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Political Science NCERT Solutions Class 9 Science Chapter 5 – The Fundamental Unit of Life
Class 9 Science
Last Updated: 15 April 2026
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हिंदी में (Hindi)
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Important Points
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Practice MCQ Questions (30 questions)
Q1. Who discovered the cell?
✓ Correct Answer: A
Q2. What is the basic unit of life?
✓ Correct Answer: B
Q3. What is the function of the plasma membrane?
✓ Correct Answer: B
Q4. Which of the following is not a unicellular organism?
✓ Correct Answer: C
Q5. What is the function of mitochondria?
✓ Correct Answer: B
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Frequently Asked Questions (FAQ)
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Tough Words (Glossary)
Cork
Meaning: Outer bark of a tree used in microscopy samples
अर्थ: पेड़ की छाल का बाहरी भाग (कॉर्क)
"Hooke observed cells in a thin slice of cork."
Microscope
Meaning: Instrument that magnifies small objects
अर्थ: सूक्ष्मदर्शी यंत्र
"We used a microscope to see onion cells."
Cell
Meaning: Basic structural and functional unit of life
अर्थ: जीवन की मूल इकाई (कोशिका)
"All living organisms are made of cells."
Epidermis
Meaning: Outer skin layer of an organ like onion peel
अर्थ: बाहरी त्वचा/एपिडर्मिस
"Peel the epidermis of onion for the slide."
Glass slide
Meaning: Flat piece of glass for mounting samples
अर्थ: नमूना रखने की काँच पट्टी (स्लाइड)
"Put the peel on a glass slide."
Safranin
Meaning: Red biological stain for cells
अर्थ: कोशिकीय लाल रंग (सैफरैनिन)
"Add safranin to stain the cells."
Cover slip
Meaning: Small thin glass sheet placed over sample
अर्थ: नमूने के ऊपर रखने की पतली काँच पट्टी (कवर स्लिप)
"Avoid air bubbles under the cover slip."
Compound microscope
Meaning: Microscope with multiple lenses for high magnification
अर्थ: एकाधिक लेंस वाला उच्च आवर्धन सूक्ष्मदर्शी
"Observe under a compound microscope."
Organelles
Meaning: Specialised structures within a cell
अर्थ: कोशिका के विशेष अंग (ऑर्गेनेल्स)
"Organelles perform specific functions."
Plasma membrane
Meaning: Outer boundary of the cell
अर्थ: कोशिका झिल्ली (प्लाज़्मा मेम्ब्रेन)
"The plasma membrane controls entry and exit."
Selectively permeable
Meaning: Allows only certain substances to pass
अर्थ: विचयनीय अभेद्य/चयनात्मक पारगम्य
"Cell membrane is selectively permeable."
Diffusion
Meaning: Movement from high to low concentration
अर्थ: उच्च से निम्न सांद्रता की दिशा में संचरण (विसरण)
"Oxygen enters cells by diffusion."
Osmosis
Meaning: Diffusion of water through a selectively permeable membrane
अर्थ: चयनात्मक झिल्ली के पार पानी का विसरण (परासरण)
"Plant roots absorb water by osmosis."
Hypotonic solution
Meaning: Solution with higher water (lower solute) than the cell
अर्थ: कोशिका की तुलना में अधिक जल वाला विलयन (अधिजलीय)
"Cells swell in a hypotonic solution."
Isotonic solution
Meaning: Solution with equal water concentration as the cell
अर्थ: कोशिका के समान जल सांद्रता वाला विलयन (समदलीय)
"Cells keep their size in isotonic solution."
Hypertonic solution
Meaning: Solution with lower water (higher solute) than the cell
अर्थ: कोशिका से कम जल वाला विलयन (अल्पजलीय)
"Cells shrink in a hypertonic solution."
Endocytosis
Meaning: Intake of material by engulfing with membrane
अर्थ: झिल्ली द्वारा पदार्थ को घेरकर अंदर लेना (एंडोसाइटोसिस)
"Amoeba feeds by endocytosis."
Cell wall
Meaning: Rigid outer layer in plant cells
अर्थ: पौध कोशिकाओं की कठोर बाहरी भित्ति
"Plant cells have a cellulose cell wall."
Cellulose
Meaning: Complex carbohydrate forming plant cell wall
अर्थ: जटिल कार्बोहाइड्रेट (सेल्यूलोज)
"Cellulose gives plants structural strength."
Plasmolysis
Meaning: Shrinkage of cell contents away from cell wall
अर्थ: कोशिका द्रव्य का भित्ति से सिमटना (प्लाज़्मोलाइसिस)
"Salt causes plasmolysis in plant cells."
Nucleus
Meaning: Control center of the cell containing DNA
अर्थ: कोशिका का नियंत्रण केंद्र (नाभिक)
"The nucleus directs cell activities."
Nuclear membrane
Meaning: Double-layered covering of nucleus
अर्थ: नाभिकीय झिल्ली
"The nuclear membrane has pores."
Chromosomes
Meaning: Thread-like structures carrying genetic information
अर्थ: आनुवंशिक सूचना वहन करने वाले धागेनुमा कण (गुणसूत्र)
"Chromosomes become visible during division."
Inheritance
Meaning: Passing of traits from parents to offspring
अर्थ: लक्षणों का पीढ़ियों में संचरण (वंशागति)
"DNA controls inheritance of traits."
DNA
Meaning: Deoxyribonucleic acid carrying genetic code
अर्थ: डीऑक्सीराइबोन्यूक्लिक अम्ल (डीएनए)
"DNA stores genetic information."
Genes
Meaning: Functional segments of DNA
अर्थ: डीएनए के कार्यशील खंड (जीन्स)
"Genes determine eye color."
Chromatin
Meaning: Entangled mass of DNA and proteins in non-dividing cells
अर्थ: गैर-विभाजित कोशिका में डीएनए-प्रोटीन का जाल (क्रोमैटिन)
"Chromatin condenses into chromosomes."
Nucleoid
Meaning: Poorly defined nuclear region in prokaryotes
अर्थ: प्रोकैरियोट्स का अविकसित नाभिकीय क्षेत्र (न्यूक्लॉयड)
"Bacteria have a nucleoid instead of a nucleus."
Prokaryotes
Meaning: Cells without a true nucleus or membrane-bound organelles
अर्थ: सत्य नाभिक/झिल्ली-बद्ध अंगों के बिना कोशिकाएँ (प्रोकैरियोट्स)
"Bacteria are prokaryotes."
Eukaryotes
Meaning: Cells with a true nucleus and organelles
अर्थ: सत्य नाभिक व झिल्ली-बद्ध अंगों वाली कोशिकाएँ (यूकैरियोट्स)
"Plants and animals are eukaryotes."
Cytoplasm
Meaning: Fluid content inside the cell membrane
अर्थ: कोशिका झिल्ली के भीतर का द्रव (सायटोoplasm/द्रव्य)
"Organelles float in the cytoplasm."
Endoplasmic reticulum (ER)
Meaning: Network of membrane-bound tubes and sheets
अर्थ: झिल्लीदार नलिकाओं/पर्तों का जाल (एंडोप्लाज़्मिक रेटिकुलम)
"ER transports proteins and lipids."
Rough ER (RER)
Meaning: ER studded with ribosomes; makes proteins
अर्थ: राइबोसोम लगे ईआर; प्रोटीन बनाता है
"RER synthesises proteins for export."
Smooth ER (SER)
Meaning: ER without ribosomes; makes lipids, detoxifies
अर्थ: राइबोसोम रहित ईआर; लिपिड बनाता, विषहरण करता है
"SER helps detoxify drugs in liver cells."
Ribosomes
Meaning: Sites of protein synthesis
अर्थ: प्रोटीन संश्लेषण के स्थल (राइबोसोम)
"Ribosomes attach to RER."
Membrane biogenesis
Meaning: Formation of cell membrane from lipids/proteins
अर्थ: कोशिका झिल्ली का निर्माण (मेम्ब्रेन बायोजेनेसिस)
"ER contributes to membrane biogenesis."
Detoxification
Meaning: Removal or neutralisation of toxins
अर्थ: विषहरण/विषाक्तता का निवारण
"SER performs detoxification in vertebrates."
Golgi apparatus
Meaning: Stack of membrane-bound sacs for packaging
अर्थ: झिल्लीदार थैलों का ढेर (गोल्जी तंत्र)
"Golgi packages proteins into vesicles."
Lysosomes
Meaning: Enzyme-filled sacs for intracellular digestion
अर्थ: एंजाइम युक्त अपघटक थैले (लाइसोज़ोम)
"Lysosomes digest worn-out organelles."
Mitochondria
Meaning: Powerhouses of the cell producing ATP
अर्थ: कोशिका के विद्युतगृह (माइटोकॉन्ड्रिया)
"Mitochondria release energy in ATP."
ATP
Meaning: Adenosine triphosphate, energy currency of cell
अर्थ: एडेनोसिन ट्राइफॉस्फेट, ऊर्जा मुद्रा
"Cells use ATP for mechanical work."
Plastids
Meaning: Plant cell organelles like chloroplasts and leucoplasts
अर्थ: पौध कोशिकाओं के अंग (प्लास्टिड्स)
"Plastids are absent in animal cells."
Chloroplasts
Meaning: Plastids containing chlorophyll for photosynthesis
अर्थ: हरितलवक; प्रकाश-संश्लेषण के लिए क्लोरोफिल युक्त
"Chloroplasts capture sunlight for food."
Stroma
Meaning: Fluid matrix inside chloroplasts
अर्थ: क्लोरोप्लास्ट का द्रव्य भाग (स्ट्रोमा)
"Enzymes of photosynthesis are in the stroma."
Chromoplasts
Meaning: Coloured plastids other than chloroplasts
अर्थ: रँगे हुए प्लास्टिड (क्रोमोप्लास्ट)
"Chromoplasts give colour to petals."
Leucoplasts
Meaning: Colourless plastids for storage
अर्थ: रंगहीन भंडारण प्लास्टिड (ल्यूकोप्लास्ट)
"Leucoplasts store starch and oils."
Vacuoles
Meaning: Storage sacs within cells
अर्थ: कोशिका के भंडारण थैले (वैक्योल)
"Plant cells have large central vacuoles."
Turgidity
Meaning: Swollen, firm state due to water uptake
अर्थ: जल ग्रहण से कड़ा/फूला होना (टर्जिडिटी)
"Vacuoles help maintain turgidity."
Mitosis
Meaning: Cell division producing two identical daughter cells
अर्थ: ऐसी कोशिका विभाजन जिसमें दो समान पुत्री कोशिकाएँ बनती हैं (माइटोसिस)
"Mitosis helps in growth and repair."
Meiosis
Meaning: Cell division producing four cells with half chromosomes
अर्थ: ऐसा विभाजन जिसमें आधे गुणसूत्र वाली चार कोशिकाएँ बनती हैं (मीओसिस)
"Meiosis forms gametes for reproduction."