Amutation in human atpase 6 (which corresponds to
e. coli subunit
a. from leucine to arginine at position 156 may allow the movement of protons across the membrane, but not the rotation of the ring of c subunits. how might this possible mechanism affect the function of atp synthase

A mutation in human ATPase 6 from leucine to arginine at position 156 may allow the movements of protons across the membrane, but not rotating of the ring of c subunits.

 This possible mechanism affect the function of ATP synthase because there would be an uncoupling of proton translocation and ATP synthesis. ATP synthase would remain sensitive to F0 proton conduction inhibitors

the backbone of the dna and rna compound is sugar phosphate.

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.