CBSE Class 8 Science Exemplar Chapter 8: Cell - Structure and Functions NCERT Solutions
This chapter delves into the fundamental unit of life: the cell. The NCERT Solutions for CBSE Class 8 Science Exemplar, Chapter 8, provide a detailed exploration of cell structure and functions. Students will understand the characteristics of unicellular organisms, differentiating them from multicellular ones. The solutions clarify why cells are microscopic and cannot be seen with the naked eye. Key components of both plant and animal cells are discussed, highlighting the presence or absence of structures like cell walls, chloroplasts, and mitochondria. The role and composition of the nucleus, including chromosomes, genes, and nucleolus, are explained. These solutions are designed to help students grasp complex biological concepts, prepare for exams, and build a strong foundation in cell biology.
Quick info
| Board | CBSE |
|---|---|
| Class | Class 8 |
| Subject | Science Exemplar |
| Session | 2026 |
| Language | English |
| Type | NCERT Solutions |
| Chapter | Chapter 8 |
Chapter summary
Chapter 8, 'Cell - Structure and Functions,' focuses on the basic building blocks of life. These NCERT Solutions cover the characteristics of unicellular organisms, the microscopic nature of cells, and the distinguishing features of animal and plant cells. It also explains the components of the cell nucleus and related terms like chromosomes and genes. The solutions provide clear explanations for multiple-choice questions and fill-in-the-blanks, aiding students in understanding cell biology concepts.
Learning outcomes
- Understand the characteristics of unicellular organisms.
- Explain why cells are microscopic.
- Identify key components of animal and plant cells.
- Differentiate between animal and plant cell structures.
- Define and identify parts of the cell nucleus, including chromosomes and genes.
- Recognize cell organelles as the components of cells.
Topics covered
Paper topics
- Unicellular Organisms
- Cell Structure
- Cell Components
- Microscopic Nature of Cells
- Animal Cells
- Plant Cells
- Cell Membrane
- Mitochondria
- Ribosomes
- Nucleus
- Chromosomes
- Genes
Important topics
- Characteristics of Unicellular Organisms
- Differences between Animal and Plant Cells
- Components of the Nucleus
- Cell Organelles
- Microscopic Nature of Cells
PDF preview
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Questions and Solutions
Multiple Choice Questions
1. Choose the correct statement with respect to unicellular organisms:
(a) in unicellular organisms, tissues work in co-ordination to perform different functions.
(b) unicellular organisms do not require food.
(c) unicellular organisms respire and reproduce.
(d) all unicellular organisms move by cilia.
Explanation: Unicellular organisms are single-celled entities that carry out all essential life functions, including respiration, digestion, and reproduction, within that single cell. Option (a) is incorrect because tissues are formed by groups of cells, and unicellular organisms consist of only one cell, thus lacking tissues. Option (b) is incorrect as all living organisms, including unicellular ones, require food for energy and survival. Option (d) is incorrect because while some unicellular organisms use cilia for movement, others employ different methods like pseudopodia or flagella, and not all move using cilia.
2. Majority of cells cannot be seen directly with our naked eyes because:
(a) organisms are generally unicellular
(b) cells are microscopic
(c) cells are present only inside the body
(d) cells are grouped into tissues
Explanation: Cells are the fundamental structural and functional units of life. Their size is extremely small, typically ranging from nanometers to micrometers. This microscopic scale necessitates the use of a microscope to observe them clearly. Therefore, they are referred to as microscopic structures.
Section 1
3. Read the different combinations of terms given below:
- cell wall, cell membrane, nucleus, plastid
- cell wall, nucleus, ribosome, chromosome
- cell membrane, mitochondria, ribosome, chromosome
- cell membrane, ribosome, mitochondria, chloroplast.
The correct combination of terms with reference to an animal cell is _____.
Explanation: Animal cells possess a cell membrane as their outer boundary, and contain organelles like mitochondria (for energy production) and ribosomes (for protein synthesis), along with chromosomes within the nucleus. Options (a) and (b) are incorrect because they include the cell wall, which is a feature of plant cells, not animal cells. Option (d) is incorrect because it includes chloroplasts, which are responsible for photosynthesis and are found in plant cells, but not in animal cells.
4. Which one of the following term is not a part of the nucleus?
- ribosome
- chromosome
- nucleolus
- gene
Explanation: Ribosomes are small organelles responsible for protein synthesis; they are typically found freely floating in the cytoplasm or attached to the endoplasmic reticulum. Chromosomes, the nucleolus, and genes are all components found within the cell nucleus. Chromosomes are structures that carry genetic information, and genes are segments of DNA located on chromosomes. The nucleolus is a dense structure within the nucleus involved in ribosome synthesis.
5. A suitable term for the various components of cells is
- tissue
- cell organelles
- chromosomes
- genes
Explanation: Cell organelles are the specialized, membrane-bound or non-membrane-bound structures within a cell that perform specific functions. A tissue is a group of similar cells performing a specific function. Chromosomes are thread-like structures found in the nucleus that carry genetic information. Genes are the basic units of heredity, located on chromosomes. Therefore, 'cell organelles' is the most appropriate term for the diverse components within a cell.
Common mistakes
- Confusing features of plant cells (like cell walls and chloroplasts) with animal cells.
- Misidentifying components of the nucleus.
- Not understanding that unicellular organisms perform all life functions within a single cell.
- Assuming tissues are present in unicellular organisms.
Revision tips
- Focus on the differences between plant and animal cells, paying attention to structures like cell walls and chloroplasts.
- Review the components of the nucleus and their functions.
- Understand the definition and characteristics of unicellular organisms.
- Use the explanations provided to clarify any doubts about why certain options are correct or incorrect.
Practice MCQs
Q1. Which of the following statements is correct regarding unicellular organisms?
Explanation: Unicellular organisms, being living entities, perform all essential life processes, including respiration and reproduction, within their single cell. They do require food and do not necessarily rely on tissues or exclusively use cilia for locomotion.
Q2. Why are most cells not visible to the naked eye?
Explanation: Cells are the fundamental units of life and are typically very small, measured in micrometers or nanometers, making them microscopic and requiring magnification to be observed.
Q3. Which combination of terms correctly describes components found in an animal cell?
Explanation: Animal cells possess a cell membrane, mitochondria, ribosomes, and chromosomes. They lack a cell wall and chloroplasts, which are found in plant cells. Option C correctly lists components present in animal cells.
Q4. Which of the following is NOT a component of the cell nucleus?
Explanation: Ribosomes are typically found floating in the cytoplasm or attached to the endoplasmic reticulum, not within the nucleus. Chromosomes, nucleolus, and genes are all integral parts of the nucleus.
Q5. What is the appropriate term for the various components within a cell?
Explanation: Cell organelles are the specialized structures within a cell that perform specific functions. Tissues are groups of cells, while chromosomes and genes are components primarily found within the nucleus.
Frequently asked questions
What is the main focus of CBSE Class 8 Science Exemplar Chapter 8?
Chapter 8 focuses on the fundamental unit of life, the cell, covering its structure, functions, and key components like the nucleus and organelles, as well as the characteristics of unicellular organisms.
Why are cells considered microscopic?
Cells are microscopic because their size is extremely small, typically ranging from micrometers to nanometers, which makes them invisible to the naked human eye and requires a microscope for observation.
What are the key differences between animal and plant cells mentioned in these solutions?
The solutions highlight that plant cells have a cell wall and chloroplasts, which are absent in animal cells. Animal cells have a cell membrane, mitochondria, ribosomes, and chromosomes.
What are cell organelles?
Cell organelles are the distinct structures within a cell that perform specific functions necessary for the cell's survival and operation, such as mitochondria for energy production or ribosomes for protein synthesis.
How do these NCERT Solutions help in exam preparation?
These solutions provide clear, rewritten explanations for each question, helping students understand the concepts thoroughly, identify common mistakes, and revise key topics effectively for their exams.
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