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NCERT Solutions For Class 9 Science Chapter 5 The Fundamental Unit Of Life
Edited By Irshad Anwar | Updated on Apr 15, 2025 06:14 PM IST
NCERT Solutions for Class 9 Science The Fundamental Unit of Life chapter introduces students to cells, the basic structural and functional units of life. It explains the discovery of the cell, the cell theory, and the different types of cells. Students also learn about various cell organelles and their functions, including the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus.
This Story also Contains
- NCERT Solutions for Class 9 The Fundamental Unit of Life PDF
- NCERT Solutions for Class 9 Science Chapter 5
- The Fundamental Unit Of Life Class 9 Questions And Answers: Solved Exercise Solutions
- Overview of the Chapter Fundamental Unit of Life
- How to solve NCERT Class 9 Science Chapter 5 questions effectively?
- NCERT Solutions for Class 9 Science Chapter-wise
- Practice Questions for Class 9 Science The Fundamental Unit of Life
The chapter covers important topics such as the plasma membrane and its functions, diffusion and osmosis, and the differences between plant and animal cells. NCERT Solutions explains how cells divide and multiply through cell division processes like mitosis and meiosis, which are essential for growth and reproduction.
NCERT Solutions for Class 9 Science provide step-by-step answers to textbook questions in a simple and easy-to-understand manner. These detailed explanations help students grasp key concepts such as cell structure, functions of cell organelles, and transport mechanisms, making it easier to prepare for exams in a structured and systematic way.
NCERT Solutions for Class 9 The Fundamental Unit of Life PDF
Students can download the complete questions with detailed answers PDF of this chapter for better learning:
Also Read,
- NCERT Notes for class 9 science chapter 5 The fundamental unit of life
- NCERT Exemplar for class 9 science chapter 5 The fundamental unit of life
NCERT Solutions for Class 9 Science Chapter 5
The detailed answers to all the questions in this chapter are given below:
Topic 5.1 - What are Living Organisms made up of? (page 51)
Ques. 1. Who discovered cells, and how?
Answer:
Cells were discovered in 1665 by Robert Hooke. He was examining a thin slice of cork using a primitive microscope designed by. He saw that the structure of the cork at a microscopic level is similar to that of a honeycomb. It had several small chambers like those in a honeycomb.
These small chambers were termed cells.
Ques. 2. Why is the cell called the structural and functional unit of life?
Answer:
The cell is called the structural and functional unit of life as it is the smallest living unit which can carry out all the living processes essential for living.
Topic 5.2 What is a cell made up of? What is the structural organization of the cell? (page 53)
Ques. 1. How do substances like CO2 and water move in and out of the cell? Discuss
Answer:
CO2 and water move in and out of the cell through the cell membrane by the process of diffusion and osmosis respectively.
Ques. 2. Why is the plasma membrane called a selectively permeable membrane?
Answer:
The plasma membrane called a selectively permeable membrane because it relatively allows the movement of substances from the inside of the cell to the outside and vice-versa.
This selectivity depends on the requirements of the cell and the substances present in the surroundings of the cell.
Topic 5.2.2 Cell Wall (page 55)
| Prokaryotic Cell | Eukaryotic Cell |
| Size: Generally small (1-10μm) 1μm=10-6m | Size: Generally large (5-100μm) |
| Nuclear region: .................................. .......................and known as...... | Nuclear region: well defined and surrounded by a nuclear membrane |
| Chromosome: single | More than one chromosome |
| Membrane-bound cell organelles absent | ................................................................... ............................................................... .................................... |
Answer:
| Prokaryotic Cell | Eukaryotic Cell |
| 1. Size generally small. | 1. Size generally large. |
| 2. Nuclear Region: Poorly defined because of the absence of cell membranes and is called the nucleoid. | 2. Nuclear Region: Well defined and surrounded by a nuclear membrane. |
| 3. Chromosome: single. | 3. More than one chromosome. |
| 4. Membrane-bound cells organelles present | 4. Membrane-bound cell organelles absent. |
Topic 5.2 What is a cell made up of? What is the structural organization of the cell? (page 57)
Ques. 1. Can you name the two organelles we have studied that contain their own genetic material?
Answer:
Two organelles which contain their own genetic material are
1. Mitochondria
2. Plastids
Answer:
If the organisation of a cell is destroyed due to some physical or chemical influence it will not be able to perform the life processes essential for living and therefore would be digested by lysozymes.
Ques. 3. Why are lysosomes known as suicide bags?
Answer:
When the cells are damaged to such an extent that they are incapable of performing certain functions which are essential for survival, the organism tries to get rid of these cells.
For this function, the lysosomes which are membrane-bound organelles burst and release digestive enzymes called lysozymes which destruct the cell and lysosomes are therefore called suicide bags.
Ques. 4. Where are proteins synthesized inside the cell?
Answer:
- Inside the cells, the proteins are synthesized at sites called ribosomes.
- These are very small structures made up of ribonucleic acids and proteins.
The Fundamental Unit Of Life Class 9 Questions And Answers: Solved Exercise Solutions
Class 9 Science Chapter 5 Exercise Question Answers are given below:
Ques1. Make a comparison and write down ways in which plant cells are different from animal cells.
Answer:
| Plant Cells | Animal Cells |
| 1. Plant cells are generally bigger than animal cells. | 1. Animal cells are relatively small. |
| 2. Plant cells have a cell wall. | 2. Animal cells do not have a cell wall. |
| 3. The nucleus is not present in the centre of the cell. | 3. The nucleus is at the center of the cell. |
| 4. The size of the vacuole is large. | 4. The size of the vacuole is small. |
| 5. A chloroplast is present. | 5. A chloroplast is absent. |
Ques 2. How is a prokaryotic cell different from a eukaryotic cell?
Answer:
| Prokaryotic Cell | Eukaryotic Cell |
| 1. A prokaryotic cell is quite small in size. ( 1 - 10 pm) | 1. A eukaryotic cell is relatively larger. (5-100 pm) |
| 2. The nuclear region is poorly defined as the nuclear membrane is absent. | 2. The nuclear membrane is present and the nuclear region is well defined. |
| 3. Organelles are not membrane-bound. | 3. Organelles are membrane-bound. |
| 4. Only one chromosome is present. | 4. More than one chromosome is present. |
Ques 3. What would happen if the plasma membrane ruptures or breaks down?
Answer:
- If the plasma membrane ruptures, the cell would eventually die because the movement of substances won't be regulated.
- This will cause important substances to move out of the cell and harmful substances from the environment to enter the cell.
Ques 4. What would happen to the life of a cell if there was no Golgi apparatus?
Answer:
- The Golgi apparatus stores and transports materials through vesicles.
- In the absence of the Golgi apparatus, these functions would stop and this will cause the death of the cell.
Ques 5. Which organelle is known as the powerhouse of the cell? Why?
Answer:
Mitochondria are known as the powerhouse of the cell as mitochondria releases energy in the form of ATP which is essential for performing all the functions of the cell.
Ques 6. Where do the lipids and proteins constituting the cell membrane get synthesized?
Answer :
- Lipids and proteins are synthesized in the endoplasmic reticulum.
- In the Rough Endoplasmic Reticulum, proteins are manufactured whereas the manufacturing of lipids take place in the Smooth Endoplasmic Reticulum.
Ques 7. How does an Amoeba obtain its food?
Answer:
- Amoeba obtains its food by the virtue of the flexibility of its shape.
- Amoeba entraps the food particle around its membrane and then engulfs it within the cytoplasm. This process is called endocytosis.
Ques 8. What is osmosis?
Answer:
Osmosis is the movement of water from a region of low concentration of solute(high water concentration) to a region of high concentration of solute(low water concentration) through a semi-permeable membrane.
Ques 9. (i) Carry out the following osmosis experiment:
Take four peeled potato halves and scoop each one out to make potato cups. One of this potato cup should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
(a) Keep cup A empty
(b) Put one teaspoon of sugar in cup B
(c) Put one teaspoon salt in cup C
(d) Put one teaspoon of sugar in the boiled potato cup D. Keep these for two hours. Then, observe the four potato cups and answer the following:
(e) Explain why water gathers in the hollowed portion of B and C.
Answer:
(i) Due to the presence of a solute (sugar in the case of B and salt in the case of C), there is a concentration difference of water in the potato cup and the trough, due to which osmosis takes place where the cells of the potato act as the semi-permeable membrane.
Ques 9. (ii) Carry out the following osmosis experiment:
Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
(a) Keep cup A empty
(b) Put one teaspoon of sugar in cup B
(c) Put one teaspoon salt in cup C
(d) Put one teaspoon of sugar in the boiled potato cup D.
Keep these for two hours. Then, observe the four potato cups and answer the following:
(ii) Why is potato A necessary for this experiment?
Answer:
Potato A is absolutely necessary because it acts as the control for the experiment. Without A we will have no reference to compare the other cases with. We can see that since there is no solute in the hollow part of this potato no osmosis has taken place.
Ques 9.(iii) Carry out the following osmosis experiment:
Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
(a) Keep cup A empty
(b) Put one teaspoon of sugar in cup B
(c) Put one teaspoon salt in cup C
(d) Put one teaspoon of sugar in the boiled potato cup D.
Keep these for two hours. Then observe the four potato cups and answer the following:
(iii) Explain why water does not gather in the hollowed-out portions of A and D.
Answer:
Since there is no solute in the hollow part of potato A no osmosis has taken place and water does not gather in the hollowed part of A.
In the case of D even after the presence of solute osmosis does not take place. Boiling this potato has destroyed the cells and thus no semi-permeable membrane is there for osmosis to take place.
Answer:
Mitosis is required for the growth and repair of the body, and meiosis is involved in the formation of gametes.
NCERT Solutions for Class 9 - Subject Wise
Overview of the Chapter Fundamental Unit of Life
Chapter 5 discusses the cell as the elementary building unit and functional unit of all living things. It discusses how the cell was discovered, the cell theory, and how prokaryotic cells differ from eukaryotic cells. The chapter discusses vital cell organelles such as the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes and describes their functions in sustaining life processes. It also explains the plasma membrane, its role in osmosis and diffusion, and how substances enter and leave cells. The chapter also acquaints students with cell division (mitosis and meiosis), which is important for growth and reproduction. By understanding this chapter, students can understand the basic principles of biology, which provide a foundation for further studies in life sciences.
Important Topics of NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit of Life
Important topics and subtopics of this chapter are listed below:
| 5.1 | What Are Living Organisms Made Up Of? |
| 5.2 | What Is a Cell Made Up Of? What Is the Structural Organisation of a Cell? |
| 5.2.1 | Plasma Membrane or Cell Membrane |
| 5.2.2 | Cell Wall |
| 5.2.3 | Nucleus |
| 5.2.4 | Cytoplasm |
| 5.2.5 | Cell Organelles |
| 5.2.5 (i) | Endoplasmic Reticulum (ER) |
| 5.2.5 (ii) | Golgi Apparatus |
| 5.2.5 (iii) | Lysosomes |
| 5.2.5 (iv) | Mitochondria |
| 5.2.5 (v) | Plastids |
| 5.2.5 (vi) | Vacuoles |
How to solve NCERT Class 9 Science Chapter 5 questions effectively?
The student should begin by understanding the structure and functions of different cell organelles like the nucleus, mitochondria and endoplasmic reticulum. Having neat labelled diagrams of plant and animal cells will improve visual learning. Practising the questions will improve the understanding of the chapter flow, charts and tables can be used for quick revision of important concepts. The Fundamental Unit of Life NCERT Solutions has all the solved exercise questions, with to-the-point answers and necessary information. Solving the exemplar problems and previous year's questions will help strengthen application-based understanding.
NCERT Solutions for Class 9 Science Chapter-wise
Below mentioned are the Chapterwise solutions:
Practice Questions for Class 9 Science The Fundamental Unit of Life
Below are a few solved practice questions:
Q1. Digestion cannot be performed by a single cell but by a group of cells. True or False
Answer:
A cell is responsible for performing different functions such as making protein, cellular digestion, cellular respiration, transportation of substances, etc. Hence the given statement is false.
Q2. What are the structures performing different functions in the cell called?
Answer:
All the functions of the cell are assigned to different structures of the cell such as mitochondria, endoplasmic reticulum, Golgi apparatus, etc. These are called organelles of the cell.
Q3. What is the function of vacuoles?
Answer:
The function of vacuole:
- The primary function of the vacuole is to store excess food and secondary metabolites in plants.
- It is also used as an excretory organelle in some of the unicellular organisms.
- It is used to store food material in Amoeba.
Q4. Lysosomes are used to store the nutrients into it. True or False
Answer:
Lysosomes contain digestive enzymes that helps in digestion of the foreign materials. Hence the given statement is false.
Q5. What is the function of lysosomes?
Answer:
Lysosomes digest the foreign substances that end up in lysosomes such as bacteria, food material and sometimes the worn-out cell organelles.
Q6. What are the different shapes of the endoplasmic reticulum?
Answer:
The endoplasmic reticulum can be of three shapes:
- Sac called as cisternae
- Tubule
- Bag-like structures called vesicles
Q7. DNA is responsible for all the characteristics of an organism. True or False
Answer:
DNA is made up of many functional units known as genes. Each gene carries a message of each characteristic of an organism.
The cell study of this chapter serves as the pillar of biology that enables students to know how life works at a microscopic level. Understanding concepts such as cell structure, organelles, and cell division becomes necessary for future studies in life sciences. NCERT Solutions has simple, step-by-step answers to textbook problems, making understanding difficult concepts convenient. These solutions assist students in revising effectively, developing problem-solving skills, and achieving success in exams with a clear understanding of basic biological concepts.
Also check NCERT Books and NCERT Syllabus here:
Frequently Asked Questions (FAQs)
1. What are the main differences between plant and animal cells?
Plant cells contain a cell wall, chloroplasts, and a large vacuole, while animal cells do not have these but contain centrioles and lysosomes. Plant cells are stiff, owing to the cell wall, whereas animal cells are elastic.
2. How do cell organelles contribute to cellular functions?
Cell organelles perform specialized functions: mitochondria produce energy, the nucleus controls activities, the Golgi apparatus processes proteins, and the endoplasmic reticulum aids transport. Together, they maintain cellular structure and function.
3. What is the significance of the cell membrane and cell wall?
The cell membrane controls movement of materials into and out of the cell to ensure homeostasis. The cell wall (in plants) gives support, protection, and shape to cells, keeping from taking too much water.
4. What is a cell?
A cell is a fundamental structural and functional unit of life. It performs fundamental biological functions, and it exists both in unicellular and multicellular organisms with organelles to carry out functions of various lives.
5. What are the different types of cells?
There are various categories of cells distinguished broadly into prokaryotic (bacteria, archaea) and eukaryotic (plants, animals, fungi, protists). Cells also exist as either somatic cells (body cells) or germ cells (germ cells as reproductive cells like sperm and egg).
6. What is the structure of a plant cell?
A plant cell has a cell wall, cell membrane, nucleus, cytoplasm, mitochondria, chloroplasts, vacuole, Golgi apparatus, ribosomes, and endoplasmic reticulum. All these organelles maintain functions such as photosynthesis, storage, and structural support.
7. What is the function of the nucleus?
The nucleus oversees cellular processes through regulation of gene expression. It harbors DNA, which stores genetic information, and the nucleolus, which synthesizes ribosomes required for protein synthesis.
8. What is the role of the cell membrane?
The cell membrane defends the cell and controls the movement of nutrients, gases, and waste. It is semi-permeable and performs selective transport of molecules without disturbing the internal environment.
9. What is the difference between plant and animal cells?
Plant cells contain a cell wall, chloroplasts, and a large vacuole, whereas animal cells do not have these but do have centrioles and lysosomes. Plant cells carry out photosynthesis, whereas animal cells use food consumption to gain energy.
10. What is a prokaryotic cell?
A prokaryotic cell is a unicellular, simple cell that lacks a nucleus or membrane-bound organelles. Bacteria and archaea are prokaryotic, with DNA freely floating in the cytoplasm.
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