Lv 5
? asked in 科學動物學 · 2 decades ago


據說擴散作用已被推翻是真的嗎? 新說法是什麼呢? 導管?~~~~~~~

2 Answers

  • 2 decades ago
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    細胞膜(無論動、植物、細菌、古細菌)均由磷脂雙層膜構成,雖不同生物所使用之磷脂並不相同,但皆具有相同特徵,即親水性部分與親脂性部分,在水中會形成雙層膜,相關圖片可由網路尋得(phospholipid bilayer)。水為一極性分子,單靠擴散作用是否能輕易通過細胞膜仍有相當爭議,可參閱此網址中的討論:http://www.sciscape.org/phpBB2/viewtopic.php?t=148...





    A water channel. Aquaporins form pores in the membranes of cells and selectively conduct water molecules through the membrane, while preventing the passage of ions (such as sodium and potassium) and other small molecules.

    Aquaporins are typically composed of identical subunit proteins. Water molecules traverse the narrowest portion of the water channel in single file. The presence of water channels increases the permeability of membranes to water by as much as ten-fold. Aquaporins prevent us from dying of dehydration by reabsorbing 99% of the water in the kidney.

    The existence of molecular water channels had been long suspected. However, their molecular identity remained unknown until the serendipitous discovery of aquaporin-1 in 1988. The protein known as AQP1 was first purified from red blood cell membranes.

    A number of different aquaporins have now been identified. They have been designated aquaporin-0, aquaporin-1, aquaporin-2, and so on while the corresponding aquaporin genes are symbolized AQP0, AQP1, and AQP-2. The results of mutations in the AQP genes differ. Mutation in AQP-0 causes cataracts. Mutations in AQP1 have been found in normal people. Mutations in the aquaporin-2 gene AQP2 cause an autosomal dominant form of nephrogenic diabetes insipidus.

    The 2003 Nobel Prize in Chemistry was shared by Peter Agre from Johns Hopkins University "for the discovery of water channels." The other half of the prize went to Roderick MacKinnon from Rockefeller University "for structural and mechanistic studies of ion channels."






  • 2 decades ago


    Source(s): 自己..
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