細胞膜是防止細胞外物質自由進入細胞的屏障,它保證了細胞內環境的相對穩定,使各種生化反應能夠有序運行。但是細胞必須與周圍環境發生信息、物質與能量的交換,才能完成特定的生理功能。因此細胞必須具備一套物質轉運體系,用來獲得所需物質和排出代謝廢物,據估計細胞膜上與物質轉運有關的蛋白佔核基因編碼蛋白的15~30%,細胞用在物質轉運方面的能量達細胞總消耗能量的三分之二。
細胞膜上存在兩類主要的轉運蛋白,即:載體蛋白(carrier protein)和通道蛋白(channel protein)。載體蛋白又稱做載體(carrier)、通透酶(permease)和轉運器(transporter),能夠與特定溶質結合,通過自身構象的變化,將與它結合的溶質轉移到膜的另一側,載體蛋白有的需要能量驅動,如:各類APT驅動的離子泵;有的則不需要能量,以自由擴散的方式運輸物質,如:纈氨酶素。通道蛋白與所轉運物質的結合較弱,它能形成親水的通道,當通道打開時能允許特定的溶質通過,所有通道蛋白均以自由擴散的方式運輸溶質。
第一節 被動運輸
- Mar 13 Thu 2008 16:30
cell biology part 1 (from china)
- Mar 13 Thu 2008 16:27
別當直昇機父母 (from:天下雜誌)
別當直昇機父母
時事深度報導頁
- Mar 13 Thu 2008 16:20
Capillary electrophoresis data-mining
Capillary electrophoresis, or CE, describes a family of techniques used to separate a variety of compounds. These analyses, all driven by an electric field , are performed in narrow tubes and can result in the rapid separation of many hundreds of different compounds. The versatility and number of ways that CE can be used means that almost all molecules, and even whole organisms can be separated using the powerful methods.
There are a number of different ways of performing CE separations. This makes the technique especially useful as it optimised for the separation you are interested in whether this be ensuring purity during manufacture, or diagnosing illness in a hospital. Separations driven by electrophoresis also have a novel separating mechanism. This makes them useful in situations where other liquid phase separation techniques are limited or impractical.
- Feb 08 Fri 2008 21:29
Fw: 甜白葡萄酒
甜酒的種類:
甜葡萄酒多數是在餐後搭配甜點時候喝的,因而有時候也被稱作「甜點酒」,包括自然發酵的甜葡萄酒,也包括加強型的波特酒(Port)、雪麗酒(Sherry)、馬德拉酒(Madeira)等。這其中以有「上帝之淚」著稱的甜白葡萄酒風格最為多樣。
- Feb 08 Fri 2008 13:46
FW: 冰酒知識
昨天上位於台北火車站微風廣場的長榮桂冠酒坊買了貧德國的冰酒
一瓶註明是Eiswein領一瓶是BA
於是回來找了一些資料
- Feb 07 Thu 2008 00:40
拒絕討厭工作 11招讓你不再難開口
「這工作為何要叫我做?」、「這根本是沒有意義的工作」……面對討厭的工作,與其抱怨不停,不妨學習聰明的拒絕方法或接招技巧,再看情況靈活運用。
- Feb 07 Thu 2008 00:21
FW: 到底,我們是為了什麼才學英文?(part I)
轉摘文章:到底,我們是為了什麼才學英文?
- Dec 20 Thu 2007 19:27
uniqlock
- Dec 20 Thu 2007 14:57
嘴砲衛生政策
....衛生署國民健康局副局長趙坤郁表示,若進一步來看,台灣國內的總生育率,從二00四年的一點一八人、到二00五年的一點一二人,明顯正在滑落中,去年台灣國內新生兒還有二十萬六千人,但按照這樣推估,今年恐怕連二十萬人都不到,若持續下去,台灣人口面臨零成長的時間點,將由原本預估的二0二一年提前至二0一七年。
- Sep 16 Sun 2007 04:43
new throught of SXX
the S1P secreted in tumor region base on
1. high SphK level and low SPL
2. some tumor require the S1P for survival
- Sep 16 Sun 2007 02:31
細胞生物學資料 (china)
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- Sep 16 Sun 2007 02:30
這是自動儲存草稿
第一節 細胞生物學簡史
從研究內容來看細胞生物學的發展可分為三個層次,即:顯微水平、超微水平和分子水平。從時間縱軸來看細胞生物學的歷史大致可以劃分為四個主要的階段:
第一階段:從16世紀末—19世紀30年代,是細胞發現和細胞知識的積累階段。
- Sep 16 Sun 2007 02:21
Data when I think about COGs
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- Sep 10 Mon 2007 15:13
CE
Capillary electrophoresis, or CE, describes a family of techniques used to separate a variety of compounds. These analyses, all driven by an electric field , are performed in narrow tubes and can result in the rapid separation of many hundreds of different compounds. The versatility and number of ways that CE can be used means that almost all molecules, and even whole organisms can be separated using the powerful methods.
There are a number of different ways of performing CE separations. This makes the technique especially useful as it optimised for the separation you are interested in whether this be ensuring purity during manufacture, or diagnosing illness in a hospital. Separations driven by electrophoresis also have a novel separating mechanism. This makes them useful in situations where other liquid phase separation techniques are limited or impractical.