1
Who first saw cells in cork?
💡 Hint:
The year is 1665.
Explanation:
Robert Hooke saw a slice of cork in 1665.
Class 9 · Science · Chapter 5 · बिहार बोर्ड (BSEB)CBSE · NCERT 2026-27
The Fundamental Unit of Life
The Fundamental Unit of Life
How to use this page:
1. Read — 5.1 onion peel · 5.2 more mounts · 5.3 egg · 5.4 raisins · 5.5 electron microscope · 5.6 Rheo · 5.7 cheek, diagram, worked example, board tip
2. Check — each lesson has its own questions; the number follows the lesson
3. Mastery ★ — all of that lesson correct. Redo the wrong ones
4. The memory figure sets a plant cell beside an animal cell and marks only the wall, the chloroplast and the large vacuole.
In the Bihar book this is chapter 5. In the NCERT 2026-27 Exploration book the cell chapter is chapter 2, so the numbers differ. Progress stays in this browser.
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- 1 The discovery of the cell — Activities 5.1 and 5.2
- 2 Membrane, diffusion and osmosis — 5.3 to 5.5
- 3 The cell wall and plasmolysis — 5.6
- 4 The nucleus and two kinds of cell — 5.7
- 5 Cytoplasm, the reticulum, Golgi and lysosomes
- 6 Mitochondria, plastids and vacuoles
- Chapter winner — every lesson at mastery ★
🎬 Shorts
This chapter has no Short on the channel yet, so ten empty cards are not shown. The notes, diagrams and checks are complete.
📄 PDF download — notes + answer key
The discovery of the cell — Activities 5.1 and 5.2
कोशिका की खोज — क्रियाकलाप 5.1 और 5.2 · Section 5.1 · Activities 5.1 · 5.2
How the name beganNotes
In 1665 Robert Hooke looked at a thin slice of cork. The little rooms looked like a honeycomb. Cork comes from the bark of a tree. Cell means a little room, and the name is still used. Those cells were dead.
In 1674 Leeuwenhoek, with a better microscope, saw free living cells in pond water. Robert Brown saw the nucleus in 1831. Purkinje in 1839 called the fluid of the cell protoplasm. Schleiden (1838) and Schwann (1839) said that plants and animals are made of cells and that the cell is the basic unit of life. Virchow (1855) added that every cell comes from a cell that already exists. After the electron microscope of 1940, the fine build of organelles could be understood.
Activity 5.1 — the onion peelActivity
Take a small piece of an onion bulb. With forceps, peel the skin from the inner concave layer. Put it at once into a watch-glass of water, or the peel will fold or dry.
Put a drop of water on a slide and lay a small flat piece of peel on it. A camel-hair brush can help. Add one drop of safranin, then a cover slip. Keep air bubbles out with a mounting needle. Look first at low power, then at high power. Ask the teacher for help.
Activity 5.2 — more temporary mountsActivity
Make temporary mounts of a leaf peel, an onion root tip, and peels from onions of different sizes. Then ask four things: whether all cells match in shape and size, whether they match in structure, whether plant parts differ, and what is similar.
Cells of one onion peel look the same whether the bulb is large or small. These small structures together make the bulb. In an animal, nerve, fat, sperm, bone, smooth muscle, blood and egg cells look different. An Amoeba keeps changing shape. A multicellular body divides the work, and inside one cell the organelles divide it.
Worked exampleExample
Question: Why is the cell called the structural and functional unit of life?
Answer: Every organism is built of cells, so the cell is the unit of structure. One cell can take in food, exchange respiratory gases and clear waste, so it is also the unit of function. In Amoeba, Chlamydomonas, Paramecium and bacteria, one cell is the whole organism.
10-second revision
- Hooke 1665, cork, dead compartments
- Virchow: a new cell comes from an old cell
- Safranin in 5.1, and no air bubble
Board tip · BSEBBoard tip
Write the discovery order: Hooke, Leeuwenhoek, Brown, Purkinje, Schleiden and Schwann, Virchow. The name with the year is enough.
Board tip · CBSEBoard tip
Remember four unicellular examples: Amoeba, Chlamydomonas, Paramecium and bacteria.
Check your understandingall correct = mastery ★
2
Every cell arises from a cell that already exists.
Explanation:
True — this is Virchow’s statement of 1855.
3
In Activity 5.1 a drop of ______ is put on the onion peel to colour it.
💡 Hint:
The stain used before the cover slip.
Explanation:
Safranin. Activity 5.7, the cheek, uses methylene blue.
4
Which of these is unicellular?
💡 Hint:
Uni means one.
Explanation:
Paramecium is an organism of one cell.
5
Why is the cell called the basic unit of life? Add the discoverer’s name in one sentence.
Model answer (board format)
Hooke saw in 1665 that living things appear to be made of separate units. Every organism is made of cells, and the parts inside a cell carry out the work of life, so the cell is the unit of both structure and function.
Check your answer:
Membrane, diffusion and osmosis — 5.3 to 5.5
झिल्ली, विसरण और परासरण — 5.3 से 5.5 · 5.2.1 · Activities 5.3 · 5.4 · 5.5
What may enter, and what is stoppedNotes
The plasma membrane is the outermost living layer of the cell. It lets some substances pass and stops others, so it is selectively permeable. If CO2 is higher inside, it leaves by diffusion. If O2 is lower inside, it enters by diffusion.
Osmosis is the passage of water across the membrane, from a higher water concentration to a lower one. In a hypotonic solution the outside has more water and the cell swells. In an isotonic solution water crosses both ways equally and the size stays the same. In a hypertonic solution the outside has less water and the cell shrinks. Some molecules also cross by a transport that spends energy.
| Outside solution | Where water is higher | The cell |
|---|---|---|
| Hypotonic | Outside | Swells |
| Isotonic | Equal | Size unchanged |
| Hypertonic | Inside | Shrinks |
Dilute hydrochloric acidCaution
In Activity 5.3 the shell dissolves in dilute acid. Do not taste the acid, do not spill it on skin, and do it in front of the teacher. The shell is mostly calcium carbonate.
Activity 5.3 — osmosis with an eggActivity
Dissolve an egg shell in dilute hydrochloric acid. A thin outer skin remains. Put this egg in pure water. After five minutes it swells, because water enters by osmosis.
Put a similar de-shelled egg in a concentrated salt solution. In five minutes it shrinks. Water leaves the egg toward the more concentrated salt solution.
Activities 5.4 and 5.5 — raisins, then the microscopeActivity
Dried raisins or apricots swell in plain water. In a concentrated sugar or salt solution they lose water and shrink. Uptake of water by roots is also osmosis. Unicellular freshwater organisms and most plant cells take up water.
The membrane is made of lipids and proteins and it is flexible. Its fine structure is seen only with an electron microscope. In Activity 5.5, read about that instrument in the library or on the internet and discuss it with the teacher. The same flexibility lets Amoeba engulf food. That process is endocytosis.
Worked exampleExample
Question: Four potato cups sit in a trough of water. B has sugar, C has salt, A is empty, and D is a boiled potato with sugar. After two hours, why does water gather in B and C, and not in A and D?
Answer: The solution inside B and C is more concentrated than the water outside, so water enters through the living membrane by osmosis. A has no solute to draw water in. The cells of D were killed by boiling, and a dead cell does not draw water by osmosis. A is the control.
10-second revision
- Diffusion: CO2 out, O2 in
- Osmosis is only about water
- Egg, 5 minutes: swells in water, shrinks in salt
Board tip · BSEBBoard tip
Write the three solution names with their meanings. Only “water moved” is incomplete.
Board tip · CBSEBoard tip
The egg is watched for five minutes and the shell is calcium carbonate. Those two facts are often asked.
Check your understandingall correct = mastery ★
1
How does extra CO2 leave the cell?
💡 Hint:
A gas crosses the membrane toward its lower concentration.
Explanation:
CO2 leaves by diffusion. The path of water is osmosis.
2
In osmosis, water crosses a selectively permeable membrane.
Explanation:
True — it is a special case of diffusion, and the substance is water.
3
A very dilute outside solution, in which the cell swells, is called ______.
💡 Hint:
Water is higher outside.
Explanation:
Hypotonic.
4
A de-shelled egg after five minutes in concentrated salt —
💡 Hint:
The salt solution is more concentrated.
Explanation:
Water leaves the egg, so the egg shrinks.
5
When the water concentration outside and in the cell is equal, the solution is ______.
💡 Hint:
Net movement is zero.
Explanation:
Isotonic. The cell does not change size.
6
What does a raisin do first in water and then in concentrated sugar? Give the reason in one line.
Model answer (board format)
In plain water the raisin takes up water by osmosis and swells. In concentrated sugar, water leaves, so it shrinks.
Check your answer:
The cell wall and plasmolysis — 5.6
कोशिका भित्ति और जीवद्रव्य कुंचन — 5.6 · 5.2.2 · Activity 5.6
The wall sits outside the membraneNotes
A plant cell has a rigid wall outside the plasma membrane. It is mainly cellulose and it gives the plant its strength. If a living plant cell loses water by osmosis, the contents shrink away from the wall. That is plasmolysis.
The walls of plants, fungi and bacteria can stand a very dilute outside medium. As water enters, the cell swells and the wall pushes back with an equal pressure. An animal cell cannot stand so large a change.
Boiling waterCaution
In Activity 5.6 the leaves are kept in boiling water for a few minutes. Steam and hot water can burn the hand. Use forceps.
Activity 5.6 — a Rheo leafActivity
Mount a Rheo leaf peel in water and look at high power. The small green granules are chloroplasts. They contain chlorophyll. Put a strong sugar or salt solution on the mount, wait one minute, and look again. In a living cell the contents pull away from the wall.
Keep some leaves in boiling water for a few minutes. This kills the cells. Then mount one, add the strong solution, and look after one minute. Plasmolysis does not occur in the dead cell. The inference: only a living cell absorbs water by osmosis.
Worked exampleExample
Question: In pure water an animal cell may burst. Why does a plant cell stay swollen instead?
Answer: Pure water is hypotonic. Water enters both cells. An animal cell has only a membrane, so it may burst. The plant wall resists the swelling and the cell stays turgid.
10-second revision
- Wall is cellulose, outside the membrane
- Plasmolysis = contents leaving the wall
- No plasmolysis in dead Rheo
Board tip · BSEBBoard tip
Keep three words in the definition of plasmolysis: living, loss of water, away from the wall.
Board tip · CBSEBoard tip
Write the three groups that have a wall: plants, fungi, bacteria. Only “plants” stays incomplete.
Check your understandingall correct = mastery ★
1
The plant cell wall is mainly made of —
💡 Hint:
A complex substance that gives strength.
Explanation:
Cellulose. The wall lies outside the plasma membrane.
2
Plasmolysis also occurs in a boiled Rheo leaf.
Explanation:
False — boiling kills the cell. Plasmolysis occurs only in a living cell.
3
Shrinkage of the contents of a living plant cell away from the wall is called ______.
💡 Hint:
After strong salt or sugar.
Explanation:
Plasmolysis.
4
Why does a plant cell not burst in a hypotonic medium? Write one difference from an animal cell.
Model answer (board format)
The cellulose wall exerts an equal pressure on the swollen cell. An animal cell has no such wall, so it may burst. The walls of fungi and bacteria do the same job.
Check your answer:
The nucleus and two kinds of cell — 5.7
केंद्रक और दो तरह की कोशिकाएँ — 5.7 · 5.2.3 · Activity 5.7
What the nucleus looks afterNotes
The nucleus has a double membrane. Pores let material pass out to the cytoplasm. Chromosomes look like rods only when the cell is about to divide. They are made of DNA and protein. Functional segments of DNA are genes. When the cell is not dividing, the DNA stays as the tangled threads of chromatin.
The nucleus has the central role when one cell divides into two. By directing the chemistry it also decides what form the cell will take as it matures. A bacterium has no nuclear membrane. The undefined region that holds nucleic acids is the nucleoid. Such organisms are prokaryotes. Those with a nuclear membrane are eukaryotes.
Activity 5.7 — a cheek cellActivity
Put a drop of water on a slide. With an ice-cream spoon, gently scrape the inner surface of the cheek. Spread the material with a needle. Add a drop of methylene blue. Do not forget the cover slip.
A dark round or oval dot near the centre is the nucleus. Onion cells had a nucleus too. A stain colours different regions to different depths. Iodine, safranin or methylene blue can all be used. The written steps of 5.1 say safranin. Activity 5.7 says methylene blue.
| Point | Prokaryote | Eukaryote |
|---|---|---|
| Size | Usually 1–10 μm | Usually 5–100 μm |
| Nuclear region | Nucleoid, no membrane | Nucleus, double membrane |
| Chromosome | Single | More than one |
| Membrane organelles | Absent | Present |
Worked exampleExample
Question: A prokaryotic cell is 2 μm long. Write that in metres.
Formula: 1 μm = 10−6 m
Substitution: 2 μm = 2 × 10−6 m
Unit: metre. That is 0.000002 m. The book writes 1 μm as 10−6 m.
10-second revision
- A gene = a functional segment of DNA
- The nucleoid has no membrane
- The stain of 5.7 is methylene blue
Board tip · BSEBBoard tip
Remember the four rows of the table: size, nucleus, chromosome, membrane-bound organelles.
Board tip · CBSEBoard tip
Keep the virus sentence separate: no membrane, so no signs of life until it enters a living body.
Check your understandingall correct = mastery ★
1
Where is a nucleoid found?
💡 Hint:
There is no nuclear membrane.
Explanation:
A prokaryote, such as a bacterium, has a nucleoid.
2
Chromosomes look like rods all the time.
Explanation:
False — the rod-like form shows only when the cell is about to divide. The rest of the time it is chromatin.
3
Functional segments of DNA are called ______.
💡 Hint:
The information of inheritance sits here.
Explanation:
Genes.
4
The stain for the cheek cell in Activity 5.7 is —
💡 Hint:
After the scrape with the spoon.
Explanation:
Methylene blue. The acid belongs to the egg activity, 5.3.
5
Convert 8 μm into metres. Write the formula, the substitution and the unit.
Model answer (board format)
1 μm = 10^(−6) m. 8 μm = 8 × 10^(−6) m = 0.000008 m.
Check your answer:
Cytoplasm, the reticulum, Golgi and lysosomes
कोशिका द्रव्य, जालिका, गॉल्जी और लाइसोसोम · 5.2.4 · 5.2.5 ER · Golgi · lysosomes
The fluid and the two reticulaNotes
In both the onion and the cheek, a large region inside the membrane takes little stain. That is the cytoplasm, the fluid inside the plasma membrane. It holds specialised organelles. In a eukaryote these are enclosed by membranes. A prokaryote has no membrane-bound organelles. A virus has no membrane, so it shows no signs of life until it enters a living body and uses that machinery.
The endoplasmic reticulum is a network of tubes and sheets. The rough form has ribosomes on it. In active cells the ribosomes make proteins. The smooth form makes fats, or lipids. Some proteins and lipids build the membrane. That is membrane biogenesis. In the liver of a vertebrate the smooth form makes many poisons and drugs harmless. RER makes proteins, SER makes fats.
Golgi packs, the lysosome cleansNotes
Camillo Golgi described this organelle. It is parallel stacks of membrane vesicles, called cisterns. They are often joined to the ER membrane. The job is to store, modify and pack products in vesicles and send them inside or outside the cell. Sometimes complex sugars are made from simple sugars. Lysosomes are also formed here.
Lysosomes are the waste system of the cell. Foreign material, such as bacteria or food, and old organelles are broken into small pieces here. The enzymes are made by the RER. If the cell is damaged or metabolism is disturbed, the sac may burst and digest its own cell. So they are suicide bags.
Worked exampleExample
Question: Where are the lipids and proteins of the membrane made?
Answer: Lipids are made in the smooth endoplasmic reticulum. Proteins are made on the ribosomes of the rough reticulum. Together they build the membrane. That is membrane biogenesis.
10-second revision
- Ribosomes are the site of proteins
- Golgi: store, modify, pack
- Lysosome enzymes come from the RER
Board tip · BSEBBoard tip
Write the RER and SER pair in one sentence, then biogenesis in a separate sentence.
Board tip · CBSEBoard tip
The reason for the suicide-bag name is the bursting. Writing only “digestion” is incomplete.
Check your understandingall correct = mastery ★
1
Where are proteins manufactured?
💡 Hint:
RER looks rough because of these particles.
Explanation:
Ribosomes. In an active cell they make proteins.
2
The smooth endoplasmic reticulum makes lipids.
Explanation:
True — fat molecules, or lipids, are the job of the SER. Proteins belong to the RER.
3
The membrane sac of digestive enzymes that can digest the cell is the ______.
💡 Hint:
The suicide bag.
Explanation:
The lysosome.
4
The main job of the Golgi apparatus is —
💡 Hint:
Stacks of cisterns.
Explanation:
It stores, modifies and packs products, then sends them on.
5
In the vertebrate liver the SER helps to make poisons and drugs harmless.
Explanation:
True — the book gives this job to the smooth reticulum of the liver.
6
What harm would the cell suffer if there were no Golgi apparatus? Write two points.
Model answer (board format)
Material made near the reticulum will not be packed and will not reach its target. Lysosomes will not form properly, and the making of complex sugars from simple sugars can also stop.
Check your answer:
Mitochondria, plastids and vacuoles
माइटोकॉन्ड्रिया, लवक और रसधानी · 5.2.5 · plant and animal cells
Energy and the green granulesNotes
Mitochondria are the powerhouses of the cell. The energy of the chemical work of life is released as ATP. ATP is the energy currency. The outer membrane is porous and the inner membrane is deeply folded, so the surface for making ATP is large. They have their own DNA and ribosomes, so they make some of their own proteins.
Plastids occur only in plant cells. There are two kinds: coloured chromoplasts and white or colourless leucoplasts. A plastid with chlorophyll is a chloroplast. It carries out photosynthesis and may also hold yellow or orange pigments. Leucoplasts store starch, oils and protein granules. Membrane layers lie in the stroma. Plastids also keep their own DNA and ribosomes. The organelles with their own genetic material are mitochondria and plastids.
The vacuole storesNotes
A vacuole is a storage sac for solid or liquid contents. In animals they are small. The central vacuole of a plant cell may take 50 to 90 percent of the volume. It is full of cell sap, which gives turgidity and rigidity. Amino acids, sugars, organic acids and some proteins stay here.
The food vacuole of Amoeba holds the food it has taken. In some unicellular organisms a specialised vacuole expels extra water and some wastes. The membrane and the organelles together run respiration, nutrition, cleaning and the making of new proteins. So the cell is the basic unit of both structure and function.
Worked exampleExample
Question: Which two organelles contain their own genetic material?
Answer: Mitochondria and plastids. Both have their own DNA and ribosomes, so both can make some proteins themselves. Plastids are not found in an animal cell.
10-second revision
- ATP is the energy currency
- Chloroplasts only in plants
- Large vacuole, 50–90 percent
Board tip · BSEBBoard tip
Write the plant and animal difference in three points: wall, chloroplast, size of the vacuole. The figure shows those three.
Board tip · CBSEBoard tip
A leucoplast stores. A chloroplast photosynthesises. Do not write them as the same.
Check your understandingall correct = mastery ★
1
The powerhouse of the cell is —
💡 Hint:
ATP is made here.
Explanation:
The mitochondrion makes ATP. ATP is the energy currency.
2
Plastids occur in both animal and plant cells.
Explanation:
False — plastids occur only in plant cells.
3
The central vacuole of some plant cells may occupy ______ percent of the volume.
💡 Hint:
It is a range, not one single number.
Explanation:
50 to 90 percent.
4
Write the three ways a plant cell differs from an animal cell.
Model answer (board format)
A plant cell has a cellulose wall and an animal cell does not. Chloroplasts occur only in the plant. The plant vacuole is large and may occupy 50–90 percent of the volume, while animal vacuoles are small.
Check your answer:
❓ Full question bank — with answers and explanations — 64 questions
Pick a type. The 30 lesson checks are separate — each lesson has as many as its topic needs. All correct earns mastery ★.
BSEB modelpractice · not annual60 tried · 0 correctMultiple choiceMCQ140 tried · 0 correctTrue / falseTrue / false70 tried · 0 correctFill in the blanksFill70 tried · 0 correctMatchMatch20 tried · 0 correctAssertion–reasonAssertion–reason40 tried · 0 correctBalancingBalancing40 tried · 0 correctIdentifyIdentify20 tried · 0 correctShort and longVSA, SA, LA120 tried · 0 correctCBSE-stylenot a PYQ60 tried · 0 correct
No question is marked as a verified past paper. The BSEB set is a model for practice. CBSE items are CBSE-style, not a copy of any year’s paper.
Multiple choice
0/14Pick one option. A wrong try brings a hint.
1
The scientist who saw the cells of cork is —
💡 Hint:
1665.
Explanation:
Robert Hooke.
2
Who coined the word protoplasm?
💡 Hint:
1839.
Explanation:
Purkinje called it protoplasm in 1839.
3
A selectively permeable membrane —
💡 Hint:
Not everyone.
Explanation:
Some substances pass in or out, and some are stopped.
4
If O2 falls inside the cell, it enters —
💡 Hint:
It is a gas, not water.
Explanation:
By diffusion.
5
In a hypertonic solution the cell —
💡 Hint:
Water is lower outside.
Explanation:
Water leaves and the cell shrinks.
6
The egg shell is mostly —
💡 Hint:
Dilute acid dissolves it.
Explanation:
Calcium carbonate.
7
Plasmolysis occurs —
💡 Hint:
The contents leave the wall.
Explanation:
Only in a living plant cell.
8
The usual size of a eukaryotic cell is —
💡 Hint:
The smaller range belongs to the prokaryote.
Explanation:
5–100 μm.
9
The site of protein synthesis is —
💡 Hint:
The particles seated on the RER.
Explanation:
The ribosome.
10
The suicide bag is —
💡 Hint:
On bursting it digests its own cell.
Explanation:
The lysosome.
11
The energy currency is —
💡 Hint:
Mitochondria make it.
Explanation:
ATP.
12
Found only in a plant cell —
💡 Hint:
The organelle of photosynthesis.
Explanation:
A chloroplast.
13
Amoeba takes food —
💡 Hint:
The membrane is flexible.
Explanation:
By endocytosis.
14
How much of the volume can the central vacuole occupy?
💡 Hint:
A plant cell.
Explanation:
50–90 percent.
True or false
0/71
According to Virchow a new cell comes from a cell that already exists.
Explanation:
True.
2
Osmosis is the crossing of any gas through the membrane.
Explanation:
False — osmosis is about water.
3
An animal cell has a cellulose wall.
Explanation:
False — the wall is in plants, fungi and bacteria.
4
A prokaryote has no membrane-bound organelles.
Explanation:
True. Ribosomes are small and the nucleoid has no membrane.
5
A leucoplast carries out photosynthesis.
Explanation:
False — a leucoplast stores starch, oils and proteins. Photosynthesis belongs to the chloroplast.
6
A virus shows the signs of life without a living cell.
Explanation:
False — it has no membrane, so it needs the machinery of a living body.
7
The Golgi apparatus is also involved in forming lysosomes.
Explanation:
True.
Fill in the blanks
0/71
In Latin, cell means a ______.
💡 Hint:
Hooke’s name.
Explanation:
A little room.
2
The nucleus was discovered in 1831 by ______.
Explanation:
Robert Brown.
3
A concentrated outside solution is called ______.
Explanation:
Hypertonic. The cell shrinks.
4
The undefined nuclear region is called the ______.
Explanation:
The nucleoid.
5
Membrane lipids are made in the ______.
Explanation:
The smooth endoplasmic reticulum.
6
The inner mitochondrial membrane is deeply ______, so the surface grows.
Explanation:
Folded.
7
In Amoeba the food stays in the ______ vacuole.
Explanation:
The food vacuole.
Match
0/21
Match the scientist with the statement.
Column B: A. Protoplasm · B. Cork cells · C. New cell from an old one · D. Nucleus
1. Hooke
2. Brown
3. Virchow
4. Purkinje
Explanation:
Hooke cork, Brown the nucleus, Virchow a pre-existing cell, Purkinje protoplasm.
2
Match the organelle with its job.
Column B: A. ATP · B. Protein · C. Digestion · D. Starch store
1. Ribosome
2. Lysosome
3. Leucoplast
4. Mitochondrion
Explanation:
Ribosome protein, lysosome digestion, leucoplast storage, mitochondrion ATP.
Assertion–reason
0/4Check both statements, then see whether the reason explains the assertion.
1
Assertion (A): The plasma membrane is selectively permeable.
Reason (R): It lets some substances pass and stops others.
Explanation:
Both are true and R explains A.
2
Assertion (A): Mitochondria have their own DNA.
Reason (R): Plastids occur only in plant cells.
Explanation:
Both are true, but R does not explain A. They are separate facts.
3
Assertion (A): Plasmolysis occurs only in a living cell.
Reason (R): A boiled Rheo leaf also shows plasmolysis.
Explanation:
A is true. R is false — boiling kills the cell and plasmolysis does not occur.
4
Assertion (A): In a hypotonic solution a plant cell bursts like an animal cell.
Reason (R): The cellulose wall presses back on the swollen cell.
Explanation:
A is false — because of the wall a plant cell does not burst. R is true.
Balance the equation
0/4This is coefficient practice. This chapter has no chemical equation. A blank coefficient means 1.
1
This is coefficient practice and not a chemical result of this chapter. Fill the coefficients for H2 + O2 → H2O.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
2
This is coefficient practice and not a chemical result of this chapter. This reaction is not in the cell chapter. Treat a blank as 1 and balance H2 + O2 → H2O.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
3
This is coefficient practice and not a chemical result of this chapter. Do not read it as an equation of osmosis. Write the coefficients for H2 + O2 → H2O.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
4
This is coefficient practice and not a chemical result of this chapter. It is only practice for making water. Balance H2 + O2 → H2O.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
Classify
0/21
Place each case in the right solution.
The cell swells
No net movement
The cell shrinks
Water is higher outside
Explanation:
Swelling is hypotonic, equal is isotonic, shrinking is hypertonic. More water outside is also hypotonic.
2
Place each fact with the prokaryote or the eukaryote.
Nucleoid
Membrane-bound organelles
Usually 1–10 μm
More than one chromosome
Explanation:
The nucleoid and the small size belong to the prokaryote. Membrane organelles and many chromosomes belong to the eukaryote.
Very short answer
0/51
Write the meaning of the word cell.
Model answer (board format)
In Latin it means a little room.
Check your answer:
2
Why is the plasma membrane called selectively permeable?
Model answer (board format)
Because it lets some substances pass into and out of the cell and stops some other substances.
Check your answer:
3
Define osmosis.
Model answer (board format)
Osmosis is the passage of water across a selectively permeable membrane from a higher water concentration to a lower one.
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4
How many layers does the nuclear membrane have?
Model answer (board format)
Two layers. Material passes through pores into the cytoplasm.
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5
Why is a lysosome called a suicide bag?
Model answer (board format)
In damage or a disturbance of metabolism it may burst, and the digestive enzymes digest their own cell.
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Short answer
0/41
Write both parts of Activity 5.3. Why did the egg swell and why did it shrink?
Model answer (board format)
The shell dissolves in dilute hydrochloric acid because it is calcium carbonate. The de-shelled egg swells in pure water in five minutes as water enters by osmosis. In concentrated salt it shrinks in five minutes as water leaves.
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2
Write the difference between a prokaryote and a eukaryote in nucleus, chromosome and organelles.
Model answer (board format)
A prokaryote has a nucleoid and no nuclear membrane. It has a single chromosome and no membrane-bound organelles. A eukaryote has a nucleus enclosed by a membrane, more than one chromosome and membrane-bound organelles.
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3
Write one job each of RER, SER and Golgi.
Model answer (board format)
Ribosomes of the RER make proteins. The SER makes lipids and, in the liver, makes poisons harmless. Golgi packs substances and sends them on, and it forms lysosomes.
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4
Convert 4 μm into metres. Show the formula and the unit. Which class of cell is this size close to?
Model answer (board format)
1 μm = 10^(−6) m. 4 μm = 4 × 10^(−6) m. This lies inside the prokaryotic range of 1–10 μm.
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Long answer
0/31
Write the differences between a plant cell and an animal cell. Add one example of osmosis and the condition for plasmolysis.
Model answer (board format)
A plant cell has a cellulose wall, chloroplasts and a large vacuole. An animal cell has no wall and no chloroplast, and its vacuoles are small. Uptake of water by a root is osmosis. Plasmolysis occurs only when a living plant cell loses water in a hypertonic medium. It does not occur in a dead cell.
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2
Write the methods of Activities 5.1 and 5.7 separately. How would you recognise the nucleus in both?
Model answer (board format)
In 5.1 keep the inner onion peel in water, lay it flat on a slide, add safranin and place a cover slip without bubbles. In 5.7 scrape the cheek gently, spread it in water, add methylene blue and place a cover slip. In both, the dark round or oval dot near the centre is the nucleus.
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3
Share the work of organelles: power, protein, packing, cleaning, photosynthesis and storage. What would stop if one organelle were missing?
Model answer (board format)
Power is the mitochondrion and ATP. Protein is the ribosome. Packing is Golgi. Cleaning is the lysosome. Photosynthesis is the chloroplast. Storage is the leucoplast and the vacuole. Without Golgi, packing and the forming of lysosomes stop. If the membrane tears, selection ends and the cell dies.
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BSEB model paper · practice
0/6This model set is for practice. It is not a question from any year’s annual examination. Annual questions will be added only when a source page is available.
1
Whose statement is the one about a pre-existing cell?
💡 Hint:
1855.
Explanation:
Virchow.
2
In an isotonic solution the cell —
💡 Hint:
Net movement is zero.
Explanation:
The size does not change.
3
The leaf in Activity 5.6 is called ______.
💡 Hint:
No plasmolysis after boiling.
Explanation:
Rheo. That is the spelling the book prints.
4
What is endocytosis? Give one example.
Model answer (board format)
Taking food or material from outside into the cell by the flexible membrane is endocytosis. Amoeba takes its food this way.
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5
This is coefficient practice, not a result of The Fundamental Unit of Life. Fill the coefficients for H2 + O2 → H2O. A blank means 1.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
6
Write the difference between diffusion and osmosis with examples. Add both situations of the egg.
Model answer (board format)
In diffusion a substance moves from higher concentration to lower. CO2 leaves and O2 enters this way. In osmosis water crosses the membrane from higher water to lower water. A de-shelled egg swells in pure water and shrinks in concentrated salt.
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CBSE-style questions
0/6These are competency-based practice questions. They are not copies of a CBSE paper.
1
A student puts sugar in a boiled potato cup and keeps a raw empty cup as the control. After two hours water has entered only the raw cup that had sugar. The best reason is —
💡 Hint:
Remember the inference of 5.6.
Explanation:
Boiling ends the living selection of the membrane. Sugar draws water, but the dead cup does not fill.
2
On a cheek slide a student added methylene blue but forgot the cover slip. What is the first correction?
💡 Hint:
The last caution of Activity 5.7.
Explanation:
The cover slip must be placed. The acid belongs to the egg activity.
3
Assertion (A): Roots take water from the soil.
Reason (R): This movement is an example of osmosis.
Explanation:
Both are true and R explains A.
4
Assertion (A): A prokaryote has a single chromosome.
Reason (R): That chromosome always has several membrane-bound organelles stuck to it.
Explanation:
A is true. R is false — a prokaryote has no membrane-bound organelles.
5
In the laboratory an egg is placed in concentrated salt and a student says it will swell. What is the mistake? What will be seen after five minutes?
Model answer (board format)
Swelling happens in pure water, because water enters the egg there. Concentrated salt is hypertonic. After five minutes the egg shrinks, because water leaves. The shell should first have been removed with dilute acid.
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6
The organisation of a cell is broken by a chemical injury. Write two possible results, one of them about the lysosome.
Model answer (board format)
Lysosomes may burst and the digestive enzymes may digest the cell. The separate organelles will not be able to do their jobs, so respiration, cleaning and protein-making will stop and the cell may die.
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🏛️ Board exam corner — Bihar Board (BSEB)— CBSE
Switch board with BSEB | CBSE above. The lessons follow the same NCERT chapter.
BSEB model · practiceBoard tip
This page has no verified annual-exam question, because no source page has been added. The model set below is practice in the board pattern.
🏛️ Model questions on one page →
The verified label will be used only when a source page for the question is available.
CBSE-style · competency-based
These are case and assertion-reason practice items. Do not treat them as past CBSE questions.
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🧠 What you learned + equation sheet
What you learned
- Hooke saw cells in 1665. Virchow said every cell comes from a cell that already exists.
- The plasma membrane is selectively permeable. CO2 and O2 move by diffusion, water by osmosis.
- The wall is cellulose. Plasmolysis happens only in a living plant cell.
- The nucleus holds chromosomes of DNA and protein. Before division the DNA is chromatin threads.
- RER makes proteins, SER makes fats. Golgi packs them. A lysosome can clean or digest the cell.
- Mitochondria and plastids have their own DNA. A large vacuole and chloroplasts mark a plant cell.
| What | Keep this |
|---|---|
| Osmosis | water, high to low, across a membrane |
| Hypotonic | cell gains water and swells |
| Hypertonic | cell loses water and shrinks |
| Size | prokaryote 1–10 μm, eukaryote 5–100 μm |
| Own DNA | mitochondria and plastids |
| Suicide bag | lysosome |
The notes are original writing. The textbook was used only for activity order and numbers. “Verified” will be used only on a question that has a source page.