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OASIS EDUCATION CENTER KANDORA
Class: 9th
The Fundamental Unit of Life Chapter Notes
• Cell is the structural and functional unit of an organism because a cell in itself is the smallest part of
an organism which is capable of functioning independently and can carry out the fundamental duties
of life like reproduction, metabolism (photosynthesis and/or respiration)
...
• Organisms which are made up of more than one cell are called multicellular organisms, eg Animals etc
(Q
...
• Organisms which are made up of many cells are called Multicellular organisms, eg Hydra,
Earthworm Man etc
...
(Q
...
(Ans) Cells were observed for the first time in a slice of cork
...
• Living cell was first observed by Leeuwenhoek in a drop of pond water
...
3) All cells arise from pre existing cells
...
All cells are alike in structure and metabolic activities
...
• The nuclear material of Prokaryotes consists of a single chromosome and lies in the cytoplasm
...
• Membrane-bound organelles are absent in all prokaryotes
...
Structure of Eukaryotic cell
• Cells vary in shape and size
...
• The variation in the shape of the cells is due to the function they have to perform as part of the tissue or
an organ system
...
1 micron i
...
ten thousandth part
of a milimetre
...
)Why do cells have different shapes?
Give an example to support your answer
...
Example: Nerve cells are long and
branched to carry signals from one part of the
body to other and white blood cells are irregular
in shape in order to engulf the pathogens in the body
...
)Why do we stain the small components of section, before seeing under the microscope? Name
a stain
...
The dyes react with cellular components
to give colour to the components
...
Components of the cell
Cell wall
• The cell wall is present only in plant cells
...
• Its function is to give strength and rigidity to the cell
...
• Cell wall between two adjacent cells is joined by middle lamella
...
• Cell wall may get depositions of substances like Lignin , Suberin etc, which make it impermeable
...
)Why plant cell have cell wall?
Ans: Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture,
etc
...
That‟s why they have cell wall
...
• It is living, elastic and made of proteins and phosphor lipids (fats)
...
• The most accepted model of Plasma membrane is the “Fluid Mosaic Model” given by Singer and
Nicholson
...
Diffusion – It is the movement of solute particles from the region of their higher concentration to the region
of their lower concentration till it reaches equilibrium
...
- If an animal cell is placed in a hypotonic solution it will it will undergo endo osmosis and will swell (become
turgid) and will burst
...
Such a cell is called Plasmolysed
cell
...
Notes Compiled by Ummer Farooq Mir
Contact: 9149836499
3
OASIS EDUCATION CENTER KANDORA
- Plant cell in hypotonic solution undergoes endo osmosis, becomes turgid but does not burst due to the
rigid cell wall
...
• Root hair absorb soil water by endo osmosis where as Gaseous exchange takes place by diffusion
...
- Endocytosis – taking in of big particles which can not cross the plasma membrane
...
(Amoeba
takes in food by this process)
- Pinocytosis – The process by which cells take in liquid substances, commonly known as cell drinking
...
Cytoplasm
• The fluid part of the cell between the cell membrane and the nuclear membrane is called the cytoplasm
...
• The matrix is a transparent semi fluid substance
...
It stores raw material
...
• Cytoplasm also shows circular movement called cyclosis, which helps in proper distribution of substances
...
Who coined the term protoplasm?
Ans : J
...
Purkinje
(Q
...
g
...
Nucleus
• It is found in all eukaryotic cells except
mature mammalian RBC, Sieve tubes and
sieve cells
...
• Number of nucleus per cell is generally one but 2 in Paramoecium (Binucleate), many in Skeletal muscle
fibres (multinucleate)
• It is the controlling centre of all cell activities and has been called the brain of the cell
...
• The nuclear membrane has minute pores which allow the selective transfer of material between the
nucleoplasm and the cytoplasm
...
• The nucleolus and the chromatin network lie suspended in the nucleoplasm
...
(Q
...
Chromatin network
• These are very fine thread-like, coiled filaments uniformly distributed in the nucleoplasm
...
• The chromosomes contain genes, which are composed of DNA (deoxyribonucleic acid)
...
)Where are chromosomes found in a cell? State their function
...
Function: Chromosomes carry genes and help in inheritance or transfer of characters from the parents to
the offspring
...
Notes Compiled by Ummer Farooq Mir
Contact: 9149836499
5
OASIS EDUCATION CENTER KANDORA
• Endoplasmic Reticulum (ER)
• Golgi Apparatus
• Mitochondria
• Plastids
• Lysosomes
• Ribosomes
• Centrosome
Endoplasmic Reticulum (ER)
This is a complex network of interconnected cisternae ,tubules and vesicles , the lumen of which is filled
with fluid
...
• SER mainly contains tubules
...
• The also help in detoxification ( removal of toxic substances
like drugs etc)
• RER - Tubes with ribosomes attached are known as rough
endoplasmic reticulum
...
• ERs provide a pathway for the distribution of nuclear material
from one cell to the other
• They also form the skeletal framework of the cell
...
• They consist of tiny, elongated, flattened sacs
called cisternae, which are stacked parallel to one
another along with some vacuoles and clusters of
vesicles
...
• The function of the Golgi Body is to secrete certain
hormones and enzymes
...
( packaging of enzymes)
• They also help in yolk formation in eggs
...
Mitochondria
Notes Compiled by Ummer Farooq Mir
Contact: 9149836499
6
OASIS EDUCATION CENTER KANDORA
• They are found in all eukaryotes but absent in mature mammalian RBC and prokaryotes
...
• Each mitochondrion is bound
by a double membrane
...
• On the crista are found knob
like structures called Oxysomes
which help in ATP synthesis
...
• The energy thus released is stored as high-energy chemicals called ATP
• The body cells use the energy stored in ATP for synthesis of new chemical compounds and other
activities
• Hence, mitochondria are termed as the “power house” of the cell
...
• Plastids are of three types
A ) Chloroplasts
• They are green and found in leaves
...
• They are double membrane structures,
• Matrix is called Stroma
...
• These thylakoids are staked to form a granum
...
• Stroma also contains ribosomes and DNA so Chloroplasta are also called Semi autonomous organelle
• The function of the chloroplast is to trap solar energy for photosynthesis
...
• Light reaction of photosynthesis takes place in grana and dark reaction (Calvincycle) in stroma
...
)Explain why chloroplasts are found only in plant cells?
Ans: Plants prepare their food by their own
...
Animals do not prepare their food by their own
...
B) Chromoplasts
• They contain yellow, orange and red, and found in flowers and fruits
...
C) Leucoplasts
• They are colourless and found in roots, seeds and underground stems
...
Leucoplasts store food in the form of carbohydrates, fats and proteins
...
• Their main function is digestion
...
• Lysosomes present in white blood cells are capable of digesting bacteria and viruses
...
• They are also capable of digesting worn out cell organelles, or
even digesting the entire damaged cell containing them
...
Ribosomes
• These are spherical, granular particles which occur freely in
the matrix or remain attached to the rough endoplasmic reticulum
...
• Their function is synthesizing proteins so called “Protein factories “ or “Engine of the cell”
...
• This is found in the cytoplasm near the outer surface of the nucleus
...
Vacuole
• Found in all eukaryotic cells
• Small and many in animal cells
• Big and few in plant cells
• Their membrane is known as tonoplast
• They are filled with cell sap (water, mineral, sugar etc)
• Food vacuoles store food
...
)Name two-cell organelles, which have DNA apart from nucleus
...
)Name the non - living parts of a cell
...
Cell wall (plants only) 2
...
Granules (cell inclusions)
(Q
...
Therefore, Lysosomes are also known as the suicidal bags of the cell
...
)Write any four differences between the plasma membrane and cell wall
...
It is made up of lipids and protein
...
It is made up of cellulose
...
It is living
...
It is dead
...
Present in both plant and animal cell
...
Found exclusively in plant cell
...
It regulates entry and exit of molecules in and out
4
...
plants
...
) Differentiate the terms: (i) Hypotonic (ii) Isotonic (iii) Hypertonic
(Ans) (i) If a medium surrounding the cell has a higher water concentration than that of the cell, the cell will
gain water by osmosis
...
(ii) If a medium has exactly the same water concentration as that of the cell, there will be no net movement
of water across the cell membrane
...
(iii)
If a medium has a lower concentration of water than the cell, meaning that it is a very concentrated
solution, the cell will lose water by osmosis
...
(Q
...
(Q
...
(Ans) It maintains osmotic pressure, thus helps in maintaining and regulating turgidity and flaccidity of the
cell
...
(Q
...
It encloses nucleus and itself is bounded by cell
membrane
...
It contains cell organelles and cell inclusions
...
It is the space within the nuclear envelop
2
...
Contact: 9149836499
9