CBSE Class 11 Biology Chapter 8: Cell: The Unit of Life NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 11 PDF

CBSE Class 11 Biology Chapter 8, 'Cell: The Unit of Life,' introduces the fundamental building block of all living organisms. This chapter explores the historical journey of cell discovery, the foundational cell theory proposed by Schleiden and Schwann, and Virchow's crucial insight that cells arise from pre-existing cells. It further elaborates on the distinct features of prokaryotic cells, highlighting the function of mesosomes. Additionally, the solutions explain the intricate processes of molecular transport across the plasma membrane, differentiating between the movement of neutral and polar molecules. Mastering these concepts is essential for a comprehensive understanding of biology, providing a solid base for future studies in cell biology and aiding in preparation for examinations.

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Board	CBSE
Class	Class 11
Subject	Biology
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 8: Cell: The Unit of Life

Chapter summary

Chapter 8, 'Cell: The Unit of Life,' NCERT Solutions for CBSE Class 11 Biology, offers a clear explanation of cell theory, its historical development, and key postulates. It differentiates between prokaryotic and eukaryotic cells, detailing structures like mesosomes and their functions. The solutions also cover the selective permeability of the plasma membrane and the processes of transport for various molecules. This chapter is foundational for understanding cellular organization and function.

Learning outcomes

Understand the historical development of cell theory.
Identify the discoverer of the cell and differentiate between cell discovery and cell theory formulation.
Explain the principle that new cells arise only from pre-existing cells.
Differentiate between prokaryotic and eukaryotic cell structures.
Describe the structure and functions of mesosomes in prokaryotic cells.
Explain the movement of neutral and polar molecules across the plasma membrane.
Understand the concept of selective permeability of the plasma membrane.

Topics covered

Paper topics

Cell Discovery
Cell Theory
Pre-existing Cells
Prokaryotic Cells
Mesosomes
Plasma Membrane
Selective Permeability
Transport of Molecules
Simple Diffusion
Polar Molecules
Mitochondria
Golgi Apparatus

Important topics

Cell Theory and its Postulates
Characteristics of Prokaryotic Cells
Structure and Function of Mesosomes
Mechanism of Transport Across Plasma Membrane
Distinction between Prokaryotic and Eukaryotic Cells

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Questions and Solutions

Exercises

Question 1

Which of the following statements is not correct?

(a) Robert Brown discovered the cell.

(b) Schleiden and Schwann formulated the cell theory.

(d) A unicellular organism carries out its life activities within a single cell.

Solution: The statement that is not correct is (a). Robert Brown discovered the nucleus of the cell, not the cell itself. The cell was discovered by Robert Hooke. Statements (b), (c), and (d) are correct principles of cell theory and cellular biology.

Question 2

New cells generate from

(a) bacterial fermentation

(b) regeneration of old cells

(d) abiotic materials

Solution: New cells generate from (c) pre-existing cells. This principle, known as the law of biogenesis, states that all living cells arise from pre-existing cells through cell division. Spontaneous generation from non-living matter or regeneration of old cells in the way described is not the mechanism for new cell formation.

Question 3

Match the following:

Column I

(a) Cristae

(b) Cisternae

Column II

(i) Flat membranous sacs in stroma

(ii) Infoldings in mitochondria

(iii) Disc-shaped sacs in Golgi apparatus

Solution: The correct matching is as follows:

Column I

Column II

(a) Cristae

(ii) Infoldings in mitochondria

Cristae are the inner folds of the mitochondrial membrane that increase the surface area for ATP synthesis.

(b) Cisternae

(iii) Disc-shaped sacs in Golgi apparatus

Cisternae are the flattened, membrane-bound sacs that make up the Golgi apparatus.

(c) Thylakoids

(i) Flat membranous sacs in stroma

Thylakoids are flattened sacs within chloroplasts, containing chlorophyll, where the light-dependent reactions of photosynthesis occur.

Question 4

Which of the following is correct?

Cells of all living organisms have a nucleus.
Both animal and plant cells have a well defined cell wall.
In prokaryotes, there are no membrane bound organelles.
Cells are formed de novo from abiotic materials.

Solution: The correct statement is (3) In prokaryotes, there are no membrane bound organelles. Let's analyze why the other options are incorrect:

Not all living organisms have a nucleus; prokaryotic cells lack a true nucleus.
Animal cells do not have a cell wall. Plant cells do, but it's not a feature of both.
Cells are not formed de novo from abiotic materials; they arise from pre-existing cells.

Therefore, the absence of membrane-bound organelles is a defining characteristic of prokaryotic cells.

Question 5

What is a mesosome in a prokaryotic cell? Mention the functions that it performs.

Solution: A mesosome is a convoluted, invaginated membranous structure found within the cytoplasm of prokaryotic cells. It is formed by the inward folding of the plasma membrane. The functions of mesosomes include:

<math>\triangleright</math> Assisting in cell wall synthesis.

<math>\triangleright</math> Playing a role in DNA replication and the distribution of replicated chromosomes to daughter cells during cell division.

<math>\triangleright</math> Increasing the surface area of the plasma membrane, which enhances the efficiency of various enzymatic activities and processes like respiration.

<math>\triangleright</math> Participating in secretion processes.

Question 6

How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?

Solution: The plasma membrane is selectively permeable, meaning it controls the passage of substances into and out of the cell. Neutral solutes, which are typically small and lipid-soluble, move across the plasma membrane via simple passive diffusion. This process involves the movement of molecules from a region of higher concentration to a region of lower concentration, down their concentration gradient, without the requirement of cellular energy.

Polar molecules, on the other hand, cannot easily pass through the hydrophobic lipid bilayer of the plasma membrane in the same way as neutral solutes. Their transport across the membrane requires the assistance of specific membrane proteins. This facilitated transport can occur through channels or carriers and may be passive (facilitated diffusion) or active (requiring energy). Therefore, polar molecules are transported across the membrane via protein-mediated mechanisms, not simple diffusion.

Common mistakes

Confusing the discoverer of the cell with the formulators of cell theory.
Incorrectly stating that cells can arise spontaneously from non-living matter.
Misunderstanding the absence of membrane-bound organelles in prokaryotes.
Inaccurate descriptions of mesosome functions.

Revision tips

Focus on the key postulates of cell theory and their historical context.
Clearly distinguish between prokaryotic and eukaryotic cell features.
Memorize the functions of specialized structures like mesosomes.
Understand the difference between passive and active transport across the plasma membrane.
Review the matching exercise to reinforce the association of cellular components with their locations or functions.

Practice MCQs

Q1. Who is credited with the discovery of the cell?

Q2. The cell theory states that new cells arise from:

Q3. Which of the following is a characteristic of prokaryotic cells?

Q4. What is the primary function of mesosomes in prokaryotic cells?

Q5. The movement of neutral solutes across the plasma membrane typically occurs via:

Frequently asked questions

Who discovered the cell, and who formulated the cell theory?

Robert Hooke discovered the cell. The cell theory was formulated by Matthias Schleiden and Theodor Schwann, with Rudolf Virchow later adding the principle that cells arise from pre-existing cells.

What is the significance of Virchow's contribution to cell theory?

Rudolf Virchow explained that all cells are formed from pre-existing cells, a crucial addition that completed the modern cell theory.

Are there membrane-bound organelles in prokaryotic cells?

No, prokaryotic cells lack membrane-bound organelles, including a nucleus. Their genetic material is found in a region called the nucleoid.

What is a mesosome and what does it do?

A mesosome is an invagination of the plasma membrane in prokaryotic cells. It aids in cell wall synthesis, DNA replication, and distribution of chromosomes.

How do neutral solutes move across the plasma membrane?

Neutral solutes move across the plasma membrane by simple passive diffusion, moving from an area of higher concentration to an area of lower concentration.

Can polar molecules move across the plasma membrane like neutral solutes?

No, polar molecules cannot easily move across the lipid bilayer like neutral solutes. They require specific transport mechanisms, often involving proteins, to cross the membrane.

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