CBSE Class 9 Biology The Fundamental Unit of Life
Introduction to Cell
Cells are the structural and functional units in organisms.
Cell theory, was formally articulated by Schleiden and Schwann in 1839.
Each cell in an organism is assigned a specific role, so its shape and size depends on that particular role.Structural Organisation of Cell
All cells contain plasma membrane nucleus and cytoplasm.
On the basis of cellular setup, the cells may be prokaryotic or eukaryotic.
On the basis of number of cells the organisms may be unicellular or multicellular.Classification
ClassificationTransport of Materials Across Cells
Diffusion, the movement of gases from their higher concentration to lower concentration helps in exchange of gases between the cell and its surrounding.
The movement of water molecules from their higher concentration to lower concentration across semi permeable membrane is called Osmosis.
The amount of substances dissolved in water determines the nature of medium and direction of net gain of water by a cell.
