Q

consists of a number of molecules, mostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells (and the plasma membrane of respiring prokaryotes)

A

electron transport chain

73
Q

Electrons removed from glucose are shuttled by NADH to the

A

“top,” higher-energy end of the chain.

74
Q

At the “bottom,” lower-energy end, O2 captures these electrons along with hydrogen nuclei (H+) , forming

A

water

75
Q

Electron transfer from NADH to oxygen is an exergonic reaction with a free-energy change of

A

-53 kcal/mol (-222 kJ/mol)

76
Q

Each “downhill” carrier is more electronegative than, and thus capable of

A

oxidizing, its “uphill” neighbor, with oxygen at the bottom of the chain.

77
Q

during cellular respiration, most electrons travel the following “downhill” route:

A

glucose → NADH → electron transport chain → oxygen

78
Q

The harvesting of energy from glucose by cellular respiration is a cumulative function of three metabolic stages.

A
  1. Glycolysis, 2. Pyruvate oxidation and the citric acid cycle, 3. oxidative phosphorylation
79
Q

occurs in the cytosol, begins the degradation process by breaking glucose into two molecules of a compound

A

Glycolysis

80
Q

compound is called

A

pyruvate

81
Q

eukaryotes, pyruvate enters the mitochondrion and is oxidized to a compound which enters the

A

citric acid cycle

82
Q

compound is called what for citric acid cycle

A

acetyl CoA

83
Q

organic compounds such as glucose store energy in their arrangements of

A

atoms

84
Q

these molecules are broken down and their energy extracted in

A

cellular respiration

85
Q

the first stage of cellular respiration occurs in the

A

cytosol

86
Q

the second and third stages occur in

A

mitochondria

87
Q

in cellular respiration, electrons are transferred from glucose to

A

electron carriers such as NAD+ and finally oxygen

88
Q

the energy released by this transfer of electrons is used to make

A

ATP

89
Q

carbon dioxide and water are given off as

A

by-products

90
Q

the stages of respiration- Glycolysis is a series of steps in which a

A

glucose molecule is broken down into two molecules of pyruvate

91
Q

as the chemical bond in glucose are broken electrons and hydrogen ions are picked up by

A

NAD+, forming NADH

92
Q

glucose is oxidized and NAD+ is

A

reduced

93
Q

a small amount of ATP is also produced in glycolysis by

A

substrate-level phosphorylation

94
Q

but most of the energy released by the breakdown of glucose is carried by the

A

electrons attached to NADH

95
Q

the pyruvate molecule are oxidized to acetyl CoA as they the _____________, releasing carbon dioxide

A

mitochondrion

96
Q

the acetyl CoA molecules enter a series of reactions called the

A

citric acid cycle

97
Q

more carbon dioxide is released as the citric acid cycle completes the

A

oxidation of glucose

98
Q

most of the energy released by the oxidation of glucose is carried by

A

NADH and FADH2

99
Q

the final stage of cellular respiration the NADH and FADH2 molecules produced in glycolysis and the citric acid cycle donate their electrons to the electron transport chain

A

oxidative phosphorylation

100
Q

electrons move down the chain to the end, where

A

oxygen exerts a strong pull on the electrons

101
Q

oxygen, electrons, and hydrogen ions combine, forming

A

water

102
Q

the electron transport chain converts the chemical energy from moving electrons to a form of

A

energy that can be used to drive oxidative phosphorylation

103
Q

which produces most of the ATP generated by

A

cellular respiration

104
Q

in eukaryotic cells, the inner membrane of the mitochondrion is the site of electron transport and another process called

A

chemiosmosis

105
Q

A smaller amount of ATP is formed directly in a few reactions of glycolysis and the citric acid cycle by a mechanism called

A

substrate-level phosphorylation

Chapter 9 Cellular Respiration and Fermentation (7 decks)

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