MCQ Answers | Class 9 Science Chapter 2 Worksheet

1. C. Cell

Cells are the smallest structural and functional units that form all living organisms and perform essential life activities.

2. B. Robert Hooke

Robert Hooke first observed cork cells through a microscope and introduced the term “cell” in 1665.

3. A. Cytoplasm 

Cytoplasm is the jelly-like material where various organelles remain suspended and cellular reactions occur.

4. B. Nucleus

The nucleus controls cellular activities and contains hereditary material important for inheritance.

5. A. Cell wall

Plant cells contain a rigid cell wall that provides shape, support, and protection.

6. C. Mitochondria

Mitochondria release energy during respiration, which is why they are called powerhouse of the cell.

7. C. Protein synthesis

Ribosomes manufacture proteins needed for growth, repair, and proper functioning of cells.

8. C. Chloroplast

Chloroplasts contain chlorophyll and help plants prepare food through photosynthesis.

9. C. Selectively permeable

The cell membrane controls movement of selected substances into and out of the cell.

10. B. Cell wall

Animal cells lack rigid cell walls unlike plant cells.

11. C. Large and permanent

Plant cells usually contain large vacuoles for storage and maintaining turgidity.

12. C. Digestive enzymes

Lysosomes contain enzymes that digest waste materials and damaged cell parts.

13. C. Nucleus

Chromosomes carrying hereditary information are located inside the nucleus.

14. C. Nucleoplasm

Nucleoplasm is the fluid material present inside the nucleus.

15. C. Protection and rigidity

The cell wall provides structural support and protection to plant cells.

16. C. Microscope

Cells are microscopic structures discovered with the help of microscopes.

17. A. Photosynthesis

Chloroplasts help plants prepare food using sunlight through photosynthesis.

18. C. Schleiden and Schwann

Schleiden and Schwann proposed the cell theory stating that organisms are made of cells.

19. B. Energy production

Mitochondria produce energy required for various cellular activities.

20. C. Cell membrane

The cell membrane regulates movement of materials into and out of the cell.

Class 9 Science Chapter 2 Worksheet

Fill in the Blanks Answers | Class 9 Science Chapter 2 Worksheet

1. cell

2. microscope

3. nucleus

4. Mitochondria

5. cell wall

6. protein

7. chloroplasts

8. cytoplasm

9. nucleus

10. selectively

Class 9 Science Chapter 2 Worksheet

Give Reason Answers | Class 9 Science Chapter 2 Worksheet

1. Give reason why cells are called building blocks of life.

Cells are called building blocks because all living organisms are made up of cells that perform life functions.

2. Give reason why plant cells possess cell walls.

Plant cells possess cell walls to provide rigidity, protection, and a fixed shape to the cell.

3. Give reason why mitochondria are important for cells.

Mitochondria release energy during respiration, which is essential for all cellular activities.

4. Give reason why cell membrane is called selectively permeable.

Cell membrane allows only selected substances to enter or leave the cell according to cellular needs.

5. Give reason why chloroplasts are important in plants.

Chloroplasts contain chlorophyll and help plants prepare food through photosynthesis.

6. Give reason why ribosomes are called protein factories.

Ribosomes manufacture proteins required for growth, repair, and functioning of the cell.

7. Give reason why vacuoles are larger in plant cells.

Large vacuoles help store materials and maintain turgidity in plant cells.

8. Give reason why nucleus is called the control centre.

The nucleus controls all cellular activities and contains hereditary information.

9. Give reason why lysosomes are called suicidal bags.

Lysosomes contain digestive enzymes that can digest damaged cell parts and sometimes the entire cell.

10. Give reason why microscopes are important in cell biology.

Microscopes help scientists observe microscopic cells and cell organelles clearly.

Class 9 Science Chapter 2 Worksheet

Short Answer Answers | Class 9 Science Chapter 2 Worksheet

1. What is a cell?

A cell is the smallest structural and functional unit of life. All living organisms are made up of cells that perform essential life activities such as respiration, growth, reproduction, and excretion. Cells may vary in shape, size, and function depending on the organism.

2. Explain the importance of the nucleus.

The nucleus is called the control centre of the cell because it regulates all cellular activities. It contains chromosomes and genetic material responsible for inheritance. The nucleus controls growth, reproduction, metabolism, and coordination inside the cell, making it one of the most important cell organelles.

3. What are mitochondria? Why are they important?

Mitochondria are double-membraned organelles responsible for producing energy through respiration. They are called powerhouse of the cell because they release energy required for cellular activities. Cells needing more energy, such as muscle cells, contain a larger number of mitochondria for efficient functioning.

4. Explain the function of cell membrane.

The cell membrane forms the outer boundary of the cell and protects internal contents. It is selectively permeable, allowing only certain substances to enter or leave the cell. This helps maintain proper balance of materials required for survival and smooth functioning of cellular activities.

5. Differentiate between plant cell and animal cell.

Plant cells possess cell walls, chloroplasts, and large vacuoles, giving them a fixed shape. Animal cells lack cell walls and chloroplasts and generally contain smaller vacuoles. Plant cells are usually rectangular, while animal cells often have irregular or rounded shapes depending on their function.

6. Explain the role of chloroplasts in plants.

Chloroplasts contain chlorophyll, the green pigment responsible for photosynthesis. They help plants prepare food using sunlight, carbon dioxide, and water. Chloroplasts are extremely important because they allow plants to produce their own food and release oxygen into the environment during photosynthesis.

7. Why are ribosomes important in cells?

Ribosomes are important because they synthesise proteins needed for growth, repair, and maintenance of cells. Proteins produced by ribosomes help perform many biological functions inside organisms. Without ribosomes, cells would not be able to produce essential substances required for survival and development.

8. Explain the importance of vacuoles.

Vacuoles store food, water, wastes, and other substances inside cells. In plant cells, large vacuoles help maintain turgidity and support the plant structure. Vacuoles also help regulate internal pressure and provide temporary storage for materials required during different cellular activities and processes.

9. What is cell theory?

Cell theory states that all living organisms are made up of cells and that cells are the basic structural and functional units of life. It was proposed by Schleiden and Schwann. The theory also explains that new cells arise from pre-existing cells through cell division.

10. Explain why cells are important for living organisms.

Cells are important because they perform all essential life processes required for survival. Growth, respiration, digestion, reproduction, and excretion occur within cells. In multicellular organisms, specialised cells perform different functions efficiently. Without cells, life processes would not occur, making survival impossible for organisms.

Class 9 Science Chapter 2 Worksheet

Long Answer Answers | Class 9 Science Chapter 2 Worksheet

1. Explain the structure and functions of a cell.

A cell consists of cell membrane, cytoplasm, nucleus, and various organelles. The cell membrane protects the cell and regulates movement of substances. Cytoplasm contains organelles that perform important activities. The nucleus controls all cellular functions and contains genetic material. Organelles such as mitochondria, ribosomes, chloroplasts, and vacuoles perform specialised tasks like energy production, protein synthesis, photosynthesis, and storage. Together, all parts help the cell survive and function properly.

2. Describe the functions of important cell organelles.

Different cell organelles perform specialised functions inside the cell. Mitochondria produce energy through respiration. Ribosomes synthesise proteins required for growth and repair. Chloroplasts perform photosynthesis in plant cells. Vacuoles store food and water. Lysosomes digest wastes and damaged parts. The nucleus controls all activities and stores hereditary information. These organelles work together in coordination to maintain life processes and proper functioning of cells.

3. Differentiate between plant cells and animal cells in detail.

Plant cells possess cell walls, chloroplasts, and large central vacuoles, giving them a fixed rectangular shape. Animal cells lack cell walls and chloroplasts and usually contain smaller vacuoles. Plant cells prepare food through photosynthesis, while animal cells depend on external food sources. Plant cells are generally more rigid due to cell walls, whereas animal cells are flexible and irregular in shape depending on their functions.

4. Explain the importance of nucleus and chromosomes.

The nucleus controls all cellular activities such as growth, metabolism, and reproduction. It contains chromosomes made of genetic material that carry hereditary information from parents to offspring. Chromosomes determine inherited traits and regulate protein production. The nucleus also helps coordinate cell division and proper functioning of the organism. Without the nucleus and chromosomes, cells would lose control and hereditary continuity.

5. Describe how the discovery of cells changed biological science.

The discovery of cells completely transformed biological science by revealing that all living organisms are made up of microscopic units called cells. Scientists began understanding body organisation, growth, reproduction, and diseases more scientifically. Cell discovery led to development of microbiology, genetics, biotechnology, and medical research. It helped explain life processes at a microscopic level and improved scientific understanding of living organisms significantly.

Class 9 Science Chapter 2 Worksheet

Analytical Question Answers | Class 9 Science Chapter 2 Worksheet

1. A plant kept in darkness for several days becomes weak and pale. Analyse the role of chloroplasts in this situation.

Chloroplasts contain chlorophyll, which absorbs sunlight for photosynthesis. When a plant remains in darkness, chloroplasts cannot perform photosynthesis properly, so food production decreases significantly. As a result, the plant lacks energy required for growth and survival. Chlorophyll may also break down, causing pale colouration. This situation shows that chloroplasts are extremely important for food production, healthy growth, and maintaining green colour in plants.

2. A scientist observes a cell without a nucleus. Analyse whether the cell can control activities properly for a long period.

The nucleus controls cellular activities and contains genetic material required for coordination, growth, and reproduction. Without a nucleus, the cell may survive temporarily but cannot regulate activities efficiently for a long period. Protein synthesis and cell division become affected due to absence of hereditary instructions. Eventually, the cell may lose functionality and die. This analysis highlights the importance of the nucleus in maintaining cellular control and survival.

3. Two cells are observed under a microscope. One has a cell wall and chloroplasts while the other does not. Analyse which cell belongs to a plant and why.

The cell containing cell wall and chloroplasts belongs to a plant because these structures are characteristic features of plant cells. The cell wall provides rigidity and protection, while chloroplasts perform photosynthesis. Animal cells do not contain chloroplasts and lack rigid cell walls. Therefore, presence of both structures clearly identifies the cell as a plant cell adapted for food production and structural support.

4. A student damages the cell membrane during an experiment. Analyse how this may affect the cell.

The cell membrane controls movement of substances into and out of the cell and protects internal contents. If it gets damaged, harmful substances may enter while essential materials may leak out. Cellular balance becomes disturbed, affecting metabolism and other life processes. Severe membrane damage may even cause cell death. This shows the cell membrane is extremely important for maintaining proper internal conditions inside the cell.

5. Why do muscle cells contain more mitochondria compared to some other body cells? Analyse scientifically.

Muscle cells require large amounts of energy for continuous contraction and movement. Mitochondria produce energy through cellular respiration, so muscle cells contain more mitochondria to meet higher energy demands efficiently. Increased mitochondria ensure proper functioning during physical activities such as running, lifting, and movement. This demonstrates how cell organelles vary in number according to the specialised functions performed by different types of cells.

Class 9 Science Chapter 2 Worksheet

Practical Application Answer | Class 9 Science Chapter 2 Worksheet

1. Scientists are developing artificial organs for patients. Explain how understanding cells and their organelles can help in this work.

Understanding cells and their organelles helps scientists design artificial organs that function similarly to natural body organs. Knowledge of cellular activities such as energy production, protein synthesis, and transport of substances allows researchers to create tissues that can survive and function properly inside the human body. Studying cell behaviour also helps scientists prevent rejection of artificial organs and improve compatibility with patients. This knowledge plays an important role in tissue engineering, regenerative medicine, and development of advanced medical treatments that can save human lives.

Class 9 Science Chapter 2 Worksheet