CBSE Class 9 Science Chapter 2: Cell: The Building Block of Life — Assertion & Reason
Download Exam Special Books for CBSE Class 9
Expert crafted · Instant PDF download · 2026-27
The following Assertion and Reason questions are based on Chapter 2: Cell: The Building Block of Life from the NCERT Class 9 Science textbook. Each question has four options — read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): Increasing magnification always guarantees that finer details of a cell will appear clear.
Reason (R): Resolution is the measure of clarity and the ability to distinguish two close points as separate.
Reason (R): Resolution is the measure of clarity and the ability to distinguish two close points as separate.
Answer: (d)
A is false, but R is true. Magnification only makes an image appear larger; without sufficient resolution, finer details may still remain unclear.
2
Assertion (A): All living cells are surrounded by a cell membrane.
Reason (R): Cells of plants, fungi, and bacteria have an additional cell wall outside the cell membrane.
Reason (R): Cells of plants, fungi, and bacteria have an additional cell wall outside the cell membrane.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. The reason states which cells possess an additional outer covering; it does not explain why the cell membrane is universal.
3
Assertion (A): The cell membrane is selectively permeable.
Reason (R): Proteins embedded in the membrane act like gatekeepers and help substances pass through it.
Reason (R): Proteins embedded in the membrane act like gatekeepers and help substances pass through it.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Membrane proteins help regulate which substances can cross the lipid bilayer.
4
Assertion (A): Osmosis is the movement of water across a selectively permeable membrane.
Reason (R): Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration and can occur without a membrane.
Reason (R): Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration and can occur without a membrane.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. The reason correctly defines diffusion and distinguishes it from osmosis, but it does not explain the assertion.
5
Assertion (A): A potato piece placed in plain water generally gains weight and swells.
Reason (R): Water moves by osmosis from the dilute external solution into potato cells, where the solute concentration is higher.
Reason (R): Water moves by osmosis from the dilute external solution into potato cells, where the solute concentration is higher.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The selectively permeable cell membrane allows water to enter the cells, increasing the potato piece's weight and size.
6
Assertion (A): When a plant cell is placed in a concentrated sugar solution, its inner contents shrink while its outer boundary can retain its shape.
Reason (R): Water leaves the cell by osmosis, but the rigid cell wall maintains the cell's outer shape.
Reason (R): Water leaves the cell by osmosis, but the rigid cell wall maintains the cell's outer shape.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Loss of water pulls the cell membrane and inner contents away from the wall, while the rigid wall remains in place.
7
Assertion (A): Bacterial cells have a well-defined nucleus enclosed by a nuclear membrane.
Reason (R): In bacterial cells, the genetic material lies in a nucleoid and is not enclosed by a nuclear membrane.
Reason (R): In bacterial cells, the genetic material lies in a nucleoid and is not enclosed by a nuclear membrane.
Answer: (d)
A is false, but R is true. Bacteria are prokaryotic; they lack a membrane-bound nucleus, and their DNA is located in the nucleoid region.
8
Assertion (A): Membrane-bound organelles enable eukaryotic cells to carry out different life processes independently at the same time.
Reason (R): Different organelles perform specialised jobs and coordinate their activities within the cell.
Reason (R): Different organelles perform specialised jobs and coordinate their activities within the cell.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Compartmentalisation assigns particular functions to organelles while allowing them to work together as a coordinated system.
9
Assertion (A): Chromosomes become visible as rod-shaped structures when a cell is about to divide.
Reason (R): Before cell division, the thread-like chromatin material becomes organised into chromosomes.
Reason (R): Before cell division, the thread-like chromatin material becomes organised into chromosomes.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The organisation and condensation of chromatin make chromosomes distinctly visible during cell division.
10
Assertion (A): The absence of a nucleus in mature human red blood cells allows them to transport more oxygen.
Reason (R): Without a nucleus, more space is available for haemoglobin inside a mature red blood cell.
Reason (R): Without a nucleus, more space is available for haemoglobin inside a mature red blood cell.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The additional space for haemoglobin increases the oxygen-carrying capacity of mature RBCs.
11
Assertion (A): Ribosomes are the sites of protein synthesis in a cell.
Reason (R): Ribosomes may occur freely in the cytoplasm or attached to the endoplasmic reticulum.
Reason (R): Ribosomes may occur freely in the cytoplasm or attached to the endoplasmic reticulum.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. The reason describes the locations of ribosomes, not why they function as sites of protein synthesis.
12
Assertion (A): Rough endoplasmic reticulum is mainly responsible for the synthesis and storage of fats and hormones.
Reason (R): Ribosomes attached to rough endoplasmic reticulum make it chiefly involved in protein synthesis and secretion.
Reason (R): Ribosomes attached to rough endoplasmic reticulum make it chiefly involved in protein synthesis and secretion.
Answer: (d)
A is false, but R is true. Smooth endoplasmic reticulum is involved in the synthesis and storage of fats and hormones, whereas rough ER mainly handles proteins.
13
Assertion (A): The Golgi apparatus functions as the packaging and shipping centre of a cell.
Reason (R): It modifies, sorts, and packages proteins or lipids into vesicles for transport, secretion, or lysosome formation.
Reason (R): It modifies, sorts, and packages proteins or lipids into vesicles for transport, secretion, or lysosome formation.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. These processing and packaging functions justify comparing the Golgi apparatus to a cellular post office.
14
Assertion (A): Mitochondria are called the powerhouses of the cell.
Reason (R): They release energy from glucose during cellular respiration and store it in ATP for cellular activities.
Reason (R): They release energy from glucose during cellular respiration and store it in ATP for cellular activities.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. ATP produced in mitochondria supplies usable energy for most cellular processes.
15
Assertion (A): Chloroplasts contain chlorophyll and participate in food synthesis in plant cells.
Reason (R): Chromoplasts are colourless plastids that mainly store starch, oils, or proteins.
Reason (R): Chromoplasts are colourless plastids that mainly store starch, oils, or proteins.
Answer: (c)
A is true, but R is false. Chloroplasts contain chlorophyll and perform photosynthesis, but colourless food-storing plastids are leucoplasts; chromoplasts contain coloured pigments.
16
Assertion (A): A large central vacuole helps keep a mature plant cell firm.
Reason (R): Water stored in the vacuole maintains pressure inside the cell, and loss of this water makes cells less firm.
Reason (R): Water stored in the vacuole maintains pressure inside the cell, and loss of this water makes cells less firm.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Vacuolar water supports internal pressure; when it is lost, cells become less firm and the plant may wilt.
17
Assertion (A): Mitosis produces two daughter cells that are genetically identical to the parent cell.
Reason (R): Each daughter cell formed by mitosis receives the same DNA and the same number of chromosomes as the parent cell.
Reason (R): Each daughter cell formed by mitosis receives the same DNA and the same number of chromosomes as the parent cell.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Equal transmission of DNA and chromosome number maintains genetic similarity during growth and tissue repair.
18
Assertion (A): Meiosis produces four daughter cells, each with half the chromosome number of the parent cell.
Reason (R): The chromosome number is reduced to half during both the first and the second divisions of meiosis.
Reason (R): The chromosome number is reduced to half during both the first and the second divisions of meiosis.
Answer: (c)
A is true, but R is false. Chromosome number is reduced during the first meiotic division; the second division is similar to mitosis and does not halve it again.
19
Assertion (A): Loss of normal control over cell division can result in tumour formation.
Reason (R): Unlike normal animal cells, cancer cells may lose contact inhibition and continue dividing uncontrollably.
Reason (R): Unlike normal animal cells, cancer cells may lose contact inhibition and continue dividing uncontrollably.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. When cells fail to stop dividing in response to normal controls, an abnormal mass of cells can form a tumour.
20
Assertion (A): Rudolf Virchow expanded the Cell Theory by stating that new cells arise only from pre-existing cells.
Reason (R): Schleiden reported that plants are made of cells, while Schwann reported that animals are made of cells.
Reason (R): Schleiden reported that plants are made of cells, while Schwann reported that animals are made of cells.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. The reason describes earlier contributions to Cell Theory, but it does not explain Virchow's statement about the origin of new cells.
❓ Frequently Asked Questions
What is covered in CBSE Class 9 Science Chapter 2 Cell: The Building Block of Life?
This chapter covers all key topics from Cell: The Building Block of Life as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 9 board exam preparation covering the complete syllabus.
Are these CBSE Class 9 Science Assertion & Reason updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 9 Science?
All chapters of CBSE Class 9 Science are covered at eBookPublisher with free Assertion & Reason for each chapter.
Can I study Cell: The Building Block of Life online for free?
Yes, complete Assertion & Reason for Cell: The Building Block of Life is available free at eBookPublisher. Study online directly — no download needed.
Where can I get a complete Assertion & Reason book for CBSE Class 9 Science?
You can purchase the complete expert-crafted Assertion & Reason book for CBSE Class 9 Science at eBookPublisher.in. Instant PDF download after payment.