Question

Cell membranes are made up of
A) Phospholipids and proteins
B) Pectin
C) cellulose
D) lipid and hemicellulose

Answer 1

Hint:Cell membrane is one of the important constituents of a cell. It separates the cytosol or the cell interior from the outside environment. It also controls the movement of molecules in and out from the cell.

Complete answer:
Cell membrane or the plasma membrane is the outer layer of the animal cell. It protects the cell from the outer environment. The cell membrane is semi permeable in nature which means it selectively allows the passage of molecules in and out of the cell.
It is made up of lipid bilayer. This lipid bilayer along with cholesterol helps in maintaining the fluidity of the cell. It also contains several integral proteins like transporters and membrane proteins. These proteins help in transport of ions and molecules across the membrane. Endocytosis and exocytosis is also one of the primary functions of cell membranes.

Pectin- Middle lamella is made up of calcium pectate or pectins.
Cellulose- It is the primary constituent of the cell wall of green plants.
Lipid and hemicelluloses- It is the chief constituent of the cell wall of plants.

The correct answer is (A). Cell membrane is made up of phospholipids and proteins.

Note: The cell membrane consists of a thin layer of phospholipids which have a hydrophilic head and hydrophobic tail. Plasma membrane also contains glycoprotein which helps in cell-cell recognition. The cell membrane consists of around 50% of proteins which help in carrying out the essential activities of the cell.