lesson -cell structure n function ( POST 2)

Good morning boys!

In the last class we learnt that-
. Cell is the basic structural and functional unit of life.
.Depending on the number of cells , organisms can be grouped as unicellular or multicellular.
. The size of a cell is related to its functions.

LEARNING OUT COMES-
By the end of this class you will be able to-
.name the three basic parts of a cell and state their functions
.distinguish between a eukaryotic and prokaryotic cell

Today we are going to learn about CELL STRUCTURE .a
A typical cell consists of three basic parts :
1. CELL MEMBRANE OR PLASMA MEMBRANE -
. It forms the outer boundary of the cell, gives shape and size  to the cell.
. It only allows certain selected substances to enter or leave the cell ( it is semi-permeable ).
. It separates the cells from one another  and also from the surrounding medium.

NOTE - In PLANT CELLS and BACTERIA there is an outer wall surrounding the cell membrane ,it is called the CELL WALL. It gives protection against temperature , high wind speed and atmospheric moisture.

2. CYTOPLASM-
.It is a thick jelly like fluid inside the cell membrane.
. It occupies the space between the cell membrane and nucleus.
. Many small cytoplasmic bodies called CELL ORGANELLES are present in the cytoplasm.

3. NUCLEUS ( control center of the cell)-
.It is a dense ,oval shaped , double layered membrane structure that contains genetic materials.

PARTS OF THE NUCLEUS-

.NUCLEAR MEMBRANE - It surrounds  the nucleus and controls the passage of certain materials in and out of the cell.
. NUCLEOPLASM - it is the dense fluid in the nucleus.
. NUCLEOLUS - It is a spherical body present in the nucleus. It contains  (RNA -ribonucleic acid )
. CHROMOSOMES  ( hereditary vehicles ) - They are thread like structures composed of DNA ( deoxyribonucleic acid ). They contain basic hereditary units called GENES ( that are responsible for passing genetic characteristics from parents to off springs ).

FUNCTIONS OF THE NUCLEUS-
1, Transmission of hereditary  characteristics.
2. Controls all life functions taking place inside the cell.

https://youtu.be/TWG4Wm1r8BM

NOTE - EUKARYOTIC CELLS HAVE A MEMBRANE BOUND NUCLEUS . PROKARYOTIC CELLS DO NOT HAVE A MEMBRANE BOUND NUCLEUS.











HOMEWORK 

 1. Read pages 129,130 of your reader.
 2. FILL IN THE BLANKS( do them orally ) :
a. The cell membrane is also called …………………
b. Cell organelles are present in the …………………
c.  ……….……… is the control centre of the cell.
d. A  …….……. cell has a membrane bound nucleus.
e. RNA is present in the ………………
f. The basic hereditary characters are called  ………….
g.  ……….….are called hereditary vehicles.
HOTS
1.Rahul has the same eye colour like his mother. What could be the reason for this ?