Cell Structure — REET Notes
This page covers the discovery of the cell, cell theory, and the major organelles of the cell for REET Level 2 (Maths-Science). REET 2024 asked scientist-linked factual questions from this topic, so every organelle and its associated scientist is explained clearly here.
- 2 questions in REET 2024
- Class 6-8 level
- 8 min read
How REET asks this topic
REET 2024 carried direct factual questions from this topic — one question was based on who discovered the nucleus, and the other was based on the organelle (plastid) that distinguishes a plant cell from an animal cell. In other words, REET asks straightforward, one-line questions on which biologist contributed what to cell biology (Hooke, Brown, Schleiden, and so on) and on the functions and comparisons of organelles — not calculations.
What a cell is, and how it was discovered
The cell is the smallest structural and functional unit of all living organisms. In 1665, Robert Hooke examined a thin slice of cork under a simple microscope and, seeing tiny empty compartments, named them 'cells' — this is considered the origin of the term's use.
Antonie van Leeuwenhoek, using microscopes he built himself that were far more powerful, was the first to observe living cells, such as bacteria and protozoa. After this, in 1831, Robert Brown discovered and described the nucleus in the cells of an orchid.
Cell theory was completed through the contributions of three scientists — Schleiden (1838) showed that all plants are made of cells, Schwann (1839) showed that all animals are made of cells too, and Virchow (1855) added that a new cell always arises from a pre-existing cell through division.
In REET Level 2's Maths-Science group, this topic is based on the NCERT Class 8 Science chapter 'Cell: Structure and Function'. It matters to a future teacher for another reason too: since Class 8 students themselves have to be taught about the cell, the exam can test not just factual recall but also the ability to explain the concept in simple language.
Key scientists in cell biology and their contribution
| Scientist | Contribution | Year |
|---|---|---|
| Robert Hooke | Observed a compartment structure in cork and named it 'cell' | 1665 |
| Antonie van Leeuwenhoek | First observation of living cells (bacteria/protozoa) | 1674 |
| Robert Brown | Discovery of the nucleus | 1831 |
| Schleiden | All plants are made of cells | 1838 |
| Schwann | All animals are also made of cells | 1839 |
| Rudolf Virchow | A new cell arises only from a pre-existing cell | 1855 |
Major cell organelles and their functions
- Nucleus
- holds the genetic material (DNA) and controls all the activities of the cell
- Mitochondria
- generates energy (ATP) through respiration, which is why it is called the 'powerhouse' of the cell
- Endoplasmic reticulum (ER)
- rough ER, studded with ribosomes, carries out protein synthesis; smooth ER synthesises fats (lipids)
- Golgi apparatus
- packages and secretes the cell's materials
- Ribosomes
- a membrane-less structure, and the main site of protein synthesis
- Lysosome
- holds digestive enzymes; if it is damaged, it can digest the cell itself, which is why it is called the cell's 'suicide bag'
- Plastids
- found only in plant cells; the chloroplast (a type of plastid) carries out photosynthesis
- Vacuole
- a plant cell has one large central vacuole that stores water and cell sap
- Cell wall
- present in plant cells (made of cellulose) and also in fungi (though a fungal cell wall is made of chitin, not cellulose); it is a rigid layer that gives shape and protection
Plant cell versus animal cell
| Feature | Plant cell | Animal cell |
|---|---|---|
| Cell wall | Present (made of cellulose) | Absent |
| Plastids | Present | Absent |
| Vacuole | One large central vacuole | Small and numerous, or usually absent |
| Centriole | Usually absent | Present in most animal cells |
Prokaryotic versus eukaryotic cell
| Feature | Prokaryotic cell | Eukaryotic cell |
|---|---|---|
| Nucleus | No well-organised nucleus; nuclear membrane absent | A well-organised nucleus, enclosed by a nuclear membrane |
| Example | Bacteria, blue-green algae | Plants, animals, fungi, protists |
| Membrane-bound organelles | Mostly absent, apart from ribosomes | Present — mitochondria, ER, Golgi apparatus, and so on |
Cell membrane, cytoplasm, and unicellular-multicellular organisms
The cell membrane is made mainly of fat (lipid) and protein and is found in every kind of cell — plant, animal and bacterial alike. It is selectively permeable, meaning it decides which substances can enter the cell and which can leave.
The semi-fluid substance between the nucleus and the cell membrane is called the cytoplasm. It is the site of most of the cell's activities, and it is where all the organelles of the cell — mitochondria, ribosomes, ER, and so on — are located.
Organisms whose body is made of just a single cell are called unicellular organisms — such as amoeba, Paramecium and bacteria. In these, that one cell alone carries out every life function, from nutrition to respiration to excretion. In contrast, multicellular organisms such as humans, animals, birds and most plants are built of millions or billions of cells, which divide the work between them, giving rise to tissues, organs and organ systems.
How to teach this to children
Classroom activity
Place an onion peel on a slide, stain it with iodine solution, and show it under a microscope — Class 8 students can see the nucleus and cell wall with their own eyes.
Teaching aids
Have children build a model of cell organelles using clay, with each organelle in a different colour — this makes remembering the structure much easier.
Common misconception
Students often confuse the cell wall and the cell membrane. Make clear that the cell wall is found only in plants/fungi and is rigid, while the cell membrane is found in all cells and is flexible and selectively permeable.
Assessment idea
Have students draw a Venn diagram comparing plant and animal cells, listing shared organelles (such as mitochondria and the nucleus) in the middle and organelles unique to each (such as the cell wall and plastids) on their respective sides — this makes their understanding easy to assess.
Memory trick
A plant cell has three extra things an animal cell doesn't — cell Wall, Plastid, and a large Vacuole. Remember the letters 'WPV' — wherever these three show up together, that's a plant cell.
REET 2024 questions (solved)
Question 125
Which was first described nucleus as a cell organelle ?
- Aल्यूवेन हॉक
- Bराबर्ट हुक
- Cराबर्ट ब्राउन
- Dकेमीलो गॉल्जी
Explanation
रॉबर्ट ब्राउन (Robert Brown) ने 1831 में ऑर्किड की कोशिकाओं में केंद्रक (nucleus) की खोज की और उसका वर्णन किया। रॉबर्ट हुक ने कॉर्क में कोशिका (1665) देखी, ल्यूवेनहॉक ने जीवित कोशिकाएँ देखीं और कैमिलो गॉल्जी ने गॉल्जी उपकरण का वर्णन किया।
Question 141
Cell organelles, which differentiate plant cell from animal cell
- Aप्लैस्टिड
- Bरसधानियाँ
- Cमाइटोकॉन्ड्रिया
- Dगॉल्जी उपकरण
Explanation
प्लैस्टिड (लवक), जैसे क्लोरोप्लास्ट, केवल पादप कोशिकाओं में पाए जाते हैं, इसलिए ये पादप कोशिका को जंतु कोशिका से अलग करते हैं। माइटोकॉन्ड्रिया और गॉल्जी उपकरण दोनों प्रकार की कोशिकाओं में होते हैं। रसधानियाँ जंतु कोशिका में भी (छोटी) हो सकती हैं, जबकि पादप कोशिका में बड़ी केन्द्रीय रसधानी होती है।
Practice questions
Question 1
Who first used the term 'cell'?
- Aल्यूवेनहॉक
- Bरॉबर्ट हुक
- Cरॉबर्ट ब्राउन
- Dश्वान
Explanation
Robert Hooke saw empty compartments in cork in 1665 and named them 'cells'. Leeuwenhoek observed living cells, and Brown discovered the nucleus.
Question 2
The structural and functional unit of all living organisms is —
- Aऊतक
- Bकोशिका
- Cअंग
- Dतंत्र
Explanation
The cell is the smallest structural and functional unit of living organisms; many cells together form tissues, organs and organ systems.
Question 3
Which of the following organelles is found only in plant cells?
- Aमाइटोकॉन्ड्रिया
- Bराइबोसोम
- Cप्लैस्टिड
- Dगॉल्जी उपकरण
Explanation
Plastids (such as chloroplasts) are found only in plant cells. Mitochondria, ribosomes and the Golgi apparatus occur in both types of cells.
Question 4
What is the 'power house' of the cell called?
- Aकेंद्रक
- Bमाइटोकॉन्ड्रिया
- Cलाइसोसोम
- Dरसधानी
Explanation
Mitochondria produce energy (ATP) through respiration, which is why they're called the cell's 'powerhouse'.
Question 5
Protein synthesis mainly occurs in which organelle?
- Aगॉल्जी उपकरण
- Bलाइसोसोम
- Cराइबोसोम
- Dरसधानी
Explanation
Ribosomes are a membrane-less structure and the main site of protein synthesis.
Question 6
Bacteria are examples of which type of cell?
- Aयूकैरियोटिक
- Bप्रोकैरियोटिक
- Cद्विकेंद्रकीय
- Dबहुकेंद्रकीय
Explanation
Bacteria lack a well-organised nuclear membrane, which is why they are an example of a prokaryotic cell.
Question 7
Who gave the principle that 'a new cell always arises from a pre-existing cell'?
- Aश्लाइडेन
- Bश्वान
- Cविरचो
- Dब्राउन
Explanation
Rudolf Virchow proposed in 1855 that a new cell always arises from the division of a pre-existing cell, which completed cell theory.
Question 8
While teaching cell organelles in Class 8, the most suitable activity for a teacher is —
- Aकेवल पाठ्यपुस्तक पढ़कर सुनाना
- Bप्याज की झिल्ली को माइक्रोस्कोप में दिखाना
- Cपरीक्षा पहले करा देना
- Dकेवल गृहकार्य में चित्र बनवाना
Explanation
Showing an onion peel under a microscope gives students direct, first-hand experience, letting them see and understand real cell structure.
Question 9
Students often mistake the cell wall and cell membrane as the same thing. The best way to clear this misconception is —
- Aदोनों को याद करने के लिए कह देना
- Bदोनों की तुलना कर उदाहरण सहित अंतर स्पष्ट करना
- Cविषय को छोड़ देना
- Dकेवल परिभाषा रटवाना
Explanation
Comparing the two with examples (rigid versus flexible, found only in plants versus found in every cell) clears up the misconception clearly — simply asking students to memorise the terms does not.
Question 10
Why is the lysosome called a 'suicidal bag'?
- Aयह कोशिका को ऊर्जा देता है
- Bइसमें पाचक एंजाइम होते हैं जो क्षतिग्रस्त होने पर कोशिका को स्वयं पचा सकते हैं
- Cयह प्रकाश संश्लेषण करता है
- Dयह आनुवंशिक पदार्थ रखता है
Explanation
The lysosome contains digestive enzymes; if its membrane ruptures, these enzymes can digest (destroy) the cell itself, which is why it is called the 'suicide bag'.
Frequently asked questions
How many questions come from Cell Structure in REET?+
REET 2024 carried 2 questions from this topic. It's a stable, important topic within science, so 1-2 questions from it can be expected most years.
What is cell theory?+
Cell theory states that all living things are made of cells, and a new cell always arises from a pre-existing cell through division. Schleiden, Schwann and Virchow all contributed to it.
What is the main difference between a plant cell and an animal cell?+
A plant cell has a cell wall, plastids and a large central vacuole, none of which are found in an animal cell. An animal cell instead has a centriole.
What is the difference between a prokaryotic and a eukaryotic cell?+
A prokaryotic cell (such as bacteria) has no well-organised nucleus, while a eukaryotic cell (such as plant or animal cells) has a clear nucleus enclosed in a membrane.
What's the difference between a unicellular and a multicellular organism?+
In a unicellular organism (such as amoeba), a single cell carries out all life functions, while in a multicellular organism (such as humans), millions of cells carry out different functions together.
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Change Log
- 17 September 2026 — English page published — mirrors the fact-checked Hindi page, independently bilingual-accuracy checked