Basa reMitochondria muKufema Kwemasero
Mitochondria inowanzonzi "simba" remasero nekuti ndiwo anogadzira simba rakawanda rinodiwa kuti munhu ararame. Simba iri rinoshandiswa pakuita zvinhu zvakasiyana-siyana, kubva pakusunga tsandanyama nekufambisa zvinhu kuburikidza nemembrane kusvika pakupatsanurwa kwemasero uye kugadzirwa kwemamorekuru akakosha. Mumamiriro ezvinhu ehupenyu, simba rinoshandiswa zvakananga nemasero rinonyanya kuva muchimiro cheATP (adenosine triphosphate). Ruzhinji rweATP runogadzirwa kuburikidza nekufema kwemasero, uye mitochondria inoita basa guru mukuita uku.
Maumbirwo eMitochondrial seBasa Rinotsigira
Kuti unzwisise mashandiro anoita mitochondria mukufema kwemasero, zvakakosha kunzwisisa chimiro chayo chikuru. Mitochondria ine membrane mbiri: membrane yekunze inopindika zvishoma nezvishoma uye membrane yemukati inosarudzwa zvakanyanya. Kamudzira yemukati inoumba mapete anonzi cristae. Mapete aya anowedzera nzvimbo yepamusoro yemembrane yemukati, zvichipa nzvimbo yakawanda yekugadzira ATP.
Mukati memukati memukati mune mitochondrial matrix, mvura ine viscous ine ma enzymes akakosha, mitochondrial DNA, uye ribosomes. Kuvapo kweDNA ne ribosomes kunoratidza kuti mitochondria ine kugona kushoma kwekugadzira mamwe mapuroteni ega, kunyangwe akawanda emapuroteni avo achiri kunyorwa neDNA yenyukireya yesero. Nzvimbo iri pakati pemukati memukati memukati memukati inonzi nzvimbo yepakati pemuviri, iyo inoita basa rakakosha mukuumbwa kweproton gradient panguva yekufema.
Chimiro ichi chine zvidimbu zvakasiyana-siyana hachisi chimiro chete, asi dhizaini yakakodzera zvakakwana kuita maitiro akaomarara uye ane nhanho dzakawanda ekufema kwemasero.
Pfupiso yeKufema Kwemasero
Kufema kwemasero inzira dzakasiyana-siyana dzemakemikari dzinoputsa mamorekuru ezvekudya—kazhinji kacho glucose—kuti zvigadzire ATP. Maitiro aya anogona kukamurwa kuita matanho makuru akati wandei: glycolysis, pyruvate oxidation, Krebs cycle (citric acid cycle), electron transport chain, uye oxidative phosphorylation. Pamatanho aya, glycolysis inoitika mu cytoplasm, nepo matanho anotevera achiitika mu mitochondria. Nemamwe mashoko, mitochondria ndiyo nzvimbo huru dzekugadzirwa kwesimba re aerobic.
Basa reMitochondria Mushure meGlycolysis
Glycolysis inoputsa molekyuru imwe chete yeglucose kuita mamorekyuru maviri epyruvate, zvichigadzira huwandu hushoma hweATP neNADH. Zvisinei, ATP inogadzirwa neglycolysis chete haina kukwana kusangana nezvinodiwa nesimba zvemasero mazhinji. Apa ndipo panopinda mitochondria.
Pyruvate inobva muglycolysis inopinda mumitochondria kuburikidza nemapuroteni ekufambisa akasarudzika ari mumukati memukati. Mukati me matrix, pyruvate inopinda mu pyruvate oxidation (inonziwo bridging reaction) kuAcetyl-CoA. Maitiro aya anogadzira NADH uye anoburitsa CO₂ sechinhu chimwe chete. Acetyl-CoA ndiyo "tiketi yekupinda" kuchikamu chinotevera, Krebs cycle.
Kutenderera kweKrebs muMitochondrial Matrix
Kutenderera kweKrebs kunoitika mu mitochondrial matrix uye chinangwa ndechekuburitsa simba rakawanda kubva ku acetyl-CoA. Mukufamba uku, acetyl-CoA inosangana ne oxaloacetate kuti igadzire citrate, iyo inobva yaita maitiro akasiyana-siyana e enzyme kuti idzokere ku oxaloacetate. Munguva iyi, CO₂ inoburitswa uye mamorekuru ekutakura maerekitironi ane simba rakawanda akadai seNADH neFADH₂ anoumbwa. Kutenderera kweKrebs kunogadzirawo huwandu hushoma hweATP (kana GTP, zvichienderana nerudzi rwesero).
Kunyangwe Krebs cycle ichiburitsa ATP, mupiro mukuru wemitochondria kusimba remasero unobva muzvigadzirwa zveNADH neFADH₂. Mamorekuru maviri aya ane maerekitironi ane simba rakawanda ayo achashandiswa mumatanho anotevera.
Cheni yekufambisa maerekitironi muMitochondrial Inner Membrane
Kamudzira kemukati memitochondrial ndiyo nzvimbo yeketani yekufambisa maerekitironi (ETC), network yakaoma yemapuroteni nemamorekuru anotakura maerekitironi. Maerekitironi anobva kuNADH neFADH₂ anotamiswa kubva kune imwe complex kuenda kune imwe. Kutamiswa kwemaerekitironi uku kunoburitsa simba zvishoma nezvishoma, pane kuti zvese panguva imwe chete, zvichibvumira kushandiswa zvakanaka.
Simba rinoburitswa rinoshandiswa kupomba ma H⁺ ions (maprotoni) kubva mu matrix kuenda munzvimbo yepakati pemembrane. Izvi zvinogadzira mutsauko mukuwanda kweproton uye kushaja kwemagetsi pakati pe matrix nenzvimbo yepakati pemembrane. Musiyano uyu unonzi electrochemical gradient kana kuti proton motivation force. Iyi gradient inomiririra "simba rinokwanisa" rinozoshandiswa kugadzira huwandu hwakawanda hweATP.
Pakupera kwecheni yekufambisa maerekitironi, maerekitironi anozogamuchirwa neokisijeni (O₂) uye anosanganiswa nemapurotoni kugadzira mvura (H₂O). Ndokusaka okisijeni ichikosha zvikuru mukufema kwemhepo: pasina okisijeni semugamuchiri wekupedzisira wemaerekitironi, cheni yekufambisa maerekitironi yaizomira, uye kugadzirwa kweATP kwaizoderera zvakanyanya.
ATP Synthase uye Oxidative Phosphorylation
ATP synthase ienzyme hombe iri mukati memukati memitochondrial membrane. Iyi enzyme inoshanda se molecular turbine. Sezvo mapurotoni achidzoka kubva panzvimbo yepakati pemembrane kuenda ku matrix kuburikidza neATP synthase, simba rekuyerera kweproton rinoshandiswa kusanganisa ADP ne inorganic phosphate (Pi) kuti igadzire ATP. Maitiro aya ekuumbwa kweATP, anotungamirwa ne NADH/FADH₂ oxidation uye proton flow, anonzi oxidative phosphorylation.
Oxidative phosphorylation inobatsira chikamu chikuru cheATP mukufema kwemasero e aerobic. Kazhinji, molekyuru imwe chete yeglucose inogona kugadzira ATP inosvika 30–32 (nhamba iyi inosiyana zvichienderana nemamiriro emasero uye rudzi rwe "shuttle" inotakura cytoplasmic NADH kuenda ku mitochondria). Paizvi, chikamu chikuru chinobva mubasa re electron transport chain uye ATP synthase mu mitochondria.
Sei Krista Yakakosha?
MaCristae mapete emukati memukati anowedzera nzvimbo yepamusoro apo electron transport chain uye ATP synthase inoitika. Kana macristae akawanda, nzvimbo yepamusoro yeATP-forming reactions yakakura. Ndokusaka masero ane simba rakawanda—akadai semasero emhasuru dzemwoyo—ane mitochondria yakawanda uye macristae akagadzirwa zvakanyanya. Maumbirwo aya anoratidza hukama hwakananga pakati pezvinodiwa nesimba resero nekukwanisa kwemitochondria kugadzira ATP.
Mitochondria uye Kudzora Kwesimba reMetabolism
Pamusoro pekugadzira ATP, mitochondria ine basa guru mukudzora mashandiro emasero. Mitochondria inogona kugadzirisa mwero wekufema kwayo zvichienderana nezvinodiwa nesimba. Kana masero achida simba rakawanda, mwero wekushandiswa kweATP unowedzera, kugadzirwa kweADP kunowedzera, uye oxidative phosphorylation inokurumidza. Kusiyana neizvi, kana simba richidikanwa richiderera, mwero wekufema unodererawo. Saka, mitochondria haingoburitse simba chete asiwo inobatsira kuchengetedza simba remasero.
Kukanganisa kweMatambudziko eMitochondrial Function
Kana basa remitochondrial rikakanganisika, kugadzirwa kweATP kunodzikira uye masero anogona kusangana nekumanikidzwa kwesimba. Mune mamwe mamiriro ezvinhu, mitochondria inogonawo kugadzira mafree radicals (ROS) sechibereko cheketani yekufambisa maerekitironi. Muhuwandu hwakadzorwa, ROS inogona kuita basa mukutumira masaini mumasero, asi huwandu hwakawanda hunogona kukanganisa mapuroteni, mafuta, uye DNA. Kukuvadzwa kweMitochondrial kunowanzobatanidzwa nematambudziko akasiyana-siyana ehutano nekukwegura, kunyange hazvo hurukuro yacho ichipfuura kufema kwemasero.
Mhedziso
Mitochondria inoita basa guru mukufema kwemasero emhepo nekuita matanho akakosha anotevera glycolysis, kunyanya pyruvate oxidation, Krebs cycle, electron transport chain, uye oxidative phosphorylation. Maumbirwo akasiyana e mitochondria—nekamera yayo yemukati yakapetwa ichiumba cristae, matrix, uye intermembrane space—inotsigira kugadzirwa kweATP kwakanaka kuburikidza nekuumbwa kweproton gradient uye kushanda kweATP synthase. Kuburikidza nemaitiro aya, mitochondria inopa simba rinokosha kuti sero riite mabasa ehupenyu. Nokudaro, kunzwisisa mashandiro e mitochondria mukufema kwemasero zvinoreva kunzwisisa imwe yenzira huru dzehupenyu padanho remasero.
