Chapter 21 The Proton-Motive Force

Front 1

What does the flow of electrons through Complexes I, III, and IV of the electron-transport chain lead to?

Back 1

transfer of protons from the matrix side to the cytoplasmic side of the inner mitochondrial membrane

Front 2

What does a proton-motive force consist of?

Back 2

pH gradient

membrane potential

Front 3

True or false: the matrix side of the inner mitochondrial membrane is basic.

Back 3

true

Front 4

True or false: the matrix side of the inner mitochondrial membrane is positive.

Back 4

false, negative

Front 5

How many molecules of ATP are synthesized by the gradient NADH-Q oxidoreductase generates?

Back 5

1

Front 6

How many molecules of ATP are synthesized by the gradient Q-cytochrome c oxidoreductase generates?

Back 6

1

Front 7

How many molecules of ATP are synthesized by the gradient cytochrome c oxidase generates?

Back 7

0.5

Front 8

What are the electrons of cytoplasmic NADH transferred into the mitochondria by? (2)

Back 8

glycerol 3-phosphate shuttle to form FADH2 from FAD

malate-aspartate shuttle to form mitochondrial NADH

Front 9

What is the entry of ADP into the mitochondrial matrix coupled to?

Back 9

exit of ATP by ATP-ADP translocase

Front 10

What is the transporter ATP-ADP translocase driven by?

Back 10

membrane potential

Front 11

How many molecules of ATP are generated when a molecule of glucose is completely oxidized to CO2 and H2O?

Back 11

about 30

Front 12

What is electron transport normally tightly coupled to?

Back 12

phosphorylation

Front 13

How is the oxidation of NADH and FADH2 regulated by respiratory (acceptor) control?

Back 13

ADP must be simultaneously phosphorylated to ATP.

Front 14

What is an example of an uncoupler?

Back 14

2,4-dinitrophenol

Front 15

How do uncouplers disrupt the coupling of electron transport and ATP synthesis?

Back 15

by carrying protons across the inner mitochondrial membrane

Front 16

Where is ATP synthase located?

Back 16

inner mitochondrial membrane

Front 17

What is ATP synthase also called? (4)

Back 17

Complex V

mitochondrial ATPase

H+-ATPase

F0F1-ATPase

Front 18

What enzyme in chloroplasts corresponds to ATP synthase?

Back 18

CF1-CF0 complex

Front 19

What is a transport protein in the inner mitochondrial membrane that carries ADP into the mitochondria and ATP out in a coupled fashion?

Back 19

ATP-ADP translocase

Front 20

What is ATP-ADP translocase also called?

Back 20

adenine nucleotide translocase (ANT)

Front 21

What is ANT?

Back 21

adenine nucleotide translocase

Front 22

reversible shuttle found in the liver and heart

Back 22

malate-aspartate shuttle

Front 23

energy inherent in the proton gradient established during the functioning of the respiratory chain

Back 23

proton-motive force

Front 24

tight coupling or coordination of the oxidation of reduced cofactors (NADH and FADH2) in the electron-transport chain and the phosphorylation of ADP to yield ATP in the mitochondrion

Back 24

respiratory control

Front 25

ensures that the rate of the citric acid cycle, where reduced cofactors are generated, corresponds to the demand for ATP

Back 25

respiratory control

Front 26

What is respiratory control also called?

Back 26

acceptor control

Front 27

What is UCP-1?

Back 27

uncoupling protein 1

Front 28

mitochondrial membrane protein that plays a role in thermogenesis by forming a pathway for the flow of protons into the mitochondria, thereby generating heat without synthesizing ATP

Back 28

uncoupling protein 1

Front 29

What is UCP-1 also called?

Back 29

thermogenin

Front 30

Why do isolated F1 subunits of ATP synthase catalyze ATP hydrolysis?

Back 30

Recall from the discussion of enzyme-catalyzed reactions that the direction of a reaction is determined by the ΔG difference between substrates and products. An enzyme speeds up the rate of both the forward and the backward reactions. The hydrolysis of ATP is exergonic, and so ATP synthase will enhance the hydrolytic reaction.

Front 31

Human beings have only about 250 g of ATP, but even a couch potato needs about 83 kg of ATP to open that bag of chips and use the remote. How is this discrepancy between requirements and resources reconciled?

Back 31

The ATP is recycled by ATP-generating processes, most notably oxidative phosphorylation.

Front 32

results in heat instead of ATP

Back 32

uncoupling protein

Front 33

catalytic subunit

Back 33

F1

Front 34

converts the proton motive force into ATP

Back 34

ATP synthase

Front 35

proton channel

Back 35

F0

Front 36

composed of a chemical gradient and a charge gradient

Back 36

proton-motive force

Front 37

proton merry-go-round

Back 37

c ring

Front 38

generates the proton gradient

Back 38

ETC

Front 39

ADP controls the rate of respiration

Back 39

respiratory (acceptor) control

Front 40

What is the mechanistic basis for the observation that the inhibitors of ATP synthase also lead to an inhibition of the ETC?

Back 40

If the proton gradient is not dissipated by the influx of protons into a mitochondrion with the generation of ATP, the outside of the mitochondrion eventually develops such a large positive charge that the ETC can no longer pump protons against the gradient.

Front 41

If actively respiring mitochondria are exposed to an inhibitor of ATP synthase, the electron-transport chain ceases to operate. Why?

Back 41

If the proton gradient cannot be dissipated by flow through ATP synthase, the proton gradient will eventually become so large that the energy released by the ETC will not be great enough to pump protons against the larger-than-normal gradient.