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Online notes for biology class 11 - What are theories of a Cell?

What are theories of a Cell? Online notes for biology class 11 

Cell Theories’ from Unit 3 – Chapter 8 Biology Class 11- Modern Version of Cell Theory

According to this theory-
  1. All living organisms (animals, plants or microbes) are made up of one or more cells or cell products.
  2. All metabolic reactions in unicellular and multicellular organisms take place inside the cells.
  3. Cells originate from other cells, i.e. no cells can originate spontaneously or de novo, but comes into being only by cell division and duplication of already existing cells.
The exception to Cell Theory
Cell theory does not have universal application, this means, there are certain living organisms which do not have true cells. A true cell has following characteristics-
  1. A set of genes (the functional region of DNA) which constitutes the blueprints for regulating cellular activities and makes new cells.
  2. A plasma membrane that permits controlling the exchange of matter and energy from outside.
  3. Metabolic machinery for sustaining life activities such as growth, reproduction, and repair of cells.

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