An overview of cell

Eukaryotes have membrane bound distinct strctures called organelles like endoplasmic reticulum (ER), the golgi complex, lysosomes, mitochondria, microbodies, and vacuoles.

The non-membrane bound organelles found in eukaryotes and prokaryotes are Ribosomes (found in cytoplasm, chloroplasts (in plants), mitochondria, rough ER)
The non-membrane bound organelle found in animal cell is centriole which helps in cell divison
(so, animal cell has 2 non-membrane organelle, plant cell -1)


Cells differ in size, shape, activities

Bacteria could be 3 to 5 µm.
Mycoplasmas the smallest cells are only 0.3 µm long. ("Mycoplasmas the smallest cells are only 0.3 µm (micrometre) long.") (1 µm = 0.000001 m = 1×10⁻⁶ m)
The egg of an ostrich is the largest isolated single cell

RBC = 7.0 µm.
Nerve cells are the looooooooooooooooooooooonnnnnnnnnnnnngest cells

There may be disc like, polygonal, columnar, cuboid, thread like or even irregular cells. The shape vary with function