Oxidative phosphorylation

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45 Terms

1

How much ATP is used by the body each day?

83 kg of ATP

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2

How many times is ATP regenerated in a day?

300x a day

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3

What is the redox potential of the oxidation of NADH and reduction of oxygen?

1.136 V

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4

What is the free energy change during the oxidation of NADH and reduction of oxygen?

-219.21 KJ/mol, negative value shows a spontaneous reaction

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5

What is the free energy required for the production of ATP?

+30.5 KJ/mol. Closer to 50 KJ/mol in cell conditions

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6

What happens to the redox potentials between complexes in the ETC?

Values decrease, free energy becomes closer to 0 as energy is lost at each stage

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7

What are the four complexes of the ETC?

NADH-coenzyme Q reductase
Succinate-coenzyme Q reductase.
Coenzyme Q-cytochrome c reductase.
Cytochrome c oxidase

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8

What molecular components are present in the complexes in the ETC?

Flavoproteins, Coenzyme Q, Cytochromes, Fe-S proteins, protein bound Cu2+

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9

What is the function of complex I?

Accepts 2e- from NADH

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10

What is the function of complex II?

Entry point for FADH2

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11

What is the function of complex III?

Oxidises reduced coenzyme Q, reduced cytochrome c

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12

What is the function of complex IV?

Reduces molecular oxygen

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13

What is the function of coenzyme Q?

Mobile electron carrier.
Highly hydrophobic, diffuses freely in the inner mitochondrial membrane

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14

What is the function of cytochrome c?

Mobile electron carrier-Carries electrons to complex IV
Water soluble, associates along the membrane surface in its reduced state

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15

What is the structure of complex I?

~900 kDa, >30 polypeptide chains.
1 FMN molecule, 7 Fe-S clusters

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16

What is the first step of complex I action?

NADH binds to complex I on the matrix side of the inner mitochondrial membrane.
2e- from NADH transferred to FMN

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17

What is the second step of complex I action?

2e- from FMNH2 transferred to a series of Fe-S centres

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18

What is the third step of complex I action?

2e- from Fe-S centre transferred to coenzyme Q

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19

What is the structure of complex II?

Contains succinate dehydrogenase.
~100-140 kDa.
FAD covalently bound to histidine residue in 68 kDa flavoprotein.
3 Fe-S clusters.
2 small subunits, with heme b

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20

What is the first step of complex II action?

Succinate converted to fumarate, FAD reduced to FADH2

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21

What is the second step of complex II action?

FADH2 transfers e- to an Fe-S centre, reduces coenzyme Q.

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22

What is the structure of complex III?

Forms a dimer, each monomer has 11 proteins and is 248 kDa.
Fe-S Rieske protein.
3 cytochromes

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23

What cytochromes are found in complex III?

b and c1. c is loosely associated

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24

What occurs in complex III?

Q cycles

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25

What occurs during the first half of the Q cycle?

One electron from coenzyme reduces cytochrome c, the other produces a semiquinone radical anion (Q-). 2H+ transported into the membrane space
Oxidised coenzyme Q returns to the Q pool

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26

What occurs during the second half of the Q cycle?

Another reduced coenzyme Q molecule enters complex III.
One electron transferred to cytochrome c the other transferred to the radical anion.
2H+ transported into the membrane space

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27

What occurs to the radical anion produced during the Q cycle?

Electron from coenzyme Q transferred to the radical, then 2H+ used to reduce the anion to coenzyme Q.

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28

What is the structure of complex IV?

13 subunits, 204 kDa.
2 Cu centres which associate with cytochromes a and a3

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29

What is the action of complex IV?

Pumps 4H+ into the intermembrane space.
4e- from cytochrome c and 4H+ from the mitochondrial matrix are used to produce water from O2

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30

Which complexes transport H+ across the inner membrane?

Complex I, III, and IV

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31

Why are no H+ transported from at complex II?

There is a small change in free energy, not large enough to transport protons across the membrane

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32

How does the transport of H+ lead to the production of ATP?

Movement of H+ from the matrix increases pH and causes a negative charge in the matrix.
H+ can then move through ATP synthase channel down a charge and concentration gradient into the matrix

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33

What is the structure of the ATP synthase channel?

Made of F1 and F0 subunits.
F1 contains α, β, γ, δ, and ε subunits.
F0 is a transmembrane protein and attached to F1, 3 hydrophobic subunits a, b, and c

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34

Which side of the mitochondrial inner membrane is negative?

Matrix side

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35

Which side of the mitochondrial inner membrane is positive?

Intermembrane space

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36

What reactions must occur for the synthesis of ATP?

Translocation of H+, catalysis of ATP synthesis.

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37

How does the translocation of H+ occur?

Carried out by F0, causes rotation of c complex and rotation of γ/ε stalk

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38

How is ATP synthesis catalysed?

Conformational change of β subunits of F1, alters binding affinity for ATP/ADP, stabilised ATP

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39

How is the H+ gradient dissipation coupled with ATP synthesis?

H+ through F0 drives γ/ε rotor. γ interactions with β subunit drive conformational change

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40

How many H+ are required for the synthesis of ATP?

Movement of 3H+ through F0 required for 1 ATP, but 4H+ moved across per ATP synthesised

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41

What is the function of the fourth H+ transported in ATP production?

Used as electrochemical energy devoted to mitochondrial ATP-ADP transport

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42

What is the P/O ratio?

The number of ATP molecules generated for every electron pair

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43

What is the P/O ratio for NADH?

10/4, 2.5

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44

What is the P/O ratio for FADH?

6/4, 1.5

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45

How can the ETC be regulated?

Substate availability, ADP/ATP levels, oxygen, proton motif force

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