UNIT 11.Although the DNA in the nucleus of each cell contains all of the genetic information for allhuman traits, only a small number of genes are actually active in a particular cell、These active genes are the codes for the proteins necessary for the specific cell type、尽管每一个细胞核中得DNA都包含有人类特性得所有遗传信息，但实际上只有小数基因在特定细胞中有活性，这些活性基因就是特有得细胞类型所必须得蛋白密码。
2.In facilitated diffusion, molecules move through a membrane from an area of greaterconcentration to an area of lesser concentration, but they need some help to do this、在易化扩散中，大分子经一层膜从高浓度区域向低浓度区域移动，但分子要完成这一工作需要某些帮助。
3.The cell membrane is selectively permeable, that is, certain substances are permitted to passthrough and others are not、细胞膜得渗透性就是有选择性得，即某些物质允许通过，而其它物质则不行。
4.Filtration means that water and dissolved materials are forced through a membrane from anarea of higher pressure to an area of lower pressure、过滤就是指水与已溶解物质经一层膜从高压区压送到低压区。
5、Active transport requires the energy of ATP to move molecules from an area of lesserconcentration to an area of greater concentration、主动转运需要ATP这种能使分子从低浓度区向高浓度区移动。
1、体内平衡取决于所有不同类型得细胞正常得发挥其功能。
(depend upon)Homeostasis depends upon the normal functions of all of the different kinds of cells、2、就人口与地域而言，这两个国家差异很大。
(with respect to)With respect to population and geographical area, these two countries vary greatly、3、染色体由脱氧核糖核酸与蛋白构成，而脱氧核糖核酸又就是细胞特征与活性得遗传密码。
(genetic code)Chromosomes are made of DNA and protein, and the DNA is the genetic code for the characteristics and activities of the cell、4、氧气从空气中扩散到血液以便在全身循环，而二氧化碳从血液散播到空气中以便排出体外。
(diffuse )Oxygen diffuses from the air to the blood to be circulated throughout the body, but carbon dioxide diffuses from the blood to the air to be exhaled from the body、5、科学不断地提供新得发现，从而进一步支持了她得假设。
(back up)Science continued to throw up discoveries which further backed up his hypothesis、UNIT 21、At either end of the age spectrum, however, temperature regulation may not be as precise as it is in older children or younger adults、然而，在年龄段两端得人群，其体温调节精确程度都不如青少年或青年人。
2、The pathways of heat loss from the body are the skin, respiratory tract, and to a lesser extent, the urinary and digestive tracts、人体散热途径就是经皮肤、呼吸道，少量经尿道与消化道散热。
3、Changes in body temperature also have an effect on metabolic rate and heat production、This becomes clinically important when a person has a fever, an abnormally high body temperature、人体体温得变化也会影响代谢率与产热。
当一个人发热、体温异常升高时，从临床上讲，体温变化就显得重要了。
4、Anabolism means synthesis or “formation” reactions, the bonding together of smaller molecules to form larger ones、合成代谢就是指综合或“形成”性反应，即把小得分子结合在一起形成更大得分子。
5、Catabolism means decomposition, the breaking of bonds of larger molecules to form smallermolecules、Cell respiration is a series of catabolic reactions that break down food molecules to carbon dioxide and water、分解代谢就是指分解，即将较大得分子链分解形成小分子。
细胞呼吸过程就就是一连串得分解代谢反应---将食物分子分解成二氧化碳与水。
1、新陈代谢就是指发生在生物体内得化学过程，可分为合成代谢与分解代谢两大类。
(metabolism)Metabolism refers to the chemical reactions that take place in the living organisms、It may be divided into two major categories: anabolism and catabolism、2、正常人得体温为37度。
随个体、年龄、活动量与每日早晚略有差异，但波动幅度不超过l℃。
(fluctuation)The normal body temperature is 37ºC, and varies by person, age, activity, and time of day, but the fluctuations are usually no more than 1、0ºC、3、在正常情况下，人体通过体温调节系统使体温保持相对稳定。
(constant)Under normal conditions, human body is able to maintain a relatively constant body temperature through the system of temperature regulation、4、与生活在热带地区得人相比，在寒冷气候下生活得人，新陈代谢率要高10-20%。
(metabolic rate)People who live in cold climates may have metabolic rates 10% to 20% higher than those who live in tropical regions、5、人体体温得调节主要就是通过汗腺得分泌及皮肤血管得收缩与舒张。
(excretion) Human body temperature is mainly regulated through the excretion of sweat gland and vasodilation and constriction of blood vessels in the skinUNIT 31、Ventricular contraction forces blood against the flaps of the right and left AV valves and closes them; the force of blood also opens the aortic and pulmonary semilunar valves、心室收缩使血液施压于左右房室瓣并使其关闭；血液得压力也使主动脉半月瓣与肺动脉半月瓣打开。
2、Palpations are usually not serious, and may be the result of too much caffeine, nicotine, oralcohol、Much more serious is ventricular fibrillation, a very rapid and uncoordinated ventricular beat that is totally ineffective for pumping blood、心悸通常不很严重，可能因摄入得咖啡因，尼古丁或酒精过量引起。
更为严重得就是室颤，室颤就是一种快速而无节律得心室跳动，可以导致心脏泵血无力。
3、Although the heart generates and maintains its own beat, the rate of contraction can bechanged to adapt to different situations、The nervous system can and does bring about necessary changes in heart rate as well as in force of contraction尽管心脏自身产生跳动并得以维持跳动，但为了适应不同情况还可以改变收缩率。