Cell Structure and Functions Part 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 multi-cellular.
-The size of a cell is related to its functions.

So, let us now move our next topic of this chapter

Important Instructions:
1. Topic highlighted in red need to copied in your notebook.
2. Topic highlighted in green need to read only.
3. Topic highlighted in black need to be read in reference to your book.
4. Web links are shared where ever required for better understanding and highlighted with blue.

Important Instructions for completion of your note book:

1. Do very neat and clean work. 
2. Draw diagrams with pencil only. Labeling is very important. No coloring required.
3. On right side of your note book, start your question-answer that are given at the end of the blog.

LEARNING OUTCOMES-
At the end of this class, learners will be able to-
-name the three basic parts of a cell.
-state the functions of the basic parts of a cell.
-distinguish between a eukaryotic and prokaryotic cell.

So, let us all start....

                                         CELL STRUCTURE 

A typical cell consists of three basic parts: (i) Cell Membrane (ii) Cytoplasm (iii) Nucleus

Each part of the cell structure performs some special functions. Let us now study that in detail.

1. CELL MEMBRANE OR PLASMA MEMBRANE -
(i)It forms the outer boundary of the cell, gives shape and size  to the cell.
(ii) It is thin delicate membrane. It only allows certain selected substances to enter or leave the cell ( it is semi-permeable ).
(iii) 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-
(i) It is a thick jelly like fluid inside the cell membrane.
(ii) It occupies the space between the cell membrane and nucleus.
(iii) 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-

(i) NUCLEAR MEMBRANE - It surrounds  the nucleus and controls the passage of certain materials in and out of the cell.
(ii) NUCLEOPLASM - it is the dense fluid in the nucleus.
(iii) NUCLEOLUS - It is a spherical body present in the nucleus. It contains  (RNA -ribonucleic acid )
(iv) 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 from generation to generation.
2. Controls all life functions taking place inside the cell. Hence, it is called as BRAIN of the cell.

https://youtu.be/TWG4Wm1r8BM

Learners, do you know cells are of two types Prokaryotic and Eukaryotic cells. You all will be learning about them in higher classes. But we should know some important features of them in this class.

Prokaryotic Cells
(i) These are primitive cells. 
(ii)They do not well defined nucleus. 
(iii) They do not have membrane bound cell organelles.
(iv) Bacteria and cyano bacteria are examples of prokaryotic cells.

Eukaryotic Cells
(i) These are advanced cells.
(ii) They have well defined nucleus.
(iii) They have membrane bound cell organelles.
(iv)  Higher plant and animals are examples of eukaryotic cells.


Have a look on the diagrams for better understanding.




HOMEWORK 

1. Read pages 129,130 of your reader.
 2. FILL IN THE BLANKS:
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.
3. What are basic parts of a typical cell?
4.Mention the function of the cell membrane of a cell.
5. Describe the structure of nucleus.
6. Write two important functions of nucleus.
7. Differentiate between prokaryotic and eukaryotic cells.
HOTS
1.Rahul has the same eye colour like his mother. What could be the reason for this ?