Question

    Exposing living tissue to subfreezing temperatures for long can cause permanent damage. Microscopic ice crystals (结晶体) cut cells and seize moisture (潮气), making donor organs unsuitable for transplantation. Thus, organs can be made cold for only a few hours ahead of a procedure. But a set of lasting new antifreeze compounds (化合物)—similar to those found in particularly hardy (耐寒的) animals—could lengthen organs’ shelf life.

Scientists at the University of Warwick in England were inspired by proteins in some species of Arctic fish, wood frogs and other organisms that prevent blood from freezing, allowing them to flourish in extreme cold. Previous research had shown these natural antifreeze molecules (分子) could preserve rat hearts at -1.3 degrees Celsius for up to 24 hours. But these proteins are expensive to extract (提取) and highly poisonous to some species. “For a long time everyone assumed you had to make synthetic (人造的) alternatives that looked exactly like antifreeze proteins to solve this problem, ”says Matthew Gibson, a chemist at Warwick who co-authored the new research. “But we found that you can design new molecules that function like antifreeze proteins but do not necessarily look like them. ”

Most natural antifreeze molecules have a mixture of regions that either attract or repel water. Scientists do not know exactly how this process prevents ice crystal formation, but Gibson thinks it might throw water molecules into push-pull chaos that prevents them from tuning into ice. To copy this mechanism, he and his colleagues synthesized spiral-shaped molecules that were mostly water-repellent—but had iron atoms at their centers that made them hydrophilic, or water-loving. The resulting compounds were surprisingly effective at stopping ice crystals from forming. Some were also harmless to the roundworm Caenorhabditis elegans, indicating they might be safe for other animals.

“These compounds are really cool because they are not proteins—they are other types of molecules that nonetheless can do at least part of what natural antifreeze proteins do, ”says Clara do Amaral, a biologist at Mount St. Joseph University, who was not involved in the research. Gibson’s antifreeze compounds will still need to be tested in humans, however, and may be only part of a solution. “We don’t have the whole picture yet, ”do Amaral adds. “It’s not just one magical compound that helps freeze-tolerant organisms survive. It’s a whole suite of adaptations.

1.What will happen if organs are kept for a long time in temperatures below zero?

A.They will have ice crystal formation inside.

B.They will not suffer permanent damage.

C.They will have longer shelf life.

D.They will be fit for transplantation.

2.What can we learn about natural antifreeze proteins?

A.They look like Gibson’s antifreeze compounds.

B.They are composed of antifreeze molecules harmless to other species.

C.They are spiral-shaped and have iron atoms at their centers.

D.They can be found in organisms living in freezing cold weather.

3.How are antifreeze molecules prevented from ice crystals?

A.By creating compounds both water-repellent and water-loving.

B.By extracting the proteins from some hardy animals.

C.By making synthetic alternatives like antifreeze proteins.

D.By copying spiral-shaped molecules mostly water-resistant.

4.What’s the main idea of the passage?

A.Push-pull chaos might prevent water molecules from turning into ice.

B.The final solution to preserving donor organs has been found recently.

C.Chemicals inspired by Arctic animals could lengthen organs’ shelf life.

D.Gibson’s antifreeze compounds can do what natural antifreeze proteins do.

Answer

1.A

2.D

3.A

4.C

【解析】

这是一篇说明文。文章介绍了受北极动物的启发科学家们发现的延长器官保存期限的方法。

1.细节理解题。根据第一段Exposing living tissue to subfreezing temperatures for long can cause permanent damage. Microscopic ice crystals cut cells and seize moisture, making donor organs unsuitable for transplantation. 将活组织暴露在低温下很长时间会造成永久性的伤害。微小的冰晶会切割细胞并夺取水分，使得捐献器官不适合移植。所以如果器官被长时间保存在零度以下的温度下，它们内部会形成冰晶。故选A。

2.直接理解题。根据第二段Scientists at the University of Warwick in England were inspired by proteins in some species of Arctic fish, wood frogs and other organisms that prevent blood from freezing, allowing them to flourish in extreme cold. 英国华威大学的科学家们受到了一些北极鱼类、木蛙和其他生物的蛋白质的启发，这些蛋白质阻止了血液的冻结，使它们在极度寒冷中得以生长。可知天然防冻蛋白，可以在生活在寒冷天气的生物体中发现。故选D。

3.细节理解题。根据第三段To copy this mechanism, he and his colleagues synthesized spiral-shaped molecules that were mostly water-repellent—but had iron atoms at their centers that made them hydrophilic, or water-loving.可知为了复制这一机制，他和他的同事合成了螺旋状的分子，这些分子主要是拒水的，但其中心有铁原子，使其具有亲水性。所以通过创造既防水又爱水的化合物防止防冻剂分子与冰晶接触。故选A。

4.主旨大意题。根据第一段 But a set of lasting new antifreeze compounds (化合物)—similar to those found in particularly hardy (耐寒的) animals—could lengthen organs’ shelf life.可知但是，一组持久的新型防冻剂化合物——类似于在特别耐寒的动物身上发现的化合物——可以延长器官的保存期。所以文章介绍了来自北极动物的化学物质可以延长器官的保质期。故选C。