22 Biology -- Cell Biology

Describe the modern cell theory. Mention the exceptions of cell theory .

Describe the modern cell theory. Mention the exceptions of cell theory .

Cell


The modern cell theory states;

a.) Cells are the basic unit of both structure and function of living organisms.

b.) The body of an organism is made up of cell and their products. 

c.) Every cell is made up of a  small mass of protoplasm (nucleus, cell- organelles and plasma membrane with or without cell wall. ) 

d.) New cells arise from the division of pre-existing cells.

e.) Growth of an organism takes place through cell division and cell growth. 

f.) Life passes from one generation to the next in the form of living cell. 

g.) A cell can divide , grow, respond and die independent of other cells in the body.

h.) The characteristics and genetic information are stored and expressed inside cells.

The exceptions of modern cell theory are;

a.) Cells are developed from pre-existing cells by cell division but not like that of crystal formation or buds from nucleus. 

b.) Mature mammalian RBC and sieve tube cells (Phloem ) of plants lack nucleus but they are considered living cells.

c.) Single cell may consist of two or more than two nuclei. 

d.) Cells of dead tissue have no protoplasm e.g. cells of sclerenchyma, vessels, tracheid, etc.

e.) Viruses are living organism (controversial ) but they lack internal organization which is found in the cell.






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