What is the middle lamella in a plant cell composed of?

What is the bridge between two plant cells made of?

Which of the following is not a function of the cell wall?
$(i)$ Provides shape to the cell.
$(ii)$ Protects the cell from mechanical damage and infection.
$(iii)$ Helps in cell-to-cell interaction.
$(iv)$ Provides a barrier to undesirable macromolecules.

Which of the following is $NOT$ a function of the cell wall?
$(I)$ Provides shape to the cell.
$(II)$ Protects the cell from mechanical damage and infection.
$(III)$ Helps in cell-to-cell interaction.
$(IV)$ Provides a barrier to undesirable macromolecules.
$(V)$ Endosmosis of water.

Middle lamella is composed mainly of

The middle lamella between plant cells is composed of which substance?