Chapter 18 Flashcards
1
Q
electrons from the reduced coenzymes NADH and FADH2 pass through a series of redox centers in the electron-transport chain before
A
reducing O2
2
Q
during electron transfer protons are translocated out of the mitochondrion to form an … whose free energy drives ATP synthesis
A
electrochemical gradient
3
Q
the mitochondrion contain soluble and membrane-bound enzymes for …
A
oxidative metabolism
4
Q
reducing equivalents are imported from the cytosol via a shuttle system. specific transporters mediate the transmembrane movements of …, … and …
A
ADP; ATP; Pi
5
Q
electrons flow from redox centers with more … reduction potentials to those with more … reduction potentials. inhibitors have been used to reveal the sequence of electron carriers and the points of entry of electrons into the electron-transport chain
A
negative; positive
6
Q
electron transport is mediated by … (Fe-S clusters, cytochromes, and Cu ions) and …. (CoQ, FMN, FAD)
A
one-electron carriers; two-electron carriers
7
Q
Complex I transfers two electrons from … to … while translocating .. protons to the intermembrane space
A
NADH; CoQ; four
8
Q
Complex II transfers electrons from … through … to …
A
succinate; FAD; CoQ
9
Q
Complex III transfers two electrons from … to two molecules of … the concomitant operation of the Q cycle translocates .. protons to the intermembrane space
A
CoQH2; cytochrome c; four
10
Q
Complex IV reduces … to … using four electrons donated by four cytochrome c and four protons from the matrix. … protons are translocated to the intermembrane space for every … electrons that reduce oxygen
A
O2; 2H2O; two; two
11
Q
as explained by the chemiosmotic theory, protons translocated into the intermembrane space during electron transport through Complexes I, III, and IV establish an … across the …
A
electrochemical gradient; inner mitochondrial membrane
12
Q
the influx of protons through the F0 component of ATP synthase drives its F1 component to synthesize ATP from ADP + Pi via the … mechanism, a process that is mechanically driven by the F0-mediated rotation of F1’s gamma subunit with respect to its catalytic alpha3beta3 assembly
A
binding change
13
Q
The P/O ratio, the number of ATPs synthesized per oxygen reduced, need not be an …
A
integral number
14
Q
agents that discharge the proton gradient can uncouple … from electron transport
A
oxidative phosphorylation
15
Q
oxidative phosphorylation is controlled by the ratio .. and by the …r atio. glycolysis and the citric acid cycle are coordinately regulated according to the need for …
A
[NADH]/[NAD+]; ATP mass action; oxidative phosphorylation
16
Q
aerobic metabolism is more efficient than anaerobic metabolism. however, aerobic organisms must guard against the damage caused by …
A
reactive oxygen species
17
Q
…: a system of linked electron carriers
A
mitochondrial electron-transport chain
18
Q
(electron-transport process) 1. by transferring their electrons to other substances, the NADH and FADH2 are reoxidized to … and … so that they can participate in additional substrate oxidation reactions
A
NAD+; FAD
19
Q
(electron-transport process) 2. the transferred electrons participate in the sequential oxidation-reduction of multiple … (groups that undergo redox rxns) in four enzyme complexes before reducing O2 to H2O
A
redox centers
20
Q
(electron-transport process) 3. the transfer of electrons is coupled to the expulsion of protons from the mitochondrion, producing a proton gradient across the inner mitochondrial membrane. the free energy stored in this electrochemical gradient drives the synthesis of ATP from ADP and Pi through …
A
oxidative phosphorylation
21
Q
A mitochondrion is bounded by a smooth outer membrane and contains an extensively invaginated inner membrane (Fig. 18-2). The number of invaginations, called ….(Latin: crests), refl ects the type of cell and its respiratory activity.
A
cristae
22
Q
The inner membrane divides the mitochondrion into two compartments, the … and the internal …. The ….is a gel-like solution that contains extremely high concentrations of the soluble enzymes of oxidative metabolism as well as substrates, nucleotide cofactors, and inorganic ions.
A
intermembrane space; matrix; matrix
23
Q
cristae form microcompartments that restrict the diffusion of substrates and ions between the … and … spaces
A
intercristal; intermembrane
24
Q
the intermembrane space is equivalent to the … in its concentrations of metabolites and ions
A
cytosol
25
the outer mitochondrial membrane contains …, proteins that permit the free diffusion of molecules of up to 10 kD
porins
26
the controlled impermeability of the inner mitochondrial membrane to most ions and metabolites permits the generation of … across this barrier and results in the …. of metabolic functions between cytosol and mitochondria
ion gradients; compartmentalization
27
The NADH produced in the cytosol by glycolysis must gain access to the mitochondrial electron-transport chain for aerobic oxidation. However, the inner m itochondrial membrane lacks an NADH transport protein. Only the electrons from cytosolic NADH are transported into the mitochondrion by one of several ingenious ….
“shuttle” systems.
28
We have already discussed the ... shuttle (Fig. 16-20), in which, when run in reverse, cytosolic oxaloacetate is reduced to malate for transport into the mitochondrion. When malate is reoxidized in the matrix, it gives up the reducing equivalents that originated in the cytosol.
malate–aspartate
29
The ...shuttle (Fig. 18-5) is expressed at variable levels in different animal tissues and is especially active in insect fl ight muscle (the tissue with the largest known sustained power output).
glycerophosphate
30
for the glycerophosphate shuttle:
… catalyzes the oxidation of cytosolic NADH by dihydroxyacetone phosphate to yield NAD+ which reenters glycolysis. the electrons of the resulting ... are then transferred to … to form FADH2 which supplies e- directly to the electron-transport chain
3-phosphoglycerol dehydrogenase; 3-phosphoglycerol; flavoprotein dehydrogenase
31
most of the ATP generated in the … through oxidative phosphorylation is used in the cytosol. the inner mitochondrial membrane contains an … (also called the …) that transports ATP out of the matrix in exchange for ADP produced in the cytosol by ATP-consuming rxns
mitochondrial matrix; ADP-ATP translocator; adenine nucleotide translocase
32
several natural products inhibit the ATP-ADP translocator, including … and its derivative ...
atractyloside (position produced by Mediterranean thistle); carboxyatractyloside
33
the atp-adp translocator must bind ligand to change from one … to the other at a physiologically reasonable rate. thus it functions as an ... by importing one ADP for every ATP
conformation; exchanger
34
the atp-adp translocator is involved in … antiport
electrogenic
35
ATP is synthesized from ADP + Pi in the mitochondrion but is utilized in the cytosol. The Pi is returned to the mitochondrion by the ..., an electroneutral Pi– H+ symport that is driven by ΔpH.
phosphate carrier
36
The transmembrane proton gradient generated by the electron-transport machinery of the inner mitochondrial membrane thus not only provides the …. driving force for ATP synthesis (Section 18-3), it also motivates the transport of the ...—ADP and Pi—required for the process.
thermodynamic; raw materials
37
We can estimate the thermodynamic efficiency of electron transport by inspecting the ... of the redox centers
standard reduction potentials
38
The standard reduction potential diff erence, Δℰ°′, for a redox reaction involving any two half-reactions is expressed Δℰ°′ =
ℰ°′ (e−acceptor) − ℰ°′ (e− donor)
39
In mitochondria, the coupling of NADH oxidation to ATP synthesis is achieved by an electron transport chain in which electrons pass through three protein complexes. This allows the overall free energy change to be broken into.... , each of which contributes to ATP synthesis by oxidative phosphorylation. Oxidation of one NADH results in the synthesis of approximately ...
three smaller parcels; 2.5 ATP
40
Oxidation of NADH and FADH2 is carried out by the electron-transport chain, a series of four protein complexes containing redox centers with progressively greater affinities for electrons (...). Electrons travel through the chain from ...to higher standard reduction potentials
increasing standard reduction potentials; lower; higher
41
Electrons are carried from Complexes ..to Complex .. by the lipid ... (CoQ or ubiquinone; so named because of its ubiquity in respiring organisms), and from Complex ..to Complex ...by the small soluble protein ...
I and II; III; coenzyme Q; II; IV; cytochrome c
42
Complex I catalyzes oxidation of … by ..
NADH; CoQ
43
Complex III catalyzes oxidation of … by …
CoQ (reduced); cytochrome c
44
Complex IV catalyzes oxidation of reduced … by .., the terminal electron acceptor of the electron-transport process
cytochrome c; O2
45
Complex II catalyzes the oxidation of … by …
This redox rxn does not release sufficient free energy to synthesize ATP; it only functions to inject the electrons from … into the electron-transport chain
FADH2; CoQ; FADH2
46
```
the rate at which … by a suspension of mitochondria is a sensitive measure of the activity of the e- transport chain. compounds that inhibit e- transport as judged by their effect on O2 consumption include:
… (plant toxin)
… (barbiturate)
… (antibiotic)
…
```
O2 is consumed; rotenone;
amytal
antimycin A
cyanide
47
Adding rotenone or amytal to a suspension of mitochondria blocks electron transport in ..; antimycin A blocks .., and CN− blocks electron transport in ... (Fig. 18-7). Each of these inhibitors also halts O2 consumption
Complex I; Complex III; Complex IV
48
Complex I (…), which passes electrons from NADH to CoQ, is the largest protein complex in the inner mitochondrial membrane.
NADH–coenzyme Q oxidoreductase)
49
Complex I contains one molecule of ... (FMN, a redox-active prosthetic group that differs from FAD only by the absence of the AMP group) and eight (in mammals), or nine or ten (in prokaryotes), ...
flavin mononucleotide; iron–sulfur clusters
50
Iron–sulfur clusters occur as the prosthetic groups of ... (also called ...). The two most common types, designated... and... clusters (at left), consist of equal numbers of iron and sulfide (S2−) ions and are both coordinated to four protein Cys sulfhydryl groups
iron–sulfur proteins; nonheme iron proteins; [2Fe-2S]; [4Fe-4S]
51
Iron–sulfur clusters can undergo ...oxidation and reduction. The oxidized and reduced states of all iron–sulfur clusters differ by ...formal charge regardless of their number of Fe atoms.
one-electron ; one
52
FMN and CoQ, which can transfer one or two electrons at a time, therefore provide an …between the two-electron donor NADH and the one-electron acceptors. Thus, NADH reduces FMN in a two-electron reaction (formally, a hydride transfer), which in turn passes these electrons, one by one, through the “wire” of Fe–S clusters, to the CoQ.
electron conduit
53
As electrons are transferred between the redox centers of Complex I,... are translocated from the matrix to the intermembrane space. This proton pumping is driven by conformational changes induced by changes in the redox state of the protein
four protons
54
a proton can be translocated by “hopping” along a chain of hydrogen-bonded groups in a transmembrane channel, just as it “jumps” between hydrogen-bonded water molecules in solution (Fig. 2-15). Such an arrangement of hydrogen-bonded groups in the protein, which may include water molecules, has been described as a ...
proton wire
55
...is a light-driven proton pump: It obtains the free energy required for pumping protons through the absorbance of light by its retinal prosthetic group. it's a model proton pump.
Bacteriorhodopsin
56
two of the helices in each of the antiporterlike subunits of complex I have centrally located kinks that provide them with the … to open and close the proton translocation channels
conformational flexibility
57
the entire process of NADH reduction, electron transport, CoQ reduction, and proton translocation occurs about … times per second, the turnover rate of complex I
200
58
complex II (…) which contains the citric acid cycle enzyme succinate dehydrogenase, passes e- from succinate to CoQ
succinate-coenzyme Q oxidoreductase
59
the free energy for e- transfer from succinate to CoQ is insufficient to drive ATP synthesis. the complex II is nevertheless important bc it allows relatively high-potential e- to enter the e- transport chain by …
bypassing complex I
60
complexes I and II do not … both accomplish the same result: the transfer of e- to CoQ from reduced substrates (NADH or succinate)
operate ins eries
61
…, which diffuses in the lipid bilayer among the respiratory complexes, serves as a sort of electron collector
CoQ
62
complex III (also known as … or …) passes e- from reduced CoQ to cytochrome C
coenzyme Q-cytochrome c oxidoreductase; cytochrome bc1
63
the … (ISP), which contains the Rieske center--two His residues (?)--is anchored by a single transmembrane helix and extends inot the intermembrane space
iron-sulfur protein
64
Complex III functions to permit one molecule of CoQH2, a two-electron carrier, to reduce two molecules of cytochrome c, a one-electron carrier. This occurs by a surprising bifurcation of the fl ow of electrons from CoQH2 to cytochrome c1 and to cytochrome b (in which, as we shall see, the fl ow is cyclic --> ...
Q-cycle
65
The essence of the Q cycle is that CoQH2 undergoes a ... in which the semiquinone, CoQ−, is a stable intermediate. This involves two independent ... for coenzyme Q: Qo, which binds CoQH2 and is located between the Rieske [2Fe–2S] center and heme bL in proximity to the intermembrane space; and Qi, which binds both CoQ− ∙ and CoQ and is located near heme bH in proximity to the matrix.
two-cycle reoxidation; binding sites
66
For every two CoQH2 that enter the Q cycle, ... is regenerated.
one CoQH2
67
The globular domain of the ISP can swing via an ∼20-Å hinge motion between the Qo site and cytochrome c1. Consequently, the ISP acquires an electron from CoQH2 in the Qo site and ….delivers it to the ...group. The CoQ− ∙ product cannot reduce the ISP (after it has reduced cytochrome c1) because the ISP has moved too far away for this to occur.
mechanically; heme c1;
68
the net rxn for the Q cycle indicates that when CoQH2 is oxidized, two reduced … molecules and … appear on the outer side of the membrane. proton transport by the Q cycle thus differs from the proton pumping mechanism of Complex I and IV; in the Q cycle, a … itself (CoQ) is the proton carrier
cytochrome c; four protons; redox center
69
the electrons that flow to cytochrome c1 are transferred to …, which, unlike the other cytochromes of the respiratory electron-transport chain, is … in the intermembrane space
cytochrome c; soluble
70
… (complex IV) catalyzes the one electron oxidations of four consecutive reduced cytochrome c molecules and the concomitant four electron reduction of one o2 molecule
cytochrome c oxidase
71
electron transfer in complex IV is .., proceeding from cytochrome c to the CuA center, then to heme a, and finally to heme a3 and Cub
linear
72
… can supply the fourth electron to cytochrome c oxidase by transiently forming a ...
Tyr 244; tyrosyl radical
73
```
(rxn sequence for cytochrome c oxidase) 1 and 2.
The O (for oxidized) state binuclear complex in which Tyr 244 is in its phenolate state, is reduced by two consecutive one-electron transfers from cytochrome c via CuA and cytochrome a, each accompanied by the acquisition of a … from the … and the release of an … This yields the .. (for reduced) complex in which Tyr 244 has assumed its phenolic state
```
proton; matrix; H2O; R;
74
(rxn sequence for cytochrome c oxidase) 3. O2 binds to the R state binuclear complex so as to ligand its Fe(II)a3 atom. it binds to the heme with much the same configuration it has in … Tyr 244 remains in its phenolic state
oxymyoglobin
75
(rxn sequence for cytochrome c oxidase) 4. internal electron … rapidly yields the oxyferryl complex in which Tyr 244 has donated an electron and a proton to the complex and thereby assumed its … state. this is known as the … state bc it was once thought to be a peroxy compound
redistribution; neutral radical; P
76
(rxn sequence for cytochrome c oxidase) 5. a third one-electron transfer from cytochrome c, together with the acquisition of a proton from the matrix, converts Tyr 244 to its … state, yielding the … (for ferryl) state in which an H2O remains liganded to Cu(II)B
phenolate; F
77
(rxn sequence for cytochrome c oxidase) 6. a fourth and final electron transfer and proton acquisition again yields the … state, thereby completing the catalytic cycle
O
78
the rxn catalyzed by cytochrome c oxidase contributes to the H+ gradient.
1st, four … or … protons are taken up from the matrix during O2 reduction by cytochrome c oxidase to yield 2H2O, depleting the matrix [H+].
2nd the 4 e- reduction rxn is coupled to the translocation of four … or … protons from the matrix to the intermembrane space
chemical; scalar; pumped; vectorial
79
cytochrome c oxidase has 2 channels
…: leads from matrix side of the protein to Tyr 244, the residue that forms a free radical
…: extends from the matrix to the vicinity of the heme a3--Cub center where it connects to the so-called …, which communicates with the intermembrane space
K-channel
D-channel
exit channel
80
the endergonic synthesis of ATP from ADP and Pi in mitochondria is catalyzed by an … (also known as …) that is driven by the e- transport process. the free energy released by e- transport through complexes I-IV must be conserved in a form that the ATP synthase can use. such energy conservation is referred to as …
ATP synthase; Complex V; energy coupling
81
chemiosmotic theory states that the free energy of electron transport is conserved by pumping H+ from the … to the … to create an electrochemical H+ gradient across the inner mitochondrial membrane. the electrochemical potential of this gradient is harnessed to synthesize ATP
mitochondrial matrix; intermembrane space
82
(key observations explained by chemiosmotic theory) 1. oxidative phosphorylation requires an intact …
2. the inner mitochondrial membrane is impermeable to ions such as H+, OH-, K+, and Cl- whose free diffusion would ...
inner mitochondrial membrane
| discharge an electrochemical gradient
83
(key observations explained by chemiosmotic theory)
3. electron transport results in the transport of … out of intact mitochondria, thereby creating a measurable electrochemical gradient across the inner mitochondrial membrane
H+
84
(key observations explained by chemiosmotic theory)
4. compounds that increase the permeability of the inner mitochondrial membrane to protons, and thereby dissipate the electrochemical gradient, allow electron transport (from NADH and succinate oxidation) to continue but …; that is, they "uncouple" electron transport from oxidative phosphorylation. conversely, increasing the acidity outside the inner mitochondrial membrane stimulates ...
inhibit ATP synthesis; ATP synthesis
85
electron transport causes Complexes I, III, and IV to transport protons across the inner mitochondrial membrane from the … a region of low [H+] to the … (which is in contact with the …), a region of high [H+]
matrix; intermembrane space; cytosol
86
… (pmf): free energy sequestered by the resulting electrochemical gradient which powers ATP synthesis
protonmotive force
87
Since the pH outside the mitochondrion is less than the pH of the matrix, the export of protons from the mitochondrial matrix (… the proton gradient) is an .. process
against; endergonic
88
ATP synthase, also known as ...and F1F0-ATPase, is a multisubunit transmembrane protein with a total molecular mass of 450 kD. Efraim Racker discovered that mitochondrial ATP synthase is composed of two functional units, … and …
proton-pumping ATP synthase; F0; F1
89
… is a water-insoluble transmembrane protein containing as many as 8 diff types of subunits
… is a water-soluble peripheral membrane protein, composed of 5 types of subunits, that is easily and reversibly dissociated from … by treatment with urea
F0; F1; F0
90
F1 component of atp synthase has ...
pseudo threefold symmetry
91
F0 component of atp synthase includes a
transmembrane ring
92
The proton-translocating ATP synthase must be able to do 3 things:
1. … protons, which is carried out by F0
2. catalyze formation of the … of ATP, which is carried out by F1
3. couple the dissipation of the proton gradient with …, which requires interaction of F1 and F0
translocate
phosphoanhydride bond
ATP synthesis
93
…: mechanism for ATP formation which species that F1 has three interacting catalytic protomers (αβ units), each in a diff erent conformational state: one that binds substrates and products loosely (L state), one that binds them tightly (T state), and one that does not bind them at all (open or O state
binding change mechanism
94
the free energy released on .. is harnessed to interconvert the L, T, and O states
proton translocation
95
the phosphoanhydride bond of ATP is synthesized only in the … state and ATP is released only in the … state
T; O
96
(binding change mechanism) 1. ADP and Pi bind to the … (L)
2. a free energy-driven conformational change converts the L site to a … (T) binding site that catalyzes the formation of ATP. This also involves conformational changes of the other two protomers that convert the ATP containing T site to an … (O) site and convert the O to an L site
loose binding site; tight; open
97
(binding change mechanism) 3. ATP is synthesized at the .. site on one subunit while ATP … from the O site on another subunit. the rxn forming ATP is essentially at equilibrium under the conditions at the enzyme's active site. the free energy supplied by the proton flow primarily facilitates the release of the newly synthesized ATP from the enzyme; that is, it drives the … transition, thereby disrupting the enzyme-ATP interactions that had previously promoted the spontaneous formation of ATP from ADP + Pi in the T site
T; dissociates; T--> O transition;
98
the binding changes are driven by the … of the catalytic assembly, α3𝛽3, with respect to other portions of the F1F0-ATPase.
rotation
99
Apparently the γ subunit, which rotates within the fixed α 3𝛽3 assembly, acts as a ...in linking the proton gradient–driven F0 engine to the conformational changes in the catalytic sites of F1.
molecular camshaft
100
the F1F0-ATPase, which generates ... ATP per turn and (at least in E. coli) has 12 c subunits in its F0 assembly, ideally forms 3/12 = ... ATP for every proton it passes from outside to inside
3; 0.25
101
The E. coli F1F0-ATPase can work in reverse, that is, it can pump protons from the inside to the outside at the expense of... (this enables the bacterium to maintain its proton gradient under anaerobic conditions, which it uses to drive various processes
ATP hydrolysis
102
Many of the actin fi laments were seen to rotate (Fig. 18-28b), and always in a ...direction when viewed looking down on the glass surface (from the outside
counterclockwise
103
ATP synthesis is tightly coupled to the …: that is, ATP synthesis requires the discharge of the proton gradient, and the proton gradient cannot be discharged without the synthesis of ATP.
proton gradient
104
the oxidation of NADH is associated with the synthesis of approximately ... ATP, and the oxidation of FADH2 with approximately ... ATP
3; 2
105
..: relate the amount of ATP synthesized (P) to the amount of oxygen reduced (O). Experimentally determined P/O ratios are compatible with the chemiosmotic
P/O ratios
106
Electrons that enter the electron-transport chain as FADH2 at Complex II bypass Complex I and therefore lead to the transmembrane movement of only .. protons, enough to synthesize ∼... ATP (corresponding to approximately two-thirds of a full rotation of the ATP synthase rotary engine). The transit of two electrons through Complex IV alone contributes .. protons to the gradient, enough for ∼... ATP (around one third of a rotation).
6; 2; 2; 1
107
the number of ATPs that are synthesized per molecule of glucose oxidized is 2.5 ATP/NADH × 10 NADH/glucose + 1.5 ATP/FADH2 × 2 FADH2/glucose + 2 ATP/glucose from the citric acid cycle + 2 ATP/glucose from glycolysis =...ATP/glucose
32
108
Electron transport (the oxidation of NADH and FADH2 by O2) and oxidative phosphorylation (the proton gradient–driven synthesis of ATP) are normally tightly coupled. This coupling depends on the ...of the inner mitochondrial membrane, which allows an electrochemical gradient to be established across the membrane by H+ translocation during electron transport.
impermeability
109
compounds such as ….(DNP) have been found to “uncouple” electron transport and ATP synthesis. DNP is a lipophilic weak acid that readily passes through membranes in its neutral, protonated state. In a pH gradient, it binds protons on the acidic side of the membrane, diff uses through the membrane, and releases the protons on the membrane’s alkaline side, thereby acting as a proton-transporting ...(Section 10-2A) and dissipating the gradient (Fig. 18-29). The chemiosmotic theory provides a rationale for understanding the action of such ...
2,4-dinitrophenol; ionophore; uncouplers
110
The presence in the inner mitochondrial membrane of an agent that increases its permeability to H+ uncouples oxidative phosphorylation from electron transport by providing a route for the ... that does not require ATP synthesis.
dissipation of the proton electrochemical gradient
111
the dissipation of an electrochemical H+ gradient, which is generated by electron transport and uncoupled from ATP synthesis, produces ...
heat
112
. The activities of the pathways that produce ATP are under strict coordinated control so that ATP is never produced ...
more rapidly than necessary.
113
, the cytochrome c oxidase reaction (the terminal step of the electron transport chain) is ...and is therefore a potential control site.
irreversible
114
…: [ATP]/[ADP]*[Pi]
ATP mass action ratio
115
Because isocitrate dehydrogenase is activated by ADP and α-ketoglutarate dehydrogenase is inhibited by ATP, the citric acid cycle slows down. This causes the citrate concentration to build up. Citrate leaves the mitochondrion via a specific transport system and, once in the cytosol, acts to restrain further ... by inhibiting ….
carbohydrate breakdown; PFK
116
the inhibition of glycolysis by fatty acid oxidation is called … or …
glucose-fatty acid cycle; Randle cycle
117
aerobic metabolism is up to ... times more efficient than anaerobic glycolysis in producing ATP
16
118
Although the four electron reduction of O2 by cytochrome c oxidase is nearly always orchestrated with great rapidity and precision, O2 is occasionally only ..., yielding oxygen species that readily react with a variety of cellular components
partially reduced
119
Several degenerative diseases, including Parkinson’s, Alzheimer’s, and Huntington’s diseases, are associated with oxidative damage to mitochondria. Such observations have led to the free-radical theory of aging, which holds that free-radical reactions arising during the course of normal oxidative metabolism are at least partially responsible for the ...
aging process
120
...destroy oxidative free radicals such as O2· and ∙OH.
Antioxidants
