NCERT Solutions Class 9 Science Chapter 5

NCERT Solutions Class 9 Science Chapter 5: Fundamental Unit of Life 

Science is an exciting subject, and it offers many concepts which will be used in the upcoming classes. Students also have the opportunity to prepare for their future careers in the medical and engineering field. It is a transition period for students who wish to take Science as a significant career option.

Class 9 Science Chapter 5 is about the fundamental unit of life. This chapter studies the fundamental entity of life, a living cell. It also covers everything related to the cells in organisms and their growth in the body. Students will get to learn more about the formation of gametes for reproduction. 

Students can access the Extramarks NCERT Solutions Class 9 Science Chapter 5 through their website. They can get detailed notes, illustrations and examples, and past years' papers through their online portal. As a result, students can efficiently study and understand the critical topics discussed in Class 9 Science Chapter 5. 

Extramarks is a leading online learning platform that provides students with the best study materials and solutions. The NCERT Solutions Class 9 Science Chapter 5 helps develop the skills necessary for advanced learning. It helps to establish a strong foundation of all concepts, where the answers are provided with  diagrams. 

For the latest updates and notifications regarding the NCERT syllabus and examination-related updates, students can visit the Extramarks' website. Students can also access NCERT Solutions Class 9, NCERT Solutions Class 10, NCERT Solutions Class 11 and NCERT Solutions Class 12.

Key Topics Covered In NCERT Solutions Class 9 Science Chapter 5

NCERT Solutions Class 9 Science Chapter 5 helps students learn all the essential concepts of the fundamental unit of life. Students can learn from the theoretical notes, diagrams, and summarised answers. With the help of Extramarks NCERT Solutions Class 9 Science Chapter 5, students will be able to understand every concept and answer any question easily.  

Some of the critical sub-topics in NCERT Solutions Class 9 Science Chapter 5 are:

Sections Sub-topics
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?
5.3 Cell Division 

What are Living Organisms Made Up of?

Living organisms are usually made up of cells. These cells are the structural and functional units of organisms. Robert Hooke discovered the existence of these cells with the help of a microscope. Later, it paved the way for discovering various other microscopic organisms. Organisms can consist of a single cell, for example amoeba. Other microorganisms are multicellular and have millions of cells. 

Each living cell holds the capacity to perform basic functions. Different parts of the human body perform different functions. It has the heart to pump blood, a stomach to digest food and so on. Just like that, a cell has got certain specific components within it known as cell organelles. All cell organelles perform a special function, which helps to make new material in the cell. 

Interestingly, every cell is found to have the same organelles,no matter what their function is or what organism they were found in. 

What is a Cell Made Up of? What is the Structural Organisation of a Cell?

If a cell is studied under a microscope, one can conclude three features in each cell: plasma membrane, nucleus, and cytoplasm. Every activity inside the cell and interactions of the cell with its environment are possible due to different features such as: 

  1. i) Plasma membrane or cell membrane

  • The cell's outermost layer isolates its contents from the outside surroundings. Plasma membranes permit specific substances to move into and out of cells. This is why the cell membrane is described as a selectively porous membrane.
  • Diffusion is a method that permits substances like O2 or CO2 to flow through cell membranes.
  • Osmosis is moving molecules of water (liquids) through a membrane that is selectively permeable. Osmosis refers to the flow of water molecules through semipermeable membranes, from high concentration areas to areas with low water concentration.
  • The cell can gain water via osmosis when the water content in the surrounding medium is higher than the one within the cells. 

To understand the functioning of the plasma membrane, students can refer to our NCERT Solutions Class 9 Science Chapter 5. Our subject matter experts have prepared detailed notes on this topic. 

  1. ii) Cell Wall

  • It is an external solid covering that plant cells possess. It also serves to be its plasma membrane. The cell wall doesn't cover the plasma membrane.
  • Cellulose is the primary ingredient in the cell wall of the plant. The cell wall is intricate and helps give plant cells their strength. Living plants can lose water through osmosis which causes shrinkage and tightening of the contents. This process is known as plasmolysis.

iii) Nucleus

  • It is a two-layered cover that protects the nucleus. The pores within the nuclear membrane permit the transfer of matter within and outside the nucleus, i.e. into the cell cytoplasm.
  • The nucleus protects the chromosomes. These can be seen as rod-shaped structures as cells are preparing to divide.
  • Chromosomes contain information regarding the inheritance of characteristics from parents and the following generation in DNA [DeoxyriboNucleic Acid molecules]. Chromosomes are composed of DNA and proteins. Genes are functional components of DNA. The nucleus is an essential element in the process of reproduction within cells.
  1. iv) Cytoplasm

When we observe a temporary amount of onion peel under a microscope, we can see a large region of each cell enclosed by the cell membrane. Eventually, this region appears to be a little stained. It is called the cytoplasm. In addition, the cytoplasm appears like a fluid content inside the plasma membrane. It contains specialised cell organelles. Further, the organelles are enclosed by membranes. Usually, in prokaryotes, the membrane-bound cell organelles are absent in the absence of a defined nuclear region. 

  1. v) Endoplasmic Reticulum 

The endoplasmic reticulum is a vast system of membrane-bound tubes and sheets. It resembles long tubules, bags that are round or oval. 

There are two kinds: rough endoplasmic reticulum and smooth endoplasmic reticulum [SER].

  1. vi) Cell Organelles

The membrane of every cell forms and surrounds it to keep its contents distinct from its external environment. The various parts of cells perform various functions and are known as organelles of cells.

  • Golgi Apparatus:

Golgi is a collection of membrane-bound vesicles arranged around and parallel to one another in cisterns or stacks. The synthesis of material close to the ER is packed and sent to different targets via the Golgi apparatus within and outside the cell. Its main functions are storage, modification, and packaging of vesicle-based products.

  • Lysosomes: 

Lysosomes constitute an element of the cell's waste disposal and elimination system. Lysosomes assist in keeping the cells clean by digesting any foreign substance and worn-out organelles of the cell.

  • Plastids: 

Plastids exist only in plant cells. There are two kinds of plastids, namely chromoplasts and leucoplasts. Chromoplasts are plastids that have colour. They are found in leaves, flowers and fruits. Plastids that have the colour chlorophyll are also known as chloroplasts.

  • Vacuoles:

Vacuoles are storage sacs for solid and liquid contents. They are small-sized in animal cells. Besides, plant cells have very large vacuoles. The central vacuole of some plant cells may occupy 50-90% of the cell volume. Plant cell vacuoles are usually full of the cell sap, offering turgidity and rigidity to the cell. Besides, many important substances in the life of the plant cell are stored in vacuoles. 

Cell Division

Every organism must make new cells grow and replace old dead injured cells and additionally to form gametes required for reproduction. The process by which new cells are made is known as cell division. Usually, there are two main cell division types: mitosis and meiosis. Further, the process of cell division by which most cells divide for growth is known as mitosis. In this process, each cell called the mother cell divides to form two identical daughter cells. The cells will eventually have the same number of chromosomes as the mother. 

To get an overview of the cell organelles and their components, students can refer to NCERT Solutions Class 9 Science Chapter 5 and other study materials such as Revision Notes, Previous Year Question Papers, and CBSE Important Questions, all available at the Extramarks website.

NCERT Solutions Class 9 Science Chapter 5: Exercise & Solutions

The NCERT Solutions for Class 9 Science Chapter 5 created by the Extramarks are based on the latest CBSE syllabus and cover all the essential topics. Students preparing for the CBSE Class 9 Term II Examination can refer to NCERT Solutions Class 9 Science Chapter 5. 

The solution guide has various types of questions, including fill in the blanks, match the following, and true or false types of questions. It covers the theoretical aspects of NCERT and offers step-by-step answers to all NCERT questions. 

Click the links below to see exercise-specific questions and their answers for NCERT Solutions Class 9 Science Chapter 5.

  • Chapter 5: Exercise 5.1 – 2 Questions
  • Chapter 5: Exercise 5.3 – 4 Questions
  • Chapter 5: Exercise 5.4 – 2 Questions
  • Chapter 5: Exercise 5.5 – 4 Questions
  • Chapter 5: Chapter Exercise – 10 Questions

Students can also explore NCERT Solutions for different classes on the Extramarks site:

  • NCERT Solutions Class 1
  • NCERT Solutions Class 2
  • NCERT Solutions Class 3
  • NCERT Solutions Class 4
  • NCERT Solutions Class 5
  • NCERT Solutions Class 6
  • NCERT Solutions Class 7
  • NCERT Solutions Class 8
  • NCERT Solutions Class 9
  • NCERT Solutions Class 10
  • NCERT Solutions Class 11
  • NCERT Solutions Class 12

NCERT Exemplar for Class 9 Science:

Science is a subject that inspires curiosity. To grasp concepts, one must have a deep understanding of the subject. Solving different questions can help students increase their knowledge. This helps students clarify their doubts and gain a solid understanding of the topic.

The NCERT exemplars were designed in the same way to help students understand the topic easily and quickly. There are different types of questions, each with a graded difficulty level. Students can expect to score well in the exam if they practice the Exemplar every day.

The NCERT Solutions Class 9 Science Chapter 5 provides solutions to the questions covered in Exemplar on the topics of fundamental units of life.

Key Features of NCERT Solutions Class 9 Science Chapter 5:

NCERT Science Solutions offers many benefits. Some of them are listed below.:

  • These solutions address all Class 9 Science Chapter 5 Questions covered in the exercises given in the textbook.
  • Students can find the solution guide on the Extramarks website, so they are easily accessible whenever they are needed.
  • To help students understand the concepts, diagrams are provided.
  • Students can find the most effective solutions on this platform, which will help them score high in their final exams.
  • Students can practice and prepare more efficiently for their final examinations. It is a thoroughly researched material made in sync with CBSE examination guidelines. When students study from it, they will get an edge over their peers. 
  • The NCERT Solutions Class 9 Science Chapter 5 will enhance students' problem-solving abilities and give them a general idea behind different types of questions. 

Q.1 Make a comparison and write down ways in which plant cells are different from animal cells.

Ans-

Features

Animal Cell

Plant Cell

Size

Small

Comparatively larger than animal cell

Cell wall

Absent

Present

Plastids

Generally absent except in Euglena

Present

Vacuoles

Small

Large

Q.2 How is a prokaryotic cell different from a eukaryotic cell?

Ans-

Features

Prokaryotic cell

Eukaryotic cell

Size

Generally small (1-10µm)

Larger than prokaryotic cells (5-100 µm)

Nuclear region

Poorly defined, nuclear membrane absent, lacks a true nucleus

Clearly defined, true nucleus is surrounded by a nuclear membrane

Nucleolus

Absent

Present

Chromosomes

Single

Many

Membrane-bound cytoplasmic organelles

Absent

Present

Q.3 What would happen if the plasma membrane ruptures or breaks down?

Ans-

Rupturing or breakdown of plasma membrane would not allow the cell to exchange substances from its surrounding through diffusion or osmosis. The selectively permeable nature of the plasma membrane will be disturbed as the cytoplasm of the cell would come in direct contact of the surrounding medium and the act of selection would stop. In case of severe rupturing of plasma membrane, the contents of the cell will leak out and would eventually cause the death of the cell.

Q.4 What would happen to the life of a cell if there was no Golgi apparatus?

Ans-

In the absence of the Golgi apparatus, following activities will not take place in a cell:

  1. Functions like storage, modification and packaging of products synthesised in the endoplasmic reticulum will not take place in a cell as all these functions are performed by the Golgi apparatus.
  2. Formation of complex sugars from simple sugars will be hampered in the absence of Golgi apparatus.
  3. Cleaning of the cell will be disturbed due to the absence of Golgi apparatus as it is involved in the formation of lysosomes that acts as a waste disposal system of a cell.

Q.5 Which organelle is known as the powerhouse of the cell? Why?

Answer-

Mitochondria are known as the powerhouse of the cell. During cellular respiration, mitochondria produce energy in the form of ATP that is required to perform various activities in a cell. ATP (Adenosine triphosphate) is known as the energy currency of the cell. Due to this, mitochondria are known as the powerhouse of the cell.

Q.6 Where do the lipids and proteins constituting the cell membrane get synthesised?

Ans-

Lipids and proteins constituting the cell membrane are synthesised in the endoplasmic reticulum. Lipids are synthesised in smooth endoplasmic reticulum. Ribosomes present on the rough endoplasmic reticulum serve as the site for protein synthesis.

Q.7 How does an Amoeba obtain its food?

Ans-

Amoeba acquires its food by the process of endocytosis. Amoeba captures food from its surroundings through its plasma membrane. Being flexible in nature, plasma membrane enables the cell to engulf food particles from the surrounding medium by extending itself into the pseudopodia.

Q.8 What is osmosis?

Ans- 

Osmosis can be defined as the movement of water molecules from a region of high water concentration to a region of low water concentration through a selectively permeable membrane.

Q.9 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 sugar in cup B
(c) Put one teaspoon salt in cup C
Put one teaspoon sugar in the boiled potato cup D
Keep these for two hours. Then observe the four potato cups and answer 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-

(i) Water gathers in the hallowed portions of set-up B and C due to osmosis. In the cup of the potato B, sugar is kept and in the potato C, salt is kept. Inside the cups of the potatoes, the concentration of water is low as compared to the cells making the hallowed portion. Hence, water from its high concentration (from the potato cell) moves to the low concentration (out of the cell and in the hallowed portion) through the plasma membrane of the cells. Due to the movement of water from the potato cells to the hallowed portion by osmosis, water gathers in the hallowed portions of the potato cup.

(ii) In this experiment, potato A acts as control set-up. A control set-up is run in an experiment to study the differences that take place in or on the object or group being experiment on. It also increases the reliability of the final result by comparing the observations of the experimental set-up and control set-up.

(iii) Water does not gather in the hallowed portions of potato A and D because potato A is kept empty and is a control set-up in the experiment. Water does not enter the potato D as osmosis did not take place in it because the potato used here was boiled. Boiling denatured the proteins present in the plasma membrane of the cells of the potato and thus, disrupted the cell membrane. A selectively permeable membrane is required for osmosis to occur which is disrupted in this case. Therefore, osmosis does not occur. Hence, water does not enter the potato D.

Q.10 Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?

Ans- 

The type of cell division which is required for the growth and repair of the body is mitosis. Mitosis maintains the same chromosome number in parent and daughter cells. Thus the daughter cells retain the characters of the parent cell. This results in the growth of tissues and the overall development of the organism. With the help of mitosis, tissues are repaired as the worn out cells are replaced. For the formation of gametes, meiotic division is required. It is also called reductional division. In this type of cell division, the chromosome number is reduced to half. Thus, this cell division occurs in diploid reproductive cells to form haploid cells that are gametes (sperm and egg).

For viewing question paper please click here

FAQs (Frequently Asked Questions)
1. How authentic is the NCERT Solutions provided in Extramarks?

The NCERT Solutions Class 9 Science Chapter 5 prepared by the Extramarks subject matter expert team is accurate and reliable. The solution guide is appropriate and follows the latest CBSE guidelines. These are the best reference materials that students can use for their CBSE Term Exams. Each concept consists of examples and pictorial representation to improve students’ visual learning and aid in the learning process. 

2. Which are the topics covered in NCERT Solutions Class 9 Science Chapter 5?

The topics and subtopics covered in the Extramarks NCERT Solution NCERT Solutions Class 9 Science Chapter 5 are:

  • What are living organisms made up of?
  • What is a cell made-up of? What is the structural organisation of a cell?
  • Plasma membrane and cell membrane
  • Cell wall
  • Nucleus
  • Cytoplasm
  • Cell organelles
  • Cell division

3. What is osmosis?

Osmosis is a process by which the molecules of a solvent pass from a solution of low concentration to a solution of high concentration through a semipermeable membrane.