Lesson 91. Lipids are a family of naturally occurring compounds grouped together on the basis of their relative insolubility in water in nonpolar solvents. These are naturally occurring molecules that can be isolated from cells and tissues by extration using nonpolar organic solvents.依据在水中的不溶解性和在非极性溶剂中的溶解性，脂肪以家族形式组成而自然出现的。
这些天然存在的分子可以通过采用非极性有机溶剂萃取的方法，在细胞和组织中分离得到。
2. Saturated fats have a uniform shape that allows them to pack together in a crystal lattice. Unsaturated fats have double bonds that introduce kinks into the hydrocarbon chain making crystal formation more difficult.饱和脂肪有一个均一一致的形状，这使得他它们能够在晶格中聚合起来。
不饱和脂肪有双键能使烃链发生扭曲，从而使晶体的形成更加困难。
3. The most abundant lipid in olive oil is glyceryl trioleate, a trimester formed from glycerol and oleic acid, a mono-unsaturated fatty acid with a cis double bond in the middle of the C18 chain.橄榄油里最丰富的脂质是三油酸甘油酯，是甘油和油酸，与一个单不饱和脂肪酸加上一个顺式双键在C18链的中间形成的一种三聚体。
4. Waxes are mixtures of esters of long chain carboxylic acids and long chain alcohols. The carboxylic acids usually have an even number of carbon atoms, ranging from 16 to 36, and the long chain alcohols also have an even number of carbon atoms, ranging from 24 to 36.蜡是一种由长链羧酸和长链醇通过脂键组成的酯的混合物。
长链羧酸通常由偶数个（16~36个）C原子组成，而长链醇也是由偶数个（24~36个）C原子组成。
Lesson105. This means that any catalyst that catalyze a reaction in one (e.g.,esterification) also catalyze the reverse(e.g., ester hydrolysis) reaction. 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.这意味着任何一个催化剂既可以催化一个反应朝一个方向进行，也可以使其朝逆方向进行。
换句话说，催化剂不会改变反应物与产品之间的能量平衡，只是降低反应物与产品之间的能量差值。
6.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 molecule, but will leave untouched a very similar molecule.硫酸作为一个H+离子来源，能催化任何由合适的羧酸和醇构成酯的反应，而许多酶的特性很高，它们可以催化一种分子反应，但不会触及另一类很相似的分子的反应。
7. This broader specificity is useful in the case of an enzyme like papain which is important in protein digestion. It can catalyze the hydrolysis of peptide (amide) bonds in a variety of proteins, which means that the body does not need to maintain a stock of more specific enzymes to tackle specific proteins.这个广泛的特异性在酶中很有用，例如木瓜蛋白酶，它在蛋白质消化中具有重要意义。
木瓜蛋白酶可以在各种蛋白质中催化肽键的水解，从而可使人体不需要更高特异性酶来专门水解特殊的蛋白质。
8. Thus we can describe them in terms of their primary, secondary, tertiary, and in many cases, quaternary structure. They are long chains of amino acid units held together by peptide bonds, looped and folded into secondary and tertiary (and often quaternary) structures by disulfide bonds, hydrophobic interactions, and salt bridges.这样我们能从蛋白质一级，二级，三级和四级结构方面来描述酶：它们是由氨基酸通过肽键结合的单位所组成，以缠绕折叠的方式，由二硫键，疏水键，盐桥而构成二级和三级结构的许多长链。
9. In such instances, the enzyme without the cofactor is called an apoenzyme, and the apoenzyme-cofactor complex is called a holoenzyme. We will see that the protein chain of an apoenzyme can have functional groups on its side chains (R groups) which are important to its catalytic function, but other important functional groups are introduced by way of cofactors.有些时候，不含辅基的酶叫脱辅基蛋白酶，辅基和脱辅基蛋白酶的复合物叫全酶。
我们将发现由脱辅基蛋白酶组成的蛋白质链的侧链上，具有对它的催化功能起重要作用的功能基团，但其他重要的功能基团则是由催化剂的辅基提供。
10. The fit can come about either because the molecule fits easily into the enzyme's active site (lock-and-key model) or because the enzyme's structure adjusts to the substrate's entry (induced fit model).匹配进入酶的活性部位，要么因为这个分子容易进入酶的活性部位，要么因为酶的结构进行调整。
Lesson 1111. These provide the energy and building materials for the countless substances that are essential to the growth and survival of living things. The manner in which nutrients become integral parts of the body and contribute to its function is dependent on the physiologic biochemical processes that govern their actions.这些营养素为无数的生物生长和生存所必需的物质提供了能量和构建物质。
在这种方式中，营养素组成机体的有机部分，并依据控制他们行为的生理和生化过程，发挥他们的功能。
12. As constituents of food we eat they not only provide energy but also provide a basis for tastes, color, texture, keeping qualities, and overall acceptability of that food, not nutrients, and therefore should consider the total role of nutritional compounds in food.作为我们所吃食物的组分，它们不仅提供了能量，而且提供了该食物的味觉、颜色、质地、质量保持和总的接受程度。
不能遗忘的是我们吃的食物不是营养素，因此我们应当考虑到食物中营养化合物总的作用。
13. They are called essential nutrients because we cannot get along without them .We need them for energy for building and maintaining body tissue, and for regulating body process—the three essential functions of food in the body.因为我们的生存离不开它们，所以被认为是必须的营养素。