Class 11 Biology · Chapter 14
Short answer:
Class 11 Biology Chapter 14 "Breathing and Exchange of Gases" Unit V (Human Physiology) ka pehla chapter hai — human respiratory system, mechanism of breathing (Boyle's law se), lung volumes/capacities, O2 aur CO2 ka transport (Bohr effect, Haldane effect, chloride shift), aur regulation of respiration yahan cover hote hain. NCERT ke end-of-chapter exercise mein 11 questions hain — neeche step-by-step solutions diye hain, saath mein important questions with answers, formula table, common mistakes aur likely exam-pattern questions.
Jaise "Chapter 1 poore Class 10 Chemistry ki neev hai" — waise hi Chapter 14 poore Human Physiology unit (Chapters 14–19) ki neev hai. Iske baad Body Fluids and Circulation, Excretory Products, Neural Control jaise chapters mein "diffusion", "partial pressure gradient" aur "Hb ka role" baar-baar wapas aata hai — jo yahin se seekhte ho.
Ye chapter 2026-27 session ke rationalised NCERT syllabus ka hi part hai — is saal koi naya NCF-aligned textbook nahi aa raha (woh 2027-28 tak defer hua hai), toh yahi purana rationalised 19-chapter structure padhoge. Rationalisation mein "Transport in Plants", "Mineral Nutrition" aur "Digestion and Absorption" jaise poore chapter hata diye gaye the — lekin "Breathing and Exchange of Gases" un exclusions mein nahi hai, ye poora chapter as-is padhaya jaata hai.
Sabse common confusion: naam sunke students isko Chapter 12 "Respiration in Plants" (cellular respiration — glycolysis, Krebs cycle, ETC) se mix kar dete hain. Dono alag hain — Chapter 14 breathing mechanics aur gas transport ke baare mein hai, cellular/biochemical respiration ke baare mein nahi (agar wahi chapter chahiye tha, dekho class 11 biology respiration in plants ncert solutions).
Poore class 11 biology syllabus 2026-27 ncert ka revision plan bana rahe ho toh Chapter 1 (the living world notes), Chapter 8 (cell the unit of life important questions + notes pdf), Chapter 9 (biomolecules important questions), Chapter 11 (photosynthesis in higher plants important questions), Chapter 16 (excretory products and their elimination ncert solutions) aur Chapter 18 (neural control and coordination notes pdf) ke saath ye chapter 14 bhi class 11 biology ncert solutions chapter wise pdf series ka hissa maano.
Chapter 14 Summary — 5 Minute Revision
Chapter 14 char bade blocks mein bata hai:
- Respiratory organs and tracts: nostrils → pharynx → larynx → trachea → bronchi → bronchioles → alveoli. Alveoli hi gas exchange ki asli site hain (thin squamous epithelium + rich capillary network).
- Mechanism of breathing: Boyle's law (P ∝ 1/V) par based — diaphragm aur intercostal muscles thoracic volume badhate/ghataate hain, jisse pressure gradient banta hai aur air andar-bahar move karti hai. Lung volumes (TV, IRV, ERV, RV) aur capacities (IC, EC, FRC, VC, TLC) yahin define hote hain.
- Exchange and transport of gases: O2 aur CO2 partial-pressure gradient ke through simple diffusion se move karte hain. O2 mostly oxyhaemoglobin (~97%) ke roop mein carry hota hai, CO2 mostly bicarbonate (~70%) ke roop mein (chloride shift ke through), baaki carbamino-Hb aur dissolved form mein.
- Regulation and disorders: medulla ka respiratory rhythm centre + pons ka pneumotaxic centre + CO2/H+ sensitive chemoreceptors respiration control karte hain (O2 se zyada CO2 sensitive hote hain). Disorders: asthma, emphysema, occupational respiratory disorders (silicosis).
In-Text Questions — Solutions
NCERT ke is chapter mein page-by-page boxed 'in-text' questions hain kya, jaise Chemistry books mein hote hain?
Nahi — Biology ke is chapter mein Chemistry jaisi numbered in-text question boxes nahi hain; poora chapter continuous text hai aur saare official questions sirf chapter ke end wale Exercise section mein diye gaye hain (11 questions — neeche exercise section dekho). Neeche 3 quick concept-check questions diye hain jo chapter padhte waqt khud se poochne chahiye, taaki flow clear rahe.
Trachea ke ring-shaped cartilage kis kaam ke hain — inhe dhyan mein rakhna kyu zaroori hai?
Cartilaginous rings trachea ko collapse hone se rokte hain jab andar pressure change hoti hai, isliye air ka smooth aur continuous flow bana rehta hai — ye ek high-yield 1-mark point hai jo diagram-labelling questions mein poocha jaata hai.
Alveoli mein hi diffusion kyu hoti hai, bronchi/bronchioles mein kyu nahi?
Kyunki alveoli ki wall bahut thin (single-layer squamous epithelium) hoti hai aur unke around dense capillary network hota hai — dono milke diffusion ke liye zaroori short distance + bada surface area dete hain. Bronchi/bronchioles sirf conducting passage hain, unki wall thick hoti hai isliye wahan exchange practically nahi hota (yehi Exercise Q3 ka core logic bhi hai).
Poore Class 11 Biology ke handwritten colour notes
IITian & district toppers ke banaye short notes — revision-ready, diagram ke saath. Board se pehle poora syllabus 3 din me revise.
Exercise Questions — Solutions (Q1–Q11)
Q1. Define vital capacity. What is its significance?
Definition: Vital Capacity (VC) woh maximum air hai jo ek forced (sabse gehri) inspiration ke baad forcefully expire ki ja sakti hai.
VC = ERV + TV + IRV (≈ 3400–4800 mL)
Significance: VC breathing ki 'depth' batati hai. Athletes, swimmers aur mountaineers mein zyada hoti hai; clinically restrictive lung diseases (jaise fibrosis) mein VC kam ho jaati hai, isliye ye ek diagnostic/fitness indicator hai.
Q2. State the volume of air remaining in the lungs after a normal breathing.
Normal (tidal) expiration ke baad jo air lungs mein reh jaati hai wo Functional Residual Capacity (FRC) kehlaati hai.
FRC = ERV + RV ≈ 1100 mL + 1200 mL = 2300 mL (approx.)
Reasoning: normal expiration mein sirf Tidal Volume (~500 mL) bahar jaata hai; ERV aur RV lungs ke andar hi rehte hain, isliye unka sum hi bacha hua air batata hai.
Q3. Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?
Do reasons step-by-step:
1. Structural fitness: Alveoli ki wall extremely thin (single-layered squamous epithelium) hoti hai aur unke around bahut dense capillary network hota hai — isse diffusion path chota aur surface area bahut bada (~70–80 m²) mil jaata hai.
2. Baaki tracts sirf conducting hote hain: Trachea, bronchi aur bronchioles ki walls moti hoti hain aur inke around exchange ke liye zaroori capillary bed nahi hota — inka role sirf air ko carry/filter/warm karna hai, gas exchange karna nahi.
Isliye actual O2–CO2 exchange sirf alveolar region mein hi practically possible hai.
Q4. What are the major transport mechanisms for CO2? Explain.
CO2 teen forms mein carry hota hai:
1. Dissolved form (~7%): seedha plasma mein dissolve hokar.
2. Carbamino-haemoglobin (~20–25%): Hb ke globin part se bindhkar (RBC mein).
3. Bicarbonate form (~70%, sabse major): tissues mein CO2 RBC mein diffuse hokar water ke saath carbonic anhydrase enzyme ki madad se react karta hai:
CO2 + H2O → H2CO3 → H+ + HCO3-
HCO3- plasma mein diffuse ho jaata hai (chloride shift ke through), lungs mein pahunchkar poori reaction reverse hoti hai aur CO2 release hokar exhale ho jaata hai.
Q5. What will be the pO2 and pCO2 in the atmospheric air compared to those in the alveolar air? (i) pO2 lesser, pCO2 higher (ii) pO2 higher, pCO2 lesser (iii) pO2 higher, pCO2 higher (iv) pO2 lesser, pCO2 lesser
Answer: option (ii) — pO2 higher, pCO2 lesser.
Reasoning with values: Atmospheric air mein pO2 ≈ 159 mmHg aur pCO2 ≈ 0.3 mmHg hota hai. Alveolar air mein (jahan gas exchange ho chuka hai, kuch O2 blood mein ja chuka aur CO2 blood se aa chuka) pO2 ≈ 104 mmHg aur pCO2 ≈ 40 mmHg hota hai. Isliye atmospheric air ka pO2 alveolar se zyada (higher) hai, aur pCO2 alveolar se kam (lesser) hai.
Q6. Explain the process of inspiration under normal conditions.
Step-by-step (Boyle's law: P ∝ 1/V):
1. Diaphragm contract hota hai → dome-shape flatten hokar neeche move karta hai.
2. External intercostal muscles contract hote hain → ribs aur sternum upar-bahar uthte hain.
3. Dono milke thoracic (pulmonary) cavity ka volume badha dete hain.
4. Volume badhne se intra-pulmonary pressure atmospheric pressure se kam ho jaata hai.
5. Air high-pressure region (atmosphere) se low-pressure region (lungs) mein flow karti hai — ye hi inspiration hai.
Q7. How is respiration regulated?
Respiration ek neural mechanism se regulate hoti hai:
1. Respiratory Rhythm Centre (medulla oblongata) — normal breathing rhythm maintain karta hai.
2. Pneumotaxic Centre (pons) — rhythm centre ke signals ko moderate karke inspiration ki duration/rate control karta hai.
3. Chemosensitive area (medulla ke paas) — CO2 aur H+ concentration ke prati bahut sensitive hai (O2 se zyada), inme increase hone par rhythm centre ko stimulate karke breathing rate badha deta hai.
4. Aorta aur carotid artery ke receptors bhi O2/CO2 changes detect karke signal bhejte hain.
Q8. What is the effect of pCO2 on oxygen transport?
pCO2 badhne (aur pH kam hone) se haemoglobin ki O2 ke liye affinity kam ho jaati hai — isse oxyhaemoglobin O2 ko jaldi release kar deta hai. Ise Bohr effect kehte hain, aur oxygen dissociation curve right-shift ho jaata hai. Ye tissues mein useful hai — jahan CO2 zyada banta hai (high metabolic activity), wahan O2 jaldi unload ho jaata hai.
Q9. What happens to the respiratory process in a man going up a hill?
Height badhne ke saath atmospheric pressure aur isliye pO2 kam ho jaata hai — body ko sufficient O2 nahi milta (hypoxia). Isse initial symptoms ho sakte hain (thakaan, saans phoolna, nausea) — isse 'altitude sickness' kehte hain. Body dheere-dheere acclimatize karta hai: breathing rate badhti hai (hyperventilation), heart rate badhta hai, aur RBC production (erythropoietin ke through) badh jaata hai taaki O2 carrying capacity compensate ho sake.
Q10. What is Chloride shift? Explain.
Tissues mein: CO2 RBC mein diffuse hokar carbonic anhydrase ki madad se H2CO3 banata hai, jo H+ aur HCO3- mein dissociate hota hai. HCO3- concentration gradient ke through RBC se plasma mein diffuse ho jaata hai. Electrochemical (ionic) balance maintain karne ke liye, iske badle Cl- ions plasma se RBC mein andar move karte hain — is HCO3--out / Cl--in exchange ko chloride shift (Hamburger shift) kehte hain. Lungs mein reaction exactly reverse hoti hai — HCO3- wapas RBC mein aata hai, Cl- bahar jaata hai, aur CO2 regenerate hokar exhale ho jaata hai.
Q11. Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
Definition: Jab haemoglobin ki percentage saturation with O2 ko pO2 ke against plot kiya jaata hai, toh jo S-shaped (sigmoid) curve milta hai use Oxygen Dissociation Curve kehte hain. Ye pCO2, H+ concentration aur temperature jaise factors ka O2-Hb binding par effect study karne ke liye use hota hai.
Sigmoidal shape ka reason: Haemoglobin ke 4 haem units hote hain aur O2 binding cooperative hoti hai — pehla O2 molecule bindhne se Hb ki shape thodi change hoti hai jisse baaki units ki O2 ke liye affinity badh jaati hai (positive cooperativity). Isi wajah se curve pehle slow, phir steeply rise karta hai, aur high pO2 par Hb fully saturate hote hi plateau ho jaata hai — yehi S-shape banata hai.
Important Equations — Ek Nazar Me
| Term | Formula / Value | Meaning |
|---|---|---|
| Tidal Volume (TV) | ≈ 500 mL | Normal breath mein aane/jaane wali air |
| Inspiratory Reserve Volume (IRV) | ≈ 2500–3000 mL | Normal inspiration ke baad extra force se li ja sakti air |
| Expiratory Reserve Volume (ERV) | ≈ 1000–1100 mL | Normal expiration ke baad extra force se nikali ja sakti air |
| Residual Volume (RV) | ≈ 1100–1200 mL | Forced expiration ke baad bhi lungs mein bachi air |
| Inspiratory Capacity (IC) | IC = TV + IRV | Max air jo normal expiration ke baad li ja sakti hai |
| Expiratory Capacity (EC) | EC = TV + ERV | Max air jo normal inspiration ke baad nikali ja sakti hai |
| Functional Residual Capacity (FRC) | FRC = ERV + RV | Normal expiration ke baad lungs mein bachi total air |
| Vital Capacity (VC) | VC = ERV + TV + IRV | Max forced expiration after max forced inspiration (RV shamil nahi) |
| Total Lung Capacity (TLC) | TLC = VC + RV | Lungs ki total capacity ≈ 4500–5800 mL |
| pO2 / pCO2 — atmospheric air | pO2 ≈ 159 mmHg; pCO2 ≈ 0.3 mmHg | Outside air ki partial pressures |
| pO2 / pCO2 — alveolar air | pO2 ≈ 104 mmHg; pCO2 ≈ 40 mmHg | Alveoli ke andar gas mixture |
| Chloride shift reaction | CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3- | Carbonic anhydrase-catalysed; HCO3- out / Cl- in exchange (RBC) |
| O2 transport share | ~97% oxyhaemoglobin + ~3% dissolved in plasma | Bulk O2 Hb ke saath bound reh kar carry hota hai |
| CO2 transport share | ~70% bicarbonate + ~20–25% carbamino-Hb + ~7% dissolved | Bicarbonate route sabse major hai |
| Bohr effect | ↑pCO2, ↓pH → ↓ O2 affinity of Hb | Tissues mein O2 unloading ko facilitate karta hai |
| Haldane effect | ↑pO2 → ↓ CO2 carrying capacity of blood | Lungs mein CO2 unloading ko facilitate karta hai |
↔ Table ko side me swipe karein
Common Mistakes — Yahan Marks Kat te Hain
- Breathing vs Respiration mix-up: Breathing sirf mechanical process (air ka in-out movement) hai; Respiration ek biochemical process hai jisme O2 use hokar cellular level par energy (ATP) banti hai. Exam mein dono ko same samajhna galat answer deta hai.
- Chapter 12 (Respiration in Plants) se confuse karna: is chapter (14) mein glycolysis/Krebs cycle/ETC nahi aata — wo cellular respiration alag chapter mein hai. Chapter 14 sirf breathing mechanics + gas transport tak limited hai.
- Boyle's law direction ulti likhna: students aksar likh dete hain ki 'pressure badhne se volume badhta hai' — sahi relation ulta hai: volume badhne se pressure ghatta hai (P ∝ 1/V), tabhi air andar aati hai.
- Vital Capacity mein RV include kar dena: VC = ERV+TV+IRV hai, Residual Volume (RV) isme shamil NAHI hota — RV sirf TLC ke formula mein aata hai (TLC = VC + RV). Ye galti bahut common hai.
- Bohr effect aur Haldane effect ko ulat-pulat likhna: Bohr effect = CO2/H+ ka O2 binding par effect; Haldane effect = O2 ka CO2 carrying capacity par effect. Dono naam swap karna ek bahut common written-exam mistake hai.
- Chloride shift ki direction bhool jaana: tissues mein HCO3- RBC se BAHAR jaata hai aur Cl- ANDAR aata hai (lungs mein exactly reverse) — students aksar sirf 'chloride shift hota hai' likh dete hain bina direction specify kiye, jisse pura marks nahi milta.
Board-Style Important Questions
- Vital capacity ki definition dijiye.
- Oxygen dissociation curve sigmoidal (S-shaped) kyu hoti hai — ek reason dijiye.
- Chloride shift kya hai? Iski direction tissues aur lungs dono jagah samjhaiye.
- Human respiratory system ka neat labelled diagram banaiye aur alveoli mein gas exchange ki prakriya samjhaiye.
- Normal breathing mein inspiration aur expiration ki mechanism Boyle's law ke through samjhaiye.
- O2 aur CO2 ke transport mechanisms detail mein likhiye, Bohr effect aur Haldane effect ka ullekh karte hue.
Aksar Poochhe Jaane Wale Sawaal
Breathing aur Respiration mein kya farak hai?
Breathing ek purely mechanical/physical process hai — lungs mein air ka in-out movement (inspiration + expiration). Respiration ek biochemical process hai jisme cell ke andar O2 use hokar glucose se ATP (energy) banti hai aur CO2 byproduct banta hai. Chapter 14 breathing/gas-transport tak focus karta hai; cellular respiration Chapter 12 (Respiration in Plants) mein cover hoti hai.
Class 11 Biology chapter wise NCERT solutions ka PDF kahan milega?
Iss series mein har chapter ke solutions alag-alag mil sakte hain — jaise ye Chapter 14, waise Chapter 1 (The Living World), Chapter 3-4 (Plant/Animal Kingdom), Chapter 8 (Cell: The Unit of Life), Chapter 9 (Biomolecules), Chapter 11 (Photosynthesis in Higher Plants), Chapter 16 (Excretory Products) aur Chapter 18 (Neural Control and Coordination) ke liye. In sabko milakar hi class 11 biology ncert solutions chapter wise pdf ka poora set banta hai — hamari site par yehi chapter-by-chapter structure follow hoti hai.
Chapter 12 'Respiration in Plants' aur Chapter 14 'Breathing and Exchange of Gases' same hai kya?
Nahi, dono bilkul alag hain. Chapter 12 cellular/biochemical respiration (glycolysis, Krebs cycle, ETC, fermentation) cover karta hai jo plants aur saare organisms mein hota hai. Chapter 14 sirf human respiratory system, breathing mechanics aur blood mein gas transport (O2/CO2) tak limited hai. Naam similar lagne ki wajah se ye ek common confusion hai.
NEET ke liye Chapter 14 kitna important hai?
NCERT ya CBSE koi official chapter-wise weightage publish nahi karte, isliye exact percentage batana galat hoga. Itna zaroor kaha ja sakta hai ki ye poore Human Physiology unit (Chapters 14-19) ka pehla chapter hai aur is unit ke concepts (partial pressure, diffusion, transport mechanisms) aage ke chapters mein bhi repeat hote hain — isliye conceptually strong hona zaroori hai, sirf is chapter ke marks ke liye nahi.
Class 11 Biology 2026-27 syllabus se kya-kya delete hua hai?
2023-24 rationalisation mein Class 11 Biology se poore chapter hataye gaye the: Transport in Plants, Mineral Nutrition, aur Digestion and Absorption. Ye rationalised (19-chapter) structure hi 2026-27 session mein bhi chalega, kyunki naya NCF-aligned textbook 2027-28 tak defer ho chuka hai. 'Breathing and Exchange of Gases' (Chapter 14) in exclusions mein nahi hai, poora chapter as-is padhaya jaata hai.
Is chapter ke exercise mein kitne questions hain aur important questions with answers kahan milenge?
NCERT ke end-of-chapter exercise mein 11 questions hain, jo upar 'exercise' section mein step-by-step solve kiye gaye hain. Additional important questions with answers (concept-based short/long answer, jaise Bohr effect, chloride shift, lung volumes) upar ke 'PYQ-pattern' aur 'intext concept-check' sections mein bhi diye gaye hain — exam revision ke liye dono saath padhna helpful rahega.
Class 11 Biology — Saare Chapters
Board exam tak sirf revision karna hai?
Class 11 Biology ke saare chapters ke colour handwritten short notes — diagrams, formulas aur important points ek jagah.
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