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Class 9 Science Chapter 5 Questions and Answers PDF (The Fundamental Unit of Life)
Vedantu offers Class 9 Chapter 5, Fundamentals of Life Science, insights into the essential principles governing life and its processes. Ch 5 science class 9 serves as a foundational exploration of life sciences, covering topics such as cell structure and functions, tissues, and various life processes occurring within organisms. Through detailed explanations and illustrations, students understand the fundamental concepts underlying living organisms' structure, behaviour, and interactions with their environment.
Table of Content
Download the FREE PDF of NCERT Solutions for Class 9 science according to the new NCERT Syllabus for Class 9 science created by Vedantu Master Teachers.
Quick Insights of “Fundamental Unit of Life” Class 9 NCERT Solutions
The fundamental unit of life, class 9, will give you insights about the general introduction, which is to understand the basic structure and function of the cell.
Chapter 5 of Science Class 9 will teach you about the various cell organelles, such as the nucleus, mitochondria, and endoplasmic reticulum, and their roles in maintaining cellular functions.
Detailed information on exploring the differences between plant and animal cells, highlighting unique features like the cell wall and chloroplasts in plant cells, and delving into cell division and its types.
The fundamental unit of life class 9 PDF can help students analyse their level of preparation and understanding of concepts.
Class 9 science chapter 5 question answers topics are included according to the revised academic year 2024-25 syllabus.
NCERT Solution for Class 9 Science Chapter 5 The Fundamental Unit of Life - 2025-26
ShareShare1. 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:
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,
Keep cup A empty
Put one teaspoon sugar in cup B
Put one teaspoon salt in cup C
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.
Lysosomes: Lysosomes contain enzymes that break down cellular waste and foreign materials, playing a crucial role in intracellular digestion and recycling.
Cell Division: Mitosis is the process of cell division, ensuring growth, repair, and maintenance by producing identical daughter cells with the same genetic information.
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.
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
Vedantu makes learning easy and enables the students to go through the exercises and Question count to avoid hustle and bustle!
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.
NCERT Solutions Class 9 Chemistry | Chapter-wise Links
Access Vedantu’s chapter-wise NCERT Chemistry Class 9 Solutions PDFs below for all other chapters.
Important Study Material Links for Class 9 Science
FAQs on NCERT Solution for Class 9 Science Chapter 5 The Fundamental Unit of Life - 2025-26
1. How should one correctly solve the NCERT question that asks for a diagram of an animal cell and a plant cell?
To solve this question as per the CBSE 2025-26 guidelines, you must draw two separate, clearly labelled diagrams. For the animal cell, ensure you include the cell membrane, cytoplasm, nucleus, mitochondria, and lysosomes. For the plant cell, it is crucial to add the cell wall, a large central vacuole, and chloroplasts, in addition to the common organelles. Correctly labelling these distinct parts is key to securing full marks.
2. What is the correct method, as per the NCERT textbook, to explain the differences between prokaryotic and eukaryotic cells?
The correct method is to present the differences in a tabular format for clarity. Key points to include are:
- Size: Prokaryotic cells are generally small (1-10 µm), while eukaryotic cells are larger (5-100 µm).
- Nucleus: A well-defined nucleus is absent in prokaryotes (region is called a nucleoid), but present in eukaryotes.
- Chromosomes: Prokaryotes have a single chromosome, whereas eukaryotes have more than one.
- Organelles: Membrane-bound organelles like mitochondria and plastids are absent in prokaryotes but present in eukaryotes.
3. According to the NCERT Solutions, how do substances like CO2 and water move in and out of the cell?
The NCERT solutions explain two primary processes:
- Diffusion: Substances like Carbon Dioxide (CO2) move from an area of high concentration to an area of low concentration across the cell membrane. This happens when cellular waste CO2 builds up inside the cell and needs to be expelled.
- Osmosis: Water moves across a selectively permeable membrane from a region of high water concentration to one of low water concentration. This is a special case of diffusion and is crucial for maintaining the cell's water balance.
4. How does the NCERT solution for Class 9 Science explain why lysosomes are known as 'suicide bags' of the cell?
The solution explains that lysosomes contain powerful digestive enzymes capable of breaking down all organic material. When a cell gets damaged or old, the lysosome may burst, and its enzymes digest its own cell. Because this process of cellular self-destruction, or autolysis, leads to the cell's death, lysosomes are aptly called 'suicide bags'.
5. Why is the plasma membrane called a selectively permeable membrane in the NCERT solutions for Chapter 5?
The NCERT solutions emphasise this term because the plasma membrane does not allow all substances to pass through it freely. It actively regulates the movement of substances in and out of the cell. It permits the entry and exit of some materials while preventing the movement of others. This selectivity is vital for maintaining the cell's internal environment, distinct from its surroundings.
6. When solving NCERT problems, why is it incorrect to state that a plant cell placed in a hypotonic solution will burst?
This is incorrect because plant cells have a rigid cell wall outside the plasma membrane. When placed in a hypotonic solution, water enters the cell via osmosis, causing it to swell. However, the rigid cell wall exerts an equal pressure (turgor pressure) against the swollen cell, preventing it from bursting. Animal cells, which lack a cell wall, would burst under the same conditions.
7. What key points should be included when solving an NCERT question on the functions of the nucleus?
A comprehensive answer based on the NCERT solutions should highlight these three key functions:
- Cellular Reproduction: The nucleus plays a central role in cell division, the process by which a single cell divides into two new cells.
- Genetic Information: It contains chromosomes, which carry genes (segments of DNA) that hold the information necessary for constructing and organising cells.
- Control Centre: The nucleus directs all the chemical activities of the cell, effectively acting as its control centre or 'brain'.
8. The NCERT solutions describe chromosomes as being composed of DNA and protein. Why is this protein component crucial for the cell's function?
The protein component, primarily histones, is crucial for packaging and structure. The long DNA molecule in a eukaryotic cell is extremely long and must fit inside the tiny nucleus. Histone proteins act like spools around which the DNA winds, allowing it to be condensed into a compact structure called chromatin. This not only saves space but also plays a key role in regulating which genes are 'turned on' or 'off'.
