Question

1. Describe how redox potential relates to the affinity for electrons.

2. Explain In addition to ATP, what is another product of the electron transport chain?

3. Describe the components of the proton-motive force, discussing the relative contributions of each component.

4. Explain how the electrochemical proton gradient established by the electron transport chain can be used to drive the synthesis of ATP.

Answer 1

1. Reduction/redox potential: The abiity or tendency of a chemical species to gain electrons is called redox/reduction potential. If the reduction potential is more positive then it indicates that the chemical species has very high affinity for electron. Usually hydrogen is taken as standard, its redox potential is zero. If a chemical substance has more electronegativity than hydrogen then it will have positive redox potential.

2. Electron transport chain is present in inner membrane of the mitochondria in eukaryotes. It has a series of enzyme complexes that transfer electron from donor to receptor. Transfer of protons occur accross the membrane creating proton gradient. This electrochemical gradient activates ATP synthase proton pump and helps in producing ATP. Other than ATP molecules, water, NAD, and FAD is also produced.

3. The two components of proton motive force are: difference in hydrogen ion concentration i.e. pH gradient and difference in charge across the membrane i.e. the membrane potential. If any of these two components are disrupted then ATP synthase will not function. Proton motive force causes the cell to act like a tiny battery. Its energy can either be used or stored for later purpose.

4. The protons produced during the electron transport chain move into the intermembrane space creating a electrochemical gradient. Proton pump helps in tansferring the protons back to matrix during which energy is liberated and is utilized by ATP synthase to produce ATP. For every three protons transfer into the matrix one ATP molecule is produced.