Types of Cell

Structure of Cell of Class 11

A multicellular organism is composed of numerous cells. The cells are of three main types:

(a) Undifferentiated or Stem Cells : Unspecialised cells which usually possess the power of division, e.g. stem apical meristem, root apical meristem, vascular cambium, cork cambium, stratum germinativum of skin, germinal epithelium, bone marrow, etc. Zygote is also an undifferentiated cell.

(b) Differentiated or Post-mitotic Cells : Cells specialized to perform specific functions. Differentiation occurs in shape, size, structure and function through an orderly switching on and off of some particular genes of the cells by means of chemicals named as inducers and repressors. It leads to better organisation, division of labour and higher efficiency. e.g. tissue cells.

(c) Dedifferentiated Cells : Differentiated cells revert to undifferentiated state to take over the function of division and the process is called dedifferentiation. It involves reactivation of certain genes that prevent differentiation, allow limited growth and induce division. Differentiation helps in healing of wounds, regeneration in animals, or vegetative propagation in plants. Cell culture experiments and formation of cork cambiun are also based on dedifferentiation.

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