4.3.5
Blood ek delivery truck hai. Oxygen ko lungs → tissues tak jaana hai, aur CO₂ ko tissues → lungs tak. Lekin dono gases plasma mein sirf thodi soluble hain — isliye nature ne clever carriers (haemoglobin) aur chemical tricks (bicarbonate) invent kiye, taaki ek chhote se blood volume mein badi matra mein gas travel kar sake.
Definition The solubility problemSirf lagbhag 1.5% O₂ aur 7% CO₂ hi plasma mein dissolved hokar travel karte hain. Agar hum sirf dissolving par depend karte, toh survive karne ke liye hume paagalon jaisi matra mein blood chahiye hoti. Isliye body gases ko haemoglobin par load karti hai (O₂ ke liye) aur zyaadatar CO₂ ko bicarbonate ions (HCO₃⁻) mein convert karti hai.
WHAT transport ho raha hai aur HOW:
Gas
Dissolved
Chemically bound
Main carrier
O₂
~1.5%
~98.5%
Haemoglobin (as oxyhaemoglobin )
CO₂
~7%
~23% carbamino + ~70% bicarbonate
Bicarbonate ion in plasma
Haemoglobin oxygen ke liye ek 4-seater car ki tarah hai. Iske 4 heme groups mein se har ek (jisme Fe²⁺ hota hai) ek O₂ molecule pakad leta hai. Jaise hi pehli seat bhar jaati hai, car "apne doors aur khol deti hai" agle ke liye — yeh cooperativity hi wajah hai ki loading curve S-shaped hai, seedhi nahi.
S-shape (sigmoid) is topic ka star hai. Flat top ka matlab hai "lungs mein O₂ thoda bhi gire, blood fully loaded rehta hai" (ek safety plateau). Steep middle ka matlab hai "tissues mein p O 2 bahut saari O₂ dump kar deti hai" — exactly wahaan jahan chahiye hoti hai.
Curve ki rightward shift (Hb O₂ zyaada aasani se release karta hai) jo active tissues ki conditions se hoti hai: ↑ CO₂, ↑ H⁺ (↓ pH), ↑ temperature, ↑ 2,3-BPG .
WHY yeh beautiful hai: Exercise karne wali muscle exactly yahi sab produce karti hai → muscle O₂ maangti hai aur Hb zyaada release karke jawab deta hai . Self-regulating!
CO₂ tissues se mostly bicarbonate ke disguise mein smuggle hoti hai. Gas ko dissolved ion mein badalna plasma ko dissolving se ~4× zyaada CO₂ carry karne deta hai.
CO₂ teen tareekon se travel karti hai:
Dissolved (~7%) — simple physical solution.Carbamino compounds (~23%) — CO₂, haemoglobin ke amino groups se bind hoti hai (iron se nahi!): Hb–NH 2 + C O 2 ⇌ Hb–NHCOOH Bicarbonate (~70%) — main route.
Definition Chloride ShiftJaise H C O 3 − Cl⁻ ions plasma se ANDAR aate hain . Yeh "chloride shift / Hamburger phenomenon" electrical neutrality maintain karta hai.
WHY zaroorat hai? Ek negative ion (H C O 3 −
Definition Haldane EffectDeoxygenated blood zyaada CO₂ carry karta hai oxygenated blood ki tulna mein.
WHY: Deoxyhaemoglobin ek better H⁺ buffer hai aur carbamino compounds zyaada aasani se banaata hai. Isliye tissues mein (jahaan Hb ne abhi O₂ release ki hai), CO₂ loading enhanced hoti hai; lungs mein (jahaan Hb O₂ pakadta hai), CO₂ push off ho jaati hai. Bohr aur Haldane ek hi partnership ke do pehlu hain.
Worked example Tissues mein (low O₂, high CO₂)Forecast: Kya hoga?
Low p O 2 Kyun? Reaction left shift hoti hai.
CO₂ RBC mein enter karti hai → carbonic anhydrase → H C O 3 − + H + Kyun? High tissue pC O 2
H + zyaada O₂ release. Yeh step kyun? H⁺ Hb ki O₂ ke liye affinity kam kar deta hai.H C O 3 − Kyun? Charge balance.
Verify: Blood tissues se deoxygenated aur CO₂-rich hokar nikalta hai. ✔
Common mistake "Oxygen iron ko oxidise karke bind hoti hai."Kyun sahi lagta hai: "Oxygen + iron = rust (oxidation)," ek natural association.
Fix: Heme mein iron Fe²⁺ hi rehta hai ; O₂ sirf loosely, reversibly hold hoti hai (oxygenation , oxidation nahi). Agar Fe oxidise hokar Fe³⁺ (methaemoglobin) ban jaaye toh O₂ carry nahi kar sakta.
Common mistake "CO₂ waise hi carry hoti hai jaise O₂ — iron par."Kyun sahi lagta hai: Dono gases hain, dono haemoglobin use karti hain, toh zaroor same site hoga.
Fix: CO₂ amino groups (globin part) se bind hoti hai, carbamino compounds banati hai; O₂ heme mein iron se bind hoti hai. Different sites — isliye ek Hb dono ek saath carry kar sakta hai.
Common mistake "Rightward shift buri hai — Hb oxygen hold nahi kar sakta."Kyun sahi lagta hai: "Oxygen release karna carry karne mein fail hona lagta hai."
Fix: Rightward (Bohr) shift helpful hai — iska matlab hai Hb O₂ exactly wahaan deliver karta hai jahan metabolism sabse zyaada hai. Lungs mein loading affect nahi hoti kyunki woh region flat plateau par hai.
Recall Quick self-test (hide answers)
O₂ ka kitna % haemoglobin se carry hota hai? → ~98.5%
Carbonic acid kaun sa enzyme banaata hai? → Carbonic anhydrase
Chloride shift ke dauran RBC mein kaun sa ion jaata hai? → Cl⁻
Us effect ka naam batao jisme CO₂/H⁺ O₂ curve ko right shift karte hain. → Bohr effect
Us effect ka naam batao jisme deoxygenation CO₂ carriage badhata hai. → Haldane effect
Recall Feynman: explain to a 12-year-oldSocho blood ek school bus hai. Oxygen ke bacche "lungs" bus stop par chadhte hain, haemoglobin naam ki bus par iron ki special seats mein baithte hain. Jab bus "bhooki muscle" stop par pahunchti hai, bacche utar jaate hain. Bus ko kachra bhi bahar le jaana hota hai — kachra CO₂ hai. Zyaadatar kachra chote compact packets (bicarbonate) mein crush ho jaata hai taaki bus par bahut saara fit ho sake. Aur yahan clever part hai: jab bus kachra se bhari hoti hai aur smelly hoti hai (acidic), oxygen ke bacche tezi se utter jaate hain — exactly wahaan jahan muscle chahti hai. Lungs par, fresh air se kachra wapas gas ban jaata hai aur bus use bahar breath karta hai.
Mnemonic CO₂ transport shares yaad karne ke liye"7-23-70 → Dissolved, Do-carbamino, Do-bicarbonate" — 7% dissolved, 23% carbamino, 70% bicarbonate. Aur "BohR = Release, HaldanE = Extra CO₂."
Haemoglobin Structure — 4 subunits cooperativity kyun dete hainGaseous Exchange in Alveoli — partial-pressure gradients jo loading/unloading drive karte hainAcid-Base Balance and pH Buffering — bicarbonate buffer systemCarbonic Anhydrase — CO₂ conversion ka speed enzymePartial Pressure and Diffusion Gradients
What percentage of oxygen is transported bound to haemoglobin? Lagbhag 98.5% (sirf ~1.5% plasma mein dissolved).
What is oxyhaemoglobin? Haemoglobin jo reversibly O₂ ke saath combine hota hai, yaani Hb(O₂)₄.
Why is O₂ binding called oxygenation, not oxidation? Iron Fe²⁺ hi rehta hai aur O₂ loosely, reversibly bound hoti hai; iron oxidise hokar Fe³⁺ nahi banta.
Why is the oxygen dissociation curve S-shaped (sigmoid)? Cooperative binding — har O₂ jo bind hoti hai agle ke liye aur aasaan kar deti hai.
What does the flat plateau of the curve mean physiologically? Blood lagbhag fully saturated rehta hai chahe lung pO₂ thoda gire — ek safety margin.
What is the Bohr effect? O₂ curve ki rightward shift (aasaan O₂ release) jo ↑CO₂, ↑H⁺, ↑temperature, ↑2,3-BPG se hoti hai.
What are the three ways CO₂ is transported? Dissolved (~7%), carbamino compounds (~23%), bicarbonate ions (~70%).
Which enzyme converts CO₂ + H₂O to carbonic acid, and where? Carbonic anhydrase, red blood cells ke andar.
Where does CO₂ bind on haemoglobin? Globin protein ke amino groups par (carbamino compounds), iron/heme par NAHI.
What is the chloride shift? Jaise HCO₃⁻ RBC se nikalta hai, electrical neutrality maintain karne ke liye Cl⁻ andar aata hai (Hamburger phenomenon).
What is the Haldane effect? Deoxygenated haemoglobin zyaada CO₂ carry karta hai (better H⁺ buffering aur carbamino formation).
What buffers the H⁺ produced when bicarbonate forms? Haemoglobin, blood ko zyaada acidic hone se bachata hai.
At the lungs, what happens to bicarbonate? Yeh H⁺ se wapas milta hai → H₂CO₃ → CO₂ + H₂O; CO₂ exhale hoti hai (reverse chloride shift hoti hai).
raises H+ and CO2 triggers
Low gas solubility in plasma
Sigmoid dissociation curve
