ETC and oxidative phosphorylation

Question 1

Energy from what is used to synthesize ATP in animal cells? + examples

Answer 1

Reduced fuels like carbs, lipids and a.a

Question 2

electron from reduced fuels are transferred to ? examples

Answer 2

to reduced cofactors like NADH and FADH2

Question 3

Production of ATP from ADP and Pi is energetically favorable or unfavorable? WHY?

Answer 3

highly unfavorable. phosphate groups are highly electronegative and DO NOT want to be in close proximity in a single molecule

Question 4

How then can we make ATP? 2 steps

Answer 4

1. electrons travel/are transported through series of thermodynamically favorable redox reactions within membrane proteins in inner mitochondrial membrane
2. use of power proton pumps to maintain electrochemical gradient in H+ ions across inner membrane

Question 5

Electron flow down energy gradient from _____ to ____

Answer 5

NADH to O2

Question 6

E’° (increases or decreases) as electrons are transported along ETC

Answer 6

Increases

Question 7

What is E’°?

Answer 7

relative affinity for electrons in electron acceptor

Question 8

large and positive E’° = more likely to be (oxidized or reduced)

Answer 8

Reduced! as electron acceptor

Question 9

Each successive bond in ETC holds (more or less) potential energy

Answer 9

less

Question 10

How does O2 enter the mitochondrial matrix

Answer 10

by diffusion through inner mitochondrial membrane

Question 11

Complex 1: name + 2 steps

Answer 11

NADH dehydrogenase
1. two electrons oxidized from NADH –> results in NAD+ + 2 e-/hydride ion transferred to ubiquinone –> QH2 –> exergonic reaction that provides E for step 2
2. pumps 4 protons form matrix to intercellular space

Question 12

Net reaction from complex 1

Answer 12

1 NADH + 5 H+ + Q –> NAD+ + 4 H+ + QH2

Question 13

Complex 2: name + what?

Answer 13

Succinate dehydrogenase
oxidation of FADH2 to reduce ubiquinone (becomes QH2)

Question 14

Complex 3: name + main function + 2 steps

Answer 14

Cytochrome C reductase
Fct: oxidize reduced QH2
1. QH2 will shed 2 e- and 2 protons: 1e- to cytochrome c + 1e- to oxidized Q + 2 p+ to intercellular space
2. E from the 2 e- transferred from QH2 pump 4 p+ into intercellular matrix

Question 15

Net reaction of complex 3

Answer 15

1 QH2 + 2 cytochrom c (oxidized) + 2 H+ matrix –> Q + 2 cyt c (reduced) + 4 H+ intercellular

Question 16

Complex 4: name + Function + 2 steps

Answer 16

Cytochrome C oxidase
FCT: oxidize reduced cytochrome C
1. O2 is reduced: takes 2 H+ from matrix to become water (O2 = end electron acceptor)
2. 2 additional H+ are pumped out of matrix as electrons move through complex 4

Question 17

Net reaction of complex 4

Answer 17

4 Cyt c + 8 H+ + O2 –> 4 cyt c (ox) + 4 H+ intercellular + 2 H2O

Question 18

Net reaction of electron flow of respiratory chain

Answer 18

2 NADH + 22 H+ (matrix) + O2 –> 2 NAD+ + 20 H+ + 2 H2O

Question 19

Goal of ETC = ? + how does it do it?

Answer 19

Goal = reduce concentration of H+ in matrix
How? direct pumping of H+ and uptake of Hydrogen for reactions