Oxidative Phosphorylation

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How do the roles of ubiquinone and cytochrome c differ from the roles of the other components of the electron transport chain?

Hint:

Q and cytochrome c are transport molecules. Their function does not result directly in ATP synthesis in that they are not pumps. Moreover, Q is the only component of the electron transport chain that is not a protein. Ubiquinone and cytochrome c are small, mobile electron carriers, whereas the other components of the electron transport chain are large complexes anchored in the inner mitochondrial membrane.

What accounts for the different number of ATP molecules that are formed through cellular respiration?

Hint:

Few tissues except muscle produce the maximum possible amount of ATP from nutrients. The intermediates are used to produce needed amino acids, fatty acids, cholesterol, and sugars for nucleic acids. When NADH is transported from the cytoplasm to the mitochondria, an active transport mechanism is used, which decreases the amount of ATP that can be made. The electron transport chain differs in composition between species, so different organisms will make different amounts of ATP using their electron transport chains.