食品专业英语lesson10.docVIP

Lesson 10 Enzymes 酶 -ase 酶 Lipid（脂类） lipase Amylum （淀粉）amylase Oxidize（氧化） reduce（还原） oxidoreductase Transfer（转移） transferase Hydrolyze （水解） hydrolase Isomer （异构体） isomerase De-（去，脱）hydrogen（氢）dehydrogenase Enzymes are the catalysts that make possible biochemical reactions. 酶是使生化反应变得可能的催化剂。 Consider that biochemistry takes place at about 37 degrees C in water and contrast that to typical reaction conditions in organic chemistry. 想一下生化反应发生在37度的水中，再和特定条件下的有机化学反应比较一下。 For example, to hydrolyze（saponify）fats we boil them with concentrated sodium hydroxide solution for a few hours. 例如，用浓的氢氧化钠溶液煮脂类几个小时使它们水解（皂化）。 Enzymes called lipases do the same thing at body temperature in minutes. 脂酶能在体温条件下在几分钟内就能完成相同的事情。 Without enzymes, our body chemistry would not occur, and life would not exist. This illustrates the impressive power of enzymes as catalysts. 没有酶，我们身体的化学反应就不可能发生，生命就不会存在。这就说明了酶作为催化剂的强大力量。 Remember that catalysts increase the rate of a reaction, but are not themselves consumed or produced by the reaction. Also, they do not change the equilibrium constant of a reaction.但请记住，催化剂只能提高反应速度，它们自身并不被反应消耗或产生。它们也不改变一个反应的平衡常数。 This means that any catalyst that catalyzes a reaction in one direction（e.g., esterification）also catalyzes the reverse（e.g., ester hydrolysis）reaction. 这意味着任何催化剂催化一个反应向一个方向（如酯化）发生，也同时催化逆反应（如酯的水解）。 To say these things another way, catalysts do not change the energy balance between reactants and products; catalysts do lower the energy barrier between reactants and products. These statements are true of enzymes as well as other types of catalysts. 换句话说，催化剂不改变反应物和产物的平衡常数，催化剂可以降低反应物与产物之间的势能。这些描述对酶和其他类型的催化剂都适用。 Characteristics Enzymes differ from simple catalysts in another very important way. Enzymes are much more specific. 酶与一般催化剂的另一个很重要的不同之处是，酶具有更强的专一性。 Sulfuric acid as a source of H+ will catalyze the formation of any ester from the appropriate alcohol and carboxylic acid, but many enzymes are so specialized that they will catalyze a reaction of one molecu