Unit 9 Question Bank

Complexes · chemiosmotic theory · ATP synthase · inhibitors · shuttles

25 MCQ · five options7 Definitions2 Written answersHarper's verified

Format note: the TMU Biochemistry paper gives five suggested answers (A–E), not four — these MCQs match that. Items tagged TMU 2019 or TMU 2020/21 come from the real papers. Answers are verified against Harper's Illustrated Biochemistry; the "marking schemes" in the source folder are other students' answer sheets, not official, so they are never used as the authority.

0 / 25 answered

1The inner mitochondrial membrane is characterised by ( ).

A. the presence of acyl-CoA synthetase and glycerolphosphate acyltransferase

B. the presence of adenylyl kinase and creatine kinase

C. free permeability to most small metabolites

D. selective permeability, with cardiolipin and the chain enzymes

E. the absence of any embedded proteins

Answer: D

The outer membrane is permeable to most metabolites and carries acyl-CoA synthetase and glycerolphosphate acyltransferase; adenylyl kinase and creatine kinase mark the intermembrane space. The inner membrane's selective permeability — particularly its impermeability to protons — is what makes the whole chemiosmotic mechanism possible.Harper's ch.13, p.127 · TMU Lecture 9 Slide 3

2Ubiquinone in higher animals contains how many isoprenoid units?

A. 4

B. 6

C. 8

D. 12

E. 10

Answer: E

Hence Q₁₀. Its structure is very similar to that of vitamins K and E and to plastoquinone. Q acts as a mobile component, collecting reducing equivalents from the fixed flavoprotein complexes and passing them to the cytochromes.Harper's ch.13 · TMU Lecture 9 Slide 9

3Which two components of the respiratory chain are MOBILE?

A. Ubiquinone and cytochrome c

B. Cytochrome b and cytochrome c₁

C. FMN and FAD

D. Complexes I and II

E. Haem a and haem a₃

Answer: A

The four complexes are large proteins fixed in the membrane and cannot reach one another. Q is lipid-soluble and diffuses within the membrane; cytochrome c is the only soluble cytochrome and moves along the outer face of the inner membrane. Together they connect the fixed complexes.Harper's ch.13, pp.128–129 · TMU Lecture 9 Slide 12

4Iron-sulfur proteins take part in electron transfer in which manner?

A. Two-electron transfer, the iron cycling between Fe²⁺ and Fe⁴⁺

B. Single-electron transfer, the iron cycling between Fe²⁺ and Fe³⁺

C. Proton transfer only

D. Transfer of a hydride ion

E. Transfer of molecular oxygen

Answer: B

Fe-S proteins (non-haem iron) are found in Complexes I, II and III and may contain one, two or four Fe atoms linked to inorganic sulfur and/or via cysteine-SH groups. They handle single-electron transfers — which is precisely the mismatch the Q cycle exists to resolve, since Q carries two electrons.Harper's ch.13, p.128

5Complex I of the respiratory chain is ( ).

A. succinate-Q reductase

B. Q-cytochrome c oxidoreductase

C. NADH-Q oxidoreductase

D. cytochrome c oxidase

E. ATP synthase

Answer: C

The four complexes are I NADH-Q oxidoreductase, II succinate-Q reductase, III Q-cytochrome c oxidoreductase and IV cytochrome c oxidase. ATP synthase is not one of the four — it is a separate enzyme driven by the proton gradient they create.Harper's ch.13, p.128

6Which respiratory chain complex does NOT pump protons?

A. Complex I

B. Complex III

C. Complex IV

D. Complex II

E. All four pump protons

Answer: D

Complex II (succinate-Q reductase) pumps no protons. This single fact explains the entire difference in ATP yield between NADH and FADH₂: electrons entering at Complex II bypass Complex I and miss the four protons it would have pumped. NADH → 4+4+2 = 10 H⁺; FADH₂ → 4+2 = 6 H⁺.Harper's ch.13, pp.128–131

7How many protons are translocated per NADH oxidised, in total?

A. 6

B. 4

C. 8

D. 12

E. 10

Answer: E

Complex I translocates 4, Complex III translocates 4, and Complex IV translocates 2 — a total of 10. For FADH₂, which enters at Complex II, the total is 6. These numbers are the modern basis for the non-integer P:O ratios.Harper's ch.13, p.131

8Which reaction of the respiratory chain is IRREVERSIBLE?

A. Reduction of O₂ to water by cytochrome c oxidase

B. Transfer of electrons from QH₂ to cytochrome c

C. Oxidation of NADH by Complex I

D. Reduction of Q by succinate

E. Reduction of FMN by NADH

Answer: A

Complex IV catalyses the only irreversible reaction in the chain, which gives direction to the movement of reducing equivalents and to the ATP production coupled to it. It also has a very high affinity for oxygen, allowing the chain to run at maximum rate until the tissue is depleted of O₂.Harper's ch.13, p.130 · TMU Lecture 9 Slide 12

9Cytochrome c oxidase contains which metals in addition to iron?

A. Molybdenum, as a molybdopterin cofactor

B. Copper, in the Cu_A and Cu_B centres

C. Manganese, in a binuclear Mn centre

D. Cobalt, as a corrin-bound Co ion

E. Zinc, in a catalytic Zn²⁺ site

Answer: B

The transfer of four electrons from cytochrome c to O₂ involves two haem groups, a and a₃, and copper. Electrons pass to Cu_A (two Cu atoms linked to protein cysteine-SH groups), then to haem a, haem a₃, then Cu_B, and finally to O₂.Harper's ch.13, p.130

10Complex IV keeps O₂ tightly bound until it is fully reduced. The purpose is to ( ).

A. increase the affinity of the enzyme for cytochrome c

B. allow four protons to be pumped simultaneously

C. minimise release of damaging superoxide intermediates

D. conserve oxygen when the tissue pO₂ is low

E. prevent carbon monoxide from binding

Answer: C

Partially reduced oxygen species are dangerous: O₂ accepting one electron gives superoxide, two electrons gives peroxide. Holding O₂ bound until all four electrons have been delivered avoids releasing them. Of the eight H⁺ removed from the matrix, four form the two waters and four are pumped.Harper's ch.13, p.130

11The chemiosmotic theory was proposed by ( ).

A. Hans Krebs, in 1937

B. Fritz Lipmann, in 1941

C. Otto Warburg, in 1931

D. Peter Mitchell, in 1961

E. Paul Boyer, in 1973

Answer: D

Mitchell's insight was that there is no chemical intermediate linking oxidation to phosphorylation — the link is a gradient. The energy of oxidation is coupled to translocation of protons from inside to outside the inner mitochondrial membrane, and the resulting proton motive force drives ATP synthesis.Harper's ch.13, p.130

12In the chemiosmotic theory, the proton motive force is an electrochemical potential difference that is ( ).

A. positive on the matrix side

B. equal on both sides of the membrane

C. confined to the outer membrane

D. generated by ATP synthase itself

E. negative on the matrix side

Answer: E

Protons are pumped out of the matrix into the intermembrane space, leaving the matrix side negative. Because the inner membrane is impermeable to ions in general and to protons in particular, they accumulate — creating the force that drives ATP synthase.Harper's ch.13, p.130

13In ATP synthase, which component forms the proton channel?

A. F₀, which spans the membrane

B. F₁, which projects into the matrix

C. The γ-subunit

D. The three β-subunits

E. Cytochrome c

Answer: A

F₀ spans the membrane and forms the proton channel; the flow of protons through it causes it — and the attached γ-subunit “bent axle” — to rotate. F₁, a ball of three α- and three β-subunits, projects into the matrix, is fixed, and contains the phosphorylation mechanism.Harper's ch.13, pp.130–131

14How many molecules of ATP are generated per complete revolution of ATP synthase?

A. One

B. Three

C. Two

D. Four

E. Six

Answer: B

ADP and P_i are taken up sequentially by the three β-subunits, and the rotating γ-subunit squeezes each in turn — hence three ATP per revolution.Harper's ch.13, p.132 · TMU Lecture 9 Slide 19

15In the binding change mechanism of ATP synthase, the energy of the proton gradient is used principally to ( ).

A. form the covalent bond between ADP and inorganic phosphate

B. transport ADP into the mitochondrion

C. change the β-subunit conformation so bound ATP is released

D. pump protons back into the matrix

E. reduce molecular oxygen to water

Answer: C

The counter-intuitive and elegant point: ATP forms on the enzyme surface almost spontaneously. The energy is spent letting go of it — prising the finished ATP off a site that binds it very tightly. Hence the name binding change rather than synthesis mechanism.Harper's ch.13, p.131

16Substrate-level phosphorylation accounts for ATP formed in ( ).

A. Complexes I, III and IV of the respiratory chain

B. the reduction of O₂ by cytochrome oxidase

C. the adenine nucleotide transporter

D. glycolysis and the succinyl-CoA step of the cycle

E. the glycerophosphate shuttle

Answer: D

There is a net direct capture of two high-energy phosphates in glycolysis, and two more per mole of glucose in the citric acid cycle during the conversion of succinyl-CoA to succinate. All of these phosphorylations occur at the substrate level — independent of the respiratory chain.Harper's ch.13, p.131

17The P:O ratio is defined as ( ).

A. the ratio of ATP to ADP in the mitochondrial matrix

B. the number of protons pumped per oxygen atom reduced

C. the ratio of oxidative to substrate-level phosphorylation

D. the proportion of oxygen consumed that appears as water

E. moles of Pi incorporated into ATP per half-mole of O₂

Answer: E

Per half-mole of O₂ — that is, per pair of electrons. ⚠️ Note the disagreement between your sources on the value: TMU slide 16 gives 3 (NADH) and 2 (FADH₂); Harper's p.131 gives 2.5 and 1.5. Your own slide 27 concedes the point.Harper's ch.13, p.131 · TMU Lecture 9 Slide 16

18The modern P:O values are non-integer because ( ).

A. about 10 H⁺ are pumped per NADH but ~4 are needed per ATP exported

B. some oxygen is consumed by reactions outside the respiratory chain

C. the measurements are inherently imprecise and vary widely

D. ATP synthase produces exactly three ATP per revolution

E. cytochrome c oxidase leaks electrons to superoxide

Answer: A

This is the reasoning behind the change from 3 and 2 to 2.5 and 1.5, and your own slide 27 states it: “as four protons are taken into the mitochondrion for each ATP exported, the P:O ratio would not necessarily be a complete integer, ie 3, but possibly 2.5.”

In the exam: quote your lecturer's figures (3 and 2), but if asked to explain, give the proton-counting reason.TMU Lecture 9 Slide 27 · Harper's ch.13, p.131

19Respiratory control means that the rate of mitochondrial respiration is governed by ( ).

A. the concentration of NADH

B. the availability of ADP

C. the partial pressure of carbon dioxide

D. the activity of ATP synthase alone

E. the number of cristae

Answer: B

Because oxidation and phosphorylation are tightly coupled — oxidation cannot proceed without concomitant phosphorylation of ADP. Most cells at rest are in state 4, ADP-limited. When work is done, ATP becomes ADP, permitting more respiration, which replenishes ATP. Demand creates its own supply signal.Harper's ch.13, pp.131–132

20Cyanide, carbon monoxide and hydrogen sulfide arrest respiration by inhibiting ( ).

A. Complex II, succinate dehydrogenase

B. Complex I, NADH dehydrogenase

C. Complex IV, cytochrome oxidase

D. Complex III, cytochrome bc₁

E. ATP synthase, complex V

Answer: C

They inhibit cytochrome oxidase and can therefore totally arrest respiration — unbypassable, because Complex IV catalyses the chain's only irreversible step. Compare: barbiturates act at Complex I (blocking FeS → Q), antimycin A and dimercaprol between cytochromes b and c, and malonate competitively inhibits succinate dehydrogenase.Harper's ch.13 · TMU Lecture 9 Slide 22

21Barbiturates such as amobarbital inhibit the respiratory chain by ( ).

A. binding the haem iron of cytochrome a₃

B. blocking the F₀ proton channel

C. competitively inhibiting succinate dehydrogenase

D. blocking transfer from FeS to Q in Complex I

E. uncoupling oxidation from phosphorylation

Answer: D

They inhibit NAD-linked dehydrogenases by blocking the transfer from FeS to Q — that is, at Complex I. At sufficient dosage they are fatal in vivo.TMU Lecture 9 Slide 22

22Oligomycin blocks BOTH oxidation and phosphorylation because ( ).

A. it destroys the respiratory chain complexes outright

B. it prevents oxygen from reaching cytochrome oxidase

C. it allows protons to leak freely across the membrane

D. it competitively inhibits ADP binding at the F₁ head

E. it blocks H⁺ flow through F₀, so the gradient stalls the pumps

Answer: E

Blocking the turbine backs up the whole dam. Because oxidation and phosphorylation are coupled, jamming ATP synthase stops the respiratory chain too. Contrast an uncoupler, which does the opposite — see the next question.Harper's ch.13 · TMU Lecture 9 Slides 14, 22

23An uncoupler such as 2,4-dinitrophenol causes ( ).

A. uncontrolled oxidation with no ATP, energy lost as heat

B. complete cessation of both oxidation and phosphorylation

C. increased ATP synthesis with unchanged oxidation

D. inhibition of the adenine nucleotide transporter

E. accumulation of protons in the intermembrane space

Answer: A

Uncouplers allow leakage of H⁺ across the membrane, collapsing the electrochemical proton gradient. The gradient never builds, so the pumps run freely — respiration becomes uncontrolled, no longer limited by ADP or P_i — and the energy emerges as heat. DNP was sold as a slimming drug and killed patients by hyperthermia; brown adipose tissue does the same thing deliberately.Harper's ch.13, pp.132–133 · TMU Lecture 9 Slide 22

24Atractyloside inhibits oxidative phosphorylation by ( ).

A. allowing protons to leak across the inner membrane

B. inhibiting the ADP/ATP transporter of the inner membrane

C. competitively inhibiting succinate dehydrogenase

D. inhibiting cytochrome c oxidase directly

E. blocking the F₀ proton channel

Answer: B

It blocks the adenine nucleotide transporter. Note that ADP supply is what limits respiration (respiratory control), so blocking its entry halts oxidative phosphorylation just as effectively as poisoning a complex.TMU Lecture 9 Slides 22–23

25The glycerophosphate shuttle yields less ATP than the malate shuttle because ( ).

A. it is blocked by atractyloside at the translocase

B. it delivers its electrons directly to oxygen

C. electrons enter at Q via a flavoprotein, bypassing Complex I

D. it operates entirely within the cytosol

E. it consumes one ATP for every cycle

Answer: C

Bypassing Complex I means losing its four protons. The malate shuttle regenerates NADH inside the matrix, so electrons enter at Complex I and get the full count — and it is of more universal utility. The glycerophosphate shuttle is present in brain and white muscle but deficient in heart muscle. This is why textbooks quote two different ATP yields for glycolysis.Harper's ch.13, pp.134–135 · TMU Lecture 9 Slides 28–29

1 Oxidative phosphorylation — 3′ · ⭐ SET IN BOTH THE 2019 AND 2020/21 PAPERS+

The system in mitochondria that couples respiration to the generation of the high-energy intermediate, ATP.

Electrons pass down the respiratory chain in the inner mitochondrial membrane to their final reaction with oxygen to form water. The free energy released is used by Complexes I, III and IV, acting as proton pumps, to translocate H⁺ from the matrix into the intermembrane space; the resulting proton motive force drives a membrane-located ATP synthase which phosphorylates ADP.

It is the greatest quantitative source of high-energy phosphate in aerobic organisms.Harper's ch.13, pp.130–131

2 The respiratory chain — 3′+

A series of redox carriers present in the inner mitochondrial membrane which collect and transport reducing equivalents, directing them to their final reaction with oxygen to form water, and couple the liberated free energy to the generation of ATP.

Its components are organised as four protein-lipid complexes spanning the membrane: I NADH-Q oxidoreductase, II succinate-Q reductase, III Q-cytochrome c oxidoreductase and IV cytochrome c oxidase. Ubiquinone (Q₁₀) and cytochrome c are the mobile components connecting the fixed complexes.Harper's ch.13, pp.126–130

3 The chemiosmotic theory — 3′+

Peter Mitchell's theory, proposed in 1961, that the energy from oxidation of components in the respiratory chain is coupled to the translocation of protons from the inside to the outside of the inner mitochondrial membrane.

The resulting proton motive force — an electrochemical potential difference, negative on the matrix side — drives the mechanism of ATP synthesis. Complexes I, III and IV act as proton pumps, and because the inner membrane is impermeable to protons they accumulate in the intermembrane space.Harper's ch.13, p.130

4 P:O ratio — 2′+

The number of moles of inorganic phosphate incorporated into ATP per half-mole of oxygen consumed — that is, per pair of electrons passing down the chain.

⚠️ Your sources disagree. TMU slide 16 gives P:O = 3 for substrates oxidised via an NAD-linked dehydrogenase and P:O = 2 via a flavoprotein-linked dehydrogenase. Harper's p.131 gives 2.5 and 1.5, because roughly 10 protons are pumped per NADH while about 4 are required per ATP exported, which does not divide into a whole number. Your own slide 27 concedes “possibly 2.5”.

Answer with the lecturer's figures; explain with the proton count.Harper's ch.13, p.131 vs TMU Lecture 9 Slides 16, 27

5 Respiratory control — 2′+

Control of the rate of mitochondrial respiration by the availability of ADP.

This arises because oxidation and phosphorylation are tightly coupled: oxidation cannot proceed via the respiratory chain without concomitant phosphorylation of ADP. Most cells in the resting state are in state 4, in which respiration is ADP-limited; when work is performed ATP is converted to ADP, allowing more respiration, which replenishes ATP.Harper's ch.13, pp.131–132

6 Uncoupler of oxidative phosphorylation — 3′+

A compound that dissociates oxidation in the respiratory chain from phosphorylation, by allowing leakage of H⁺ across the inner mitochondrial membrane and so collapsing the electrochemical proton gradient.

Uncouplers are toxic in vivo, causing respiration to become uncontrolled because its rate is no longer limited by the concentration of ADP or P_i; the energy is released as heat. The most frequently used is 2,4-dinitrophenol (DNP).

Contrast oligomycin, which blocks H⁺ conduction through F₀ and therefore stops both oxidation and phosphorylation.Harper's ch.13, pp.132–133

7 Substrate-level phosphorylation — 2′+

The formation of ATP by direct transfer of a phosphate group from a substrate, independent of the respiratory chain.

In the complete oxidation of glucose it accounts for the net two high-energy phosphates of glycolysis (at phosphoglycerate kinase and pyruvate kinase) and the phosphate generated in the citric acid cycle during the conversion of succinyl-CoA to succinate. All the remainder — the large majority — arises from oxidative phosphorylation at the respiratory chain level.Harper's ch.13, p.131

1 Describe the respiratory chain and explain how it generates ATP. 8′

Location and purpose

The respiratory chain is a series of redox carriers in the inner mitochondrial membrane which collect and transport reducing equivalents (2H) to their final reaction with oxygen to form water, coupling the free energy liberated to the generation of ATP. The reducing equivalents come chiefly from β-oxidation and the citric acid cycle in the matrix. The inner membrane is selectively permeable and thrown into folds, or cristae; it also concentrates the phospholipid cardiolipin.

The carriers

NAD⁺ collects reducing equivalents from most dehydrogenases. Flavoproteins (FMN, FAD) follow — NADH dehydrogenase is a metalloflavoprotein containing FeS and FMN. Ubiquinone (Q₁₀) and cytochrome c are the mobile components; cytochrome c is the only soluble cytochrome. Iron-sulfur proteins in Complexes I, II and III carry out single-electron transfers, the iron cycling between Fe²⁺ and Fe³⁺.

The four complexes

Complex	Name	Function	H⁺ pumped
I	NADH-Q oxidoreductase	NADH → FMN → Fe-S centres → Q	4
II	Succinate-Q reductase	FADH₂ from succinate → fumarate; electrons via Fe-S to Q	0
III	Q-cytochrome c oxidoreductase	QH₂ → cytochrome c, via the Q cycle using cyt c₁, b_L, b_H and a Rieske Fe-S	4
IV	Cytochrome c oxidase	Cytochrome c → O₂ → 2H₂O, via haems a and a₃ and Cu_A/Cu_B	2

Complex IV catalyses the only irreversible reaction in the chain, which gives direction to the whole process; it has a very high affinity for oxygen and holds O₂ bound until fully reduced, minimising release of superoxide and peroxide.

The chemiosmotic theory

Peter Mitchell (1961) postulated that the energy of oxidation is coupled to the translocation of protons from the matrix to the intermembrane space. Complexes I, III and IV act as proton pumps; because the inner membrane is impermeable to protons, they accumulate, creating a proton motive force — an electrochemical potential difference, negative on the matrix side.

ATP synthase

The proton motive force drives a membrane-located ATP synthase. F₀ spans the membrane and forms the proton channel; proton flow causes F₀ and the attached γ-subunit to rotate. F₁, a ball of three α- and three β-subunits, projects into the matrix and is fixed. By the binding change mechanism, rotation of the γ-subunit squeezes each β-subunit in turn, changing its conformation from one that binds ATP tightly to one that releases ATP and binds ADP and P_i. Three ATP are generated per revolution.

Yield

For substrate oxidised via Complexes I, III and IV the P:O ratio is 3 by the lecture figures (2.5 by current Harper's); via Complexes II, III and IV it is 2 (Harper's 1.5). The difference arises because electrons entering at Complex II bypass Complex I and its four protons. Either way, the respiratory chain accounts for the large majority of ATP formed during catabolism, the remainder arising from substrate-level phosphorylation in glycolysis and the citric acid cycle.

Control

Because oxidation and phosphorylation are tightly coupled, the rate of respiration is controlled by the availability of ADP — respiratory control. Energy not captured as high-energy phosphate is liberated as heat, which keeps the system far from equilibrium and contributes to maintenance of body temperature.

Marking guide: location and purpose of the chain 1 · the carriers, including the two mobile ones 1 · the four complexes named with functions 2 · chemiosmotic theory with Mitchell and proton pumping 1.5 · ATP synthase F₀/F₁ and the binding change mechanism 1.5 · P:O ratios or respiratory control 1.

2 Elucidate the actions of the inhibitors and uncouplers of oxidative phosphorylation. 8′ — 'elucidate'

The classification

Agents affecting oxidative phosphorylation are classified as inhibitors of the respiratory chain, inhibitors of oxidative phosphorylation, and uncouplers of oxidative phosphorylation. The distinction between the last two is the most examinable point in the topic.

1 · Inhibitors of the respiratory chain

Agent	Site
Barbiturates (amobarbital)	Inhibit NAD-linked dehydrogenases by blocking transfer from FeS to Q — Complex I. At sufficient dosage they are fatal in vivo
Antimycin A, dimercaprol (BAL)	Between cytochrome b and cytochrome c — Complex III
H₂S, carbon monoxide, cyanide	Cytochrome oxidase (Complex IV); can totally arrest respiration
Malonate	Competitive inhibitor of succinate dehydrogenase — Complex II

The classic poisons are so lethal because Complex IV catalyses the chain's only irreversible reaction: there is no bypass.

2 · Inhibitors of oxidative phosphorylation

Oligomycin completely blocks oxidation and phosphorylation by acting on a step in phosphorylation — specifically it blocks conduction of H⁺ through F₀.

Atractyloside inhibits the transporter of ADP into and ATP out of the mitochondrion — the adenine nucleotide transporter. Since respiration is controlled by ADP availability, blocking its entry is as effective as poisoning a complex.

3 · Uncouplers

Uncouplers dissociate oxidation in the respiratory chain from phosphorylation by allowing leakage of H⁺ across the membrane, collapsing the electrochemical proton gradient. They are toxic in vivo, causing respiration to become uncontrolled, since its rate is no longer limited by the concentration of ADP or P_i. The commonest is 2,4-dinitrophenol (DNP).

The crucial contrast

Both oligomycin and an uncoupler abolish ATP synthesis, but they have opposite effects on oxidation, and the reason is coupling:

Oligomycin plugs the F₀ channel. Protons cannot return to the matrix, the gradient builds until the pumps can no longer work against it, and oxidation stops as well. Blocking the turbine backs up the whole dam.
An uncoupler lets protons return without passing through ATP synthase. The gradient never builds, so the pumps run freely: oxidation accelerates and becomes uncontrolled while phosphorylation ceases, and the energy emerges as heat.

Clinical relevance

Cyanide and carbon monoxide kill by disrupting the haem proteins cytochrome oxidase and haemoglobin respectively. DNP was marketed as a slimming agent — fuel is burned without ATP production — but patients died of hyperthermia, since respiration was no longer ADP-limited and all the energy appeared as heat. The physiological version of the same mechanism operates in brown adipose tissue, which uncouples deliberately for thermogenesis.

Marking guide: three-way classification stated 1 · at least three respiratory chain inhibitors with sites 2 · oligomycin and atractyloside with mechanisms 1.5 · uncouplers defined with DNP named 1.5 · the contrast between oligomycin and an uncoupler explained by coupling 1.5 · one clinical application 0.5.