fundamental unit of life class 9 notes
Cell Definition :
A Cell is defined as the smallest , basic unit of the life that is responsible for all of life's process .
" Cell are structural , functional and biological unit of all living beings . They are called building blocks of the life "
Robert hooke was the first Biologist who discovered cells in 1665.
Discovery Of Cells :
Robert Hooke discovered the cell in 1665 . Robert hooke observed a piece of bottle cork under a compound microscope and noticed tiny structure that reminded him of small rooms.
Role of cells : They provide structure to the body and convert the nutrients taken form the food into energy.
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| fundamental unit of life |
Characteristic of cells
- Cell provide structure and support to the body of an organism.
- Every cell has one nucleus and membrane bound organelles .
- Cell store hereditary information .
Types of Organisms on the Basis of Number of Cells
All organisms are made up of cells.
- Unicellular Organisms : The organisms which are made up only one cell.
- Mulitcellular Organisms ; The organisms which are made up of many cells. Example - human being, animals
Types of Cells :
Cells are similar to factories with different labourers and departments that work towards a common objective , various types of cells perform different function based on cellular structure , there are two types of cells .
- Prokaryotes
- Eukaryotes
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Prokaryotes
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Eukaryotes
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Have no nucleus. ·
They are single celled microorganisms. ·
The size range
is between .01 to .05 nano
meter ·
Cell division by binary fission . |
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Have a true nucleus. ·
They are multicelullar microorganisms. ·
The size of cell range between 10- 100 nano
meter. ·
Plasma membrane is responsible for monitoring
the transport of nutrients in and out of the cell. ·
Cell division by mitosis or meiosis. |
Cell Structure ;
The cell structure comprises individual components with specific function essential to carry out life process. These component include cell wall , cell membrane , cytoplasm , nucleus, and cell organelles .
Cell Membrane
Cell membrane is outer covering of a cell, is also called plasma membrane . Cell membrane support and protect the cells .It control the movement of substance in and out of the cells. It is selectively permeable in nature.
Cell Wall:
The cell wall is the most prominent part of the plant's cell structure .it is made of cellulose , hemicellulose .It protect the plasma membrane. It provide shape and support to the cells.
It is absent in animal cell. Also help in transport of various substances in and out of the cell.
Nucleus:
- It sends signal to the cells to grow mature , divide and die.
- The nucleus contains the hereditary material of the cell the DNA.
- Nucleus is surrounded by nuclear envelop that separate the DNA from the rest of the cells.
- It was discovered by Robert Brown in 1831.
- It control all the metabolic activates of the cell.
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Cytoplasm :
The cytoplasm is a thick clear jellly like substance present inside the cell membrane .
Most of the chemical reactions within a cell take place in this cytoplasm. It dissolves cellular wastes.
Cell Organelles:
Cell organelles are specific structure present inside a particular type of cell that perform specific function .There are numerous cell organelles .
Nucleolus :
The nucleolus is the site of ribosome synthesis , also it is involved in controlling cellular activities and cellular reproduction . Nucleolus contain RNA.
Chromosomes :
Chromosome play a crucial role in determining the sex of an individual. Each human cells contain 23 pairs of chromosome .Chromosome found only eukaryotic animal cells.
Endoplasmic Reticulum:
Endoplasmic reticulum is involved in the transportation of substances throughout the cells. It play a primary role in the metabolism of carbohydrates Synthes of lipids, steroids and proteins . It also help in membrane propagation. It is absent in Prokaryotic cell.
Endoplasmic reticulum are two types
(i) Smooth reticulum
(ii) Rough reticulum
Golgi Apparatus :
Golgi bodies are the cell's post office as it is involved in the transportation of material within the cell. It was discovered by Camilo Golgi. It is absent in Prokaryotic cell. It involved in the formation of the lysosomes.
Mitochondria :
The power house of the cell. It is called so because it produce ATP. The cell energy currency. Rod shaped organelles .Mitochondria have two membrane covering.