Question

Electron Transport Chain (McKee 364-372).  

1. Describe the initial substrates of the electron transport chain based on the cofactors that supply one pair of electrons
2. Describe the final product based on the acceptor of one pair of electrons from the electron transport chain
3. Describe the locations of ubiquinone (UQ) and cytochrome C (Cyt C) in relation to the electron transport chain
4. Describe the source of electrons for the reaction between oxidized UQ and reduced UQ (UQH₂) based on the redox reaction catalyzed by Complex I
5. Describe the source of electrons for the reaction between oxidized and reduced Cyt C (Cyt C_ox and reduced Cyt C_red, respectively) based on the redox reaction catalyzed by Complex III
6. Describe the source of electrons for the reaction between atomic oxygen (O) and H₂O oxidized based on the redox reaction catalyzed by Complex III
7. Describe how UQ is recycled for the reaction catalyzed by Complex I based on the reaction catalyzed by Complex III
8. Describe how Cyt C_ox is recycled for the reaction catalyzed by Complex III based on the reaction catalyzed by Complex IV

Answer 1

1. during the process of electron transport chain system (ETC), two things mainly happened. first water is formed as ETC deposits spent electrons into new water molecule. molecular oxygen is the final acceptor that convert in to water which can be reused by body. second it creates proper condition for ATP to be produced by oxidative phosphorylation. this is known as porton motive force and it is the product of ETC transporting hydrogen ion to one side of the inner mitochondrial membrane.

2. ubiquinone is located in inner membrane of mitochondria and in ETC it is located between complex I and complex III. it also receive electron from complex II. cytochrome C is located in outer side of inner mitochondrial membrane. in electron trasport chain system it located between complex III and complex IV.

3. nicotinamide adenine dinucleotide (NADH) from krebs cycle is the source of electron for complex I.

4. the main source of electron for complex III is NADH and FADH2 via complex I and complex II respectively. they give electron to ubiquinone which ultimate pass to next stage ie.conplex III.

5. actual the synthesis of water molecule from molecular oxygen and hydrogen ion or electron from ETC occured in complex IV. molecular oxygen act as terminal acceptor of electron. these electron comes from NADH and FADH2 via complex I and complex II. these electron subsequently goes to complex III via ubiquinone and futher proceed to complex IV via cytochorme C.

6. Q cycle play an important role in recycling of ubiquinone. ubiquinone handover the electron to cytochrome bc1 complex. and reduce ubiquinone convert in to oxidised ubiquinone after loosing two electron. this complex sequentially transferred electron to cytochrome C.

7. after acceptance of electron form cytochrome bc1 complex, oxidized cytochrome C become reduce and sequentially transfer these electron to cu containing comple IV. after this cytochrome C now become oxidized and able to take electron from complex III.