All cells contain a semi-fluid matrix called cytoplasm. It is the main arena of cellular activities and chemical reactions. This keeps the cell in ‘living state’.
All cells contain non-membrane bound organelles called Ribosomes. These are found in the cytoplasm, chloroplasts (in plants), mitochondria and on rough ER.
Cells differ in size, shape and activities.
o Smallest cells: Mycoplasmas (0.3 μm in length)
o Largest isolated single cell: Egg of ostrich.
o Longest cells: E.g. Nerve cell.
o Size of bacteria: 3 to 5 μm.
o Human RBCs are about 7.0 μmin diameter.
Based on the functions, shape of cells may be disc-like, polygonal, columnar, cuboid, thread like, or irregular.
Cells are 2 types: Prokaryoticcells& Eukaryotic cells
