III Respiratory chain ( 呼吸链 ) 1. Concept ： Respiratory chain, or electron-transport chain (...

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.

By LI Dehong

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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 polyp

henol oxidase system (多酚氧化酶体系 )(in plants).

By LI Dehong

We’d focus on Respiratory chain since it can produce ATP.?

1. Concept (Cont.)

III Respiratory chain

A2e + BA +B 2e

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

III Respiratory chain

2. Components of respiratory chain

1). Intracellular site \ location

III Respiratory chain

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2. Components of respiratory chain (Cont.)

III Respiratory chain

Cristae: 嵴

Matrix: 基质

Movie 1

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 ) 2Hhydroxybenzene (酚 ) Cytochrome proteins

(see also next slide)

2. Components of respiratory chain (Cont.)

III Respiratory chain

2). 5 components form 4 enzyme complex and relevant co-factors:

NADH-Q reductase: co-enzyme NAD+ \ NADP+ (Vt PP, Vt B5)

2. Components of respiratory chain (Cont.)

III Respiratory chain

Complex I

Succinate-Q reductase) [琥珀酸 -Q 还原酶 ]:

prosthetic group: FAD (Vt B2)

III Respiratory chain

Complex II

III Respiratory chain

NADH dehydrogenase (NADH-Q reductase)

NADH+H+

NAD+

FMN

FMNH2 Fe3+£ S

Fe2+£ S CoQ

CoQH2

Succinate[琥珀酸 ]dehydrogenase (Succinate-Q reductase)

succinate

Fumarate

FAD

FADH2 Fe3+£ S

Fe2+£ S CoQ

CoQH2

III Respiratory chain

FeS protien:

transfer 1 electron

Fe3+ + e Fe2+

Cys = cysteine

-SH = sulfhydryl group

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

III Respiratory chain

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)

2. Components of repiratory chain (Cont.)

III Respiratory chain

Cyt b Cyt c1→Cyt c→Cyt a→Cyt a3→ O2 Fe-S

Fe3+ + e Fe2+

III Respiratory chain

Structure of hemachrome & its connection with protein

III Respiratory chain

Structure of cyt c & cyt c1

III Respiratory chain

Absorbance of cytochromes

o 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.

o 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

2. Components of respiratory chain (Cont.)

III Respiratory chain

\\Complex IV

\\Complex III

3). Order /Sequence of transporters in respiratory chain

SNADHFMNFeSCoQ

SuccinateFAD

cyt bFeScyt c1 cyt ccyt aa3O2Complex II

Complex III

Complex I

III Respiratory chain

Complex IV

(The components are sequenced by the redox potentials [氧化还原电位 ] of the components of respiratory chain)

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• Respiratory Chain (see also Fig 6.6, p189)

III Respiratory chain

I

II III IV

III Respiratory chain

Respiratory Complex I & II

Movie 2

III Respiratory chain

Movie 3

III Respiratory chain

Movie 4

III Respiratory chain

Let’s go back to

the very beginning of this topic:

Where and how does ATP be produced?

3 steps can produce ATP: (3 enzyme complex)

NADH CoQ (The Potential of NADH is -3.2 V)

CoQ cyt ccyt c O2

potential of respiratory chain lowerhigher (negativepositive)

The lower the reductive potential, the easy the electron losing.

3. Product of ATP

(I)(III)(IV)

III Respiratory chain

En

ergy

III Respiratory chain

potential of respiratory chainnegativepositive(负正 )

lower higher [能量 : 高低 ]

The lower the reductive potential, the easy the electron losing.

3. Product of ATP (Cont.)

III Respiratory chain