The fundamental unit of life

The fundamental unit of life

37)      The membrane-bound cell organelles are absent in prokaryotic cells. 

38)      Differences between plant cell and animal cell.

	Plant cell	Animal cell
1	Plant cells are generally large in size.	Animal cells are smaller than plant cells.
2	Plant cells possess plastids.	Animal cells lack plastids.
3	Cell wall is present	Cell wall is absent.
4	Mature plant cells possess a large, central and permanent vacuole.	Animal cells possess many small and temporary vacuoles.
5	Centrosome and centrioles are absent in plant cells.	Centrosome and centrioles are present in animal cells.

39)      The basic structural organization of the cell helps it to perform important functions like respiration, nutrition, excretion and protein synthesis.

  Top definitions

1)                   Cell - An autonomous self-replicating structure that forms the structural, functional and biological unit of all living organisms. 

2)                   Prokaryotic cell – A cell characterized by the absence of a distinct, membrane-bound nucleus or membrane-bound organelles, and by DNA that is not organized into chromosomes.

2)     Nucleoid – An undefined nuclear region of the prokaryotic cell, containing the genetic material (nucleic acids).

3)     Eukaryotic cell – A cell containing a membrane-bounded nucleus and membrane-bounded organelles.

4)     Unicellular organism – Organism having only one cell.

5)     Multicellular organism - Organism consisting of more than one cell, wherein the differentiated cells perform specialized functions in the organism.

6)     Diffusion – The spontaneous movement of a substance from a region of its higher concentration to a region of its lower concentration.

7)     Osmosis – The movement of water through a semi-permeable membrane from a region of high water concentration to a region of low water concentration.

8)     Hypertonic solution - A solution that has a higher solute concentration than the one to which it is compared (eg - some kind of cell).

9)     Hypotonic solution - A solution that has a lower solute concentration than the one to which it is compared (eg - some kind of cell).

Isotonic solution - A solution that has the same tonicity as another solution with which it is compared.

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