Why is the plasma membrane called a selectively permeable membrane?

Mention the differences seen between prokaryotic and eukaryotic cells regarding:
$(i)$ Nuclear region
$(ii)$ Cell organelles
$(iii)$ Chlorophyll.

$(a)$ What are the consequences of the following conditions?
$(i)$ $A$ cell having higher water concentration than the surrounding medium.
$(ii)$ $A$ cell having lower water concentration than the surrounding medium.
$(iii)$ $A$ cell having equal water concentration to its surrounding medium.
$(b)$ Name the materials of which the cell membrane and cell wall are composed.

Amoeba acquires its food through a process,termed

$A$ cell will swell up if

We eat food composed of all the nutrients like carbohydrates,proteins,fats,vitamins,minerals,and water. After digestion,these are absorbed in the form of glucose,amino acids,fatty acids,glycerol,etc. What mechanisms are involved in the absorption of digested food and water?