NCERT Solutions for Class 9th Science_ Chapter 5 The Fundamental Unit of Life _ AglaSem Schools Class 9 Notes | EduRev

Class 9 : NCERT Solutions for Class 9th Science_ Chapter 5 The Fundamental Unit of Life _ AglaSem Schools Class 9 Notes | EduRev

 Page 1


NCERT Solutions for Class 9th Science:
Chapter 5 The Fundamental Unit of Life
 
By Anand Meena - August 6, 2014
NCERT Solutions for Class 9th Science: Chapter 5 The
Fundamental Unit of Life
National Council of Educational Research and Training (NCERT) Book Solutions for Class 9 
Subject: Science 
Chapter: Chapter 5 – The Fundamental Unit of Life
Class 9 Science Chapter 5 The Fundamental Unit of Life NCERT Solution is given below.
Question 1: 
Who discovered cells and how? 
Answer: 
Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive
microscope to observe cells in a cork slice.
Question 2: 
Why is the cell called the structural and functional unit of life? 
Answer: 
Cells constitute various components of plants and animals. A cell is the smallest unit of life
and is capable of all living functions. Cells are the building blocks of life. This is the reason
why cells are referred to as the basic structural and functional units of life. All cells vary in
their shape, size, and activity they perform. In fact, the shape and size of the cell is related
to the specific functions they perform.
—
Question 1: 
How do substances like CO2 and water move in and out of the cell? Discuss. 
Answer: 
The cell membrane is selectively permeable and regulates themovement of substances in
and out of the cell. Movement of CO2: 
CO2 is produced during cellular respiration. Therefore, it is present in high concentrations
Page 2


NCERT Solutions for Class 9th Science:
Chapter 5 The Fundamental Unit of Life
 
By Anand Meena - August 6, 2014
NCERT Solutions for Class 9th Science: Chapter 5 The
Fundamental Unit of Life
National Council of Educational Research and Training (NCERT) Book Solutions for Class 9 
Subject: Science 
Chapter: Chapter 5 – The Fundamental Unit of Life
Class 9 Science Chapter 5 The Fundamental Unit of Life NCERT Solution is given below.
Question 1: 
Who discovered cells and how? 
Answer: 
Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive
microscope to observe cells in a cork slice.
Question 2: 
Why is the cell called the structural and functional unit of life? 
Answer: 
Cells constitute various components of plants and animals. A cell is the smallest unit of life
and is capable of all living functions. Cells are the building blocks of life. This is the reason
why cells are referred to as the basic structural and functional units of life. All cells vary in
their shape, size, and activity they perform. In fact, the shape and size of the cell is related
to the specific functions they perform.
—
Question 1: 
How do substances like CO2 and water move in and out of the cell? Discuss. 
Answer: 
The cell membrane is selectively permeable and regulates themovement of substances in
and out of the cell. Movement of CO2: 
CO2 is produced during cellular respiration. Therefore, it is present in high concentrations
inside the cell. This CO2 must be excreted out of the cell. In the cell’s external
environment, the concentration of CO2 is low as compared to that inside the cell.
Therefore, according to the principle of diffusion, CO2 moves from a region of higher
concentration (inside the cell) towards a region of lower concentration (outside the cell).
Similarly, O2 enters the cell by the process of diffusion when the concentration of O2 inside
the cell is low as compared to its surroundings.
Movement of water: 
Water moves from a region of high concentration to a region of low concentration through
the plasma membrane. The plasma membrane acts as a semi-permeable membrane, and
this movement of water is known as osmosis. However, the movement of water across the
plasma membrane of the cell is affected by the amount of substance dissolved in water.
Question 2: 
Why is the plasma membrane called a selectively permeable membrane? 
Answer: 
Thecell membraneor the plasma membraneis known as a selectively permeable membrane
because it regulates the movement of substances in and out of the cell. This means that
the plasma membrane allows the entry of only some substances and prevents the
movement of some other materials.
—
Question 1: 
Fill in the gaps in the following table illustrating differences between prokaryotic
and eukaryotic cells. 
Page 3


NCERT Solutions for Class 9th Science:
Chapter 5 The Fundamental Unit of Life
 
By Anand Meena - August 6, 2014
NCERT Solutions for Class 9th Science: Chapter 5 The
Fundamental Unit of Life
National Council of Educational Research and Training (NCERT) Book Solutions for Class 9 
Subject: Science 
Chapter: Chapter 5 – The Fundamental Unit of Life
Class 9 Science Chapter 5 The Fundamental Unit of Life NCERT Solution is given below.
Question 1: 
Who discovered cells and how? 
Answer: 
Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive
microscope to observe cells in a cork slice.
Question 2: 
Why is the cell called the structural and functional unit of life? 
Answer: 
Cells constitute various components of plants and animals. A cell is the smallest unit of life
and is capable of all living functions. Cells are the building blocks of life. This is the reason
why cells are referred to as the basic structural and functional units of life. All cells vary in
their shape, size, and activity they perform. In fact, the shape and size of the cell is related
to the specific functions they perform.
—
Question 1: 
How do substances like CO2 and water move in and out of the cell? Discuss. 
Answer: 
The cell membrane is selectively permeable and regulates themovement of substances in
and out of the cell. Movement of CO2: 
CO2 is produced during cellular respiration. Therefore, it is present in high concentrations
inside the cell. This CO2 must be excreted out of the cell. In the cell’s external
environment, the concentration of CO2 is low as compared to that inside the cell.
Therefore, according to the principle of diffusion, CO2 moves from a region of higher
concentration (inside the cell) towards a region of lower concentration (outside the cell).
Similarly, O2 enters the cell by the process of diffusion when the concentration of O2 inside
the cell is low as compared to its surroundings.
Movement of water: 
Water moves from a region of high concentration to a region of low concentration through
the plasma membrane. The plasma membrane acts as a semi-permeable membrane, and
this movement of water is known as osmosis. However, the movement of water across the
plasma membrane of the cell is affected by the amount of substance dissolved in water.
Question 2: 
Why is the plasma membrane called a selectively permeable membrane? 
Answer: 
Thecell membraneor the plasma membraneis known as a selectively permeable membrane
because it regulates the movement of substances in and out of the cell. This means that
the plasma membrane allows the entry of only some substances and prevents the
movement of some other materials.
—
Question 1: 
Fill in the gaps in the following table illustrating differences between prokaryotic
and eukaryotic cells. 
—
Question 1: 
Can you name the two organelles we have studied that contain their own genetic material? 
Answer: 
Mitochondriaandplastids are the two organelles that contain their own genetic material.
Both these organelles have their own DNA and ribosomes.
Question 2: 
If the organisation of a cell is destroyed due to some physical or chemical influence, 
what will happen? 
Answer: 
Cell is the smallest unit of life, which is capable of all living functions. If the organisation of
a cell is destroyed due to some physical or chemical influence, then the ability of the cell to
perform all living functions such as respiration, nutrition, excretion, etc. would be affected.
Page 4


NCERT Solutions for Class 9th Science:
Chapter 5 The Fundamental Unit of Life
 
By Anand Meena - August 6, 2014
NCERT Solutions for Class 9th Science: Chapter 5 The
Fundamental Unit of Life
National Council of Educational Research and Training (NCERT) Book Solutions for Class 9 
Subject: Science 
Chapter: Chapter 5 – The Fundamental Unit of Life
Class 9 Science Chapter 5 The Fundamental Unit of Life NCERT Solution is given below.
Question 1: 
Who discovered cells and how? 
Answer: 
Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive
microscope to observe cells in a cork slice.
Question 2: 
Why is the cell called the structural and functional unit of life? 
Answer: 
Cells constitute various components of plants and animals. A cell is the smallest unit of life
and is capable of all living functions. Cells are the building blocks of life. This is the reason
why cells are referred to as the basic structural and functional units of life. All cells vary in
their shape, size, and activity they perform. In fact, the shape and size of the cell is related
to the specific functions they perform.
—
Question 1: 
How do substances like CO2 and water move in and out of the cell? Discuss. 
Answer: 
The cell membrane is selectively permeable and regulates themovement of substances in
and out of the cell. Movement of CO2: 
CO2 is produced during cellular respiration. Therefore, it is present in high concentrations
inside the cell. This CO2 must be excreted out of the cell. In the cell’s external
environment, the concentration of CO2 is low as compared to that inside the cell.
Therefore, according to the principle of diffusion, CO2 moves from a region of higher
concentration (inside the cell) towards a region of lower concentration (outside the cell).
Similarly, O2 enters the cell by the process of diffusion when the concentration of O2 inside
the cell is low as compared to its surroundings.
Movement of water: 
Water moves from a region of high concentration to a region of low concentration through
the plasma membrane. The plasma membrane acts as a semi-permeable membrane, and
this movement of water is known as osmosis. However, the movement of water across the
plasma membrane of the cell is affected by the amount of substance dissolved in water.
Question 2: 
Why is the plasma membrane called a selectively permeable membrane? 
Answer: 
Thecell membraneor the plasma membraneis known as a selectively permeable membrane
because it regulates the movement of substances in and out of the cell. This means that
the plasma membrane allows the entry of only some substances and prevents the
movement of some other materials.
—
Question 1: 
Fill in the gaps in the following table illustrating differences between prokaryotic
and eukaryotic cells. 
—
Question 1: 
Can you name the two organelles we have studied that contain their own genetic material? 
Answer: 
Mitochondriaandplastids are the two organelles that contain their own genetic material.
Both these organelles have their own DNA and ribosomes.
Question 2: 
If the organisation of a cell is destroyed due to some physical or chemical influence, 
what will happen? 
Answer: 
Cell is the smallest unit of life, which is capable of all living functions. If the organisation of
a cell is destroyed due to some physical or chemical influence, then the ability of the cell to
perform all living functions such as respiration, nutrition, excretion, etc. would be affected.
Question 3: 
Why are lysosomes known as suicide bags? 
Answer: 
Lysosomes are membrane-bound vesicular structures that contain powerful
digestive enzymes. These enzymes are capable of breaking down any foreign food particle
or microbes entering the cell. Sometimes, lysosomes can cause self-destruction of a cell by
releasing these digestive enzymes within the cells. Hence, they are also known as ‘suicidal
bags’.
Question 4: 
Where are proteins synthesized inside the cell? 
Answer: 
Ribosomesare the site for protein synthesis. Ribosomes are very small structures found
either in a free state, suspended in the cytoplasm, or attached to the surface of the
endoplasmic reticulum. They are composed of ribonucleic acids and proteins.
—
Question 1: 
Make a comparison and write down ways in which plant cells are different from animal
cells. 
Answer: 
Page 5


NCERT Solutions for Class 9th Science:
Chapter 5 The Fundamental Unit of Life
 
By Anand Meena - August 6, 2014
NCERT Solutions for Class 9th Science: Chapter 5 The
Fundamental Unit of Life
National Council of Educational Research and Training (NCERT) Book Solutions for Class 9 
Subject: Science 
Chapter: Chapter 5 – The Fundamental Unit of Life
Class 9 Science Chapter 5 The Fundamental Unit of Life NCERT Solution is given below.
Question 1: 
Who discovered cells and how? 
Answer: 
Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive
microscope to observe cells in a cork slice.
Question 2: 
Why is the cell called the structural and functional unit of life? 
Answer: 
Cells constitute various components of plants and animals. A cell is the smallest unit of life
and is capable of all living functions. Cells are the building blocks of life. This is the reason
why cells are referred to as the basic structural and functional units of life. All cells vary in
their shape, size, and activity they perform. In fact, the shape and size of the cell is related
to the specific functions they perform.
—
Question 1: 
How do substances like CO2 and water move in and out of the cell? Discuss. 
Answer: 
The cell membrane is selectively permeable and regulates themovement of substances in
and out of the cell. Movement of CO2: 
CO2 is produced during cellular respiration. Therefore, it is present in high concentrations
inside the cell. This CO2 must be excreted out of the cell. In the cell’s external
environment, the concentration of CO2 is low as compared to that inside the cell.
Therefore, according to the principle of diffusion, CO2 moves from a region of higher
concentration (inside the cell) towards a region of lower concentration (outside the cell).
Similarly, O2 enters the cell by the process of diffusion when the concentration of O2 inside
the cell is low as compared to its surroundings.
Movement of water: 
Water moves from a region of high concentration to a region of low concentration through
the plasma membrane. The plasma membrane acts as a semi-permeable membrane, and
this movement of water is known as osmosis. However, the movement of water across the
plasma membrane of the cell is affected by the amount of substance dissolved in water.
Question 2: 
Why is the plasma membrane called a selectively permeable membrane? 
Answer: 
Thecell membraneor the plasma membraneis known as a selectively permeable membrane
because it regulates the movement of substances in and out of the cell. This means that
the plasma membrane allows the entry of only some substances and prevents the
movement of some other materials.
—
Question 1: 
Fill in the gaps in the following table illustrating differences between prokaryotic
and eukaryotic cells. 
—
Question 1: 
Can you name the two organelles we have studied that contain their own genetic material? 
Answer: 
Mitochondriaandplastids are the two organelles that contain their own genetic material.
Both these organelles have their own DNA and ribosomes.
Question 2: 
If the organisation of a cell is destroyed due to some physical or chemical influence, 
what will happen? 
Answer: 
Cell is the smallest unit of life, which is capable of all living functions. If the organisation of
a cell is destroyed due to some physical or chemical influence, then the ability of the cell to
perform all living functions such as respiration, nutrition, excretion, etc. would be affected.
Question 3: 
Why are lysosomes known as suicide bags? 
Answer: 
Lysosomes are membrane-bound vesicular structures that contain powerful
digestive enzymes. These enzymes are capable of breaking down any foreign food particle
or microbes entering the cell. Sometimes, lysosomes can cause self-destruction of a cell by
releasing these digestive enzymes within the cells. Hence, they are also known as ‘suicidal
bags’.
Question 4: 
Where are proteins synthesized inside the cell? 
Answer: 
Ribosomesare the site for protein synthesis. Ribosomes are very small structures found
either in a free state, suspended in the cytoplasm, or attached to the surface of the
endoplasmic reticulum. They are composed of ribonucleic acids and proteins.
—
Question 1: 
Make a comparison and write down ways in which plant cells are different from animal
cells. 
Answer: 
Question 2: 
How is a prokaryotic cell different from a eukaryotic cell? 
Answer: 
Question 3: 
What would happen if the plasma membrane ruptures or breaks down? 
Answer: 
If the plasma membrane of a cell is ruptured, then the cell will die. The plasma membrane
regulates the movement of substances in and out of the cell by diffusion or osmosis. Thus,
if the plasma membrane is ruptured, then the cell might leak out its contents.
Question 4: 
What would happen to the life of a cell if there was no Golgi apparatus? 
Answer: 
If there was no Golgi apparatus in the cell, then most activities performed by the Golgi
apparatus will not take place. 
(i) Membranes of the Golgi apparatus are often connected to ER membranes. It collects
simpler molecules and combines them to make more complex molecules. These are then
packaged in small vesicles and are either stored in the cell or sent out as per the
requirement. Thus, if the Golgi apparatus is absent in the cell, then the above process of
storage, modification, and packaging of products will not be possible. 
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