Class 9 Cell Structure and functions - Notes,Test paper, Board Questions and solution
The Cell & Fundamental Unit of life - Extra Score Notes
Download The Cell & Fundamental Unit of life - Solved Test paper-01 Download The Cell & Fundamental Unit of life - Solved Test paper-02 Download The Cell & Fundamental Unit of life - Solved Test paper-03 Download The Cell & Fundamental Unit of life - Solved Test paper-04 Download The Cell & Fundamental Unit of life - Solved Test paper-05 Download The Cell n Fundamental Unit of life -Notes Download The Cell n Fundamental Unit of life - Chapter Notes Download File |
|
|
|
The classical branch of biology that deals with the study of structure, function and life history of a cell is called “Cell Biology”
We know that the body of all living organisms is made up of cells which carryout certain basic functions. Hence the cells are called “Basic structural and functional units of living organisms”.CELL WALL:
It is an outer-rigid protective covering of plant cells made up of cellulose.
It is involved in the transport or movement of materials in and out of the cell.
It maintains the shape of the plant cell.
It protects the internal organelles from external injuries
PLASMA MEMBRANE:-
It is the semi – permeable outer covering of most of the animal cells
It consists of outer and inner layers of proteins and a middle layer of lipids.
It regulates flow of selected materials into and out of the cell, so it is called selectively permeable membrane.
It provides the mechanical support and external frame to the protoplasm (cytoplasm + nucleus).
CYTOPLASM:-
The space between the plasma-membrane and the nucleus is filled by jelly like fluid made up of organic and in organic substance. The liquid found inside cells is known as cytosol.
It helps in exchange of materials between different cell organelles.
Breaking down of glucose (glycolysis) takes place in the cytoplasm.
NUCLEUS:-
It is a spherical body lies inside the cell.
It controls all activities within cell.
It has a double layered permeable covering called nuclear membrane.
The nucleus contains chromosomes, which are visible as rod-shaped structures only when the cell is about to divide.
Chromosomes contain parental information in the form of DNA. Functional segments of DNA are called genes
In a cell which is not dividing, this DNA is present as part of chromatin material. Chromatin material is visible as entangled mass of thread like structures. Whenever the cell is about to divide, the chromatin material gets organized into chromosomes
The nucleoli present in the nucleus helps in the formation of Ribosomes.
ENDOPLASMIC RETICULUM (E.R): It was discovered and named so by Porter.
Endoplasmic reticulum is interconnected system of tubes that transport various substances among cell organelles.
At places it is connected with the Plasma membrane as well as with the nuclear envelope.
Endoplasmic reticulum is of two main types- smooth ER and rough ER.
Rough ER is called rough because it has Ribosomes attached to its surface. Protein molecules are synthesized by Ribosomes and collected and are pinched off in vesicles. The vesicles often move to the Golgi apparatus for additional protein packaging and distribution.
Smooth ER (SER) acts as a storage organelle. It is important in the creation and storage of lipids and steroids. Steroids are a type of ringed organic molecule used for building the muscle
HTML Comment Box is loading comments...