Noma ngabe ufunde i-biology esikoleni esiphakeme, noma ufunda ngokuzuza kwemisipha, uzwile ngakho Umjikelezo weKrebs. Yisinye sezigaba zokuthamba kokuphefumula kwamaselula okwenzeka emzimbeni wethu. Kuyaziwa nangegama lomjikelezo we-citric acid futhi kuyisigaba semethabolic esenzeka kumatrix we-mitochondrial wawo wonke amaseli ezilwane.
Kulesi sihloko, sizochaza izici zomjikelezo we-Krebs, isinyathelo ngesinyathelo, nokubaluleka kwawo jikelele.
Izigaba zokuphefumula kwamaselula
Ngaphambi kokuthi sichaze ukuthi yini umjikelezo wama-krebs, kufanele sikhumbule ukuthi ukuphefumula kwamaselula kusebenza kanjani, ngoba kubaluleke kakhulu. Ake sibone ukuthi yiziphi izigaba zokuphefumula kwamaselula. Kwenzeka ngezigaba ezintathu eziyinhloko:
- I-Glycolysis: kuyinqubo lapho i-glucose yehlukaniswa yaba izingxenye ezincane. Phakathi nale nqubo kwakhiwa i-pyruvate noma i-pyruvic acid ezoholela ku-Acetyl-CoA.
- Umjikelezo weKrebs: Emjikelezweni weKrebs, i-Acetyl-CoA ixhunywe ku-CO2.
- Uchungechunge lokuphefumula: Lapha iningi lamandla likhiqizwa ukudluliswa kwama-electron asuka ku-hydrogen. La mandla avela ekuqedweni kwezinto ezihilelekile kuzo zonke izinyathelo zangaphambilini.
Uyini umjikelezo wama-krebs
Kusebenza kanjani ukuphefumula kwamaselula, okufakwe kwesinye sezinyathelo zalo mjikelezo, ake sibone ukuthi imayelana nani. Siyazi ukuthi kungumjikelezo onzima futhi unemisebenzi eminingi esiza imetabolism yeselula. Ngaphandle kwalo mjikelezo, wonke amaseli abengeke akwazi ukufeza imisebenzi ebalulekile emzimbeni wethu. Inhloso enkulu yomjikelezo wama-krebs ukukwazi ukukhuthaza ukuwohloka kwemikhiqizo yokugcina yemethabolism yama-carbohydrate, lipids namanye ama-amino acid.
Lapho sidla ukudla kufanele sazi ukuthi ama-macronutrients amakhulu ama-carbohydrate, amaprotheni namafutha. Amaprotheni nawo akhiwa ama-amino acid. Ngalesi sizathu, kwinqubo yokondla umjikelezo wama-krebs ubaluleke kakhulu. Zonke izinto ezifakwe emzimbeni ngokudla ziba ku-Acetyl-CoA ngenkululeko ye-CO2 ne-H2O nokuhlanganiswa kwe-ATP.
Ngenxa yalokhu kuhlanganiswa, kulapho kukhiqizwa khona amandla okufanele asetshenziswe amaseli ukwenza imisebenzi yawo. Sinabaxhumanisi abahlukahlukene kuzo zonke izigaba zomjikelezo abazisebenzisayo njengezandulela ekuhlanganisweni kwama-amino acid namanye ama-biomolecule. Ngenxa yalo mjikelezo singathola amandla kuma-molecule wokudla okuphilayo. La mandla esiwatholayo singawadlulisela kuma-molecule ukuze asetshenziswe emisebenzini yeselula futhi singenza imisebenzi yethu ebalulekile nayo yonke imisebenzi ebonakalayo yosuku lwethu usuku nosuku.
Ngaphakathi komjikelezo wama-krebs sithola ukuphendula okuthile kwamakhemikhali ikakhulukazi i-oxidative emvelweni. Konke ukusabela kudinga umoya-mpilo ukuze kwenzeke. Ukuphendula ngakunye kwamakhemikhali kunokubamba iqhaza kwamanye ama-enzyme atholakala kwi-mitochondria yamaseli. Onke ama-enzyme anesici esikhulu sokukwazi ukuvuselela ukusabela kwamakhemikhali. Uma sikhuluma ngokunciphisa ukusabela sikhuluma ngokwazi ukukhuphula izinga lapho ama-reactants aguqulwa abe yimikhiqizo.
Izinyathelo zomjikelezo wama-krebs
Kunokuphendula okuningana kwamakhemikhali phakathi nalo mjikelezo odinga ukwenziwa komoya-mpilo. Ukusabela kokuqala kwamakhemikhali yi-decodboxylation ye-oxidative ye-pyruvate. Kulokhu kusabela, i-glucose etholakala ekonakaleni kwama-hydrate anempandla iguqulwa ibe ngama-molecule amabili we-pyruvic acid noma i-pyruvate. Iglucose yehliswa ngeGlycolysis futhi iba ngumthombo obalulekile we-Acetyl-CoA. I-oxidative decarboxylation ye-pyruvate iqala ngomjikelezo we-citric acid. Lokhu kusabela kwamakhemikhali kufana nokuqedwa kwe-carbon dioxide ne-pyruvate ekhiqizwa eqenjini le-acetyl elibophezela ku-coenzyme A. Kule mpendulo yamakhemikhali, i-NADH ikhiqizwa njengemolekyuli ethwala amandla.
Lapho i-molecule ye-Acetyl-CoA isakhiwe, kulapho umjikelezo we-kreb wenzeka matrix we-mitochondria. Inhloso yale ngxenye ukukwazi ukuhlanganisa uchungechunge lwe-oxidation yeselula ukuze ixube wonke ama-carbons futhi ukwazi ukuwaguqula abe yi-carbon dioxide. Ukuze kwenzeke konke lokhu kuphendula kwamakhemikhali, ubukhona be-oxygen buyadingeka ngaso sonke isikhathi. Ngakho-ke, Sishilo ngaphambi kokuqala ukuchaza umjikelezo wama-krebs ukubaluleka kokuphefumula kwamaselula.
Konke kuqala nge-enzyme citrate synthetase esebenza ukuvuselela ukuphendula kwamakhemikhali lapho kudlulisela khona iqembu le-Acetyl ku-oxaloacetic acid eyakha i-citric acid kanye nokukhishwa kwe-coenzyme A. Igama lalo mjikelezo lihlobene ukwakheka kwe-citric acid nakho konke ukuphendula kwamakhemikhali okwenzeka lapha.
Ezinyathelweni ezilandelayo, okunye ukusabela kwe-oxidation kanye ne-decarboxylation kwenzeka. Lokhu kusabela kubangela ukuba i-ketoglutaric acid yakheke. Phakathi nenqubo, i-carbon dioxide iyakhululwa futhi i-NADH ne-H yakheka. Le ketoglutaric acid ithola ukusabela kwe-oxidative decarboxylation eyenziwa yi-enzyme complex ehlanganisa i-Acetyl CoA ne-NAD. Konke lokhu kusabela kuzoholela ku-succinic acid, i-NADH kanye ne-molecule ye-GTP ezodlulisela amandla ayo ku-molecule ye-ADP ekhiqiza i-ATP.
Izinyathelo zokugcina zalo mjikelezo ngakho bagxila kuphela eqinisweni lokuthi i-acid ye-succinic ingaxutywa ukuze yenze i-fumaric acid. Lolu hlobo lwe-asidi lwaziwa ngegama le-fumarate. I-coenzyme yayo yi-ADF. Lapha kuzokwakhiwa i-FADH2, engenye ye-molecule yamandla othwala amandla. Ekugcineni, i-fumaric acid ayimnandi ukukwazi ukwakha i-malic acid eyaziwa nangokuthi i-malate. Ukuqeda umjikelezo wama-krebs, I-malic acid iqala ukufaka i-oxidize ukuze yenze kancane kancane i-oxaloacetic acid. Ngale ndlela, umjikelezo uqalwa phansi futhi konke ukusabela esikubalulile kwenzeka futhi kusukela ekuqaleni.
Ngiyethemba ukuthi ngalolu lwazi ungafunda kabanzi ngomjikelezo wama-krebs nezici zawo.