Glikogen

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visualisasi lintas bagean skematik glikogen: Protein inti glikogenin dikepung karo cabang-cabang unit glukosa. Kabeh granula global bisa ngemot udakara 30.000 unit glukosa. [1]
Tampilan struktur atom saka siji untai unit glukosa ing molekul glikogen.
Glikogen (granula ireng) ing spermatozoa saka cacing pipih; mikroskop elektron transmisi, skala: 0,3 m

Glikogen ya iku polisakarida glukosa rantai akéh sing dadi salah sawijining bentuk panyimpenan energi ing kewan,[2] jamur, lan bakteri. [3] Struktur polisakarida nuduhaké wujud panyimpenan utama glukosa ing awak. Fungsi glikogen minangka salah siji saka rong bentuk cadangan energi, glikogen kanggo jangka pendek lan bentuk liyané yaiku toko trigliserida ing jaringan adipose (yaiku lemak awak) kanggo panyimpenan jangka panjang. Ing manungsa, glikogen digawé lan disimpen utamané ing sel ati lan otot balung. [4] [5] Ing ati, glikogen bisa ngasilaké 5-6% bobot seger organ, lan ati saka wong diwasa, bobote 1,5 kg, bisa disimpen udakara 100-120 gram glikogen. [4] [6] Ing otot balung, glikogen ditemokaké ing konsentrasi kurang (1-2% massa otot) lan otot balung kanggo wong diwasa kanthi bobote 70 toko kg udakara 400 gram glikogen. [4]

Jumlah glikogen sing disimpen ing awak, utamané ing otot lan ati, biasané gumantung karo latihan fisik, tingkat metabolisme basal, lan pola makan [7] (khusus serat tipe oksidatif 1 [8] [9] ). Tingkat glikogen otot istirahat sing beda bisa digayuh kanthi ngganti jumlah partikel glikogen, tinimbang nambah ukuran partikel sing ana [10] sanajan umume partikel glikogen ing istirahat luwih cilik tinimbang maksimal teoritis. [11] Jumlah glikogen uga akéh ditemokaké ing jaringan lan sel liyané, kalebu ginjel, sel getih abang, [12] [13] [14] sel getih putih, [15] lan sel glial ing otak . [16] Rahim uga nyimpen glikogen sajrone meteng kanggo menehi nutrisi kanggo embrio. [17]

Kira-kira 4 gram glukosa ana ing getih manungsa sawayah-wayah; [18] ing individu sing pasa, glukosa getih tetep tetep ing level iki kanthi biaya nyimpen glikogen ing ati lan otot balung. [18] Toko glikogen ing otot balung minangka salah sawijining panyimpenan energi kanggo otot kasebut; [18] Nanging, gangguan glikogen otot ngalangi penyerapan glukosa otot saka getih, saengga nambah jumlah glukosa getih sing kasedhiya kanggo digunakaké ing jaringan liya. [18] Toko glikogen ati dadi toko glukosa kanggo digunakaké ing awak, utamané sistem saraf pusat . [18] Otak manungsa nganggo udakara 60% glukosa getih ing individu sing cepet lan ora aktif. [18]

Glikogen minangka analog pati, polimer glukosa sing fungsine minangka panyimpenan energi ing tanduran . Nduweni struktur sing padha karo amylopectin (komponen pati), nanging luwih akéh bercabang lan kompak tinimbang pati. Kalorone minangka bubuk putih ing kahanan garing. Glikogen ditemokaké ing bentuk granula ing sitoskol / sitoplasma ing pirang-pirang jinis sel, lan duwe peran penting ing siklus glukosa . Glikogen dadi cadangan energi sing bisa cepet dikepungaké kanggo nyukupi kebutuhan glukosa, nanging glukosa sing kurang kompak tinimbang cadangan energi trigliserida ( lipid ). Kuwi uga ditemokaké minangka cadangan panyimpenan ing akéh protokol parasit. [19] [20] [21]

Struktur saka Glikogen[besut | besut sumber]

Hubungan 1,4-α-glycosidic ing oligomer glikogen
Hubungan 1,4-α-glycosidic lan 1,6-glikosidik ing oligomer glikogen

Glikogen minangka biopolimer bercabang sing kalebu rantai linear residu glukosa kanthi dawa rantai rata-rata udakara 8-12 unit glukosa lan 2.000-60.000 residu saben molekul glikogen. [22] [23] Unit glukosa digandhengaké kanthi linear kanthi ikatan glikosida α (1 → 4) saka siji glukosa menyang glukosa liyané. Cabang digandhengaké karo rantai sing diikat saka glikosidik α (1 → 6) antara glukosa pertama cabang anyar lan glukosa ing rantai batang. [24] Amarga cara glikogen disintesis, saben granul glikogen duwe inti protein glikogenin.[25]

Glikogen ing sel otot, ati, lan lemak disimpen ing bentuk hidrasi, kasusun saka telu utawa patang bagean banyu saben bagean glikogen sing ana gandhengané karo 0,45 millimole (18 mg) kalium saben gram glikogen. [26] Glukosa minangka molekul osmosis, lan bisa mengaruhi tekanan osmosis ing konsentrasi dhuwur sing bisa nyebabaké kerusakan sel utawa mati yen disimpen ing sel tanpa dimodifikasi. [27] Glikogen minangka molekul non-osmosis, mula bisa digunakaké minangka solusi kanggo nyimpen glukosa ing sel tanpa ngganggu tekanan osmosis. [27]

Fungsine Glikogen[besut | besut sumber]

Ing Ati[besut | besut sumber]

Ana ing panganan sing ngemot karbohidrat utawa protein sing dipangan lan dicerna, tingkat glukosa getih mundhak, lan pankreas gawé insulin . Glukosa getih saka vena portal mlebu ing sel ati ( hepatosit ). Insulin tumindak ing hepatosit kanggo ngrangsang tumindak sawétara enzim, kalebu sintesis glikogen . Molekul glukosa ditambahaké ing rantai glikogen sajrone insulin lan glukosa isih akéh. Ing kahanan postprandial utawa "panganan" iki, ati njupuk luwih akéh glukosa saka getih tinimbang sing dibabaraké.

Sawise panganan dicerna lan tingkat glukosa wiwit mudhun, sekresi insulin dikurangi, lan sintesis glikogen mandheg. Yen dibutuhaké kanggo energi, glikogen dipecah lan malih dadi glukosa. Fosforilase glikogen minangka enzim utama gangguan glikogen. Sajrone 8-12 jam sabanjure, glukosa sing asale saka glikogen ati minangka sumber utama glukosa getih sing digunakaké dening sisa awak kanggo bahan bakar.

Glukagon, hormon liya sing diproduksi dening pankreas, ing pirang-pirang aspek minangka countersignal kanggo insulin. Kanggo nanggepi tingkat insulin sing kurang normal (nalika kadar glukosa getih mudhun ing kisaran normal), glukagon disekresi nambah jumlah lan ngrangsang kalorone glikogenolisis (pemecahan glikogen) lan glukoneogenesis (produksi glukosa saka sumber liyané).

Ing Otot[besut | besut sumber]

Glikogen sel otot bisa uga digunakaké minangka sumber glukosa sing kasedhiya kanggo sel otot. Sel liyané sing ngemot jumlah sithik nggunakaké lokal uga. Amarga sel otot ora duwe glukosa-6-fosfatase, sing dibutuhaké kanggo ngirim glukosa menyang getih, glikogen sing disimpen kasedhiya mung kanggo panggunaan internal lan ora dituduhaké karo sel liyané. Iki beda karo sel ati, sing, yen dikarepaké, gampang ngilangi glikogen sing disimpen dadi glukosa lan dikirim liwat aliran getih minangka bahan bakar kanggo organ liya. [28]

Sejarahe Glikogen[besut | besut sumber]

Glikogen ditemokaké dening Claude Bernard. Eksperimen kasebut nuduhaké manawa ati ngemot zat sing bisa nyebabaké nyuda gula kanthi tumindak "fermentasi" ing ati. Ing taun 1857, dheweke nerangaké isolasi zat sing diarani " la matière glycogène ", utawa "zat pembentuk gula". Ora suwe sawise ditemokaké glikogen ing ati, A. Sanson nemokaké manawa jaringan otot uga ngemot glikogen. Formula empiris kanggo glikogen saka ( C6H10O5 ) n diadegaké karo Kekulé ing taun 1858. [29]

Paripustaka[besut | besut sumber]

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