Cell: The Unit of Life — ICSE Class 9 Biology Important Questions
13 ICSE Class 9 Biology practice questions on Cell: The Unit of Life, each with a full model answer, covering 5 topics from the chapter in the question formats used in the exam.
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- 13
- Questions
- 5
- Topics
- 4
- Key concepts
- ₹0
- With answers
Well-tested ICSE Cell: The Unit of Life questions cover the cell theory, the structure and functions of organelles (nucleus, mitochondria, chloroplast, ribosomes, endoplasmic reticulum, Golgi body, lysosomes, vacuoles), differences between prokaryotic and eukaryotic cells, and differences between plant and animal cells. A well-labelled diagram of a plant or animal cell is asked almost every year.
About Cell: The Unit of Life
In the ICSE Class 9 Biology chapter Cell: The Unit of Life you study the cell as the basic structural and functional unit of life, the cell theory, the structure and functions of cell organelles, the differences between prokaryotic and eukaryotic cells, and the comparison between typical plant and animal cells.
Key concepts & formulas
Proposed by Schleiden and Schwann: (1) all living things are made of cells, (2) the cell is the basic unit of structure and function, (3) all cells arise from pre-existing cells (Virchow).
The control centre of the cell; contains chromatin (DNA) which carries hereditary information, bounded by a nuclear membrane and containing the nucleolus.
Mitochondria are the 'powerhouse', releasing energy as ATP by respiration. Chloroplasts (in plant cells) are the 'kitchen', making food by photosynthesis using chlorophyll.
Plant cells have a cell wall, large central vacuole and plastids (chloroplasts); animal cells lack these but have centrioles and a small or no vacuole.
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Important questions with answers
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Multiple-choice questions (1 mark)
The organelle known as the 'powerhouse of the cell' is the:
- (a)
Ribosome
- (b)
Mitochondrion
- (c)
Golgi body
- (d)
Lysosome
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Answer: (b) Mitochondrion.
Mitochondria release energy in the form of ATP during cellular respiration, so they are called the powerhouse of the cell.
Which structure is present in a plant cell but absent in an animal cell?
- (a)
Nucleus
- (b)
Cell wall
- (c)
Mitochondria
- (d)
Cell membrane
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Answer: (b) Cell wall.
The rigid cellulose cell wall is present only in plant cells; animal cells have only a flexible cell membrane.
Lysosomes are called 'suicidal bags' of the cell because they:
- (a)
Store food
- (b)
Contain digestive enzymes that can destroy the cell
- (c)
Synthesise proteins
- (d)
Carry out photosynthesis
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Answer: (b) Contain digestive enzymes that can destroy the cell.
Lysosomes contain powerful hydrolytic enzymes; when a cell is damaged or dead they burst and digest the cell, hence 'suicidal bags'.
A cell lacks a true nucleus and membrane-bound organelles. This cell most likely belongs to:
- (a)
A leaf mesophyll
- (b)
A human liver
- (c)
A bacterium
- (d)
An onion peel
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Answer: (c) A bacterium.
Bacteria are prokaryotes; they have no true membrane-bound nucleus or organelles. The other options are eukaryotic cells.
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Practise free with the AI tutor →Assertion–Reason questions (1 mark)
Assertion (A): Chloroplasts are found in plant cells but not in animal cells.
Reason (R): Chloroplasts contain the green pigment chlorophyll needed for photosynthesis.
- (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
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Answer: (b) Both statements are true, but R only explains the function of chloroplasts. It does not explain why they are absent in animal cells (animals cannot photosynthesise), so R is not the correct explanation of A.
Very short answer questions (2 marks)
State the cell theory.
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The cell theory states that:
- All living organisms are made up of one or more cells.
- The cell is the basic structural and functional unit of life.
- All new cells arise from pre-existing cells (added by Virchow).
It was proposed by Schleiden and Schwann.
Give the functions of (i) ribosomes and (ii) the Golgi apparatus.
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(i) Ribosomes: They are the site of protein synthesis in the cell.
(ii) Golgi apparatus: It packages, processes and secretes materials (such as proteins and enzymes) and helps in forming lysosomes.
Short answer questions (3 marks)
Describe the structure and functions of the nucleus.
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Structure: The nucleus is a spherical, dense organelle usually located near the centre of the cell. It is bounded by a double nuclear membrane with pores, and contains a fluid called nucleoplasm, a dense nucleolus, and thread-like chromatin (made of DNA and protein) which condenses into chromosomes during division.
Functions:
- It controls all the activities of the cell, so it is called the control centre.
- The chromatin carries hereditary information (genes) from one generation to the next.
- It directs protein synthesis and cell division.
Differentiate between prokaryotic and eukaryotic cells (any three points).
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| Prokaryotic cell | Eukaryotic cell |
|---|---|
| True nucleus is absent; genetic material lies free in cytoplasm | True nucleus with nuclear membrane is present |
| Membrane-bound organelles are absent | Membrane-bound organelles (mitochondria, ER, etc.) are present |
| Generally small in size (1-10\, m) | Generally larger (10-100\, m) |
| Example: bacteria, blue-green algae | Example: plant and animal cells |
Draw a well-labelled diagram of a typical plant cell.
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A typical plant cell shows a cell wall, cell membrane, nucleus, large central vacuole, chloroplasts, mitochondria and cytoplasm:
Key labels: cell wall, cell membrane, nucleus, chloroplast, mitochondrion and the large central vacuole.
Long answer questions (5 marks)
Compare a plant cell and an animal cell with respect to any five features.
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| Feature | Plant cell | Animal cell |
|---|---|---|
| Cell wall | Present (made of cellulose) outside the cell membrane | Absent; only cell membrane present |
| Plastids | Present (chloroplasts, etc.) | Absent |
| Vacuole | A single large central vacuole | Small or absent; many tiny vacuoles |
| Centriole | Usually absent | Present, helps in cell division |
| Shape | Usually fixed and rectangular | Usually rounded and irregular |
Common features: Both have a cell membrane, cytoplasm, nucleus, mitochondria, endoplasmic reticulum, ribosomes and Golgi apparatus. The differences mainly arise because plants make their own food and need support, while animals do not.
Describe the structure and function of any five cell organelles.
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Five important cell organelles are:
-
Mitochondrion: A double-membraned, sausage-shaped organelle; the inner membrane is folded into cristae. It carries out cellular respiration and releases energy as ATP, so it is the powerhouse of the cell.
-
Endoplasmic reticulum (ER): A network of membranous tubules connected to the nuclear membrane. Rough ER (with ribosomes) makes proteins; smooth ER makes lipids and helps in transport within the cell.
-
Golgi apparatus: A stack of flattened membranous sacs. It modifies, packages and secretes proteins and forms lysosomes.
-
Ribosomes: Tiny granular structures, free or attached to ER; they are the sites of protein synthesis.
-
Lysosomes: Small sacs filled with digestive enzymes; they digest worn-out organelles and foreign particles, and are called suicidal bags because they can destroy the cell.
Each organelle performs a specific role so that the cell functions efficiently.
Case-based questions (4 marks)
A student observes two cells X and Y under a microscope. Cell X has a rigid outer boundary, a large central vacuole and green oval bodies. Cell Y has no rigid boundary, a small vacuole, a rounded shape and a pair of small rod-like bodies near the nucleus.
(i) Identify whether cell X is a plant or an animal cell, giving one reason.
(ii) Name the green oval bodies seen in cell X and state their function.
(iii) Name the pair of rod-like bodies seen in cell Y.
(iv) State one function common to both cells that keeps them alive.
Show model answer
(i) Cell X is a plant cell, because it has a rigid outer boundary (cell wall) and a large central vacuole, which are features of plant cells.
(ii) The green oval bodies are chloroplasts; they contain chlorophyll and carry out photosynthesis to make food.
(iii) The pair of rod-like bodies near the nucleus in cell Y are centrioles (centrosome), which help in cell division in animal cells.
(iv) Both cells carry out respiration in their mitochondria to release energy, which keeps them alive.
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Do these Cell: The Unit of Life questions follow the latest ICSE syllabus?
Yes — they are aligned to the CISCE 2026–27 syllabus for ICSE Class 9 Biology, so nothing here is outside the current course.
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