Cell membranes act as barriers to most, but not all, molecules. Development of a cell membrane that could allow some materials to pass while constraining the movement of other molecules was a major step in the evolution of the cell. Cell membranes are differentially permeable barriers separating the inner cellular environment from the outer cellular(or external)environment. Water potential is the tendency of water to move from an area of higher concentration to one of lower concentration. Energy exists in two forms: potential and kinetic. Water molecules move according to differences in potential energy between where they are and where they are going. Gravity and pressure are two enabling forces for this movement. These forces also operate in the hydrologic(water)cycle. Remember in the hydrologic cycle that water runs downhill(likewise it falls from the sky, to get into the sky it must be acted on by the sun and evaporated, thus needing energy input to power the cycle). Diffusion is the net movement of a substance(liquid or gas)from an area of higher concentration to one of lower concentration. You are on a large(10ft×10ft×10ft)elevator. An obnoxious individual with a lit cigar gets on at the third floor with the cigar still burning. You are also unfortunate enough to be in a very tall building and the person says “Hey we’re both going to the 62nd floor!“ Disliking smoke you move to the farthest corner you can. Eventually you are unable to escape the smoke! An example of diffusion in action. Nearer the source the concentration of a given substance increases. You probably experience this in class when someone arrives freshly doused in perfume or cologne, especially the cheap stuff. Since the molecules of any substance(solid, liquid, or gas)are in motion when that substance is above absolute zero(0 degrees Kelvin or -273 degrees C), energy is available for movement of the molecules from a higher potential state to a lower potential state, just as in the case of the water discussed above. The majority of the molecules move from higher to lower concentration, although there will be some that move from low to high. The overall(or net)movement is thus from high to low concentration. Eventually, if no energy is input into the system the molecules will reach a state of equilibrium where they will be distributed equally throughout the system. The cell membrane functions as a semi-permeable barrier, allowing a very few molecules across it while fencing the majority of organically produced chemicals inside the cell. Electron microscopic examinations of cell membranes have led to the development of the lipid bilayer model(also referred to as the fluid-mosaic model). The most common molecule in the model is the phospholipid, which has a polar(hydrophilic)head and two nonpolar(hydrophobic)tails. These phospholipids are aligned tail to tail so the nonpolar areas form a hydrophobic region between the hydrophilic heads on the inner and outer surfaces of the membrane. This layering is termed a bilayer since an electron microscopic technique known as freeze-fracturing is able to split the bilayer.

The president is often awakened by a noisy crowd which assembles on the White House. concentrates assumes involves gathers

Overcoming setbacks takes time, efforts and perseverance. maintenance assistance persistence determination

Initial reports were that multiple waves of warplanes bombed central Baghdad, hitting oil refineries and the airport. beating knocking hurting striking

The president is often awakened by a noisy crowd which assembles on the White House. concentrates assumes involves gathers

Overcoming setbacks takes time, efforts and perseverance. maintenance assistance persistence determination

The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, but this is largely because,【C1】______animals, we stand upright. This means that our noses are【C2】______to perceiving those smells which float through the air, missing the majority of smells which stick to surfaces. In fact, though, we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of【C3】______human smells even when these are【C4】______to far below one part in one million. Strangely, some people find that they can smell one type of flower but not another, whereas others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate【C5】______smell receptors in the nose. These receptors are the cells which sense smells and send【C6】______to the brain. However, it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when【C7】______to it often enough. The explanation for insensitivity to smell seems to be that brain finds it inefficient to keep all smell receptors working all the time but can【C8】______new receptors if necessary. This may also explain why we are not usually sensitive to our own smells we simply do not need to be. We are not【C9】______of the usual smell of our own house but we notice new smells when we visit someone else’s. The brain finds it best to keep smell receptors【C10】______for unfamiliar and emergency signals such as the smell of smoke, which might indicate the danger of fire.

Most people would be impressed by the high quality of medicine available to most Americans. There is a lot of specialization, a great deal of attention to the individual, a vast amount of advanced technical equipment, and intense effort not to make mistakes because of the financial risk which doctors and hospitals must face in the courts if they handle things badly. But the Americans are in a mess. The problem is the way in which health care is organized and financed. Contrary to public belief, it is not just a free competition system. To the private system has been joined a large public system, because private care was simply not looking after the less fortunate and the elderly. But even with this huge public part of the system, which this year will eat up 84.5 billion dollars— more than 10 percent of the U.S. budget—large numbers of Americans are left out. These include about half the 11 million unemployed and those who fail to meet the strict limits on income fixed by a government trying to make savings where it can. The basic problem, however, is that there is no central control over the health system. There is no limit to what doctors and hospitals charge for their services. Other than what the public is able to pay. The number of doctors has shot up and prices have climbed. When faced with toothache, a sick child, or a heart attack, all the unfortunate person concerned can do is pay up. Two-thirds of the population are covered by medical insurance. Doctors charge as much as they want knowing that the insurance company will pay the bill. The medical profession has as a result become America’s new big businessmen. The average income of doctors has now reached $100,000 a year. With such vast incomes the talk in the doctor’s surgery is as likely to be about the doctor’s latest financial deal, as about whether the minor operation he is recommending at several thousand dollars is entirely necessary. The rising cost of medicine in the U.S.A. is among the most worrying problem facing the country. In 1981 the country’s health cost climbed 15.9 percent—about twice as fast as prices in general.

Please read the following article in Chinese carefully, and then write a summary of 200 words in English on the ANSWER SHEET. Make sure that you cover all the major points of the article. 医德之风随着经济体制市场化改革的逐步深入，我国自20世纪80年代以来对传统的医疗制度进行了一系列的改革。但是，由于医疗制度的复杂性，国内对出台的医疗制度改革方案还存在不少意见分歧。随着医疗卫生改革的不断深入，医德医风建设也面临着新的问题，卫生行业的不正之风已引起了全社会的关注。在新形势下，如何加强医德医风建设，改善行业作风，是摆在医院管理者面前的重大课题。在医疗卫生战线上，广大职工能够自觉遵守社会主义医德原则和规范，在平凡而又光荣的岗位上兢兢业业地履行白衣天使的职责，以高尚的医德医风、精湛的医疗技术战斗在救死扶伤的第一线，为保障人民群众的身体健康作出了贡献，受到社会各界和人民群众的好评。但是因受市场经济负面效应的影响，少数医务工作者政治学习有些放松，为人民服务的思想观念有些淡薄，在行业作风建设的认识上产生了误区，表现为重经济效益、轻社会效益，服务意识不强，对患者检查不仔细，诊疗不认真，不按规章制度办事，缺乏责任心。目前热点问题反应较多的是给病员开大处方、检查多、用好药多、费用高，增加了患者的负担。这些问题都属于医德问题，虽是少数人的事，但其影响不可低估，它使医患之间产生了鸿沟，甚至互不信任，直接影响到医疗卫生战线的形象，同时还会给党和政府造成不良影响。目前我国医疗系统医德医风存在的问题主要有：(1)部分医务人员不讲救死扶伤的人道主义医德观，不讲为人民服务的宗旨，把医疗服务视为商品交换，用等价交换原则看待医患关系，这些少数的害群之马，严重践踏了医疗道德，损坏了医务人员的形象。目前，有些医务人员事业心不强，有的医生满足于一般性的应付，上班无精打采，看病马马虎虎，对患者缺乏感情，缺乏责任心；有的甚至酿成医疗事故，造成医患纠纷；有的给患者留下后遗症，带来终生痛苦：有的使危重患者错过了抢救时间，使患者失去了宝贵的生命。(2)为医不廉，收受好处。有的患者总是怕医生不尽心，觉得送了红包心里才踏实，一些医护人员也就泰然笑纳。有的医生道德素质较差，暗示甚至索要好处。有的医生被医药代表买通，为了按一定比例获取提成而乱施高价药。至于接受请客吃饭，收点土特产则已经不当一回事了。(3)不平衡和消极埋怨的心理。市场经济使一些行业在一定时期内有较大的赢利，社会上一一部分人员收入过高，与医务人员的收入差距较大，一些医务人员产生了“拿手术刀不如拿剃头刀的”不正常心态，这种心态在医务人员中有一定的市场。(4)部分医务人员在经济利益的驱使下，医德医风削弱，义务感淡薄，在医疗活动中不讲医德，把单纯追求经济利益作为最高准则，认为医疗工作也应全面适应市场经济，一切以经济效益为依据，以赚钱获利为日的，拒绝执行国家有关规定和医德规范，一切向钱看。一些医疗机构盲目花高价购进大最诊断和治疗设备，为急于收回投资和产生利润，不顾患者需要不需要，照样开单检查。有的医院要搞基本建设，改善环境，就给各科室下创收任务，要求必须完成规定指标，否则不发奖金。如少数医院和科室或个别医生无病当有病看，小病当大病看，不需检查也检查，尽量使用昂贵药品。有的医生习惯于开大处方，不管什么病，都要用最好的药。这些做法，不仅加重了患者负担，而且造成了医疗资源的浪费。

Let’s begin today by discussing enzymes. Enzymes are what make many of the body’s biochemical reactions possible. Actually biochemical reactions can take place without them, but at much lower rates. In fact an enzyme may cause a reaction to proceed billions of times faster than it would otherwise. Before I go on to the biochemical specifics of how this works, let me provide a figurative example. I think it will help illustrate the power of enzymes more clearly. Now, suppose you got a bag and you put a bunch of locks in it, just small padlocks. Then you put in all the keys that go with the locks. And you closed the bag and shook it hard. No matter how long you shook, chances are very small that any key would get inserted in any of the locks. But if you took them all out of the bag and this time used your hands to insert the keys in the locks, you could combine them much quicker. Enzymes act like your hands, quickly allowing chemical reactions that would otherwise take much longer. Now, there are two reasons that enzymes are so effective at enabling biochemical reactions. First, enzymes greatly reduce the amount of energy required to start the reactions, and with less energy needed the reactions can proceed a lot faster than they could without the enzyme. The second reason is that a small amount of an enzyme is needed to enable the biochemical reaction. That’s because the chemical structure of the enzyme itself does not become altered as if enables the reaction. So a single enzyme can be used to start the same biochemical reaction over and over again. Questions 21 - 25 are based on the passage you have just heard. 21. What is the passage mainly about? 22. What point does the professor make about an enzyme when it is involved in a biochemical reaction? 23. What do enzymes do to help start a biochemical reaction? 24. Why does the professor talk about locks and keys? 25. What is enzymes? The impact of enzymes on chemical reactions. The way the body produces enzymes. The structure of enzymes. Types of chemical products created with enzymes.

Peter was seen crying when he came out of the office. We can deduce that he must have been punished. confer refer prefer infer

On September 2, 1937, President Roosevelt signed legislation that was to have far-reaching consequences for American wildlife. effect disaster challenge magic

Sometimes the messages are conveyed through deliberate ’conscious gestures’, other times, our bodies talk without our even knowing it. definite intentional interactive delicate

The scenery on the way was truly spectacular, with beautiful mountains, rivers and valleys, and I took a lot of pictures from the window. notorious amazing noble diplomatic

Providing first-class service is one of the tactics the airline adopts to attract passengers. methods attitudes thoughts solutions

The boss felt suspicious about the truth of the account, therefore, he determined to get down to having a good check. mistrustful furious considerate depressed

On September 2, 1937, President Roosevelt signed legislation that was to have far-reaching consequences for American wildlife. effect disaster challenge magic

Sometimes the messages are conveyed through deliberate ’conscious gestures’, other times, our bodies talk without our even knowing it. definite intentional interactive delicate

Initial reports were that multiple waves of warplanes bombed central Baghdad, hitting oil refineries and the airport. beating knocking hurting striking

The scenery on the way was truly spectacular, with beautiful mountains, rivers and valleys, and I took a lot of pictures from the window. notorious amazing noble diplomatic

The boss felt suspicious about the truth of the account, therefore, he determined to get down to having a good check. mistrustful furious considerate depressed

This passage is mainly concerned with______.

According to the author, the two forms that energy exists in are______.

The author mention the word “perfume“ in Paragraph 3 for the purpose of______.

Molecules of a system will reach a state of equilibrium______.

The development of the lipid bilayers model______.