Question

Describe the process of electron transport provided by NADH and FADH2 through the electron transport chain

Answer 1

Most of the ATP generated during the aerobic catabolism of glucose is derived from a process that begins with moving electrons through a series of electron transporters that undergo redox reactions. This process is known as the electron transport chain.

Steps:

-It causes hydrogen ions to accumulate within the matrix space.

-A concentration gradient forms in which hydrogen ions diffuse out of the matrix space by passing through ATP synthase.

-The current of hydrogen ions powers the catalytic action of ATP synthase, which phosphorylates ADP, producing ATP.

In the electron transport chain there is a series of electron transporters which are accumulated in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen. In the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water.

What happens here is the NADH and FADH2 molecules are affixed with electrons and are transferred to the inner membrane of the mitochondria.

These molecules travel down the electron transport chain, releasing the electrons that they once had.

The end result is loads of energy ie, 34 ATP (energy molecule).

1.How electrons from NADH are driven in the electron transport chain

For NADH molecules to be transported in the chain we have four protein complexes present in the membrane

NADH ubiquinone oxidoreductase - complex 1

Cytochrome C reductase - complex 3

Cytochrome C oxidase - complex 4

There is also a mobile electron protein called as cytochrome C complex - this complex transports an electron from complex 3 to complex 4

There are large concentration of protons in the matrix and this should be transported to create an electro chemical gradient so as to produce ATP from proton created force.

- NADH is converted to NAD+ and H+ by complex 1 and a total of 2 electrons are lost these electrons reduces ubiquinone to ubiquinol.

-This ubiquinol freely diffuses within the membrane, and Complex I translocates four protons (H+) across the membrane,into the intermembrane space thus producing a proton gradient.

-Meanwhile ubiquinol looses the two accepted electrons and pumps 2 protons to the intermembrane space.

-The two other electrons sequentially pass across the protein to the ubiquinone where the quinone part of ubiquinone is reduced to quinol. And the 2electron are accepted by the iron sulphur cholesterol first with which 2 protons are pumped into the intermembrane pace. (In total, four protons are translocated: two protons reduce quinone to quinol and two protons are released from two ubiquinol molecules.)

-Cytochrome C and mobile electron from here carries single electron to cytochrome 4. A single electron is carried at a time from complex 3 to complex 4. This election is transferred to copper ions and then to cytochrome And finally electron is accepted by oxygen molecules and forms water.

-In this last phase 2 protons are pumped to intermembrane space thus completing the chain.

2. Electron transport chain for FADH2 molecules

-Here we have complex 2 ( succinate coQ reductase) instead of complex 1

-Succinate is converted to fumerate by succinate dehydrogenase at complex 2 - this is a step in citric acid cycle and 2 electron released here is transported to FAD which converts to FADH2 this FADH2 loses 2 electron to iron sulphur cholesterol and finally to COQ which gets reduced to COQH2 and in that process 4 protons are pumped into the intermembrane space. Rest of the steps are same here except that the complex 1 part is skipped in FADH2.