Biomolecules: Class 11 Biology Chapter 9 Hinglish mein

Flower bed se thodi mitti uthao aur usi bed mein ugi ek spinach ki leaf todo. Ek zinda hai aur doosri nahi. Phir bhi agar dono ko lab mein elemental analysis ke liye bheja jaaye, to dono reports lagbhag same elements batayengi: carbon, hydrogen, oxygen, nitrogen, calcium, sodium wagairah. Life ke koi apne private elements nahi hote. Kisi organism mein milne wala har element rocks, paani aur hawa mein bhi milta hai.

Fark hai proportion ka. Carbon tumhare body ke mass ka lagbhag paanchwa hissa hai, lekin Earth ke crust ka sirf 0.02 % ke aas-paas, aur hydrogen ki kahani bhi aisi hi hai. Silicon, jo crust ka doosra sabse common element hai, tumhare andar na ke barabar hai (Fig. 9.1). Living matter mainly carbon aur hydrogen ke compounds se bana hai. Yeh chapter unhi compounds ke baare mein hai. Tum dekhoge ki chemists unhe tissue se kaise nikalte hain aur chhote molecules judkar giant molecules kaise banate hain. Phir tum giants ki ek family se miloge, enzymes, jo har cell ki chemistry chalate hain. Hindi mein is chapter ko जैव अणु (jaiv anu) kehte hain.

9.1 Chemical Composition ko Analyse Kaise Karein?

Elements jaanna sirf shuruaat hai, kyunki cell loose atoms ka thaila nahi hai. Tissue mein kaun se compounds hote hain? Iska jawab dhoondhne ka pehla step ek seedha-saada lekin powerful separation hai (Fig. 9.2). Kuch spinach leaves ya mutton ka ek tukda mortar mein daalo, trichloroacetic acid ($\mathrm{C}\mathrm{l}{\phantom{X}}_3\mathrm{C}\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$) milao aur pestle se tab tak pees lo jab tak gaadha paste na ban jaaye. Phir paste ko beaker ke upar rakhe cheesecloth ya cotton par daalo. Do fractions milte hain. Jo liquid neeche nikal jaata hai, yaani filtrate, use acid-soluble pool kehte hain; jo solid kapde par ruk jaata hai, yaani retentate, woh acid-insoluble fraction hai. Akele filtrate mein hi hazaaron tarah ke organic molecules hote hain.

Aise mixture mein ek single compound ko kaise pehchanoge? Use alag karo, purify karo, phir analyse karo. Chromatography jaise methods mixture ko step by step tab tak alag karte hain jab tak ek compound akela na bache, aur phir spectrometers jaise instruments uska formula aur atoms ki arrangement batate hain; yeh methods tum aage ki classes mein padhoge. Living tissue se aane wale har carbon compound ke liye hum biomolecule word use karte hain.

Inorganic matter ke liye ek sakht test chahiye, jo sample ko khatam kar deta hai, aur teen baar weigh karne se poori kahani pata chalti hai. Plant ya animal se seedha liya gaya sample apna wet weight deta hai. Oven mein tab tak rakhne par jab tak aur paani na nikal sake, woh apna dry weight deta hai. Aakhir mein use flame mein tab tak garam kiya jaata hai jab tak har carbon compound carbon dioxide aur water vapour ban kar jal na jaaye. Jo bachta hai woh chutki bhar grey ash hai, aur ash mein calcium, magnesium aur potassium jaise inorganic elements hote hain.

Inorganic substances acid-soluble fraction mein bhi milte hain. Khud paani ke alawa, $\mathrm{N}\mathrm{a}{\phantom{X}}^{+}$, $\mathrm{K}{\phantom{X}}^{+}$, $\mathrm{C}\mathrm{a}{\phantom{X}}^{2+}$ aur $\mathrm{M}\mathrm{g}{\phantom{X}}^{2+}$ jaise cations, chloride, phosphate ($\mathrm{P}\mathrm{O}{\phantom{X}}_4{\phantom{X}}^{3-}$) aur sulphate ($\mathrm{S}\mathrm{O}{\phantom{X}}_4{\phantom{X}}^{2-}$) jaise anions, aur $\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$ aur $\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}{\phantom{X}}_3$ jaise salts hote hain. Dono tarah ke analysis ek doosre ko complete karte hain: elemental analysis batata hai ki tissue mein kaun se elements hain, aur compound analysis batata hai ki unhe kaun se molecules, organic aur inorganic, carry karte hain.

Organic molecules ko kaise sort karein? Ek chemist unhe unke functional groups (alcohols, acids, amines wagairah) ke hisaab se rakhega. Ek biologist unhe cell mein unke role ke hisaab se rakhta hai, jisse yeh families banti hain: amino acids, fatty acids aur doosre lipids, nitrogen bases apne nucleosides aur nucleotides ke saath, aur sugars. Hum ek-ek family se milte hain.

Amino acids

Methane, $\mathrm{C}\mathrm{H}{\phantom{X}}_4$, se shuru karo aur uske teen hydrogens badlo: ek ko amino group ($\mathrm{N}\mathrm{H}{\phantom{X}}_2$) se, ek ko acidic carboxyl group ($\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$) se aur ek ko variable R group se. Result ek amino acid hai. Beech wala carbon, jis par ab H, $\mathrm{N}\mathrm{H}{\phantom{X}}_2$, $\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ aur R hain, α-carbon hai, isliye in molecules ko α-amino acids kehte hain; chemically yeh substituted methanes hain (Fig. 9.3).

R group decide karta hai ki amino acid kaun sa hai. Chemically bahut saare R groups possible hain, lekin living things ke proteins sirf 20 tarah ke amino acids se bante hain. Glycine mein R group ek single hydrogen atom hai, alanine mein methyl group ($\mathrm{C}\mathrm{H}{\phantom{X}}_3$), serine mein hydroxymethyl group ($\mathrm{C}\mathrm{H}{\phantom{X}}_2\mathrm{O}\mathrm{H}$) aur cysteine mein sulphur wala group ($\mathrm{C}\mathrm{H}{\phantom{X}}_2\mathrm{S}\mathrm{H}$).

Kyunki har amino acid mein same amino aur carboxyl groups hote hain, behaviour ke zyadatar fark R se aate hain. R mein extra acidic ya basic groups gino, to yeh teen groups mein bant jaate hain. Glutamic acid aur aspartic acid acidic hain, lysine aur arginine basic hain, aur valine aur leucine neutral hain. Tyrosine, phenylalanine aur tryptophan mein ring jaisi side chains hoti hain aur yeh aromatic amino acids hain.

Amino aur carboxyl groups ionizable hain: yeh proton le ya chhod sakte hain, isliye amino acid ka charge aas-paas ke pH par depend karta hai (Fig. 9.4). Strongly acidic solution mein dono groups protons pakde rehte hain aur molecule cation hota hai, $\mathrm{H}{\phantom{X}}_3\mathrm{N}{\phantom{X}}^{+}-\mathrm{C}\mathrm{H}\mathrm{R}-\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$. Neutral pH ke paas carboxyl group apna proton kho deta hai, aur banta hai $\mathrm{H}{\phantom{X}}_3\mathrm{N}{\phantom{X}}^{+}-\mathrm{C}\mathrm{H}\mathrm{R}-\mathrm{C}\mathrm{O}\mathrm{O}{\phantom{X}}^{-}$. Is form par ek positive aur ek negative charge hota hai, isliye net charge zero hai: yeh ek zwitterion hai. Strongly basic solution mein amino group bhi apna extra proton chhod deta hai, aur anion $\mathrm{H}{\phantom{X}}_2\mathrm{N}-\mathrm{C}\mathrm{H}\mathrm{R}-\mathrm{C}\mathrm{O}\mathrm{O}{\phantom{X}}^{-}$ bachta hai.

Lipids

Lipids cell ke chikne, paani mein insoluble molecules hain. Sabse simple hain fatty acids: ek carboxyl group jo hydrocarbon R group se juda hota hai. R ek single carbon (methyl group) se lekar 19 carbons ki chain tak hota hai, isliye fatty acid mein kul 2 se 20 carbon atoms hote hain. Palmitic acid, jo palm oil mein bahut hota hai, mein carboxyl carbon ko milakar 16 carbons hain; arachidonic acid mein 20.

Jis chain mein sirf single C–C bonds hon woh saturated hai: woh seedhi hoti hai aur apne padosiyon ke saath tight pack hoti hai. Ek ya zyada C=C double bonds chain ko unsaturated banate hain, aur zyadatar natural fatty acids mein har double bond chain mein ek mod (kink) daal deta hai (Fig. 9.5).

Glycerol teen carbon wala alcohol hai jiske har carbon par ek –OH group hai: trihydroxypropane, $\mathrm{C}{\phantom{X}}_3\mathrm{H}{\phantom{X}}_8\mathrm{O}{\phantom{X}}_3$. Har –OH ek fatty acid ke carboxyl group se react karke ester bana sakta hai, aur ek water molecule nikalta hai. Ek fatty acid jude glycerol ko monoglyceride, do wale ko diglyceride aur teen wale ko triglyceride kehte hain. Triglycerides ko hi hum fats aur oils kehte hain, aur dono mein fark sirf melting point ka hai.

Oils room temperature se neeche pighalte hain aur liquid rehte hain; fats solid hote hain. Delhi ki sardi mein coconut oil ki bottle safed aur solid ho jaati hai jabki paas rakha mustard oil patla hi rehta hai. Coconut oil mein saturated fatty acids zyada hain, jinki seedhi chains aasaani se solid mein pack ho jaati hain, jabki mustard oil mostly unsaturated hai. Ghee aur butter mein bhi saturated fats zyada hote hain, isliye thandi subah woh bhi isi wajah se jam jaate hain.

Triglyceride ka ek fatty acid hata kar phosphate group lagao, aur us phosphate se ek chhota organic group (aksar nitrogen wala) jodo: result ek phospholipid hai. Lecithin, jiska extra group choline hai, ek common example hai. Ek paani pasand head aur do paani se bachne wali tails ke saath, phospholipids ka shape bilkul waisa hai jo cell membranes banane ke liye chahiye. Brain aur nerves mein isse bhi complex lipids bhare hote hain, aur cholesterol, jo fatty acids se nahi balki chaar judi rings se bana hai, ek aur lipid hai jisse tum aksar miloge.

Nitrogen bases, nucleosides aur nucleotides

Carbon aur nitrogen dono atoms se bani rings, yaani heterocyclic rings, ek aur family ka core hain. Iske paanch main members, nitrogen bases, hain adenine, guanine, cytosine, thymine aur uracil. Yeh kam hi akele ghoomte hain. Base ko sugar se jodo to woh nucleoside ban jaata hai; us sugar par ester link se ek phosphate bhi lagao to tumhare paas nucleotide hai (Fig. 9.11, jo Section 9.6 mein bana hai). Naam ek regular pattern follow karte hain (Table 9.1). Nucleotides ko, aur kuch nahi, ek saath jodo to DNA ya RNA milta hai, yaani genetic material jo hereditary information store karta hai aur aage pass karta hai.

Aakhri family hai sugars (carbohydrates). Inki units monosaccharides hain: glucose ($\mathrm{C}{\phantom{X}}_6\mathrm{H}{\phantom{X}}_{12}\mathrm{O}{\phantom{X}}_6$), ek six-carbon sugar ya hexose jo zyadatar cells ko fuel deta hai, aur ribose ($\mathrm{C}{\phantom{X}}_5\mathrm{H}{\phantom{X}}_{10}\mathrm{O}{\phantom{X}}_5$), ek five-carbon sugar ya pentose jo RNA mein milta hai, sabse common hain. Do monosaccharides jud kar disaccharide banate hain, jaise sucrose (cane sugar) ya lactose (milk sugar). Inki lambi chains Section 9.5 ke polysaccharides hain.

9.2 Primary aur Secondary Metabolites

Biomolecules hazaaron mein hain, aur kyunki har ek life ki chemistry, yaani uske metabolism, mein banta ya use hota hai, isliye biologists inhe metabolites bhi kehte hain. Do tarah ke metabolites maane jaate hain. Primary metabolites hain amino acids, sugars, fatty acids, nucleotides aur Section 9.1 ki doosri families. Yeh har cell mein milte hain, animal ho ya plant, aur har ek ka growth, energy supply ya heredity mein ek jaana-pehchana kaam hai.

Secondary metabolites plants, fungi aur microbes ki khaasiyat hain (Fig. 9.6): opium poppy ka alkaloid, beetroot ka pigment, jasmine ki khushboo, babool ke ped se rista gum, rubber tree ka latex, ek mould ka banaya antibiotic, chai ke flavonoids, kisi masale ka flavour. Hazaaron pata hain. Inmein se kai ke baare mein abhi tak koi nahi jaanta ki yeh unhe banane wale organism ke liye kya karte hain. Kuch saaf taur par use survive karne mein madad karte hain, jaise pollinators ke liye flower ko rang dena ya use charne wale animal ko zeher dena, isliye yeh uski ecology ke liye zaroori hain. Aur inmein se kai logon ke liye medicines, dyes, flavours, perfumes aur raw materials ke roop mein keemti hain (Table 9.2).

9.3 Biomacromolecules

Acid-soluble pool ke molecules ko weigh karo to ek pattern dikhta hai: har ek chhota hai, jiska molecular mass 18 daltons (paani) se lagbhag 800 Da ke beech hai. Ek dalton (Da) carbon-12 atom ke mass ka barahwa hissa hai, lagbhag ek hydrogen atom ke mass jitna.

Kapde par ruka material alag kahani batata hai. Wahan sirf chaar classes ke organic compounds milte hain, proteins, nucleic acids, polysaccharides aur lipids, aur in chaar mein se teen 10 000 Da ya usse zyada ke giants hain (Fig. 9.7). Isliye size biomolecules ko do groups mein baant deta hai. Lagbhag 1000 Da se neeche micromolecules hain, jinhe aam taur par sirf biomolecules kehte hain, aur yeh acid-soluble pool banate hain. Giants macromolecules hain, jinhe biomacromolecules bhi kehte hain.

Lipids ek paheli hain: inke molecules kabhi lagbhag 800 Da se zyada nahi hote, phir bhi yeh giants ke saath pahunch jaate hain. Socho ki loose eenton aur patli plastic sheets se bani ek building tod di jaati hai. Eentein chhanni se beh jaati hain, lekin phati plastic mud kar chhoti band thailiyan ban jaati hai jo malbe ke saath ruk jaati hain. Cell mein plastic sheets hain membranes, jo zyadatar lipid se bani hain. Peesne se cell membrane aur organelles ki membranes tukdon mein phat jaati hain, jo khud ko band karke chhoti water-insoluble thailiyan bana leti hain jinhe vesicles kehte hain, aur vesicles acid-insoluble material ke saath peeche reh jaate hain. Isliye lipids macromolecular fraction mein apni arrangement ki wajah se aate hain, apne size ki wajah se nahi; sahi maayne mein lipids macromolecules nahi hain.

Dono fractions ko phir se milao to poora tissue mil jaata hai: chhote ghule hue molecules, jo moti taur par cytoplasm ke contents dikhate hain, plus cytoplasm aur organelles ke macromolecules. Sab kuch maatra ke hisaab se rank karo to winner koi biomolecule hai hi nahi. Paani har living organism mein sabse zyada paaya jaane wala chemical hai (Fig. 9.8).

9.4 Proteins

Proteins polypeptides hain: amino acids ki bina branch wali chains. Chain mein padosi ek peptide bond se jude hote hain. Yeh tab banta hai jab ek amino acid ka carboxyl group agle ke amino group se react karta hai, aur ek water molecule nikal jaata hai (Fig. 9.9). Isliye har chain ke ek end par free amino group aur doosre end par free carboxyl group hota hai.

Starch aur cellulose, jinse tum aage miloge, ek hi tarah ki unit baar-baar repeat karte hain; aise polymer ko homopolymer kehte hain. Protein iske bajaye 20 tak alag tarah ke amino acids (glycine, leucine, histidine, methionine wagairah) ko ek fixed order mein jodta hai, isliye woh heteropolymer hai.

Tumhara body kuch amino acids doosre molecules se bana sakta hai; yeh non-essential amino acids hain. Kuch ko woh bana nahi sakta, ya kaafi tezi se nahi bana sakta, isliye unhe khaane se aana padta hai: yeh essential amino acids hain. Isiliye diet mein proteins zaroori hain. Digestion unhe amino acids mein tod deta hai, jo essential amino acids dete hain. 11Adults ko nau essential amino acids chahiye, jinmein lysine, tryptophan, methionine aur leucine shaamil hain.

Ek protein tumhare saliva mein enzyme ho sakta hai, khoon mein hormone, cell membrane mein pump ya channel, ya germs se ladne wala antibody (Table 9.3). Do records yaad rakhne laayak hain. Collagen animal world mein sabse zyada paaya jaane wala protein hai. RuBisCO (ribulose bisphosphate carboxylase-oxygenase), woh enzyme jo photosynthesis mein carbon dioxide fix karta hai, poore biosphere mein sabse zyada paaya jaane wala protein hai.

9.5 Polysaccharides

Saikdon ya hazaaron monosaccharides ko ek chain mein jodo to tumhare paas ek polysaccharide hai, insoluble fraction ka teesra tarah ka macromolecule. Hairaani ki baat hai ki sabse zaroori teen polysaccharides bilkul ek hi unit, glucose, se bane hain. Cellulose plant cell walls ka fibre hai, isiliye cotton aur paper (lakdi ya bamboo ke pulp se bana) lagbhag pure cellulose hain. Starch plant ka energy store hai, potato ya chawal ke daane mein, aur glycogen animals mein iska barabar ka store hai, jo liver aur muscle mein rakha jaata hai. Har ek sirf ek tarah ka monosaccharide use karta hai, isliye har ek homopolymer hai. Har polysaccharide glucose se nahi bana: inulin, jo dahlia tubers aur chicory roots mein store hota hai, fructose se bana hai.

Sugars ke beech har link ki ek direction hoti hai, isliye chain ke dono ends alag hote hain. Ek end, jo convention ke hisaab se right mein draw hota hai, reducing end hai; doosra, left wala, non-reducing end hai. Glycogen bahut branched hota hai, aur har branch apne non-reducing end par khatam hoti hai, isliye glycogen molecule ke kai non-reducing ends hote hain lekin sirf ek reducing end (Fig. 9.10).

Shape bhi matter karti hai. Starch chains mud kar helices banati hain, aur iodine molecules ($\mathrm{I}{\phantom{X}}_2$) coil ke andar ghus sakte hain; starch–iodine complex blue hota hai (concentrated hone par blue-black). Cellulose chains seedhi aur paas-paas padi rehti hain, iodine pakadne ke liye koi helix nahi hota, isliye cellulose blue rang nahi deta. Yahi fark starch ke iodine test ka base hai.

Sugars ko jodne se pehle chemically modify bhi kiya ja sakta hai. Chitin, arthropod exoskeletons ka mazboot material (prawn ka shell, housefly ka wing), ek amino-sugar se bana hai, aur yeh fungi ki cell walls bhi banata hai. Glucosamine aur N-acetylgalactosamine aise complex polysaccharides mein milne wale doosre modified sugars hain, aur inmein se zyadatar, cellulose ki tarah, homopolymers hain.

9.6 Nucleic Acids

Nucleic acids, yaani polynucleotides, list poori karte hain. Yeh, polysaccharides aur polypeptides insoluble fraction ke asli giants hain, uske true macromolecules; lipids, yaad rakho, bas uske saath chale aate hain.

Ek nucleotide ko todo to teen chemically alag tukde milte hain (Fig. 9.11): ring jaisa nitrogenous base, five-carbon pentose sugar aur phosphoric acid se bana ek phosphate group. Bases wahi paanch hain jo Section 9.1 mein mile the, aur unke ring skeletons unhe do families mein baant dete hain. Adenine aur guanine purine naam ke double-ring skeleton par bane hain, isliye yeh substituted purines hain. Cytosine, thymine aur uracil single-ring pyrimidine skeleton par bane hain: yeh substituted pyrimidines hain.

Do sugars possible hain. Ribose ke carbon 2′ par ek –OH group hota hai; 2′-deoxyribose mein wahan sirf ek hydrogen hota hai (deoxy ka matlab hai 'oxygen ke bina'). Sugar se nucleic acid ka naam padta hai: deoxyribose se deoxyribonucleic acid (DNA) banta hai aur ribose se ribonucleic acid (RNA). Bases mein bhi thoda fark hai: DNA thymine use karta hai aur RNA uracil, jabki dono adenine, guanine aur cytosine use karte hain. Class 12 mein tum dekhoge ki yeh chains kaise pair banati hain, apni copy banati hain aur information le jaati hain.

9.7 Proteins ki Structure

Structure jaise word ka alag sciences mein alag matlab hota hai. Washing soda ki structure poocho to chemist shayad bas $\mathrm{N}\mathrm{a}{\phantom{X}}_2\mathrm{C}\mathrm{O}{\phantom{X}}_3$ likh de; glucose ke baare mein poocho to shayad kaagaz par flat bani ek ring dikhayi jaaye; ek crystallographer tumhe three-dimensional model dega. Proteins describe karte waqt biologists chaar levels ki ek seedhi use karte hain, har level apne neeche wale par bana (Fig. 9.12).

Level one, primary structure, bas amino acids ka order hai, jaise 20 letters wali alphabet se likha koi word. Convention ke hisaab se ise free amino group wale end, yaani N-terminal amino acid, se free carboxyl group wale end, yaani C-terminal amino acid, tak likhte hain. Ek letter badlo to matlab badal sakta hai: sickle-cell anaemia mein haemoglobin ka sirf ek amino acid badalna bimari ke liye kaafi hai.

Level two, secondary structure, un local shapes ko describe karta hai jo chain ke chhote hisse lete hain. Kuch hisse spring ki tarah mud kar helix banate hain; kuch flat zigzag strands mein paas-paas lete hain, ya loops banate hain. Proteins mein milne wala coil, α-helix, hamesha right-handed hota hai, aur zigzag strands β-pleated sheets banate hain. Backbone ke paas-paas ke hisson ke beech hydrogen bonds dono ko shape mein rakhte hain.

Phir poori chain, helices aur sheets samet, khud par mud kar ek compact three-dimensional shape banati hai. Jeb mein gaanth ban kar uljhe lambe earphone cable ke baare mein socho, bas fark yeh hai ki protein har baar ek hi tarah fold hota hai. Yeh overall fold level three hai, tertiary structure. Hydrogen bonds, ionic attractions, paani se bachne wali side chains ka ek jagah jamaa hona aur cysteines ke beech covalent disulphide (S–S) bonds ise jode rakhte hain. Proteins jo kuch karte hain, uska zyadatar is fold par depend karta hai: ise khol do, to enzyme kaam karna band kar deta hai.

Level four sirf un proteins par lagta hai jo ek se zyada folded polypeptides se bane hain, jinme se har ek ko subunit kehte hain. Subunits jis tarah ek saath fit hote hain, chahe row mein, ring mein ya compact cluster mein, woh quaternary structure hai. Adult human haemoglobin (Hb) ke chaar subunits hain: do ek jaisi α chains aur do ek jaisi β chains (${\alpha }_2{\beta }_2$).

9.8 Enzymes

Cell mein lagbhag har reaction ek enzyme se tez hota hai. Lagbhag saare enzymes proteins hain; kuch catalytic power wale RNA molecules hain, jinhe ribozymes kehte hain.

Kisi bhi protein ki tarah, enzyme ki primary, secondary aur tertiary structure hoti hai. Folded enzyme ko ek ubad-khabad gend ki tarah socho jiski surface par gaddhe hain. Zyadatar gaddhe bas folding ka result hain, lekin ek khaas hai: active site, ek daraar jiska shape aur chemical groups ki lining ek khaas molecule, substrate, ko usmein baithne deti hai. Reaction wahin hota hai, aur isi site ke zariye enzyme apni kamaal ki speed haasil karta hai.

Heat enzymes ko industrial catalysts se sabse saaf taur par alag karti hai. Ammonia banane wala iron catalyst lagbhag 450 °C aur bahut high pressure par kaam karta hai, aur car ke exhaust converter mein platinum kaam karne ke liye garam hona hi chahiye. Iske ulat, zyadatar enzymes lagbhag 40 °C se upar bikharne lagte hain. Garam paani ke sroton aur deep-sea vents ke microbes, yaani thermophiles, exception hain: unke enzymes 80–90 °C par bhi kaam karte rehte hain. Yahi heat stability unhe keemti tools banati hai; Class 12 mein tum Taq polymerase se miloge, jo 72 °C par DNA copy karta hai. Neeche ka comparison baaki fark batata hai.

9.8.1 Chemical Reactions

Enzyme kya karta hai yeh samajhne ke liye pehle saaf hona chahiye ki reaction kya hai. Jab koi substance sirf shape ya state badalta hai, jaise barf pighalna ya paani ubalna, to uske molecules ke andar koi bond nahi tootta: yeh physical change hai. Jab bonds tootte hain aur naye bonds bante hain, jisse naye substances bante hain, to yeh change chemical reaction hai. Silver nitrate aur common salt ke solutions milane se silver chloride ka safed precipitate banta hai, yeh ek inorganic reaction hai.22$\mathrm{A}\mathrm{g}\mathrm{N}\mathrm{O}{\phantom{X}}_3+\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}\stackrel{}{\to }\mathrm{A}\mathrm{g}\mathrm{C}\mathrm{l}\downarrow +\mathrm{N}\mathrm{a}\mathrm{N}\mathrm{O}{\phantom{X}}_3$ Sucrose ka glucose aur fructose mein tootna, jo table sugar digest karte waqt hota hai, ek organic reaction hai.

Koi physical ya chemical process kitni tezi se hota hai, woh uska rate hai: har unit time mein kitna product banta hai ((9.1)). Rate ko ek direction do, to biochemists use velocity kehte hain.

Temperature lagbhag har process ke rate par asar daalta hai. Ek kaam ka rule of thumb: rate har 10 °C badhne par lagbhag double hota hai aur har 10 °C ghatne par aadha ho jaata hai ((9.2)).

Catalyst reaction ko behad tez chala sakta hai, aur enzymes champion catalysts hain. Carbon dioxide ka paani se milkar carbonic acid banana ek achha example hai ((9.3)). Akele yeh reaction bahut dheema hai. Red blood cells ke cytoplasm mein maujood enzyme carbonic anhydrase ise lagbhag ek crore guna tez kar deta hai. Tab ek enzyme molecule har second carbonic acid ke laakhon molecules bana sakta hai.

Ek cell mein hazaaron tarah ke enzymes hote hain, har ek apna reaction chalata hai, aur reactions chains mein aate hain: ek enzyme ka product agle ka substrate hota hai. Aisa sequence, jismein har step ek enzyme (ya ek enzyme complex) chalata hai, metabolic pathway hai. Jaise, glucose das enzyme-catalysed reactions se pyruvic acid banta hai ((9.4)): inhe tum Chapter 12, Respiration in Plants mein follow karoge.

Aisa pathway kahan khatam hota hai, yeh conditions par depend karta hai, kyunki end mein ek-do extra reactions jode ja sakte hain. Bharpoor oxygen wala achhi supply wala cell pyruvic acid ko aage oxidation ke liye rakhta hai. Sprinter ki jaangh ki muscle, jismein oxygen kam hai, use lactic acid mein badal deti hai. Phoolte bread dough mein yeast use ethanol aur carbon dioxide mein badal deta hai.

9.8.2 Enzymes Chemical Conversions ki Itni High Rates Kaise Laate Hain?

Jis molecule par enzyme kaam karta hai use substrate (S) kaho aur jo woh banta hai use product (P), to reaction $\mathrm{S}\stackrel{}{\to }\mathrm{P}$ hai. Catalysis ek mulaqaat se shuru hota hai. Substrate molecules idhar-udhar diffuse karte hain jab tak ek active site mein na pahunch jaaye, aur tab enzyme aur substrate ek pal ke liye enzyme–substrate complex, ES, ki tarah jud jaate hain. ES nahi, to reaction nahi: har catalysed conversion is complex se hokar guzarta hai. Enzyme ki pakad mein substrate ek pal bhar ki, high-energy arrangement mein mud jaata hai, jise transition state kehte hain. Bonds tootna aur banna poora hota hai, aur product door chala jaata hai.

S se P tak ke safar ko ek pahadi darre (mountain pass) ke paar paidal chalne ki tarah socho (Fig. 9.13). Height potential energy dikhati hai, aur raaste par doori reaction ki progress. Stable molecules ghaatiyon mein rehte hain; unstable beech ki arrangements dhalaan par hain, aur transition state choti par.

End wali ghaati start wali se neeche ho sakti hai: tab reaction energy chhodta hai (yeh exothermic hai) aur chalte rehne ke liye garam karne ki zaroorat nahi. Lekin dhalaan wala safar bhi chadhaai se shuru hota hai. Substrate ki average energy se choti ki oonchai activation energy hai, aur har reaction, chahe energy chhode ya le, ise chukata hai. Enzyme pahaad mein neeche kaati gayi ek tunnel jaisa hai. Start aur finish ghaatiyan bilkul wahin rehti hain, isliye nikalne wali energy nahi badalti, lekin chadhaai bahut chhoti ho jaati hai, aur har second kahin zyada molecules paar pahunch jaate hain.

9.8.3 Enzyme Action ka Nature

Equation ki tarah likhein to catalysis ka ek round (9.5) jaisa dikhta hai. Enzyme (E) aur substrate (S) reversibly milkar kam der tikne wala, bahut reactive ES complex banate hain; ES ek enzyme–product complex, EP, mein badalta hai; aur EP toot kar product (P) aur free enzyme deta hai. E dono ends par bina badle dikhta hai: enzyme udhaar liya jaata hai, kharch nahi hota.

Chalti tasveer ki tarah dekhein to catalytic cycle ke chaar stages hain (Fig. 9.14):

1. Bind. Ek substrate molecule active site mein baith jaata hai.
2. Fit. Uske aane se enzyme apna shape thoda badalta hai aur uske chaaron taraf kas kar band ho jaata hai (induced fit).
3. React. Itni kas kar pakad mein, active site substrate ke bonds tod deti hai, aur enzyme–product complex banta hai.
4. Release. Products nikal jaate hain, aur khaali enzyme agle substrate molecule ko usi cycle se le ja sakta hai.

Kyunki enzyme har baar recycle hota hai, uski zara si maatra bahut zyada substrate process kar sakti hai.

9.8.4 Enzyme Activity par Asar Daalne Wale Factors

Enzyme tabhi tak kaam karta hai jab tak uska folded shape bana rahe, isliye jo bhi cheez uski tertiary structure ko bigaadti hai woh uski activity badal deti hai. Chaar cheezein sabse zyada matter karti hain: temperature, pH, kitna substrate maujood hai, aur woh chemicals jo enzyme se chipak kar use regulate karte hain (Fig. 9.15).

Temperature aur pH

Enzyme ki activity ko temperature ya pH ke against plot karo to ek pahaadi jaisa curve milta hai. Uski choti optimum temperature ya optimum pH dikhati hai, aur dono taraf activity gir jaati hai, isliye har enzyme sirf ek kaafi patli range mein kaam ka hai. Lekin temperature wali pahaadi ki dono sides ek jaisi nahi hain. Thandi side par enzyme bas dheema ho jaata hai, kuch der ke liye switch off: use garam karo to woh phir kaam karta hai, yeh ek wajah hai ki fridge khaane ko fresh rakhta hai. Garam side par heat protein ko khol deti hai, is change ko denaturation kehte hain, aur yeh nuksaan permanent hai.

Enzyme ka optimum pH us jagah ke hisaab se hota hai jahan woh kaam karta hai. Pepsin, jo acidic stomach mein protein digest karta hai, pH 2 ke paas sabse achha kaam karta hai. Trypsin, jo alkaline small intestine mein kaam karta hai, pH 8 ke paas sabse achha hai, aur salivary amylase neutral ke paas wala pH pasand karta hai.

Substrate ka concentration

Enzyme molecules ko railway station ke autorickshaws aur substrate molecules ko aane wale passengers ki tarah socho. Jab passengers kam hain, to zyada log aane ka matlab har minute zyada trips. Jab har rickshaw busy ho jaata hai, to extra passengers bas line mein lag jaate hain, aur har minute trips ki ginti badhna ruk jaati hai. Jab temperature aur pH steady rakhe jaate hain aur enzyme ki fixed maatra mein substrate milaya jaata hai, to enzyme bhi aisa hi behave karta hai. Reaction ki velocity pehle tezi se, phir dheere chadhti hai, aur aakhir mein ek maximum velocity, $V_{max}$, par ruk jaati hai (Fig. 9.15, aakhri step). Enzyme molecules substrate molecules se bahut kam hote hain, isliye high substrate concentration par har active site bhari hoti hai: enzyme saturated hai.

Curve par ek aur nishaani hai. Jis substrate concentration par velocity apne maximum ke aadhe, $V_{max}\mathrm{/}2$, tak pahunchti hai, use $K_m$ kehte hain. Chhote $K_m$ wala enzyme kam substrate concentration par hi aadhi speed tak pahunch jaata hai, jo dikhata hai ki woh apne substrate ko mazbooti se bind karta hai.33$K_m$ Michaelis constant hai, jiska naam Leonor Michaelis ke naam par hai, jinhone Maud Menten ke saath 1913 mein yeh curve describe kiya.

Inhibitors

Kuch chemicals enzyme se judkar use dheema ya band kar sakte hain. Is tarah enzyme ko dheema karna ya rokna inhibition hai, aur iske liye zimmedaar chemical inhibitor hai.

Kuch inhibitors nakal karke kaam karte hain. Ek competitive inhibitor asli substrate se itna milta-julta hota hai ki active site use accept kar leti hai, phir bhi koi reaction nahi hota; jab tak woh site mein baitha hai, asli substrate bahar rehta hai, aur enzyme ka output gir jaata hai (Fig. 9.17). Classic case succinic dehydrogenase ka hai, woh enzyme jo succinate par kaam karta hai. Malonate mein wahi do charged carboxylate ends hote hain, bas beech mein ek carbon kam, aur yeh enzyme ko competitively inhibit karta hai (Table 9.7).

Kyunki inhibitor aur substrate same sites ke liye compete karte hain, enzyme ko substrate se bhar dene par inhibitor bahar ho jaata hai aur activity wapas aa jaati hai. Medicine bimari failane wale bacteria (bacterial pathogens) ke khilaaf yahi trick use karti hai. Jaise, sulpha drugs PABA naam ke compound ki nakal karti hain jo bacteria ko vitamin folic acid banane ke liye chahiye, aur is tarah woh use use karne wale bacterial enzyme ko jam kar deti hain.

9.8.5 Enzymes ka Classification aur Nomenclature

Biochemists ne kai hazaar enzymes ko characterise kiya hai, aur woh zyadatar ko catalyse hone wale reaction ki kism ke hisaab se chhe classes mein rakhte hain (Table 9.8). Har class 4–13 subclasses mein bati hai, aur har enzyme ko chaar numbers ka ek code milta hai. Jaise, salivary α-amylase EC 3.2.1.1 hai: class 3 (ek hydrolase), phir ek subclass, ek sub-subclass aur ek serial number.

9.8.6 Co-factors

Kuch enzymes pure protein hote hain. Kai doosre tab tak bekaar baithe rehte hain jab tak ek non-protein helper, cofactor, unse na jud jaaye. In enzymes ke akele protein part ko apoenzyme kehte hain; cofactor lagne ke baad poore active enzyme ko aksar holoenzyme kehte hain. Cofactors teen tarah ke hote hain (Fig. 9.18).

Prosthetic group ek organic cofactor hai jo apne apoenzyme se mazbooti se juda rehta hai; yahi pakka judaav iski pehchaan hai. Haem iska textbook example hai. Yeh catalase aur peroxidase ki active site mein baitha hota hai, do enzymes jo hydrogen peroxide ko khatam karte hain (catalase use todta hai: $2\mathrm{H}{\phantom{X}}_2\mathrm{O}{\phantom{X}}_2\stackrel{}{\to }2\mathrm{H}{\phantom{X}}_2\mathrm{O}+\mathrm{O}{\phantom{X}}_2$).

Co-enzymes bhi organic hote hain, lekin sirf dheele aur thodi der ke liye jude hote hain: ek co-enzyme catalysis ke pal ke liye enzyme se judta hai aur phir chala jaata hai, aksar agli baar kisi bilkul alag enzyme ki madad karne. Kai co-enzymes vitamins se bante hain, isiliye humein vitamins bahut kam maatra mein chahiye lekin unke bina hum beemar pad jaate hain. Niacin, ek B vitamin, NAD (nicotinamide adenine dinucleotide) aur NADP dono ka hissa hai.

Metal ions bridge ka kaam karte hain. Ion active site ki side chains se coordination bonds dwara pakda rehta hai aur substrate ke saath bhi ek ya zyada coordination bonds banata hai. Carboxypeptidase, ek protein digest karne wala enzyme, is tarah zinc par depend karta hai.

Cofactor hata do to apoenzyme apna reaction catalyse nahi kar paata, yeh sabse saaf saboot hai ki cofactor catalytic machinery ka hissa hai.