Electron Transport Chain

1. Oxidative phosphorylation and energy calculation of aerobic
respiration
Submitted to : Tridip Boruah
Asst. Professor
Dept. of Botany
MC. College ,Barpeta
Submitted by : Kaku Deka
Msc 2nd Sem

2. Content
 Introduction
 Oxidative phosphorylation
Complex 1
Complex 2
Complex 3
Complex 4
 ATP calculation
 Summary

3. Introduction
 The large amount of free energy released during the oxidation of NADH and
FADH2 is used in the formation of ATP . This ATP formation process is called
Oxidative phosphorylation .
 Oxidative phosphorylation occur in inner mitochondrial membrane in eukaryotes.
 It is the last steps of aerobic respiration .
 Oxidative step : Electron transport chain
NADH + H +O2 NAD+ + H2O
FADH2 + O2 FAD+ + H2O
 Phosphorylation step
ADP + Pi ATP

4. The four major respiratory enzyme complexes are present in the inner
mitochondrial membrane . These are
NADH coenzyme Q reductase or NADH dehydrogenase ( Complex 1)
Succinate – coenzyme Q reductase ( Complex 2)
Cytochrome bc1 complex or coenzyme Q cytochrome c reductase
(Complex 3)
Cytochrome c oxidase ( Complex 4)

5. Oxidative phosphorylation

6. Complex 1
• It is large L shaped complex
• Complex 1 accept e- from NADH+ + H+ & transfer to the oxidised ubiquinone and
simultaneously 4 H+ is transfer from matrix to inner membrane site .
• FMN & Fe – S major co – factor .

7. Complex 2
• It is also participate in TCA cycle .
• It accept the electron from FADH and transfer to the ubiquinone ,it is responsible
for oxidation of FADH .
• It is not a transmembrane protein i.e it can not any proton (H+) does not pump
any proton .
• Prosthetic groups :FAD &Fe-S .

8. Complex 3
• It is responsible for pumping of proton .
• It oxidised the reduced ubiquinone and transfer the e- to cytochrome c
simultaneously 4H+ pump matrix to IMC .( Inter membrane space )
• Prosthetic group :Heme & Fe – S

9. Complex 4
• It accept e- from reduced cytochrome c and transfer to the oxygen which form H2O
in matrix .
• It also pump 2H+ matrix to IMC .
• Prosthetic group : Heme & Cu +

10. Energy calculation of aerobic respiration
Reaction No Consumption / Gain of ATP
per hexose molecule
Remarks
Glycolysis(EMP – Pathway )
1
3
6
7
10
Consumption = 1ATP
Consumption = 1 ATP
Gain = 2*2.5 = 5 ATP
Gain = 2*1 =2 ATP
Gain = 2 *1 = 2 ATP
Net = 9 – 2 = 7 ATP
For phosphorylation of hexose
For phosphorylation of hexose – P
By terminal oxidation of 2NADH
By substrate level phosphorylation .
By substrate level phosphorylation
Kreb cycle ( TCA Cycle )
(a) Oxidative Decarboxylation of Pyruvic Acid
11
(b) Oxidation of Acetyl Moiety of Acetyl – Co
A
14
15
16
17
19
Gain 2*2.5 = 5ATP
Net gain = 5 ATP
Gain 2* 2.5 = 5 ATP
Gain 2* 2.5 = 5 ATP
Gain 2* 1 = 2 ATP
Gain 2* 2 =4 ATP
Gain 2* 2.5 = 5 ATP
Net gain = 21 ATP
By terminal oxidation of 2NADH
By terminal oxidation of 2NADH
By terminal oxidation of 2NADH
By substrate level phosphorylation directly or through
GTP
By terminal oxidation of 2 FADH2
By terminal oxidation of 2 NADH
Total net gain ATP mol .in aerobic respiration = 7 + 5+ 21 = 33 ATP

11. Summary
• Oxidative phosphorylation , is a complex and tightly regulated process that plays a
central role in cellular energy metabolism , by used the energy released during
electron transfer and proton pumping ,cells are able to generate efficiently .
• In aerobic respiration ,full oxidation of one glucose molecule can yield 33 ATP .

12. Reference
• Life Sciences by Pathfinder .
• Fundamentals of Plant physiology by Dr v K Jain .