20. the ETC

Question 1

define oxidative phosphorylation

Answer 1

the culmination of energy-yielding metabolism in aerobic organisms

Question 2

what type of electron carriers were produced by glycolysis, pyruvate oxidation, and CAC

Answer 2

reduced electron carriers (NADH and FADH2)

Question 3

what happens to the electrons of the reduced electron carriers during the ETC

Answer 3

the electrons are passed to proteins, and oxygen is the ultimate electron acceptor, and the energy of oxidation is used to make ATP

Question 4

where is the ETC

Answer 4

in the inner mitochondrial membrane

Question 5

for the ETC, where in the cell do the reduced electron carriers arrive

Answer 5

in the mitochondrial matrix side of the IMM

Question 6

in the ETC where in the cell is the H+ gradient generated

Answer 6

in the intermembrane space of the mitochondria

Question 7

for the ETC where in the cell does the ATP go as it’s made from ATP synthase

Answer 7

mitochondrial matrix

Question 8

what two processes make up oxidative phosphorylation

Answer 8

the ETC and chemiosmosis

Question 9

what happens once O2 accepts the electrons at the end of the ETC

Answer 9

water is made

Question 10

T or F: electron movement through the ETC is spontaneous

Answer 10

true

Question 11

why is electron movement through the ETC spontaneous

Answer 11

each subsequent carrier has a higher reduction potential (ie each carrier wants the electrons more) until we reach oxygen

Question 12

how is the energy extracted from the oxidation reactions of the ETC conserved

Answer 12

the energy is used to establish a proton gradient across the IMM

Question 13

what is the purpose of establishing a proton gradient across the IMM

Answer 13

the electrochemical potential will drive ATP synthesis, and the conversion to ATP is unfavorable which is why it requires the energy input from the gradient

Question 14

T or F: ATP production in the ETC is considered to be substrate level phosphorylation

Answer 14

false; because the ATP production is not a result of a direct reaction between ADP and some high-energy phosphate carrier

Question 15

describe the outer membrane of the mitochondria

Answer 15

relatively porous, allows passage of metabolites but not proteins through large transmembrane porin complexes

Question 16

describe the IMM of the mitochondria

Answer 16

similar environment to the cytosol, high H+ concentration than the matrix

Question 17

describe the inner membrane of the mitochondria

Answer 17

impermeable to almost all metabolites (they need specific transporters to pass), have cristae which increase SA, location of ETC and ATP synthase

Question 18

describe the matrix of the mitochondria

Answer 18

lower H+ concentration than the IMM, location of the CAC and PDH complex

Question 19

define redox pair

Answer 19

an electron donor and an acceptor in a redox reaction

Question 20

what is ∆Eo′

Answer 20

standard reduction potential

Question 21

what are the units for ∆Eo′

Answer 21

volts (V)

Question 22

what is the formula for finding ∆Eo′ from the redox reaction

Answer 22

∆Eo′ = Eo′(electron acceptor) -Eo′(electron donor)

Question 23

what does a high ∆Eo′ value mean

Answer 23

greater electron affintiy

Question 24

how is ∆Eo′ related to ∆Go′

Answer 24

∆Go′ = –nF∆Eo′

Question 25

what is F in the reaction ∆Go′ = –nF∆Eo′

Answer 25

Faraday's constant (96,480 J/V x mol)

Question 26

what is the ∆Eo′ for the entire ETC

Answer 26

1.14 V

Question 27

what are the three key mechanisms of electron transfer through the respiratory chain

Answer 27

direct transfer (ie Fe3+ to Fe2+), transfer as an H (H+ and e-), and transfer as a hydride ion (:H- has 2 e-)

Question 28

define reducing equivalent

Answer 28

used to designate a single electron equivalent transferred in a redox reaction

Question 29

other than NADH and FADH2, which carriers are used in the ETC

Answer 29

ubiquinone, cytochromes, and iron-sulfur proteins

Question 30

how many electrons can quinone carry

Answer 30

1 or 2

Question 31

how many electrons can quinone pick up

Answer 31

1 for each electron

Question 32

T or F: ubiquinone is mobile

Answer 32

true

Question 33

list the other two names of ubiquinone

Answer 33

coenzyme Q, or Q

Question 34

what is ubiquinone called when reduced

Answer 34

QH2

Question 35

what are cytochromes

Answer 35

proteins with iron containing heme prosthetic groups

Question 36

how many electrons can cytochromes carry

Answer 36

1

Question 37

how many types of cytochromes does the mitochondria have

Answer 37

3: a, b, and c

Question 38

T or F; cytochromes absorb visible light

Answer 38

true

Question 39

why do cytochromes absorb visible light

Answer 39

due to the ringed delocalized electrons

Question 40

describe the structure of each cytochrome

Answer 40

a has a long isoprenoid tail, and both a and b are tightly bound to large protein complexes, but c is not

Question 41

what characteristic does cytochrome c have since it isn't attached to a large protein complex like a and b are

Answer 41

it associates with the outer surface of the IMM through electrostatic interactions, allowing it shuttle electrons between two less mobile complexes

Question 42

describe the structure of iron-sulfur proteins

Answer 42

iron atom is associated with a sulfur atom (from Cys, inorganic sulfur, or both). Together they make an Fe-S center of varying complexity

Question 43

how many electrons can Fe-S proteins carry

Answer 43

1

Question 44

how many Fe-S proteins are involved in the ETC

Answer 44

at least 8

Question 45

how are the electron carriers of the ETC organized

Answer 45

organized into membrane-embedded supramolecular complexes

Question 46

how many supramolecular complexes are there in the ETC

Answer 46

4

Question 47

what are the two pathways of the supramolecular complexes of the ETC

Answer 47

1 to 3 to 4 | 2 to 3 to 4

Question 48

T or F: electrons move from complex 1, through 2 and 3, and then to 4

Answer 48

false; electrons will never go through all 4. They either go 1,3,4 or 2,3,4

Question 49

complex I: what carriers do electrons move between

Answer 49

NADH to Q

Question 50

complex I: describe the structure

Answer 50

45 dif polypeptide chains and 8 Fe-S centers

Question 51

complex I: where is the NADH binding site

Answer 51

the matrix side

Question 52

complex I: what happens to the electrons when NADH binds to its binding site

Answer 52

noncovalently found flavin monocucleotide (FMN) accepts the 2 electrons. Fe-S centers pass electrons one at a time towards the Q binding site

Question 53

complex I: describe the exergonic and endergonic transfers that occur as electrons move

Answer 53

exergonic: hydride ion and a proton from the matrix go to Q endergonic: transfer of 4 protons from the matrix to the IMM against their gradient

Question 54

complex I: how many protons are pumped into the IMM

Answer 54

4

Question 55

complex II: which carriers move the electrons

Answer 55

succinate to Q

Question 56

complex II: describe the structure of succinate dehydrogenase

Answer 56

4 subunits: 2 membrane bound and 2 extending into the matrix

Question 57

complex II: describe the electron movement

Answer 57

succinate donates electrons to FAD to produce FADH2, then they move through a series of Fe-S centers until they reach the Q binding site where we get QH2

Question 58

complex II: how many protons are moved into the IMM

Answer 58

ZERO

Question 59

complex III: what carriers do electrons move between

Answer 59

ubiquinol to cytochrome C

Question 60

complex III: describe the two key transfers that occur

Answer 60

exergonic of two electrons from ubiquinol (QH2) to two molecules of soluble cytochrome c endergonic of 4 protons into the IMM against their gradient

Question 61

complex III: how many protons are pumped into the IMM

Answer 61

4

Question 62

complex III: how many electrons can cytochrome c hold at a time

Answer 62

only 1

Question 63

complex III: what is the result of cytochrome c only being able to hold 1 of the 2 electrons at a time

Answer 63

QH2 will go back and forth as it shuttles electrons and protons across (the Q cycle)

Question 64

the Q cycle: describe the first half of the process

Answer 64

one QH2 on the IMS side releases two protons into the IMS. One of the lost electrons moves towards the matrix and the other goes to cytochrome c. This leaves us with Q, and a partially reduced cytochrome c

Question 65

the Q cycle: describe the second half of the process

Answer 65

a Q on the matrix side accepts the lone electron (Q-) and a second molecule of QH2 repeats the process (2 H+ donated to IMS, one electron to Q- = QH2 and one to cytochrome c = fully reduced cytochrome c)

Question 66

the Q cycle: describe the net effects

Answer 66

one QH2 becomes fully oxidized (two were, but we produced one QH2 too), two cyt c molecules are reduced (one electron received by each), 4 H+ into the IMS, two protons from the matrix are consumed

Question 67

complex IV: what carriers are involved

Answer 67

cytochrome c to O2

Question 68

complex IV: what is the role of copper

Answer 68

copper is complexed with two SH groups from Cys to form a binuclear center called CuA

Question 69

complex IV: what is the role of heme

Answer 69

CuA will donate the electron from cytochrome c through some heme groups, and the hemes will pass the electron to O2

Question 70

complex IV: how many protons are pumped into the IMM for every electron pair

Answer 70

2

Question 71

from the 2 electrons donated from NADH, what is made?

Answer 71

10 H+ into the IMS, 1 H2O made

Question 72

from the 2 electrons from FADH2, what is produced?

Answer 72

6 H+ into the IMS, 1 H2O made

Question 73

what is the affect of the difference in the number of the H+ pumped into the IMS from NADH and FADH2

Answer 73

the difference in the H+ pumped into the IMS impacts the amount of ATP made (NADH --> 2.5 ATP) (FADH2 --> 1.5 ATP)

Question 74

which electron carrier is better at making ATP; NADH or FADH2

Answer 74

NADH

Question 75

describe the two components of the proton motive force

Answer 75

1. the chemical potential energy due to the dif in conc. of H+ across a membrane 2. the electrical potential energy die to the separation of charge when an H+ moves across a membrane without a counterion

Question 76

describe regulation of the ETC

Answer 76

- ATP is only formed as fast as it can be used | - glycolysis, pyruvate oxidation, CAC, ETC, and chemiosmosis are all accelerated or inhibited together