The right answers are: Phospholipids and protein. And Selective membrane.
(It is the cell wall which is composed by cellulose and increase strength to the cell)
Phospholipids are the essential constituents of cell membranes where, with cholesterol molecules, they are organized into a lipid bilayer in which the hydrophobic tails are oriented towards the interior of the structure whereas the polar heads form the two surfaces of the bilayer.
Biological membranes are a selective barrier between the inside and the outside of a cell or a cell compartment (organelle). They, therefore, have the property of selective permeability, which makes it possible to control the entry and the exit of the different molecules and ions between the external and the internal environment. This allows each cell organelle, but also the entire cell to have a composition different from the external one.
