Block 2 101112 Oxidative Phosphorylation

Front 1

Where does oxidative phosphorylation occur? Why is that so?

Back 1

in the inner mitochondrial membrane because the outer mitochondrial membrane is permeable because of the VDAC pores but the inner mitochondrial membrane is a barrier that creates the proton gradient

Front 2

Which side of innermitochondrial membrane is positively charged and negatively charged.

Back 2

The matrix side of the inner mitochondrial membrane is negatively charged the the cytosolic side of the inner mitchondrial membrane is positively charged.

Front 3

What 2 gradients contribute to the proton motive force?

Back 3

The change in pH due to the proton gradient (more acidic on cytosolic side)

The change in membrane potential do to the proton gradient (positive on cytosolic side and negative on matrix side)

Front 4

What is reduction potential?

What is characterized by negative reduction potential? by positive reduction potential?

Back 4

reduction potential the measurement of electron transfer potential

(-) reduction potential: wants to give up its electrons (lower affinity) so it is a good reducing agent (agent is oxidized when reducing others)

(+) reduction potential: wants to take electrons so it is a good oxidizing agent (oxidizes others while being reduced itself)

Front 5

What is the relationship between the standard free energy change and the change in the reduction potential?

Back 5

∆Go' = -nF ∆E'0

n = number of electrons
F = Faraday constant (23.06 kcal mol-1 V-)
∆E'0 = change in reduction potential (volts)
∆Go' = standard free energy change (kcal mol-1)

Front 6

In oxidation phosphorylation, the electrons are moving from a negative reduction potential (high energy) to postitive reduction potential (low energy). Where does this energy go towards?

Back 6

Energy is used to pump protons cross the inner mitochondrial membrane

Front 7

The electron transport chain converts energy from the electron motive force (from TCA cycle and glycolysis) to______.

Back 7

proton motive force

Front 8

What are the different electron carriers in the electron transport chain?

Back 8

NADH
FADH2
FMN
ubiquinone (co enzyme Q)
cytochrome C
FeS clusters
Hemes
Copper ions

Front 9

What are the different oxidative states of ubiquinone (coenzyme Q)

Back 9

oxidized form: (Q) ubiquinone
intermediate form: (QH-) semiquinone
reduced form: (QH2) ubiquinol
radical form: (Q-) semiquinone radical

Front 10

What is unique about cytochrome C structure? How many electrons does it carry?

Back 10

Carries 1 electron
Contains heme group attached via 2 Cys (C type)
highly conserved

water soluble so resides in innermembrane space

Front 11

What are the 4 complexes of the electron transport chain that span the inner mitochondrial membrane?

Back 11

CxI: NADH-Q oxidoreductase
CxII: Succinate-Q reductase
CxIII: Q-cytochrome C oxidoreductase
CxIV: Cytochrome c oxidase

Front 12

Explain the redox rxn in CXI of the electron transport chain. What is the net reaction?

Back 12

NADH (matrix side) donates 2e- to FMN which delivers the 2e- to the Fe-S cluster fuck in NADH-Q oxidoreductase to reduce Q to the QH2 form (2 H+ picked up too). This causes the pumping of 4 H+ protons to the cytosolic side

NADH + Q + 5H+ matrix---->NAD+ + QH2 + 4H+ cytosolic

Front 13

What occurs at the CX II of the electron transport chain

Back 13

No proton transport occurs in succinate-Q oxidoreductase. In the TCA cycle succinate is converted to fumarate by succinate dehydrogenase which involves the release of FADH2 from FAD. 1 electron is carried through the FeS cluster of succinate-Q reductase cx and reduce Q to QH2

Front 14

Describe the Cx III structure and reaction.

Back 14

On the matrix side of Q-cytochrome C oxidoreductase, there are binding sites for ubiquinones and on the cytosolic side there are Fe-S ceter which is coordinated by 2 His (not Cys) = rieske iron-sulfur center

**switching from a 2 electron carrier to a 1 electron carrier (Q cycle)

QH2 + 2Cyto Cox + 2H+matrix --->Q + 2cyto Cred + 4H+ cytosolic

Front 15

Describe the Cx IV structure and the net reaction.

Back 15

Cytochrome c oxidase is maide of 13 protein subunits, 2 heme A (where reduction of O2 takes place) and 2 copper centers

4 cyto Cred + 8H+matrix + 02---->4cyto Cox + 2H20 + 4H+cytosolic

cytochrome C oxidase catalyses 4 electron reduction of oxygen to water

Front 16

Describe in detail the reaction of cx IV

Back 16

1. electron is transfered to Cu(b)

Front 17

What enzymes take care of the small amount of superoxide and peroxide (ROS) that leak from cytochrome C?

Back 17

superoxide dismutase: superoxide-->peroxide

catalase: peroxide-->water

Front 18

How many protons are pumped from each complex from NADH? how many protons are pumped per 2e- from FADH2?

Back 18

30 protons are pumped from NADH (10 protons/2e- from NADH)

6 protons from FADH2 (6 protons per FADH2)

Front 19

How many electrons does 1 acetyl in the TCA cycle generate from oxidation?

Back 19

8e-

Front 20

What are the mobile factors is oxidative phosphorylation that shuttle electrons between complexes?

Back 20

Q and cytochrome C

Front 21

How many molecules of oxygen are reduced to how many molecules of water in oxidative phosphorylation?

Back 21

1 molecule of oxygen is reduced to 2 molecules of water

Front 22

Which complex provides the link between the TCA cycle and oxidative phosphorylation?

Back 22

CX II- succinate-Q complex

Front 23

What is the structure of ATP synthase? What are the connections between F0 and F1?

Back 23

there is a motor component (F0) which is the proton channel that is hydrophobic and contains the C ring. The stator component (F1) which is the ATPase part that contains 5 subunits: A3, B3, G(breaks the symmetry of ring), and E (A3 and B3 from the hexameric ring)

1) exterior column= (a,b2,and g0
2)ge stalk

Front 24

Describe the binding change mechanism of ATPase.

Back 24

Each time the G-subunit rotates 120 degrees, the AB dimer subunites of ATP synthase changes conformations between the O(open) L(loose) and T(tight) states

O->L: ADP + Pi trapped in subunit)
L->S: favors ATP formation
T->O: ATP released

Front 25

How does proton flow through F0 drive the rotation of the G subunit of ATP synthase?

Back 25

A proton goes down one of the proton half channels (cytosolic channel) on the A subunit, this enables the C ring to turn and the proton is released through the matrix half-channel (Asp-61 is protonated/deprotonated during rotation: subunit C)

Front 26

How many ATP molecules are synthesized by each 360 rotation of the C ring?

Back 26

3 ATP

Front 27

Why can there be times when oxidation of glucose yields 30 ATP and sometimes 32 ATP?

Back 27

Depends on what shuttles are used:
1)Less ATP is harvested from cytosolic NADH (from glycolysis) that mitochondrial NADH. To transport NADH into the mitochondria, must used the glycerol 3-phosphate shuttle because there is not a carrier for NADH across the mitochondrial membrane so electrons are transfered to FAD-->FADH2. This shuttle is active in tissues with high energy requirements

2)Malate-aspartate shuttle: oxaloacetate can't pass mitochondrial membrane so it is converted to malate via malate dehydrogenase and it crosses the membrane as malate and it converted back to oxaloacetate giving off NADH and then oxaloacetate is converted to aspartate so it can pass back through the mitochondria membrane to start the cycle over again

Front 28

What 3 enzymes are part of CX II and donate electrons as FADH2?

Back 28

succinate dehydrogenase

glycerol 3-phosphate dehydrogenase

fatty acyl CoA dehydrogenase

Front 29

How is ATP transferred outside of the mitochondria?

Back 29

Via ATP-ADP translocase: ADP binds to enzyme on cytosolic side and causes a conformational change releases the ADP on the matrix side, then on the matrix side ATP binds and causes a conformational change which allows ATP to be released on the cytosolic side

Front 30

Give the break down of how complete oxidation of glucose yields 30/32 ATP.

Back 30

Glycolysis: 2 ATP + (2NADH x 1.5/2.5) = 5-7
Pyruvate ->acetyl CoA: 2 NADH x 2.5=5
TCA: 3 NADH/Acetyl-CoA (x2) = 6x2.5=15
1 FADH2/Acetyl-CoA (x2)=2 x 2.5=3
succinyl CoA->GTP (x2) = 2

TOTAL: 30/32

Front 31

What happens to O2 consumption when there is an increase of ADP?

Back 31

when energy charge is low (so ATP used up) the rate of O2 consumption is increased (increase oxidative phosphorylation)

Front 32

What happens when proton gradient is uncoupled and what protein channels are involved?

Back 32

uncoupling proteins (specific one=thermogenin) allow for H+ to flow back into the matrix of the mitochondria so that ATP is not properly made. THis causes increased O2 consumption, oxidation of NADH and energy is not stored but released as heat

Front 33

Where are each of these UCP protein channels located?
UCP-1
UCP-2
UCP-3
UCP-4
UCP-5

Back 33

UCP-1: brown adipose
UCP-2: most cells
UCP-3: skeletal muscle
UCP-4 and 5: brain

Front 34

How is cyanide a toxin to oxidation of glucose?

Back 34

it blocks cytochrome C oxidase