The Fundamental Unit of Life Notes

Nature and occurrence:

• Nucleus is an important component of the cell.
• It acts as control centre of activities of the cell hence it is also known as Brain of the Cell.
• It is spherical organelle located in the centre of the cell in animal cells.
• In plants, it is pushed towards the side of the cell.
• In some cells, it maybe oval irregular or lobed as in case of white blood cells.

Structure:

Nature and occurrence:

• It is a network of tubular structure which forms a kind of intracellular skeleton.
• These tubes are membrane bound and are found in cytoplasm.
• These extend from nuclear membrane to plasma membrane.
• They are absent in prokaryotic organisms.

Structure:

Nature and Occurrence:

• These are small, dense, spherical and granular units found attached over the endoplasmic reticulum in eukaryotes and freely scattered in prokaryotes.
• Among eukaryotic cells, red blood cells do not possess this organelle.
• They are heavier in eukaryotes and lighter in prokaryotes.

Structure: