STD 11 - 9. Biomolecules — BIOLOGY STD 11 Science — Question

$I$. a membrane    $II$. a proton pump    $III$. a proton gradient

Select the correct option

$(i)$ Provides shape to the cell.

$(ii)$ Protects the cell from mechanical damage and infection.

$(iii)$ Helps in cell to cell interaction.

$(iv)$ Provides barrier to undesirable macromolecules.