The Fundamental Unit Of Life

What you will learn

• The fundamental organisational unit of life is the cell.

• Cells are enclosed by a plasma membrane composed of lipid and proteins.

• The cell membrane is an active part of the cell. It regulates the movement of materials between the ordered interior of the cell and the outer environment.

• In plant cells, a cell wall composed mainly of cellulose is located outside the cell membrane.

• The presence of the cell wall enables the cells of plants, fungi and bacteria to exist in hypotonic media without bursting.

• The nucleus in eukaryotes is separated from the cytoplasm by double-layered membrane and it directs the life processes of the cell.

• The ER functions both as a passageway for intracellular transport and as a manufacturing surface.

• The Golgi apparatus consists of stacks of membrane-bound vesicles that function in the storage, modification and packaging of substances manufactured in the cell.

• Most plant cells have large membranous organelles called plastids, which are of two types – chromoplasts and leucoplasts.

• Chromoplasts that contain chlorophyll are called chloroplasts and they perform photosynthesis.

• The primary function of leucoplasts is storage.

• Most mature plant cells have a large central vacuole that helps to maintain the turgidity of the cell and stores important substances including wastes.

• Prokaryotic cells have no membrane-bound organelles, their chromosomes are composed of only nucleic acid, and they have only very small ribosomes as organelles.

• Cells in organisms divide for growth of body, for replacing dead cells, and for forming gametes for reproduction.