The only cell organelle seen in prokaryotic cells is

$(i)$ Why is the cell called the structural and functional unit of life?
$(ii)$ Why is the plasma membrane called a selectively permeable membrane?
$(iii)$ Name the factor which decides the movement of water across the plasma membrane.

The given diagram shows the longitudinal section of collenchyma tissue. Label the parts '$M$','$N$','$O$',and '$P$' in the given diagram.

What makes lysosomes such effective digestive bags?

Name two double membraned cell organelles.

How do lysosomes perform the functions of defence,digestion and cleansing in the cell?