when liquid water changes into solid ice, it increases in mass
The branched structure isomer will require less energy to melt than the straight chain isomer
explanation
Branched structure isomer has weak intermolecular forces of attraction as compared to straight chain isomers. In addition the branched isomer has a low boiling point as compared to straight chain isomers. Since boiling require the of the intermolecular forces tend to have lower boiling point than straight chain
I think it’s the cell membrane if you’re talking about animal cells and plant cells.