NCERT Solutions For Class 9 Science Chapter 5 The Fundamental Unit Of Life (2025-26)

1. Who discovered cells and how?

Ans: The dead cells were first discovered by Robert Hooke in 1665. He observed in cork cells that the cells are like honeycomb structures with the help of a basic microscope while the living cells were first discovered by Antoine van Leuwenhoek after the discovery of the electron microscope.

2. Why is the cell called the structural and functional unit of life?

Ans: Cell is the basic unit of life and is present in all living organisms. Each living cell performs its specific functions that are the characteristics of all living forms. The cell consists of various cell organelles which help the cell to live and perform all its functions. The various cell organelles perform their special function that includes making new material in the cell, removal of the waste material from the cell and so on. Thus, cells are called basic structural and functional units of life as they perform all these functions.

3. How do substances like $\mathbf{CO_2}$ and water move in and out of the cell? Discuss.

Ans: By the process of diffusion the substances like carbon dioxide and water move in and out of a cell from the region of high concentration to the region of low concentration. When the concentration of carbon dioxide and water is higher outside the cell than carbon dioxide and water moves inside the cell and when the concentration of carbon dioxide and water is lower outside the cell and is higher inside the cell then they move out of the cell.

4. Why is the plasma membrane called a selectively permeable membrane?

Ans: The plasma membrane or the cell membrane is known as a selectively permeable or semipermeable membrane because it is responsible for the regulation of the various substances in and out of the cell. This results in the entry of certain substances and inhibits the entry of other substances through the plasma membrane.

5. Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells.

Ans:

6. Can you name the two organelles we have studied that contain their own genetic material?

Ans: The two organelles we have studied that contain their own genetic material are mitochondria and plastids. Mitochondria help in respiration in the cell while plastids are responsible for the process of photosynthesis in leaves.

7. If the organization of a cell is destroyed due to some physical or chemical influence, what will happen?

Ans: If the organization of a cell is destroyed due to some physical or chemical influence then the cell will not be able to perform many basic functions like photosynthesis, respiration, nutrition, etc., and may also result in the stopping of all life activities in the cell. Due to the cell damage, the lysosome bursts, and their enzymes digest such cells.

8. Why are lysosomes known as suicide bags?

Ans: Lysosomes are the cell organelles that are vesicular structures and contain the digestive enzymes. The function of these enzymes inside the lysosomes is to break down any foreign body that enters the cell. Sometimes, the lysosome may also act suicidal by releasing the digestive enzymes inside the cell and leads to self-destruction. Thus lysosomes are known as suicidal bags.

9. Where are proteins synthesized inside the cell?

Ans: Proteins are the building blocks of the body that are made up of various amino acids. They are synthesized inside the ribosomes that are the small structures present in the cytoplasm or might be attached to the surface of the endoplasmic reticulum. The endoplasmic reticulum is called the rough endoplasmic reticulum due to the presence of ribosomes on its surface. 

10. Make a comparison and write down ways in which plant cells are different from animal cells.

Ans: The difference between the plant cells and the animal cells are:

Animal Cell	Plant Cell
Animal cells are found to be smaller when compared to the plant cells.	Plants cells are found to be larger in size.
The cell wall is absent.	The cell wall is present.
Plastids are absent except Euglena.	They consist of plastids to perform photosynthesis.
Vacuoles are much smaller in size than plant cells and are several in numbers.	One central large vacuole is present.

11. How is a prokaryotic cell different from a eukaryotic cell?

Ans: The difference between a prokaryotic cell and a eukaryotic cell are:

12. What would happen if the plasma membrane ruptures or breaks down?

Ans: The function of the plasma membrane is to act as a semipermeable membrane and regulate the entry and exit of the various substances in and out of the cell by the process of diffusion or osmosis and if the plasma breaks or ruptures then the contents of the cell might leak. This will result in the cells getting less nutrition than required.

13. What would happen to the life of a cell if there was no Golgi apparatus?

Ans: The function of the Golgi apparatus is packaging and transferring substances from one part of the cell to another. If the Golgi apparatus is absent in a cell then packaging of the proteins or the arrangement of the structural protein will not take place inside a cell. Proteins are essential for cells to perform various metabolic functions and if the proteins fail to reach the cell then this metabolism in the cell will not take place and eventually this will cause the cell to die.

14. Which organelle is known as the powerhouse of the cell? Why?

Ans: Mitochondria are known as the powerhouse of the cell as they produce the energy which is required by the cell to perform various functions. The energy which is released by the mitochondria is in the form of ATP molecules and is required for various chemical activities needed for. The energy stored in ATP is used by the body to make new chemical compounds and to perform mechanical work. Thus, mitochondria are known as the powerhouse of cells.

15. Where do the lipids and proteins constituting the cell membrane get synthesized?

Ans: Lipids and proteins are the essential part of the plasma membrane which is synthesized through the endoplasmic reticulum. The endoplasmic reticulum is found to be of two types based on the substances they synthesize. The smooth endoplasmic reticulum is responsible for the synthesis of lipids while the rough endoplasmic reticulum is responsible for the synthesis of proteins.

16. How does an Amoeba obtain its food?

Ans: Amoeba contains pseudopodia which are responsible for engulfing as well as removing food. The process by which amoeba acquires their food is called endocytosis. The plasma membrane of the amoeba is quite flexible thus enabling the cell to engulf the food particles and other materials from its external environment and also excrete the waste outside through the process called exocytosis.

17. What is osmosis?

Ans: The process of movement of water molecules from a region of high water concentration to a region of low water concentration through a selectively permeable membrane is called osmosis. This process continues until the solute concentration reaches equilibrium. The movement of water takes place across a concentration gradient to maintain equity on both sides of the cell.

18. 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,

1. Keep cup A empty

2. Put one teaspoon sugar in cup B

3. Put one teaspoon salt in cup C

4. Put one teaspoon of sugar in the boiled potato cup D.

Keep these for two hours. Then observe the four potato cups and Solution the following:

(i) Explain why water gathers in the hollowed portion of B and C.

(ii) Why is potato A necessary for this experiment?

(iii) Explain why water does not gather in the hollowed-out portions of A and D.

Ans: The Solutions Are as Follows:

(i) The concentration of water that surrounds the potato is found to be more than inside which results in the flow of water inside the potato by the process of osmosis. Thus, the water gathers in the hollowed portions of setup B and C.

(ii) Potato A in this experiment is necessary since it is kept as a control set-up that helps in comparing the changes that have taken place in the other two setups of the experiment. By this, we can easily detect the changes in the different setups.

(iii) Since there is no change in the concentration of water in cup A so the water will not gather in the hollowed-out portions while in the case of cup D, due to boiling plasmolysis has taken place which leads to the absence of osmosis thus here also the water will not gather in the hollowed-out portions.

Class 9 Chemistry Chapter 5 Quick Overview of Topics

Detailed Structure of Topics and Subtopics Covered in Chemistry class 9 Chapter 5 NCERT Solutions is given below: 

Some Important Concepts of Class 9 Chapter 5 -  Fundamental Unit of life

Class 9 NCERT solutions help the students to go through the Concepts easily. Here, find the Important topics of  Chapter 5 -  Fundamental Unit of Life to crack your exams.

1. Lysosomes: Lysosomes contain enzymes that break down cellular waste and foreign materials, playing a crucial role in intracellular digestion and recycling.

2. Cell Division: Mitosis is the process of cell division, ensuring growth, repair, and maintenance by producing identical daughter cells with the same genetic information.

3. Meiosis: Meiosis is a type of cell division in sexually reproducing organisms, leading to the formation of gametes (sperm and egg cells) with genetic variation due to crossing over and independent assortment.

4. Cell Cycle: The cell cycle encompasses phases like interphase (growth and DNA replication) and mitotic phase (mitosis and cytokinesis), tightly regulated by checkpoints to ensure accurate cell division and proper cellular functions.

Chapter 5 Science Class 9 Exercises with Question Count

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Benefits of Class 9 NCERT Solutions For Chemistry Chapter 5 

The Vedantu’s Class 9 NCERT Solutions For Chemistry Chapter Chapter 5 Fundamentals Unit of Life provided here in PDFs offer various benefits, including:

• Detailed explanations and step-by-step solutions for all topics in Chapter 5.

• Solutions curated by experienced educators to ensure accuracy and clarity.

• Covers important concepts like cell cycle, cell division, and processes like Meiosis.

• Clear and concise explanations using precise chemical terminology.

• In-depth analysis of key concepts and their applications in real-life scenarios.

• A detailed explanation of important reactions such as the Plastids, vacuoles, and Golgi apparatus.

• Solutions to a variety of problems to strengthen analytical and problem-solving abilities.

Related Study Materials for Class 9 Chemistry Chapter 5 NCERT Solutions

Students can access extra study materials on the Fundamental Unit of Life. These resources are available for download and offer additional support for your studies.

Conclusion

The NCERT Solutions for Class 9 Science Chapter 5 - "The Fundamental Unit of Life" provides a comprehensive understanding of the chapter's content. This chapter focuses on the fundamental unit of life, which is the cell. NCERT Solutions offers detailed explanations, diagrams, and examples to help students grasp the concepts effectively.

The solutions cover various topics related to cells, including the discovery of cells, the structure and functions of different cell organelles, and the differences between plant and animal cells. They also provide answers to the questions and exercises given at the end of the chapter, aiding students in their exam preparation.

By studying these solutions, students can gain a deeper insight into the structure and functions of cells, understand the importance of cells in living organisms, and appreciate the complexity of cellular organisation. The solutions also promote critical thinking and scientific inquiry by encouraging students to explore the diverse aspects of cell biology. 

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