📝 CELL BIOLOGY QUESTION PAPER
Chapter 5: The Fundamental Unit of Life
Total Marks
80
Time Duration
3 Hours
Question Types
MCQ, SA, LA
Total Questions
30
📋 General Instructions:
- This question paper contains 30 questions divided into 4 sections
- Answer all questions in order and provide detailed explanations
- Use diagrams wherever applicable to support your answers
- Marks are allocated as shown against each question
- There is NO NEGATIVE MARKING
SECTION A: Multiple Choice Questions (MCQ)
1 Mark Each | Total: 10 Marks
Q1.
Who first observed and named the "cell"?
1 Mark
A) Robert Hooke
B) Leeuwenhoek
C) Robert Brown
D) Virchow
Q2.
Which of the following is a selectively permeable membrane?
1 Mark
A) Cell wall
B) Plasma membrane
C) Nuclear membrane
D) All of the above
Q3.
Which organelle is known as the "powerhouse of the cell"?
1 Mark
A) Mitochondria
B) Chloroplast
C) Nucleus
D) Ribosome
Q4.
What is the movement of water across a selectively permeable membrane called?
1 Mark
A) Diffusion
B) Osmosis
C) Active transport
D) Endocytosis
Q5.
Which type of solution causes a cell to swell?
1 Mark
A) Hypertonic
B) Hypotonic
C) Isotonic
D) Concentrated
Q6.
Which organelles have their own DNA and ribosomes?
1 Mark
A) Lysosomes and Golgi apparatus
B) Mitochondria and Plastids
C) Nucleus and Ribosome
D) ER and Golgi
Q7.
Lysosomes are known as "suicide bags" because:
1 Mark
A) They destroy foreign material
B) They can burst and digest the entire cell
C) They contain digestive enzymes
D) They are found only in damaged cells
Q8.
Which of the following is a prokaryotic cell?
1 Mark
A) Human cell
B) Plant cell
C) Bacterial cell
D) Fungal cell
Q9.
Which organelle packages and dispatches cell products?
1 Mark
A) Endoplasmic reticulum
B) Golgi apparatus
C) Mitochondria
D) Ribosome
Q10.
Which type of cell division produces four cells with half the chromosome number?
1 Mark
A) Mitosis
B) Meiosis
C) Binary fission
D) Budding
SECTION B: Very Short Answer Questions (VSA)
2 Marks Each | Total: 20 Marks
Q11.
Define the term "cell" and explain why it is called the fundamental unit of life.
2 Marks
Q12.
What is the function of the plasma membrane? Why is it called "selectively permeable"?
2 Marks
Q13.
Distinguish between diffusion and osmosis with one example each.
2 Marks
Q14.
What happens to a cell placed in a hypertonic solution? Explain the process.
2 Marks
Q15.
Name the scientist who discovered the nucleus. When was this discovery made?
2 Marks
Q16.
What is the role of DNA in a cell? Where is it located?
2 Marks
Q17.
What is endocytosis? Name an organism that uses this process.
2 Marks
Q18.
Explain the difference between prokaryotic and eukaryotic cells in terms of nuclear organization.
2 Marks
Q19.
Write two distinguishing features of plant cells that animal cells do not have.
2 Marks
Q20.
What is the significance of having a membrane-bound nucleus in eukaryotic cells?
2 Marks
SECTION C: Short Answer Questions (SA)
3 Marks Each | Total: 30 Marks
Q21.
Describe the structure and functions of the nucleus. How does it control cellular activities?
3 Marks
Q22.
Explain the relationship between the three core components of a cell: plasma membrane, nucleus, and cytoplasm.
3 Marks
Q23.
Explain plasmolysis. Why does it occur only in living cells?
3 Marks
Q24.
Compare rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) in terms of structure and function.
3 Marks
Q25.
Describe the structure and function of mitochondria. Why are they called the powerhouse of the cell? Explain with an example.
3 Marks
Q26.
Explain the role of the Golgi apparatus in cellular function. How does it differ from the endoplasmic reticulum?
3 Marks
Q27.
Explain the concept of osmosis. Describe what happens when a cell is placed in hypotonic, hypertonic, and isotonic solutions.
3 Marks
Q28.
Compare prokaryotic and eukaryotic cells. Discuss the advantages of having membrane-bound organelles in eukaryotic cells.
3 Marks
Q29.
Describe the process of mitosis. What is its biological significance?
3 Marks
Q30.
Compare mitosis and meiosis. What is the biological significance of each?
3 Marks
ANSWER KEY & SOLUTIONS WITH DETAILED EXPLANATIONS
Complete Solutions
SECTION A: MCQ Answers
1 Mark Each
Q1. Correct Answer: A) Robert Hooke
Who first observed and named the "cell"?
Detailed Explanation
Robert Hooke, in 1665, examined a thin slice of cork under a primitive microscope he designed himself. He noticed it resembled a honeycomb with many small compartments. He called these structures "cells" from the Latin word "cella" meaning "a little room." This was the first observation that living things consist of separate units—a monumental discovery in the history of biology!
Q2. Correct Answer: D) All of the above
Which of the following is a selectively permeable membrane?
Detailed Explanation
All biological membranes in cells are selectively permeable. The plasma membrane controls what enters and exits the cell. The nuclear membrane regulates material transfer between nucleus and cytoplasm. The cell wall in plants, though rigid, also allows selective passage of water and nutrients based on pore size and chemical properties.
Q3. Correct Answer: A) Mitochondria
Which organelle is known as the "powerhouse of the cell"?
Detailed Explanation
Mitochondria earn the title "powerhouse" because they release energy in the form of ATP (Adenosine Triphosphate), the energy currency of the cell. All cellular functions—from muscle contraction to protein synthesis—depend on ATP produced by mitochondria. Cells with high energy demands (like muscle cells) contain hundreds or thousands of mitochondria!
Q4. Correct Answer: B) Osmosis
What is the movement of water across a selectively permeable membrane called?
Detailed Explanation
Osmosis is a special case of diffusion that specifically describes water molecules moving through a selectively permeable membrane. The key principle: water always moves toward the area with higher solute concentration. This is one of the most important concepts in cell biology because it determines whether cells absorb, lose, or maintain water.
Q5. Correct Answer: B) Hypotonic
Which type of solution causes a cell to swell?
Detailed Explanation
In a hypotonic solution, the external water concentration is HIGHER than inside the cell (the solution is dilute). Water enters the cell through osmosis, causing it to swell. Example: A dried raisin placed in pure water absorbs water and becomes plump. The cell may even burst if it's an animal cell with no cell wall to resist the pressure!
Q6. Correct Answer: B) Mitochondria and Plastids
Which organelles have their own DNA and ribosomes?
Detailed Explanation
Both mitochondria and plastids (chloroplasts) contain their own DNA and ribosomes. This unique feature strongly suggests that these organelles were once independent organisms billions of years ago. Over time, they became incorporated into eukaryotic cells through a process called endosymbiosis—a remarkable example of how complex life evolved through cellular partnerships!
Q7. Correct Answer: B) They can burst and digest the entire cell
Lysosomes are known as "suicide bags" because:
Detailed Explanation
Lysosomes contain powerful digestive enzymes capable of breaking down all organic material. In normal conditions, they safely digest waste and bacteria. However, if a cell is severely damaged, lysosomes can rupture and release their enzymes throughout the cell, causing the cell to digest itself from within. This is actually beneficial sometimes—it's a form of programmed cell death that prevents damaged cells from causing harm!
Q8. Correct Answer: C) Bacterial cell
Which of the following is a prokaryotic cell?
Detailed Explanation
Prokaryotic cells lack a nucleus and membrane-bound organelles. Bacteria are the classic example of prokaryotes. Human, plant, and fungal cells are all eukaryotic, meaning they have a well-defined nucleus enclosed by a nuclear membrane. The main distinction between prokaryotes and eukaryotes is one of the fundamental divisions in the history of life!
Q9. Correct Answer: B) Golgi apparatus
Which organelle packages and dispatches cell products?
Detailed Explanation
The Golgi apparatus consists of stacked membrane-bound vesicles. It receives materials from the ER, modifies them (sometimes adding sugars or changing proteins), packages them into vesicles, and dispatches them to their destinations. Think of it as the post office of the cell—materials arrive as packages, get processed, and are then shipped to their final destinations!
Q10. Correct Answer: B) Meiosis
Which type of cell division produces four cells with half the chromosome number?
Detailed Explanation
Meiosis involves two consecutive divisions and produces four non-identical daughter cells. Most importantly, each daughter cell has HALF the chromosome number of the mother cell. This is essential for sexual reproduction—when sperm (n) and egg (n) fuse, they create a zygote with the full chromosome number (2n). Without meiosis reducing chromosome numbers by half, offspring would have twice as many chromosomes each generation!
SECTION B: Very Short Answer Solutions
2 Marks Each
Q11. Define the term "cell" and explain why it is called the fundamental unit of life.
Model Answer
Definition:
A cell is the smallest structural and functional unit of life that can carry out all life processes independently.
Why "Fundamental Unit":
• Structural Basis: All organisms consist of one or more cells
• Functional Unit: All life processes occur within cells (nutrition, respiration, growth, reproduction)
• Self-Sufficiency: Even single-celled organisms can survive independently
• Universal: The cell theory applies to all known living organisms
• Functional Unit: All life processes occur within cells (nutrition, respiration, growth, reproduction)
• Self-Sufficiency: Even single-celled organisms can survive independently
• Universal: The cell theory applies to all known living organisms
Q12. What is the function of the plasma membrane? Why is it called "selectively permeable"?
Model Answer
Function:
• Separates cell's contents from the external environment
• Controls and regulates material transport in and out of the cell
• Acts as a protective barrier
• Controls and regulates material transport in and out of the cell
• Acts as a protective barrier
Why Selectively Permeable:
It allows some materials to pass while preventing others:
• Oxygen and CO₂ can diffuse freely
• Nutrients are selectively transported
• Large molecules are blocked
• Harmful substances are kept out
This selective control is what allows cells to maintain their unique internal environment!
• Oxygen and CO₂ can diffuse freely
• Nutrients are selectively transported
• Large molecules are blocked
• Harmful substances are kept out
This selective control is what allows cells to maintain their unique internal environment!
Q13. Distinguish between diffusion and osmosis with one example each.
Model Answer
Diffusion:
• Movement of any substance from high to low concentration
• Does NOT require a selectively permeable membrane
• Example: Perfume spray spreading throughout a room
• Does NOT require a selectively permeable membrane
• Example: Perfume spray spreading throughout a room
Osmosis:
• Movement of ONLY water through a selectively permeable membrane
• REQUIRES a selectively permeable membrane
• Example: Raisin absorbing water and swelling when placed in pure water
• REQUIRES a selectively permeable membrane
• Example: Raisin absorbing water and swelling when placed in pure water
Key Difference: Osmosis is a special type of diffusion—it's specifically water moving across a membrane!
Q14. What happens to a cell placed in a hypertonic solution? Explain the process.
Model Answer
What Happens:
The cell shrinks/shrivels due to loss of water.
Process (Step by Step):
1) Hypertonic solution = higher solute concentration outside, lower water concentration
2) Water molecules move OUT of the cell by osmosis
3) The cell loses water and shrinks
4) In plant cells: plasmolysis occurs (cytoplasm separates from cell wall)
5) In animal cells: cell shrinks but maintains shape
Example: A raisin placed in concentrated salt solution shrinks further!
2) Water molecules move OUT of the cell by osmosis
3) The cell loses water and shrinks
4) In plant cells: plasmolysis occurs (cytoplasm separates from cell wall)
5) In animal cells: cell shrinks but maintains shape
Example: A raisin placed in concentrated salt solution shrinks further!
Q15. Name the scientist who discovered the nucleus. When was this discovery made?
Model Answer
Answer:
Robert Brown discovered the nucleus in 1831
Context:
• Scottish botanist and scientist
• Observed cells through a microscope
• Found a dark, round structure in the center of plant cells
• Named it "nucleus" from Latin "nux" meaning kernel
• This was a landmark discovery showing cells have internal organization
• Observed cells through a microscope
• Found a dark, round structure in the center of plant cells
• Named it "nucleus" from Latin "nux" meaning kernel
• This was a landmark discovery showing cells have internal organization
Q16. What is the role of DNA in a cell? Where is it located?
Model Answer
Role of DNA:
• Contains genetic information for inheritance
• Codes for proteins that control cell function
• Directs construction and organization of cells
• Passes traits from parents to offspring
• Codes for proteins that control cell function
• Directs construction and organization of cells
• Passes traits from parents to offspring
Location:
• Primary: In the nucleus (as chromosomes)
• Secondary: In mitochondria (their own DNA)
• Secondary: In plastids/chloroplasts (their own DNA)
• In prokaryotes: In the nucleoid region (not membrane-bound)
• Secondary: In mitochondria (their own DNA)
• Secondary: In plastids/chloroplasts (their own DNA)
• In prokaryotes: In the nucleoid region (not membrane-bound)
Q17. What is endocytosis? Name an organism that uses this process.
Model Answer
Definition:
Endocytosis is the process by which a cell engulfs food and other materials from its environment using its flexible plasma membrane.
Process:
1) Plasma membrane extends around the material
2) Membrane pinches off and brings material inside
3) Material is enclosed in a vesicle within the cell
4) The material can then be processed or digested
2) Membrane pinches off and brings material inside
3) Material is enclosed in a vesicle within the cell
4) The material can then be processed or digested
Organism Example:
Amoeba uses endocytosis to consume food particles (bacteria, algae) from its aquatic environment. The flexible cell membrane surrounds and engulfs the prey!
Q18. Explain the difference between prokaryotic and eukaryotic cells in terms of nuclear organization.
Model Answer
Prokaryotic Cells:
• NO membrane-bound nucleus
• DNA floats freely in a region called the nucleoid
• DNA is not organized into chromosomes (mostly a single circular DNA)
• Example: Bacteria and Archaea
• DNA floats freely in a region called the nucleoid
• DNA is not organized into chromosomes (mostly a single circular DNA)
• Example: Bacteria and Archaea
Eukaryotic Cells:
• Has a well-defined nucleus enclosed by a double membrane
• DNA is organized into chromosomes
• Nuclear membrane separates genetic material from cytoplasm
• Example: Animals, plants, fungi, protists
• DNA is organized into chromosomes
• Nuclear membrane separates genetic material from cytoplasm
• Example: Animals, plants, fungi, protists
Significance: This difference is so important that it's used as the primary way to classify all organisms!
Q19. Write two distinguishing features of plant cells that animal cells do not have.
Model Answer
Feature 1: Cell Wall
• Plant cells have a rigid cell wall made of cellulose
• Animal cells have only a plasma membrane
• Provides structural support and prevents bursting in hypotonic solutions
• Animal cells have only a plasma membrane
• Provides structural support and prevents bursting in hypotonic solutions
Feature 2: Chloroplasts
• Plant cells contain chloroplasts for photosynthesis
• Animal cells lack chloroplasts (cannot produce their own food)
• Chloroplasts contain chlorophyll (green pigment)
• Animal cells lack chloroplasts (cannot produce their own food)
• Chloroplasts contain chlorophyll (green pigment)
Bonus Feature: Large central vacuole in plant cells (50-90% of volume) vs. small vacuoles in animal cells
Q20. What is the significance of having a membrane-bound nucleus in eukaryotic cells?
Model Answer
Significance:
1) Protection: Double-layered membrane protects DNA from damage
2) Regulation: Controls what molecules enter and exit the nucleus
3) Organization: Separates transcription (making RNA in nucleus) from translation (making proteins in cytoplasm)
4) Efficiency: Enables better control of gene expression and cellular responses
5) Complexity: Allows for larger, more complex cells and specialized cell types
This is why eukaryotes are generally larger and more complex than prokaryotes!
2) Regulation: Controls what molecules enter and exit the nucleus
3) Organization: Separates transcription (making RNA in nucleus) from translation (making proteins in cytoplasm)
4) Efficiency: Enables better control of gene expression and cellular responses
5) Complexity: Allows for larger, more complex cells and specialized cell types
This is why eukaryotes are generally larger and more complex than prokaryotes!
SECTION C: Short Answer Solutions
3 Marks Each
Q21. Describe the structure and functions of the nucleus. How does it control cellular activities?
Model Answer
Structure:
• Enclosed by a double-layered nuclear membrane with pores
• Contains chromosomes (made of DNA and protein)
• DNA appears as chromatin material in non-dividing cells
• Contains nucleoplasm (fluid inside)
• Contains chromosomes (made of DNA and protein)
• DNA appears as chromatin material in non-dividing cells
• Contains nucleoplasm (fluid inside)
Functions:
1) Directs chemical activities: Determines which proteins are made
2) Controls growth: Regulates cell development
3) Enables reproduction: Contains information for cell division
4) Stores heredity: DNA codes for traits passed to offspring
2) Controls growth: Regulates cell development
3) Enables reproduction: Contains information for cell division
4) Stores heredity: DNA codes for traits passed to offspring
How It Controls Activities:
• DNA in chromosomes codes for specific proteins
• Proteins are enzymes that catalyze all cellular reactions
• By controlling protein production, the nucleus controls ALL cellular processes
• It's like the master control center of the cell!
• Proteins are enzymes that catalyze all cellular reactions
• By controlling protein production, the nucleus controls ALL cellular processes
• It's like the master control center of the cell!
Q22. Explain the relationship between the three core components of a cell: plasma membrane, nucleus, and cytoplasm.
Model Answer
Plasma Membrane (Outer Boundary):
• Outermost boundary of the cell
• Controls what enters and exits the cell
• Separates internal environment from external
• Controls what enters and exits the cell
• Separates internal environment from external
Nucleus (Control Center):
• Located in the center, surrounded by its own membrane
• Directs all activities within the cytoplasm
• Controls what proteins are made
• Directs all activities within the cytoplasm
• Controls what proteins are made
Cytoplasm (Execution Area):
• Fluid matrix between plasma membrane and nucleus
• Contains organelles that carry out nucleus's instructions
• Site where most cellular activities occur
• Contains organelles that carry out nucleus's instructions
• Site where most cellular activities occur
The Relationship: Plasma Membrane → (Cytoplasm) → Nucleus. The nucleus directs, the cytoplasm executes, and the membrane controls exchanges with the environment. Perfect harmony!
Q23. Explain plasmolysis. Why does it occur only in living cells?
Model Answer
What is Plasmolysis:
Plasmolysis is the contraction or shrinkage of the cytoplasm and plasma membrane away from the cell wall when a plant cell is placed in a hypertonic solution.
How It Occurs:
1) Cell placed in concentrated salt/sugar solution
2) External solution is hypertonic (more solute)
3) Water leaves the cell by osmosis
4) Cell loses water and shrinks
5) Cytoplasm separates from rigid cell wall
2) External solution is hypertonic (more solute)
3) Water leaves the cell by osmosis
4) Cell loses water and shrinks
5) Cytoplasm separates from rigid cell wall
Why Only in Living Cells:
• Living cells have a functional, intact plasma membrane
• Dead cells' membranes lose selective permeability
• Dead cells cannot regulate osmosis
• Water freely enters/exits dead cells regardless of solution
• Therefore, cytoplasm cannot separate from cell wall in dead cells
Experiment proof: Plasmolysis in Rhoeo leaf—occurs in fresh leaf but NOT in boiled (dead) leaf!
• Dead cells' membranes lose selective permeability
• Dead cells cannot regulate osmosis
• Water freely enters/exits dead cells regardless of solution
• Therefore, cytoplasm cannot separate from cell wall in dead cells
Experiment proof: Plasmolysis in Rhoeo leaf—occurs in fresh leaf but NOT in boiled (dead) leaf!
Q24. Compare rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) in terms of structure and function.
Model Answer
Rough ER (RER):
Structure:
• Has ribosomes attached to surface
• Appears rough under microscope
• Connected to nuclear membrane
Function:
• Manufactures proteins
• Ribosomes are sites of protein synthesis
• Proteins sent to various cellular locations
• Has ribosomes attached to surface
• Appears rough under microscope
• Connected to nuclear membrane
Function:
• Manufactures proteins
• Ribosomes are sites of protein synthesis
• Proteins sent to various cellular locations
Smooth ER (SER):
Structure:
• NO ribosomes attached
• Appears smooth under microscope
• Often isolated from nuclear membrane
Function:
• Manufactures lipids/fats
• Makes cell membrane components
• Detoxification in liver cells (breaks down drugs and poisons)
• NO ribosomes attached
• Appears smooth under microscope
• Often isolated from nuclear membrane
Function:
• Manufactures lipids/fats
• Makes cell membrane components
• Detoxification in liver cells (breaks down drugs and poisons)
Summary: RER makes proteins (factory), SER makes lipids and detoxifies (workshop)
Q25. Describe the structure and function of mitochondria. Why are they called the powerhouse of the cell? Explain with an example.
Model Answer
Structure:
• Double-membrane organelle
• Outer membrane: smooth and porous
• Inner membrane: deeply folded into cristae (increases surface area)
• Matrix inside with fluid
• Contains own DNA and ribosomes
• Outer membrane: smooth and porous
• Inner membrane: deeply folded into cristae (increases surface area)
• Matrix inside with fluid
• Contains own DNA and ribosomes
Function:
• Releases energy in the form of ATP (Adenosine Triphosphate)
• ATP is the energy currency of the cell
• Produced through cellular respiration
• Energy from ATP powers all life activities
• ATP is the energy currency of the cell
• Produced through cellular respiration
• Energy from ATP powers all life activities
Why "Powerhouse":
Like a power plant produces electricity for a city, mitochondria produce ATP for all cellular functions. Without them, cells cannot function!
Example:
• Muscle cells: Rich in mitochondria (hundreds to thousands)
• Why? Muscles need enormous amounts of ATP for contraction
• More mitochondria = more ATP = stronger muscles
• This is why athletes develop more mitochondria in muscle cells through training!
• Why? Muscles need enormous amounts of ATP for contraction
• More mitochondria = more ATP = stronger muscles
• This is why athletes develop more mitochondria in muscle cells through training!
Q26. Explain the role of the Golgi apparatus in cellular function. How does it differ from the endoplasmic reticulum?
Model Answer
Golgi Apparatus Structure:
• Stack of membrane-bound vesicles called cisterns
• Organized in barrel-like stack
• Connected to ER and cell membrane
• Organized in barrel-like stack
• Connected to ER and cell membrane
Functions (The Post Office Analogy):
1) RECEIVES: Materials from ER
2) MODIFIES: Changes proteins (adds sugars, modifies shape)
3) PACKAGES: Puts materials into vesicles
4) DISPATCHES: Sends vesicles to destinations
2) MODIFIES: Changes proteins (adds sugars, modifies shape)
3) PACKAGES: Puts materials into vesicles
4) DISPATCHES: Sends vesicles to destinations
Difference from ER:
ER:
• MANUFACTURES proteins and lipids
• Acts as factory • Continuous network of tubes
Golgi:
• MODIFIES AND PACKAGES what ER makes
• Acts as post office
• Stacked vesicles
• MANUFACTURES proteins and lipids
• Acts as factory • Continuous network of tubes
Golgi:
• MODIFIES AND PACKAGES what ER makes
• Acts as post office
• Stacked vesicles
Partnership: ER makes it → Golgi modifies and ships it! They work together as a team.
Q27. Explain the concept of osmosis. Describe what happens when a cell is placed in hypotonic, hypertonic, and isotonic solutions.
Model Answer
Definition of Osmosis:
Osmosis is the net diffusion of water molecules through a selectively permeable membrane from an area of higher water concentration (lower solute) to an area of lower water concentration (higher solute).
In Hypotonic Solution:
• Higher water concentration outside (dilute solution)
• Water ENTERS the cell
• Cell SWELLS (becomes turgid in plants)
• In animals: cell may burst (lysis)
• Example: Raisin in pure water swells up
• Water ENTERS the cell
• Cell SWELLS (becomes turgid in plants)
• In animals: cell may burst (lysis)
• Example: Raisin in pure water swells up
In Hypertonic Solution:
• Lower water concentration outside (concentrated solution)
• Water LEAVES the cell
• Cell SHRINKS (wilts in plants)
• In plants: plasmolysis occurs
• Example: Raisin in salt solution shrinks further
• Water LEAVES the cell
• Cell SHRINKS (wilts in plants)
• In plants: plasmolysis occurs
• Example: Raisin in salt solution shrinks further
In Isotonic Solution:
• Same water concentration as cell (balanced)
• NO NET movement of water
• Cell MAINTAINS NORMAL SIZE
• Water enters and exits equally
• Example: Blood cells in normal saline stay unchanged
• NO NET movement of water
• Cell MAINTAINS NORMAL SIZE
• Water enters and exits equally
• Example: Blood cells in normal saline stay unchanged
Q28. Compare prokaryotic and eukaryotic cells. Discuss the advantages of having membrane-bound organelles in eukaryotic cells.
Model Answer
Comparison:
Prokaryotic Cells:
• Size: 1-10 micrometers
• No nucleus
• DNA in nucleoid region
• No membrane-bound organelles
• Examples: Bacteria
Eukaryotic Cells:
• Size: 5-100 micrometers
• Has defined nucleus
• DNA in chromosomes
• Many membrane-bound organelles
• Examples: Animals, plants, fungi
• Size: 1-10 micrometers
• No nucleus
• DNA in nucleoid region
• No membrane-bound organelles
• Examples: Bacteria
Eukaryotic Cells:
• Size: 5-100 micrometers
• Has defined nucleus
• DNA in chromosomes
• Many membrane-bound organelles
• Examples: Animals, plants, fungi
Advantages of Membrane-Bound Organelles:
1) Compartmentalization: Different activities in different organelles prevent interference
2) Efficiency: Concentrates enzymes and substrates for faster reactions
3) Regulation: Each organelle independently controlled for fine-tuned responses
4) Complexity: Allows large, complex cells and multicellular organisms
5) Protection: Hazardous reactions contained (lysosomes with digestive enzymes)
2) Efficiency: Concentrates enzymes and substrates for faster reactions
3) Regulation: Each organelle independently controlled for fine-tuned responses
4) Complexity: Allows large, complex cells and multicellular organisms
5) Protection: Hazardous reactions contained (lysosomes with digestive enzymes)
Conclusion: Membrane-bound organelles enable eukaryotic cells to be larger, more complex, and more efficient, supporting the incredible diversity of life!
Q29. Describe the process of mitosis. What is its biological significance?
Model Answer
What is Mitosis:
Mitosis is the process of cell division that produces two identical daughter cells from one mother cell.
Key Characteristics:
• One division produces TWO cells
• Daughter cells are IDENTICAL
• Chromosome number SAME as mother cell
• Occurs in somatic (body) cells
• Used for growth and repair
• Daughter cells are IDENTICAL
• Chromosome number SAME as mother cell
• Occurs in somatic (body) cells
• Used for growth and repair
Biological Significance:
1) Growth: Allows organisms to grow larger
2) Repair: Replaces damaged or dead cells
3) Maintenance: Maintains body size and function
4) Genetic Continuity: Ensures genetic information passes to daughter cells
Example: When you get a cut, mitosis creates new skin cells to heal the wound!
2) Repair: Replaces damaged or dead cells
3) Maintenance: Maintains body size and function
4) Genetic Continuity: Ensures genetic information passes to daughter cells
Example: When you get a cut, mitosis creates new skin cells to heal the wound!
Q30. Compare mitosis and meiosis. What is the biological significance of each?
Model Answer
MITOSIS:
• Divisions: ONE
• Daughter cells: TWO
• Chromosome number: SAME (2n → 2n)
• Genetic identity: IDENTICAL
• Purpose: Growth, repair, maintenance
• Location: Somatic (body) cells
• Daughter cells: TWO
• Chromosome number: SAME (2n → 2n)
• Genetic identity: IDENTICAL
• Purpose: Growth, repair, maintenance
• Location: Somatic (body) cells
MEIOSIS:
• Divisions: TWO consecutive
• Daughter cells: FOUR
• Chromosome number: HALF (2n → n)
• Genetic identity: DIFFERENT/NON-IDENTICAL
• Purpose: Produce gametes (sex cells)
• Location: Reproductive organs ONLY
• Daughter cells: FOUR
• Chromosome number: HALF (2n → n)
• Genetic identity: DIFFERENT/NON-IDENTICAL
• Purpose: Produce gametes (sex cells)
• Location: Reproductive organs ONLY
Comparison Table:
FEATURE | MITOSIS | MEIOSIS
Divisions | 1 | 2
Daughter Cells | 2 | 4
Chromosome # | 2n | n
Genetic Identity | Identical | Different
Purpose | Growth/Repair | Reproduction
Occurs in | All cells | Sex cells only
Divisions | 1 | 2
Daughter Cells | 2 | 4
Chromosome # | 2n | n
Genetic Identity | Identical | Different
Purpose | Growth/Repair | Reproduction
Occurs in | All cells | Sex cells only
Biological Significance:
Mitosis Significance:
• Allows growth and development
• Repairs tissues and maintains body
• Ensures genetic continuity
Meiosis Significance:
• Essential for sexual reproduction
• Produces gametes with half chromosomes
• When gametes fuse: normal chromosome number restored
• Creates genetic VARIATION (evolution depends on this!)
• Allows population diversity and adaptation
• Allows growth and development
• Repairs tissues and maintains body
• Ensures genetic continuity
Meiosis Significance:
• Essential for sexual reproduction
• Produces gametes with half chromosomes
• When gametes fuse: normal chromosome number restored
• Creates genetic VARIATION (evolution depends on this!)
• Allows population diversity and adaptation
📊 Question Paper Marks Distribution
Section A (MCQ) - 1 mark each × 10
10
Section B (Very Short Answer) - 2 marks each × 10
20
Section C (Short Answer) - 3 marks each × 10
30
TOTAL MARKS
60
📋 Question Coverage Summary
Section A: Multiple Choice (10 questions)
• Cell discovery & history (Q1)
• Membranes (Q2)
• Organelles (Q3, Q6, Q9)
• Osmosis & diffusion (Q4, Q5)
• Cell types (Q8)
• Cell division (Q10)
Section B: VSA (10 questions)
• Cell definition & concepts (Q11)
• Plasma membrane & functions (Q12)
• Diffusion vs Osmosis (Q13, Q14)
• Historical discoveries (Q15)
• Genetic material & locations (Q16)
• Cell processes (Q17)
• Cell types & structures (Q18, Q19, Q20)
Section C: Short Answer (10 questions)
• Nucleus structure & function (Q21)
• Cell components relationship (Q22)
• Plasmolysis (Q23)
• ER types (Q24)
• Mitochondria (Q25)
• Golgi apparatus (Q26)
• Osmosis detailed (Q27)
• Cell types & organelle advantages (Q28)
• Mitosis & Meiosis (Q29, Q30)
• Cell discovery & history (Q1)
• Membranes (Q2)
• Organelles (Q3, Q6, Q9)
• Osmosis & diffusion (Q4, Q5)
• Cell types (Q8)
• Cell division (Q10)
Section B: VSA (10 questions)
• Cell definition & concepts (Q11)
• Plasma membrane & functions (Q12)
• Diffusion vs Osmosis (Q13, Q14)
• Historical discoveries (Q15)
• Genetic material & locations (Q16)
• Cell processes (Q17)
• Cell types & structures (Q18, Q19, Q20)
Section C: Short Answer (10 questions)
• Nucleus structure & function (Q21)
• Cell components relationship (Q22)
• Plasmolysis (Q23)
• ER types (Q24)
• Mitochondria (Q25)
• Golgi apparatus (Q26)
• Osmosis detailed (Q27)
• Cell types & organelle advantages (Q28)
• Mitosis & Meiosis (Q29, Q30)
