1. III Respiratory chain (呼吸链)
By LI Dehong
III Respiratory chain (呼吸链)
1. Concept：
Respiratory chain, or electron-transport chain (电子传递链), is one of the redox chains in organism.
redox chain (氧化还原链):
Metabolic pathway consist of (oxidative)
metabolic intermediates,
H donors,
transfers,
H final acceptor and
relevant enzyme system. ?

2. III Respiratory chain (呼吸链)
By LI Dehong
III Respiratory chain (呼吸链)
1. Concept：(Cont.)
Redox chians include 5 chains:
respiratory chain,
microsomal oxidative system (微粒体氧化体系),
peroxidase system (过氧化物酶氧化体系),
ascorbate oxidative system (抗坏血酸氧化体系) and polyphenol oxidase system (多酚氧化酶体系)(in plants). ?
We’d focus on Respiratory chain since it can produce ATP.

3. III Respiratory chain
1. Concept (Cont.)
A2e + BA +B 2e

4. H final acceptor of respiratory chain: O2
III Respiratory chain
1. Concept: (Cont.)
H final acceptor of respiratory chain: O2
product: H2O
Transfers of respiratory chain: H, H+, e.
Classification of respiratory chain:
Respiratory chains can be classified into 2 kinds by the initial H donor <co-factor>.
NADH+H+ respiratory chain
FADH2 respiratory chain

5. 2. Components of respiratory chain
III Respiratory chain
2. Components of respiratory chain ?
1). Intracellular site \ location

6. 2. Components of respiratory chain (Cont.)
III Respiratory chain
2. Components of respiratory chain (Cont.)
Cristae: 嵴
Matrix: 基质
Movie 1

7. 2. Components of respiratory chain (Cont.)
III Respiratory chain
2. Components of respiratory chain (Cont.)
2). 5 components form 4 enzyme complex and relevant co-factors:
NADH-Q reductase: coenzyme NAD+ \ NADP+ (Vt PP, Vt B5)
Succinate-Q reductase: prosthetic group \ FAD (Vt B2)
FeS Protein: (transfer one electron)
CoQ: The only non-protein component in respiratory chain. It occurs in organism widely. (ubiquinone, 泛醌)
Role as H transfer: quinone (醌) 2Hhydroxybenzene (酚)
Cytochrome proteins
(see also next slide)

8. 2. Components of respiratory chain (Cont.)
III Respiratory chain
2. Components of respiratory chain (Cont.)
2). 5 components form 4 enzyme complex and relevant co-factors:
NADH-Q reductase: co-enzyme NAD+ \ NADP+ (Vt PP, Vt B5)
Complex I

9. Succinate-Q reductase) [琥珀酸-Q 还原酶]: prosthetic group: FAD (Vt B2)
III Respiratory chain
Succinate-Q reductase) [琥珀酸-Q 还原酶]:
prosthetic group: FAD (Vt B2)
Complex II

10. NADH dehydrogenase (NADH-Q reductase)
III Respiratory chain
NADH dehydrogenase (NADH-Q reductase)
Succinate[琥珀酸]dehydrogenase (Succinate-Q reductase)

11. FeS protien: transfer 1 electron Fe3+ + e Fe2+ III Respiratory chain
Cys = cysteine
-SH = sulfhydryl group

12. quinone hydroxybenzene
III Respiratory chain
CoQ: The only non-protein component in respiratory chain. It occurs in organism widely. (ubiquinone, 泛醌)
Role as H transfer：
(醌)  2H  (酚)
quinone hydroxybenzene

13. 2. Components of repiratory chain (Cont.)
III Respiratory chain
2. Components of repiratory chain (Cont.)
Cytochromes (细胞色素蛋白):
1) Transfer one electron;
2) Prosthetic group: hemachrome (血红素, 含铁卟啉<Fe-porphyrin>)
(Fig. 7-4, p151)
Fe3+ + e Fe2+
Cyt b Cyt c1→Cyt c→Cyt a→Cyt a3→ O2
Fe-S

14. Structure of hemachrome & its connection with protein
III Respiratory chain
Structure of hemachrome & its connection with protein

15. Structure of cyt c & cyt c1
III Respiratory chain
Structure of cyt c & cyt c1

16. Absorbance of cytochromes
III Respiratory chain
Absorbance of cytochromes

17. 2. Components of respiratory chain (Cont.)
III Respiratory chain
2. Components of respiratory chain (Cont.)
5 kinds of cytochromes: cyt b, cyt c1, cyt c, cyt aa3.
The 5 kinds cyt all contain Fe (cyt a3 contains also Cu+).
They bind tightly to mitochondrion except cyt c.
To form 2 enzymes:
CoQH2-cyt c reductase: cyt b, FeS, cyt c.
function: catalyze electron CoQH2  cyt c
Cyt c oxidase: cyt aa3.
function: catalyze electron cyt c  cyt aa3
\\Complex III
\\Complex IV

18. ? 3). Order /Sequence of transporters in respiratory chain
III Respiratory chain
3). Order /Sequence of transporters in respiratory chain
Complex I ?
SNADHFMNFeSCoQ
SuccinateFAD
cyt bFeScyt c1 cyt ccyt aa3O2
Complex II
Complex IV
Complex III
(The components are sequenced by the redox potentials [氧化还原电位] of the components of respiratory chain)

19. Respiratory Chain (see also Fig 6.6, p189)
III Respiratory chain
Respiratory Chain (see also Fig 6.6, p189) I II
III IV

20. Respiratory Complex I & II
III Respiratory chain
Respiratory Complex I & II
Movie 2

21. III Respiratory chain
Movie 3

22. III Respiratory chain
Movie 4

23. the very beginning of this topic:
III Respiratory chain
Let’s go back to
the very beginning of this topic:
Where and how does ATP be produced?

24. 3. Product of ATP 3 steps can produce ATP: (3 enzyme complex)
III Respiratory chain
3. Product of ATP
3 steps can produce ATP: (3 enzyme complex)
NADH  CoQ (The Potential of NADH is -3.2 V)
CoQ  cyt c
cyt c  O2
potential of respiratory chain
lowerhigher (negativepositive)
The lower the reductive potential, the easy the electron losing.
(I)
(III)
(IV)

25. potential of respiratory chain negativepositive (负正) lower  higher
III Respiratory chain
potential of respiratory chain
negativepositive
(负正)
lower  higher
[能量: 高低]
The lower the reductive potential, the easy the electron losing.
Energy

26. III Respiratory chain
3. Product of ATP (Cont.)