sstyphi 亂說話

Les lysosomes
Les vésicules golgiennes ne servent pas toutes pour la sécrétion de protéines hors de la cellule. Certaines vésicules contiennent des enzymes digestives qui agissent à l'intérieur même de la cellule et qui ne peuvent être laissées libres dans le cytoplasme: on parle des lysosomes.
Du point de vue structural, les lysosomes sont de petites vésicules membraneuses de formes et de dimensions variables; une cellule peut en contenir plusieurs centaines. Les lysosomes contiennent un grand nombre d'enzymes différentes capables d'hydrolyser c'est-à-dire de digérer de grosses molécules comme des protéines, des glucides, des lipides, des acides nucléiques. Ces enzymes sont des hydrolases actives seulement à un pH de 5; ce pH acide du milieu lysosomial est maintenu grâce à des échanges actifs d'ions acides vers le milieu interne des lysosomes. La rupture accidentelle des membranes lysosomiales et le déversement des enzymes dans le cytoplasme est généralement sans conséquence puisque le pH du cytoplasme est neutre ce qui inactive alors les enzymes lysosomiales.

第一章：緒論
1、 填空題：
1、 細胞生物學是細胞整體、超微結構和分子水平上研究 及其 規律的科學。、

Abstract Annual Review of Physiology Vol. 60: 601-617 (Volume publication date March 1998) (doi:10.1146/annurev.physiol.60.1.601) CELL CYCLE REGULATION AND APOPTOSIS1 K. L. King* and ­J. A. Cidlowski#­ *Department of Molecular and Cellular Physiology, University of Cincinnati Medical Center, P. O. Box 670576, Cincinnati, Ohio 45267-0576; #National Institutes of Health, National Institute of Environmental Health Sciences, P.O. Box 12233 MD E2-02, Research Triangle Park, North Carolina 27709; e-mail: cidlowski@niehs.nih.gov Tissue homeostasis requires a balance between cell proliferation and death. Apoptosis and proliferation are linked by cell cycle regulators, and apoptotic stimuli affect both cell proliferation and death. Glucocorticoids induce G1 arrest and apoptosis in transformed lymphoid cells. Decreased expression of the cell cycle components c-myc and cyclin D3 is essential for glucocorticoid-induced growth arrest and death in dividing cells. Other G1 regulators, such as p53, pRb, and E2F, have also been implicated in apoptosis. Mice lacking either p53 or E2F display aberrant cell proliferation and tumor formation, suggesting that these proteins are involved in the elimination of abnormal cells through apoptosis. In contrast, pRb induces G1 arrest and suppresses apoptosis in cultured cells. Mice that lack pRb are nonviable and show ectopic mitosis and massive cell death, suggesting that pRb is an apoptotic suppressor. Further analysis of common components of apoptotic and cell cycle machinery may provide insight into the coordinated regulation of these antagonistic processes. 以上內容來自 Journal of Bioenergetics and Biomembranes (Historical Archive) Publisher: Springer Science+Business Media B.V., Formerly Kluwer Academic Publishers B.V. ISSN: 0145-479X (Paper) 1573-6881 (Online) DOI: 10.1007/BF00770028 Issue:  Volume 19, Number 5 Date:  October 1987 Pages: 427 - 442 Mini-Review Proton conductance through phospholipid bilayers: Water wires or weak acids? John Gutknecht1 (1)  Department of Physiology, Duke University, and Duke Marine Laboratory, 28516 Beaufort, North Carolina Received: 2 February 1987  Revised: 15 May 1987   Abstract  The proton/hydroxide (H+/OH–) permeability of phospholipid bilayer membranes at neutral pH is at least five orders of magnitude higher than the alkali or halide ion permeability, but the mechanism(s) of H+/OH– transport are unknown. This review describes the characteristics of H+/OH– permeability and conductance through several types of planar phospholipid bilayer membranes. At pH7, the H+/OH– conductances (G H/OH) range from 2–6 nS cm–2, corresponding to net H+/OH– permeabilities of (0.4–1.7)×10–5 cm sec–1. Inhibitors ofG H/OH include serum albumin, phloretin, glycerol, and low pH. Enhancers ofG H/OH include chlorodecane, fatty acids, gramicidin, and voltages >80 mV. Water permeability andG H/OH are not correlated. The characteristics ofG H/OH in fatty acid (weak acid) containing membranes are qualitatively similar to the controls in at least eight different respects. The characteristics ofG H/OH in gramicidin (water wire) containing membranes are qualitatively different from the controls in at least four different respects. Thus, the simplest explanation for the data is thatG H/OH in unmodified bilayers is due primarily to weakly acidic contaminants which act as proton carriers at physiological pH. However, at low pH or in the presence of inhibitors, a residualG H/OH remains which may be due to water wires, hydrated defects, or other mechanisms. Key Words  Proton conductance - proton permeability - phospholipid bilayer membrane - weak acid - water wire - fatty acid - gramicidin The references of this article are secured to subscribers. 以上內容來自

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

別當直昇機父母
時事深度報導頁

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.