专业英语教案10酶
2020-03-02 07:52:34 来源：范文大全收藏下载本文
Leon 10 Enzymes酶
Enzymes are gigantic molecules with typical molecular weights ranging from about 6000 to more than 600,000.酶是大分子，大多数分子量在6000到60万间。 Moreover, enzymes are much more complex structurally than the catalysts considered thus far in the section, and their catalytic sites are far more intricate.而且，酶在结构上比这章中迄今所讨论的催化剂要复杂的多，他们的催化位置也十分复杂。 Enzymes have evolved by the life proce to be extremely specific catalyst; each enzyme is a catalyst for only one biological reaction or, sometimes, one cla of reaction.生命过程中酶是十分特殊的催化剂，每个酶是只催化一种（有时是一类）生物反应的催化剂。 The typical enzyme has a catalytic site that bonds specifically to a single reactant and activates it.典型的具有一个催化点，只能健合特定的单一反应物并激活它。 The catalytic site is multifunctional, bonding to the reactant at more than one position, almost to the exclusion of all but closely similar molecules (often products), and these similar molecules are reaction inhibitors.催化位置是多功能的，键合到反应物上多于一个位置，除了相似的分子或产品外，几乎排除所有的位置，这些相似的分子是反应阻聚剂。 Enzymes catalyze conversion of biological molecules with very high selectivities and at high rates, typically in the range of 10 to l000 molecules/(enzymes).酶以高选择性高速度催化生物分子的转化，每个酶催化的典型范围为10到1000分子
Each enzyme has a unique three-dimensional structure that usually includes a pocket or cleft presenting an array of functional groups positioned to bond to complementary functional groups of the reactant molecule.酶具有独一无二的三维结构，通过包括缺陷，能够与反应物分子的功能团完全结合。 The region of the cleft is a three-dimensional microenvironment, and the bonding of the reactant is comparable to a highly specific chemisorption.缺陷的区域是三维的微环境，对于反应物的键合具有高化学选择性。 Nature\'s proce of Darwinian selection has led to the biosynthesis of individual enzyme molecules each of which is in eence a unique multifunctional catalytic site that allows bonding and conversion of a particular reactant or cla of reactants.达尔文的自然进化论导致了单个酶分子的生物合成，允许特定反应物的转化。 Other chemical properties of enzymes besides those of the catalytic site are important also: the functional groups on the outer surface, for example, determine the enzyme\'s affinity for particular locations in the biological cell, such as the aqueous environment of the cytoplasm or the hydrophobic environment of a cell wall or other membrane.除了催化位置外，酶的其它化学性质也很重要：外部空间的官能团决定了生物细胞特定位置酶的亲和性，如细胞质的水性环境或细胞壁或其它膜的疏水性。
Enzymes catalyze biological reactions; and since living organisms usually exist only at relatively mild temperatures, most enzymes function only under these conditions.由于生物体通常存在于相对温和的环境下，酶催化的生物反应通常在这样的条件下进行。 Enzymes are delicate and do not retain their structures under conditions much outside the range characteristic of living organisms, although they may function in vitro in atypical environments such as nonaqueous solvents.虽然酶的结构在生物体以外的范围内不能保证，但是也可能在体外这种非水性溶剂的环境中起作用。 Some organisms, such as those living in hot springs, have adapted to relatively high temperatures, and they could not exist without enzymes that are stable and active at these temperatures.在温泉中存在的某些有机体已经适应了相对高的温度，在这样的温度下，如果没有酶，有机体会变得不稳定。
There is a great variety of biological reactions, including, for example, (1) the break down of proteins and sugars occurring in the digestive tracts of animals, (2) the biosynthetic reactions that lead to growth and replacement of living organisms, (3) photosynthesis, and (4) oxidations that proceed by intricate pathways that convert food (e.g., sugars, proteins, etc.) into CO2 water and energy in a biologically useful form.例如，有大量的生物反应，（1）动物的消化道内发生蛋白质和糖的断裂，（2）生物合成反应导致活的有机体的生长和取代，（3）光合作用，（4）通过氧化，以错综复杂的方式把食物转化为CO2，水和生物利用形式的能量。
Many enzyme-catalyzed reactions take place in biological cells.许多酶催化反应发生在生物细胞内。
The contents of cells are organized into well-defined domains.细胞是很好的界定区域。 The cytoplasm is an aqueous biological soup with many molecules, including reactants, products, and enzymes in solution.细胞质是由许多分子的水相细胞浆，包括反应物，产品，酶。 The membranes are much more highly structured.膜是高度构造的。 Enzymes are also present in membranes and in cellular subunits called organelles.酶也包含在膜和细胞子单元中，称为细胞器。 These bound enzymes are sometimes present in arrays that can be described as aembly lines.这些酶有机以序列的形式出现，被描述为装配线。 Evidently, the product of reaction in one enzyme is transported to the next enzyme in line so that a sequence of reactions takes place efficiently.很明显地，一个酶反应的产品进行装配线的下一个酶，使反应高效的依次发生。 Nature\'s catalysts function in highly sophisticated reactors.在高度复杂的反应器中发生自然的催化反应。
Enzymes are usually named for the reactions they catalyze.酶通常以其催化的反应命名。 For example, lysozyme catalyzes reactions that lead to the breakdown by hydrolysis (lysing) of polysaccharides; isomerases catalyze isomerization reactions; dehydrogenases catalyze dehydrogenation reactions; and so forth.例如，溶菌酶催化的反应使多糖水解，异构酶催化异构化反应，脱氢酶催化脱氢反应，等等。 More specifically, alcohol dehydrogenases catalyze alcohol dehydrogenations, and L-lactate dehydrogenase catalyzes the dehydrogenation of L-lactate (to give pyruvate).更特别的是，醇脱氢酶催化醇的脱氢，L－乳酸脱氢酶催化L－乳酸的脱氢（得到丙酮酸盐）。 Because the composition and structure of one kind of enzyme from one plant, animal, or bacterium may be different from those of the same kind of enzyme from another plant, animal, or bacterium, a further specification includes the source, for example, horse liver alcohol dehydrogenase.因为植物、动物或细菌中酶的组成和结构不同于其它植物、动物或细菌中相同类型的酶，所以需要更进一步的分类，例如，马肝醇脱氢酶。
人人范文网 m.inrrp.com.cn 手机版