CHAPTER 5
THE FUNDAMENTAL UNIT OF LIFE
ANIMAL CELL
PLANT CELL
This article brings you the CBSE Class 9 Science notes on chapter 5 'FUNDAMENTAL UNIT OF LIFE'. These chapter notes are prepared by the subject expert and cover every important topic from the chapter. In between these notes, exercise questions are provided. Students must solve these questions to test their understanding about the learned topics. These questions will help you to track your preparation level and get a hold on the subject.
In this chapter 5 'FUNDAMENTAL UNIT OF LIFE we cover following topics -
Discovery of cell, Cell, Classification of organisms on the basis of Cell, Shape and size of the Cell, Diffusion, Osmosis, Types of Osmosis , Types of Osmotic Solutions, Plasma membrane or Cell membrane, Cell Wall, Function of Cell wall, Nucleus, Types of plastids, Cytoplasm, Cell Organelles, Functions of Vacuoles and Plastids, Types of Endoplasmic Reticulum.
Important Notes Of CHAPTER 5 'FUNDAMENTAL UNIT OF LIFE of CLASS 9 SCIENCE.
1) Discovery Of Cell-
•Cells were first discovered by ROBERT HOOKE in 1665. He observed the cell in a cork slice with the help of a primitive microscope.
• Leeuwenhoek(1674) with the improved microscope discovered the free living cells in pond water for first time.
• Robert Brown (1831) discovered the nucleus of the cell.
•Purkinje in 1839 coined the term 'protoplasm' for the fluid substance of the cell.
• The cell theory of plant and animal and that the cell is the basic unit of life, was presented by Schleiden(1838) and Schwan(1839).
•The cell theory was further expanded by Virchow(1855) by suggestimg that all cell arise from pre existing cell.
• With the discovery of the electrone microscope in 1940, it was possible to observe the complex structure of the cell and its various organelles
2) Cell:- Cell is the structural and functional unit of life
3) Cell organisms are classified as :-
• Unicellular:- Organisms which are made up of single cell.
•Multicellular:- Organisms which are made up of many cell.
eg:- Plants, animals and fungi.
4) Shape and size of the Cells:- Some cells can change their shapes like amoeba, WBC but plants and animal cells have almost fixed shapes.
a) Smallest Cell- PPLG (Mycoplasma)
b) Largest Cell- Ostrich Cell.
c) Longest animal Cell- Nerve Cell
5) Diffusion :- Movement of solute particles from higher concentration to lower concentration is called Diffusion.
Example:- Exchange of gases during respiration.
6) Osmosis:- The movement of solvent particles from lower concentration to higher concentration in presence of semi permeable membrane is called Osmosis.
Example:- Absorption of water by roots.
7) Types of Osmosis:-
a) Endosmosis:- Movement of water inside cell is called Endosmosis. It takes place when cell is placed in low concentration solution.
b) Exosmosis:- Movement of water out from cell is called Exosmosis. It takes place when cell is placed in high concentration Solution.
8) Types of osmotic solution:-
a) Hypotonic:- The solution which have lower concentration than others.
b) Hypertonic:- The solution which have higher concentration than others.
c)Isotonic:- The solution which have equal concentration than others.
9) Plasmic membrane or cell membrane:-
• It is outermost delicate covering of cell.
•It is also called selectively permeable membrane or semi permeable membrane because it allows entry of selective substance only.
• It is made up of a bi- lipid layer of proteins.
10) Cell Wall:- Rigid, semi elastic, semi transparent and protective covering present outside the plasma membrane in plant cell, fungi and prokaryotic. It is made up of cellulose in plants, fungal cellulose.
11) Function of Cell Wall:-
•It provides shapes to the cell.
•It provide mechanical strength to plants.
• Protect against pathogens and mechanical injury.
•Growth of the cell wall determines the growth of cell.
• Cell wall prevents bursting of cell on endosmosis.
12) Nucleus:-
The nucleus was the first organelle to be discovered. Nucleus consist of nuclear membrane, chromosomes,chromatin,nucleolus, ribosomes.
13) Types of plastids:-
• Chloroplasts:- These plastids are green due to the presence of chlorophyll pigment, and hence are responsible for photosynthesis.
• Chromoplasts:- These are coloured plastids containing pigments. Other than chlorophyll are found in fruits,flower,roots and stressed and aging leaves and are responsible for their distinctive color.
•Leucoplasts:- Leucoplasts are colourlrss plastids that store pods they are found in storage organs such as Fruits, tubers and seeds.
14) Cytoplasm:- The cytoplasm is the fluid content inside the plasma membrane. It also contains many speacialised specific function for the cell.
15) Cell Orgaelles:- Cell organelles perform specific function with in a cell. They are enclosed by membrane. Some important examples of cell organelles are endoplasmic reticulum, mitochondria,golgi apparatus, lysosomes, plastids and vacuoles.
•Endoplasmic Reticulum:-
a) Network of tubular and vesicular structure which are interconnected with one another.
b) Some parts are connected to the nuclear membrane,while others are connected to the cell membrane.
c) Two Types- Smooth(lacks ribosomes) and Rough( with ribosomes).
d) It gives internal support to the cytoplasm.
• Golgi Body:-
a) Discovered by Camillo Golgi.
b) Formed by stacks of 5-8 membranous sacs.
c) Sacs are usually flattened and are called cristernae.
d) It has two ends:- Sis face situated near the endoplasmic reticulum and trans face situated near the cell membrane.
•Plastids:-
a) Plastids are double membrane bound organelle found inside plants and some algae.
b) They are responsible for activities related to making and storing food.
c) They often contain different types pigment that can change the colour of the cell.
• Mitochondria:-
a) Mitochondria is known as the Powerhouse of the Cell.
b) Mitochondria have two membrane covering.
c) The outer membrane is porous while is other membrane is deeply folded.
•Vacuoles:-
a) Vacuoles are storage sacs for solid or liquid content.
b) Vacuoles are small sized animals cell which plant cell have very large vacuoles.
c) Vacuoles can hold food for later use or waste for removal.
•Lysomes:-
a) Small, spherical, single membrane sac.
b) Found throughout the cytoplasm.
c) Filled with hydrolytic enzymes.
d) Occurs in most, animal cell and in few.
16) Functions of Vacuoles and Plastids:-
a)Vacuoles:
• The vacuoles is the storage structure in a cell.
•It can hold food for later use or waste for removal.
•In plant cells the vacuole can also store water.
b) Plastids:
•Plastids provide colour to fruits and flowers.
•They help in storage of proteins, Starch and oil.
• Plastids trap solar energy to manufacture food through the process of photosynthesis.
17. Types of Endoplasmic Reticulum:
•Rough Endoplasmic Reticulum (RER)
It has Ribosomes on its surface. The RER synthesiser (makes) and packages proteins.
•Smooth Endoplasmic Reticulum:-
It does not contain ribosomes. The SER helps in the storage of proteins and lipids.
These are the complete notes of CHAPTER 5 THE FUNDAMENTAL UNIT OF LIFE OF SCIENCE NCERT CLASS 9. Hope these notes helpful to better understand the CHAP5 THE FUNDAMENTAL UNIT OF LIFE.
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