9th cells

 class 9th science

ICSE/ CBSE Notes-

For more Notes click this link https://cbsenotesallsub.blogspot.com/

 CELL- The fundamental unit of life

 cells

 1- A cells is considered to be the fundamental unit of life

 2- A cell is defined as the basic smallest structural and functional unit of an organism.

3- They are complex units that are microscopic in nature.

4- It can carry out the life process like reproduction, nutrition respiration

5- A cell is capable of independent existence 

6-A cell forms a basic structural  and fundamental unit of life.

cells

cells structure

Discovery of the Cell

Robert Hooke in 1665 observed slices of cork under a simple magnifying device. Cork is a part of the bark of a tree.

• The term ‘cell’ was first invention by Robert Hooke in the year 1665 when he noticed slice of cork by a microscope

Shape and size of Cells

1- According to the functions performed by the cells they are different shapes and sizes

2-The neurons or nerve cells are long so that they can carry messages from one part of the body to another.

3- The largest cell in the human body is the -OVUM

fig Ovum

4- The longest cell in the human body is Neurons or Nerve Cells

 fig-Nerve cell

5- The smallest cell of the human body is Sperms

fig- Sperms

According to number of cell organisms are -

1-unicellular organisms

An organism can be made up of a single cell unit and they are called unicellular organisms like an amoeba, paramecium, etc. 

fig- amoeba

fig

2-multicellular organism

An organism made up of many cells is called a multicellular organism like human beings, plants etc

multicellular

Types of Cells

There are two types are cells are given below

1-Prokaryotic

2-Eukaryotic cells

Prokaryotic – Size: generally small ( 1-10 µm) 

• The nucleus is not well defined and known as a  Nucleoid 
• Single, circular chromosome.
• Membrane-bound organelles absent. Eg: Bacterial cell

Eukaryotic – Size: generally large ( 5-100 µm).

• The nucleus is well defined and surrounded by a nuclear membrane.
• Possess more than one and linear chromosome.
• Membrane-bound cell organelles are present. Eg: Human cell.

              Where 1 µm = 10 $-6$m.

Plasma Membrane

1-The plasma membrane is also known as Cell membrane.

2-It forms the external covering of most cells

3-It is made of Lipids and Proteins.

4-The cell membrane separates cells from one another and also the internal contents from the surrounding medium.

5-It is porous and allows the movement of substances or materials both inward and outward.

Functions of the Plasma Membrane

Basic function of the plasma  membrane are given billow 

1- Plasma Membrane  is the structure of the cell which provides a definite shape to the cell.

2-  The plasma membrane regulates the transport of materials entering and exiting the cell.

3-Plasma membrane system act as a barrier and offers protection of the cell

4- The fluid nature of the plasma membrane makes it flexible

for  OSMOSIS  click the link

https://cbsenotesallsub.blogspot.com/2021/11/osmosis.html

class 9th physics 

https://cbsenotesallsub.blogspot.com/2021/11/class-9th-physics-motion.html