Notes of class 9 : Structure of Cell

Generalised cell :- Different kinds of cells show some basic structural plan which may be expressed in the term of generalised cell.

In a generalised cell there are three basic parts :-

1. Cell membrane/ Plasma membrane/ Plasma lemma
2. Nucleus
3. Cytoplasm

Organelles :- As organs are functioning in the body of organism for its survival and normal life, the cells also need help of many small structures present inside it for its proper functioning. These small structures inside cell are called the cell organelles.

In the diagram above animal cell and plant cell are compared by considering their generalised form and cell organelles present in it.

Some cell organelles are present only in animal cell some are present only in plant cell and some cell organelles are present in animal as well as in plant both.

Cell wall :-

• Cell wall is present in plant cells only. It is outer most covering of plant cell.
• Cell wall is made up of cellulose ( A kind of complex carbohydrate ; Polysaccharide ). The cellulose is nonliving material so cell wall is also nonliving part of cell.
• Cell wall surrounds the cell membrane in the plant cell.
• Cell wall provide shape and rigidity to the plant cell.
• The cell wall is freely permeable i.e. it allows solvent and solute to pass trough it according to concentration gradient.
• Cell walls of two adjacent plant cells are attached with the help of "middle lamillae".

Plasmodesmata :- 

• The plasmodesmata are minute openings between cell walls of adjacent cells.
• Cytoplasm of one plant cell is continue with adjacent plant cell through plasmodesmata.
• Through plasmodesmata one plant cell can communicate with adjacent plant cell.

Cell membrane :- 

• The cell membrane is outer most covering of animal cell and it is present in the plant cell just below cell wall.
• Cell membrane is made up of lipid ( Fat ) and protein. The cell membrane is living component of a cell.
• Cell membrane is selective permeable i.e. it allows material to pass through them in case of requirement.