Respiratio,n in Plants | NEET Hinglish Free Notes | Class 11 Biology
1. Introduction With 💖Learn Sufficient Notes💖
- Hum sab breathe karte hain zinda rehne ke liye, lekin breathing itni important kyun hai? Jab hum breathe karte hain to actually kya hota hai? Kya sab living things jaise plants aur microbes bhi breathe karte hain? Agar haan, to wo kaise karte hain? Sabhi living organisms ko energy ki zarurat hoti hai daily activities jaise absorption, transport, movement, reproduction, aur even breathing khud ke liye. Lekin ye energy kahan se aati hai? Hum jaante hain ki hum food khate hain energy ke liye, lekin ye energy food se kaise milti hai aur body use kaise karti hai? Kya sab foods same amount ki energy dete hain? Kya plants khate hain? Wo apni energy kaise lete hain? Aur micro-organisms ka kya—kya unhe bhi energy ke liye food chahiye hota hai?
- Ye alag-alag questions lag sakte hain, lekin actually, ye sab ek dusre se related hain. Breathing ka process closely connected hai food se energy release karne ke process se. Life ke liye jo bhi energy chahiye, wo oxidation se aati hai large molecules ko jo food kehlate hain. Green plants aur cyanobacteria apna khud ka food bana sakte hain. Wo photosynthesis ka use karke light energy capture karte hain aur use chemical energy me convert karte hain, jo carbohydrates jaise glucose, sucrose, aur starch me store hoti hai. Lekin green plant ke sabhi parts photosynthesis nahi kar sakte—sirf wo cells jinke paas chloroplasts hote hain, jo usually plant ke outer layers me hote hain, wo ye kar sakte hain. Isliye plant ke doosre non-green parts ko food jo photosynthesis ke dauran bana, receive karna padta hai. Yehi wajah hai ki food ko plant ke sabhi parts me move karna zaruri hai.
- Animals apna khud ka food nahi bana sakte. Wo heterotrophs hote hain aur food lete hain ya to directly plants se (jaise herbivores) ya indirectly dusre animals ko khaa kar (jaise carnivores). Saprophytes, jaise fungi, apna food dead aur decaying matter se lete hain. Aakhir me, almost all food jo respiration me use hota hai, wo photosynthesis se aata hai. Ye chapter cellular respiration ko explain karta hai, jo ek process hai jisme food cells ke andar break hota hai taaki energy release ho. Ye energy phir use hoti hai ATP banane ke liye, wo molecule jo usable energy store karta hai.
- Photosynthesis hoti hai chloroplasts ke andar eukaryotic cells me, jabki complex food molecules ka breakdown energy ke liye hota hai cytoplasm aur mitochondria me. C–C bonds ko oxidation ke through cells ke andar todne ka process, jo bahut saari energy release karta hai, usse respiration kehte hain. Jo substances is process ke liye use hote hain, unhe respiratory substrates kehte hain. Zyada tar time, carbohydrates ka use hota hai energy release karne ke liye, lekin kuch conditions me, proteins, fats, aur organic acids bhi kuch plants dwara use kiye ja sakte hain.
- Cell ke andar, ye oxidation ek saath nahi hoti. Energy ek hi step me release nahi hoti, aur na hi freely release hoti hai. Iske bajay, energy dheere-dheere chhote steps me release hoti hai, enzymes ke dwara control ki jaati hai, aur chemical energy ke form me ATP me store hoti hai. Ye energy directly use nahi ki ja sakti, isliye pehle ATP banane me use hoti hai, aur baad me ATP breakdown hota hai jahan bhi cell ko energy ki zarurat hoti hai. Is wajah se, ATP ko cell ki energy currency kehte hain. ATP me stored energy alag-alag processes me use hoti hai jo energy demand karte hain, aur respiration ke dauran bachi hui carbon skeletons cell me dusre important molecules banane ke liye use hote hain.
2. Understanding Plant Breathing Mechanism
- Kya plants breathe karte hain? Iska answer itna simple nahi hai. Haan, plants ko oxygen (O₂) chahiye respiration ke liye aur wo carbon dioxide (CO₂) bhi release karte hain. To, unke paas tarike hote hain apne cells ko oxygen available karane ke. Lekin animals ke unlike, plants ke paas gas exchange ke liye special organs nahi hote. Iske bajay, wo chhote openings ka use karte hain, jaise stomata aur lenticels is purpose ke liye. Kuch important reasons hain ki plants respiratory organs ke bina bhi jee sakte hain. Pehla, plant ka har part apna gas exchange handle karta hai. Gases ko ek part se dusre part me move karne ki zarurat nahi hoti. Dusra, plants ko animals jitna gas exchange nahi chahiye. Roots, stems, aur leaves ka respiration animals ke cells ke mukable bahut slow hota hai. Sirf photosynthesis ke dauran, bahut saara gas exchange hota hai, aur har leaf apni needs ko dhyan me rakh kar bana hota hai. Aur jab leaf cell photosynthesis kar raha hota hai, wo apne andar oxygen produce karta hai, to oxygen ki koi shortage nahi hoti.
- Teesra, even large plants me bhi, gases ko travel karne ka distance bahut chhota hota hai. Almost all living cells plant me surface ke paas hote hain, to gases easily un tak pahunch sakti hain. Aap soch rahe honge thick stems aur roots ke baare me. In parts me, living cells thin layers me hote hain bas bark ke neeche, aur unke paas lenticels hote hain gas exchange allow karne ke liye. Inner cells dead hote hain aur sirf support dete hain, isliye unhe oxygen ki zarurat nahi hoti. Iske alawa, parenchyma cells leaves, stems, aur roots me loosely packed hote hain, jo ek network of air spaces banata hai aur gases ko plant ke andar move karne me help karta hai.
- Jab glucose completely break down (ya combusted) hota hai, to ye carbon dioxide (CO₂), water (H₂O), aur energy deta hai, jismein se zyada tar energy heat ke form me nikalti hai:
- C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
- Lekin agar plant cell ye energy use karna chahta hai, to ye heat ke form me waste nahi honi chahiye. Isliye, plant glucose ko ek special tarike se, chhote steps me todta hai, taaki energy ATP ke form me store ho sake. Yehi respiration ka main idea hai.
- Respiration ke dauran, cell oxygen use karta hai aur carbon dioxide, water, aur energy produce karta hai. Ye process oxygen ki zarurat hoti hai, lekin kuch cells aise places me rehte hain jahan oxygen available nahi hoti. Aap aise situations ya organisms ke baare me soch sakte hain? Scientists believe karte hain ki Earth par pehle living cells aise environment me jeete the jahan oxygen nahi tha. Aaj bhi, kuch organisms aise conditions me adapt ho gaye hain. Kuch ko facultative anaerobes kehte hain (ye oxygen ke saath ya bina oxygen ke jee sakte hain), aur kuch ko obligate anaerobes kehte hain (ye oxygen ke saath survive nahi kar sakte). Sabhi living organisms, even aaj bhi, enzymes rakhte hain jo glucose ko partial taur par oxygen use kiye bina tod sakte hain. Ye process, jahan glucose todkar pyruvic acid banta hai, usse glycolysis kehte hain.
3. Breakdown of Glucose in Cytoplasm
- Word glycolysis do Greek words se aata hai: “glycos”, matlab sugar, aur “lysis”, matlab splitting. Glycolysis ka process scientists Gustav Embden, Otto Meyerhof, aur J. Parnas ne explain kiya, isliye isse aksar EMP pathway kehte hain. Jo organisms oxygen use nahi karte, unke liye glycolysis hi ek matra tareeka hai respiration ka. Glycolysis cell ke cytoplasm me hota hai aur sabhi living organisms me occur karta hai. Is process me, glucose ko partial taur par todkar do molecules of pyruvic acid banaye jaate hain. Plants me, is process me use hone wala glucose ya to sucrose se aata hai, jo photosynthesis ke dauran banta hai, ya stored carbohydrates se. Enzyme invertase sucrose ko glucose aur fructose me todta hai, jo easily glycolysis pathway me enter kar sakte hain. Glucose aur fructose ko pehle enzyme hexokinase ke dwara glucose-6-phosphate me convert kiya jata hai. Phir, ye compound fructose-6-phosphate me convert hota hai. Iske baad, dono glucose aur fructose glycolysis me same set of reactions follow karte hain.
- Glycolysis ke 10 steps hote hain, har ek step alag enzyme se control hota hai, aur ye glucose se pyruvate (ya pyruvic acid) banane me lead karta hai. Is process me, dhyan dena padta hai ki ATP aur NADH + H⁺ kab use hote hain ya bante hain. ATP do steps me use hota hai: pehla, jab glucose glucose-6-phosphate me convert hota hai, aur dusra, jab fructose-6-phosphate fructose-1,6-bisphosphate me convert hota hai. Fructose-1,6-bisphosphate phir do three-carbon molecules me split hota hai — dihydroxyacetone phosphate aur glyceraldehyde-3-phosphate (PGAL). Ye dono forms easily interchange ho sakte hain. Glycolysis me ek key point tab hota hai jab PGAL convert hota hai 1,3-bisphosphoglyceric acid (BPGA) me. Is step me, NAD⁺ convert hota hai NADH + H⁺ me, jab hydrogen atoms PGAL se remove hote hain aur NAD⁺ ko pass hote hain. Ye ek oxidation reaction hai. Phir, BPGA convert hota hai 3-phosphoglyceric acid (PGA) me, aur is step me ATP banta hai. Ek aur ATP banta hai jab phosphoenolpyruvate (PEP) pyruvic acid me convert hota hai. To, ek molecule of glucose se, aapko BPGA step se 2 ATP aur PEP step se 2 aur ATP milte hain, total 4 ATP bante hain, lekin shuru me 2 ATP use huye the, to net gain 2 ATP hai. Aapko 2 NADH molecules bhi milte hain.
- Glycolysis ka end product pyruvic acid hai, aur iska kya hota hai, ye cell ke type aur uski need par depend karta hai. Pyruvic acid ke 3 main fates hote hain. Pehla, lactic acid fermentation, dusra, alcoholic fermentation, aur teesra, aerobic respiration (jo oxygen ke presence me hota hai). Fermentation un organisms me hota hai jo oxygen ke bina jeete hain, jaise kuch bacteria aur unicellular fungi (e.g., yeast). Lekin glucose ka complete breakdown carbon dioxide (CO₂) aur water (H₂O) me karne ke liye, living beings aerobic respiration use karte hain, jisme Krebs cycle include hota hai aur oxygen required hoti hai.
4. Fermentation: An Oxygen-Independent Respiration
Fermentation ek biological process hai jo oxygen ke bina (anaerobic conditions) hota hai, jahan glucose sirf partially oxidize hota hai. Organisms jaise yeast me, glucose glycolysis ke through pyruvic acid me convert hota hai, jo phir ethanol aur carbon dioxide me badal jata hai. Is conversion me do key enzymes ka role hota hai: pyruvic acid decarboxylase aur alcohol dehydrogenase. Iske contrast me, kuch bacteria pyruvic acid ko lactic acid me convert karte hain alag biochemical reactions ke through. Animal muscle cells me bhi, jab intense physical activity ke dauran oxygen limited hota hai, pyruvic acid lactic acid me convert hota hai. Ye process enzyme lactate dehydrogenase ke dwara catalyze hota hai aur NADH + H⁺ reducing agent ke roop me involve hota hai, jo phir NAD⁺ me reoxidise hota hai taaki glycolysis continue kar sake.
Dono types of fermentation – alcoholic aur lactic acid – bahut kam energy dete hain. In fact, ye glucose molecule me present total energy ka 7% se bhi kam release karte hain, aur sirf chhoti fraction ATP ke form me store hoti hai. Ye processes by-products bhi produce karte hain jo high concentration me harmful ho sakte hain – jaise acids ya alcohols. Yeast, alcohol fermentation ke dauran, sirf around 13% alcohol concentration tolerate kar sakte hain, uske baad environment unke liye toxic ho jata hai aur wo mar jaate hain. Isliye, naturally fermented alcoholic beverages ka alcohol content is level se zyada nahi ho sakta. Higher concentrations achieve kiye jaate hain processes jaise distillation se.
Kyuki fermentation glucose ka complete breakdown allow nahi karta, energy extract limited hoti hai. Organisms ko glucose ko completely oxidise karke maximum energy extract karne ke liye, aerobic respiration ka process use hota hai. Ye eukaryotic cells ke mitochondria me hota hai aur molecular oxygen (O₂) required hoti hai. Aerobic respiration me, glucose carbon dioxide aur water me break hota hai, aur bahut saari energy release hoti hai, jismein se zyada tar ATP ke form me capture hoti hai, jo cell ki energy currency hai. Ye complete oxidation aerobic respiration ko bahut efficient banata hai aur ye higher organisms me primary mode of respiration hai.
5. Cellular Energy Release via Aerobic Mechanism
Aerobic respiration ek biological process hai jo cells ke mitochondria ke andar hota hai, jahan glycolysis ka final product—pyruvate—cytoplasm se mitochondrial matrix me transport hota hai. Is process me do key stages involved hain. Pehla, pyruvate complete oxidation undergo karta hai ek series of reactions ke through, jismein uske sab hydrogen atoms systematically remove hote hain, aur result hota hai teen molecules of carbon dioxide (CO₂) per pyruvate molecule. Dusra, hydrogen atoms ke saath removed electrons molecular oxygen (O₂) ko transfer hote hain, aur ye transfer ATP synthesis ke saath coupled hota hai, jo cell ki energy currency hai. Ye dono stages mitochondria ke andar compartmentalized hain—jabki pyruvate ka oxidation mitochondrial matrix me hota hai, electron transport aur ATP synthesis processes inner mitochondrial membrane par hote hain.
Glycolysis se carbohydrates ka pyruvate cytosol se mitochondria me transport hota hai, jahan ye oxidative decarboxylation undergo karta hai, ek complex process jo pyruvate dehydrogenase enzyme complex ke dwara catalyze hota hai. Is enzyme ko coenzymes jaise NAD⁺ (Nicotinamide Adenine Dinucleotide) aur Coenzyme A, saath hi magnesium ions (Mg²⁺) ki zarurat hoti hai. Is reaction me, pyruvic acid NAD⁺ aur Coenzyme A ke saath react karta hai aur produce karta hai acetyl CoA, CO₂, NADH, aur H⁺. Ek glucose molecule se derived do pyruvate molecules ke metabolism se, do NADH molecules generate hote hain.
Resulting acetyl CoA phir enter karta hai tricarboxylic acid cycle (TCA cycle) me, jo Krebs cycle ke naam se bhi jaana jata hai, aur jo pehle scientist Hans Krebs ne describe kiya tha. Ye cycle acetyl CoA ka complete breakdown aur additional NADH, FADH₂, aur ATP production me vital role play karta hai, ek series of enzymatic reactions ke through, jo living organisms me aerobic energy production ke liye central hain.
5. Metabolic Pathway Releasing Energy and CO₂
(OAA) aur water ke saath, aur citric acid banta hai. Is process me citrate synthase enzyme help karta hai, aur Coenzyme A (CoA) release hota hai. Phir citric acid isocitrate me convert hota hai, jo do steps se guzarta hai jahan carbon dioxide (CO₂) remove hoti hai. Ye steps result karte hain α-ketoglutaric acid aur phir succinyl-CoA ke formation me. Iske baad, succinyl-CoA phir se oxaloacetic acid (OAA) me convert hota hai, jo cycle ko continue karne me help karta hai.
Is step me, ek molecule of GTP (guanosine triphosphate) banta hai, jo substrate-level phosphorylation ka ek type hai. GTP phir GDP me convert hota hai, aur saath hi ATP ADP se banta hai. Is cycle me teen steps hain jahan NAD⁺ NADH + H⁺ me convert hota hai, aur ek step jahan FAD⁺ FADH₂ me convert hota hai. Is cycle ko continue rakhne ke liye, cell ko oxaloacetic acid continuously banana padta hai aur NADH ko wapas NAD⁺, aur FADH₂ ko wapas FAD⁺ me convert karna padta hai.
Is part of respiration ka overall result ye hai ki ek glucose molecule se, cell produce karta hai CO₂, eight molecules of NADH + H⁺, do molecules of FADH₂, aur sirf do molecules of ATP TCA cycle me. Is point par, oxygen (O₂) use nahi hui hai, aur abhi tak zyada ATP molecules nahi bane hain. Aap soch rahe honge ki ye abhi bhi respiration kyu kehlata hai. Reason ye hai ki NADH + H⁺ aur FADH₂ jo is cycle me bane hain, wo next step me important role play karenge, jahan oxygen involved hota hai aur bahut zyada ATP banta hai.
6. Energy Generation by Electron Carriers
Respiration ka next step hai NADH + H⁺ aur FADH₂ me stored energy ko release aur use karna. Ye tab hota hai jab ye oxidised hote hain Electron Transport System (ETS) me. Is process me, electrons ek series of molecules ke through pass hote hain aur finally oxygen (O₂) tak pahunchte hain, jisse water (H₂O) banta hai. Electrons ke move karne ka path Electron Transport System (ETS) kehlata hai, aur ye mitochondria ke inner membrane me located hai.
NADH ke electrons, jo mitochondrial matrix me citric acid cycle ke dauran bane, ek protein NADH dehydrogenase (complex I) ko pass hote hain. Wahan se, electrons ek molecule ubiquinone ko move karte hain, jo inner membrane me hota hai. Ubiquinone electrons ko FADH₂ se bhi accept karta hai complex II ke through, jo TCA cycle me succinate ke oxidation se aata hai. Reduced ubiquinone, ya ubiquinol, phir electrons ko cytochrome c ko pass karta hai cytochrome bc₁ complex (complex III) ke through. Cytochrome c ek small protein hai jo electrons complex IV tak le jaata hai, jo cytochrome c oxidase complex hai. Is complex me cytochromes a aur a₃ aur do copper centers hote hain.
Jab electrons ye complexes I se IV tak move karte hain, ye ATP synthase (complex V) se linked hote hain, jo ATP banata hai ADP aur inorganic phosphate se. ATP ka amount electron donor ke type par depend karta hai: ek molecule NADH se 3 ATP bante hain, aur ek molecule FADH₂ se 2 ATP bante hain. Ye poora process tab hi hota hai jab oxygen present ho (aerobic respiration), lekin oxygen ka role sirf final stage tak limited hai. Phir bhi, ye important hai kyunki oxygen system se hydrogen remove karta hai aur final hydrogen acceptor ke roop me kaam karta hai.
Photosynthesis ke opposite, jahan light energy proton gradient banati hai, respiration me energy oxidation-reduction reactions se proton gradient create hoti hai. Isliye is process ko oxidative phosphorylation kehte hain. Aap pehle hi seekh chuke ho ki kaise ATP chemiosmotic hypothesis ke through banta hai. Electron transport system se energy ATP synthase (complex V) dwara ATP banane me use hoti hai. Ye enzyme do parts me hota hai: F₁ aur F₀. F₁ part membrane ke bahar hota hai aur wahi site hai jahan ATP banta hai ADP aur inorganic phosphate se. F₀ part membrane me hota hai aur proton (H⁺) ke liye channel banata hai. F₀ ke through protons ka flow F₁ part ko drive karta hai ATP banane ke liye. Ek molecule of ATP banane ke liye, 4 protons (4H⁺) intermembrane space se mitochondrial matrix me proton gradient follow karte hue move karte hain.
7. Energy Accounting of Cellular Respiration
- Hum try kar sakte hain ATP ka net gain calculate karne ke liye, ek glucose molecule ke complete breakdown se, lekin ye sirf theoretical estimate hai. Ye calculations kuch assumptions par based hain. Pehla, assume kiya jata hai ki glycolysis, TCA cycle, aur Electron Transport System (ETS) ke sab steps perfect order me ek ke baad ek hote hain. Dusra, assume kiya jata hai ki glycolysis me bane NADH ko mitochondria me bheja jata hai aur oxidative phosphorylation me use kiya jata hai. Teesra, assume kiya jata hai ki in processes me bane substances ko dusre compounds banane ke liye use nahi kiya jata. Aur last, assume kiya jata hai ki sirf glucose respiration ke liye use ho raha hai aur koi aur substances cycle me enter ya exit nahi kar rahe.
- Lekin real living cells me ye conditions fully true nahi hoti. Sab metabolic pathways ek saath kaam karte hain, strict order me nahi. Substances kabhi bhi pathways me join ya leave kar sakte hain jab zarurat ho. ATP banaaya aur use kiya jata hai cell ki needs ke hisaab se, aur enzyme actions ki speed kai tariko se control hoti hai. Phir bhi, ye calculation samajhne me help karta hai ki cell energy ko kitna efficiently extract aur store kar sakta hai. Theoretical model ke hisaab se, ek glucose molecule aerobic respiration ke dauran total 38 ATP molecules de sakta hai.
- Ab, chaliye fermentation aur aerobic respiration ke differences dekhte hain. Fermentation me, glucose sirf partially todha jata hai, jabki aerobic respiration me, glucose completely carbon dioxide (CO₂) aur water (H₂O) me break hota hai. Fermentation me, har glucose molecule se sirf 2 ATP molecules bante hain, lekin aerobic respiration me, bahut zyada ATP molecules produce hote hain. Saath hi, fermentation me, NADH wapas NAD⁺ me bahut dheere convert hota hai. Lekin aerobic respiration me, ye reaction bahut tezi aur efficiently hoti hai.
8. Link Between Catabolism and Anabolism
Glucose respiration ke liye main aur sabse commonly used substrate hai. Usually, sabhi doosre carbohydrates ko pehle glucose me convert kiya jata hai tab jaake wo respiration me use ho sakte hain. Lekin, doosre types ke molecules jaise fats aur proteins bhi use ho sakte hain, lekin ye respiratory pathway me later steps me enter karte hain, beginning me nahi.
For example, fats ko pehle glycerol aur fatty acids me todna padta hai. Fatty acids phir acetyl CoA me convert hote hain before entering respiration process. Glycerol change hota hai PGAL (phosphoglyceraldehyde) me aur pathway join karta hai. Proteins ko protease enzymes ke through amino acids me todte hain, aur deamination ke baad ye pathway me enter karte hain—ya to pyruvate, acetyl CoA, ya Krebs cycle ke various steps me, unke type ke hisaab se.
Kyuki respiration mainly food molecules ko todkar energy release karne me involve hai, isliye isse often catabolic process kaha jata hai, aur respiratory pathway ko usually catabolic pathway consider kiya jata hai. Lekin, kya ye idea fully correct hai? Humne already dekha ki different substrates respiratory pathway me different points se enter karte hain energy release karne ke liye. Lekin same compounds pathway se bahar nikal kar dusre molecules banane me bhi use ho sakte hain.
For example, jab fatty acids energy ke liye use hote hain, ye acetyl CoA me todte hain. Lekin jab body ko fatty acids banane hote hain, ye acetyl CoA respiration pathway se use karta hai. Isliye, pathway fatty acids ke breakdown aur making dono me help karta hai. Same proteins ke liye bhi true hai – respiration ke intermediate compounds dono breakdown aur making me use hote hain.
Molecules ko todne ke process ko catabolism, aur naye molecules banane ke process ko anabolism kehte hain. Kyuki respiratory pathway dono catabolism aur anabolism me help karta hai, isliye isse amphibolic pathway kehna better hai, sirf catabolic pathway nahi.
9. Ratio of CO₂ Released to O₂ Consumed
Ab, chaliye respiration ka ek aur important part samajhte hain. Aerobic respiration me oxygen (O₂) use hota hai, aur carbon dioxide (CO₂) release hoti hai. Respiratory quotient (RQ), jise respiratory ratio bhi kehte hain, wo ratio hai volume of CO₂ produced aur volume of O₂ used during respiration ke beech. Isse calculate karte hain is formula se:
RQ = volume of CO₂ evolved / volume of O₂ consumed
RQ ka value organism ke use kiye gaye respiratory substrate ke type par depend karta hai. Agar carbohydrates jaise glucose use hote hain aur completely break down hote hain, to CO₂ release aur O₂ consume ka amount same hota hai, isliye RQ = 1. For example, reaction:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Yahan RQ = 6/6 = 1.
Lekin jab fats respiration me use hote hain, to unhe zyada oxygen chahiye aur kam carbon dioxide release hoti hai, isliye RQ < 1 hota hai. For example, jab tripalmitin (C₅₁H₉₈O₆) fat use hota hai:
2C₅₁H₉₈O₆ + 145O₂ → 102CO₂ + 98H₂O + energy
To RQ = 102/145 ≈ 0.7.
Jab proteins respiratory substrate ke roop me use hote hain, to RQ ≈ 0.9 hota hai.
Lekin real living organisms me usually mixture of substrates jaise carbohydrates, fats, aur proteins ek saath respiration me use hote hain. Pure fats ya pure proteins almost kabhi bhi sirf ek hi respiratory source ke roop me use nahi hote.
10. Key Concept Recap
Animals ke opposite, plants ke paas special breathing systems ya organs nahi hote gaseous exchange ke liye. Iske bajaye, wo small openings use karte hain, jaise stomata aur lenticels, jisse gases diffusion ke through move kar sakti hain. Plants me zyadatar living cells air ke close hote hain aur easily gases exchange kar sakte hain.
Jis process me carbon-carbon (C–C) bonds large organic molecules me oxidation ke through break hote hain aur energy release hoti hai, usse cellular respiration kehte hain. Respiration ke liye most preferred substrate glucose hai, lekin fats aur proteins bhi energy release karne ke liye use ho sakte hain.
Respiration ka pehla step cytoplasm me hota hai, jahan glucose enzyme-controlled steps ke through do molecules of pyruvic acid me break hota hai. Is process ko glycolysis kehte hain. Pyruvate ke saath kya hota hai, ye oxygen availability aur organism ke type par depend karta hai. Agar oxygen nahi hai (anaerobic conditions), to lactic acid fermentation ya alcohol fermentation ho sakti hai. Fermentation anaerobic conditions me kai prokaryotes, unicellular eukaryotes, aur germinating seeds me hoti hai.
Eukaryotic organisms me, agar oxygen present hai, to aerobic respiration hoti hai. Is case me, pyruvic acid mitochondria me enter karta hai aur acetyl CoA me convert hota hai, jisse carbon dioxide (CO₂) release hoti hai. Ye acetyl CoA tricarboxylic acid (TCA) cycle, ya Krebs’ cycle, me jata hai, jo mitochondrial matrix me hoti hai. Krebs’ cycle ke dauran, NADH + H⁺ aur FADH₂ bante hain.
In molecules me stored energy, glycolysis ke NADH + H⁺ ke saath, ATP banane me use hoti hai. Ye process Electron Transport System (ETS) ke through hota hai, jo mitochondria ke inner membrane me hota hai. Jab electrons ETS me move karte hain, energy release hoti hai jo ATP banane ke liye use hoti hai. Is process ko oxidative phosphorylation kehte hain. Is step me oxygen (O₂) final electron acceptor ke roop me kaam karta hai aur water banta hai.
Respiratory pathway ko amphibolic pathway kehte hain kyunki ye dono kaam me help karta hai: breaking down (catabolism) aur building up (anabolism) of substances. Respiratory Quotient (RQ) ka value use kiye gaye substrate ke type par depend karta hai.
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