Cell- the basic unit of life ( Eukaryotic Cells) | How cell division?

-  Eukaryotic Cell 

         All eukaryotic cells possess s true nucleus, that is their, genetic material is surrounded by a nuclear envelope. All protists, fungi, plant and animals are eukaryotes. They posses membrane-bound organelles, such as endoplasmic reticulum, golgi bodies, etc. 

-  Cell Wall 

       Plant cells are Surrounded by a non living, rigid permeable outer layer known as cell wall. It provides structural integrity and protection to the cell. It is made up of cellulose. Cell wall of adjacent cells are joined together by a jelly like substance called middle lamella. 

-  Cell Membrane

         It is made up of protein and lipids. Cell membrane is Semi-permeable which means that it allow entry and exit of only some materials. 

-   Protoplasm

       The Living material comprising, cytoplasm, nucleus and other organelles is called protoplasm. 

-  Cytoplasm

       It is the fluid content inside the cell membranes, It contains many membrane-bound organelles. 

Recommend topics:- 

Prokaryotic Cell, its Shape, its Size, Discovery

 

- Cell Division in Eukaryotes

      Cell division in Eukaryotes is more complex than in prokaryotes and involves two process

   1- Karyokinesis: division of nucleus

   2- Cytokinesis : division of cytoplasm 

There are two different types of cell division : 

   1:- Mitosis

   2:- Meiosis

1:- Mitosis :- In this type of cell division, there is formation of daughter cells that are genetically identical to the parent cell. Daughter cells produced by mitosis possess the same number of chromosomes as that of parent cell. Mitosis can be divided in four stages : 

      1- Prophase 

      2- Metaphase

      3- Anaphase

      4 - Telophase

Process 

 • Each chromosomes makes an identical copy of itself. 

 • The chromosomes line up across the centre of the cell. 

 • One complete set of Chromosomes moves to each of the cell. 

 • The cell starts to divide in two and split apart. Each new cell is a daughter cell. The daughter cells contain identical chromosomes in their nucleic and carry identical genes to the parent cell. 

In animals, mitosis occur generally only in diploid somatic cells, whereas in some lower plants, mitosis can occurs in haploid cells also. A cell that contains two sets of chromosomes ( two copies of the same chromosomes) is called diploid cell, whereas only one set of chromosomes is called haploid cell. Mitosis occurs as a part of normal cell growth and to replace worn out cells.

  -  Meiosis 

        Meiotic cell division occurs during sexual reproduction leading to gamete formation. The daughter cells formed possess half the number of chromosomes than tha parent cell. Meiosis involves two sequential cycles of division:

     1- Meiosis I

     2- Meiosis II

 Both meiosis I and II can be again subdivided into four stages as given below. 

     Stage of Meiosis I

  a- Prophase I

  b- Metaphase I

  c-  Anaphase I

  d- Telophase I

      Stages of Meiosis

   a- Prophase II

   b- Metaphase II

   c- Anaphase II

   d- Telophase II

  - Main differences between mitosis and meiosis are given in the table below. 

Mitosis - Occurs generally in somatic cells. 

Meiosis - Occurs in Germany cells. 

Mitosis - During normal growth of cell

Meiosis - During gamete formation

Mitosis - Two daughter cells are formed

Meiosis - For daughter cells are formed 

Mitosis - Chromosomes number remains the same

Meiosis - Chromosomes number reduces half

 - Who discover cell and how? 

 = Robert Hooke was discovered cell in 1665 while he was observing a thin slice of cork under a microscope. He observed a structure similar to honeycomb and named this structure 'call. 

 - Define mitosis and it's significance. 

 = Mitosis is the kind of cell division that result in the formation of two daughter cells that are genetically identical to the parent cell. Daughter cells possess the same number of chromosomes as of parent cell. Mitosis occurs as a part of normal cell growth and to replace worn out cells. 

 - Short note on Diploid and Haploid cells with example. 

 = A cell that contains two sets of chromosomes chromosomes, that is, two copies of the same chromosomes, one from each parent is called (any cell other than gametes), there are 46 chromosomes whereas human gamete is haploid with 23 chromosomes. 

    

1