Question

1. Where, specifically, is the Electron Transport Chain (ETC) of cellular respiration located within the cell?

2. What do the “taxi” molecules from glycolysis and the citric acid cycle do with their electrons when they reach the ETC?

3. What happens, physically, to the electrons in the electron transport chain? 4. What happens, in terms of energy, as electrons move through the electron transport chain?

Answer 1

• The ETC refers to Electron Transport Chain. It is found in the mitochondria.
• It consists of a series of protein complexes called complex-l, complex-ll,complex-lll and complex-lV, electron carriers called cytochrome-c and ubiquinone and ATP synthase enzyme.
• Complex-l refers to NADH dehydrogenase complex; Complex-ll refers to Succinate dehydrogenase complex; Complex-lll refers to Cytochrome bc1 complex, Complex-lV refers to cytochrome oxidase complex.
• These complexes and electron carriers transfer electrons by redox reaction.
• An electron donor gets oxidized by donating its electron, while an electron acceptor gets reduced by receiving the electron.
• This transfer of electrons is coupled with transfer of protons across the membrane. Hence, a proton gradient is created which is utilized to generate ATP.
• The electrons thus transferred is received by oxygen, which acts as the terminal electron acceptor in aerobic respiration, since it is electronegative.
• The oxygen then combines with hydrogen to form water molecule.

1) The ETC is located in the lining of the inner mitochondrial membrane.

2) The taxi molecules transfer the electrons to the ETC.

3) The electrons get transferred from electron donor to the electron acceptor. They flow along the ETC.

4) As electrons move through the ETC, energy is released which is used to create proton gradient by pumping the protons across the membrane. This gradient is then utilized to synthesize ATP.