It is apparent that amino acids had an important role in the development of the larger and more complex molecules that were necessary for the development of early life on Earth. They are the chief components of proteins. Two environmental circumstances in the early years of Earth history may have been important in the natural synthesis of amino acids. Prior to the accumulation of the ozone layer in Earth’s upper atmosphere, ultraviolet rays bathed Earth’s surface. Ultraviolet radiation is capable of separating the atoms in mixtures of water, ammonia, and hydrocarbons and of recombining those atoms into amino acids. A second form of energy capable of accomplishing this feat is electrical discharge in the form of lightning. Either together or separately, lightning and ultraviolet radiation may have stimulated the production of amino acids at shallow depths in lakes or oceans.
Researchers have sought to test whether amino acids could be created from the chemicals of a primitive Earth. Scientists in the mid-nineteenth century had succeeded in manufacturing some relatively simple organic compounds in the laboratory. However. it was not until 1953 that the laboratory synthesis of amino acids and other molecules of roughly similar complexity was announced Stanley Miller, at the suggestion of Harold Urey. performed the now-famous experiment. He created an atmosphere in an apparatus that at that time was thought to be like Earth’s earliest atmosphere. It was a methane, ammonia, hydrogen, and water vapor atmosphere As the mixture was circulated through the glass tubes, sparks of electricity (simulated lightning) were introduced into the mixture. At the end of only eight days, the condensed water in the apparatus had become turbid and deep red. Analysis of the crimson liquid showed that it contained a large quantity of amino acids as well as somewhat more complicated organic compounds that enter into the composition of all living things.
In additional experiments by other biochemists, it was shown that similar organic compounds could also be produced from gases (carbon dioxide, nitrogen, and water vapor) of the preoxygenic atmosphere. The main requirement for the success of the experiments seemed to be the lack, or near absence, of free oxygen (oxygen not combined with any other element). To the experimenters, it now seemed almost inevitable that amino acids would have developed in Earth’s pre-life environment. Because amino acids are relatively stable, they probably increased gradually to levels of abundance that would enhance their abilities to join together into more-complex molecules leading to proteins.
To come together and form protein-like molecules, amino acids must lose water. This loss can be accomplished by heating concentrations of amino acids to temperatures of at least 140°℃. Volcanic activity on the primitive crust would be capable of providing such temperatures. However, the biochemist S. W. Fox discovered that the reaction also occurred at temperatures as low as 70°C if phosphoric acid was present. Fox and his co-workers were able to produce protein-like chains from a mixture of eighteen common amino acids. They called these structures proteinoids and reasoned that billions of years ago, they were the transitional structures leading to true proteins. This was not a wild guess, for Fox was able to find proteinoids similar to those he created in his laboratory among the lavas and cinders adjacent to the vents of Hawaiian volcanoes. Apparently, amino acids formed in the volcanic vapors and were combined into proteinoids by the heat of escaping gases.
Hot, water-based solutions of proteinoids will, on cooling, form into tiny spheres that show many characteristics common to living cells. These proteinoid microspheres, as they are called, have a film-like outer wall through which liquids can move; exhibit budding as do yeast organisms; and can be observed to divide into “daughter” microspheres. They occasionally cluster together in lines to form filaments, as in some bacteria. and they exhibit a streaming movement of internal particles similar to that observed in living cells Although complete long-chain nucleic acids (e.q., DNA) have not been experimentally produced under pre-life conditions, short stretches of ordered sequences of nucleic acid components have now been produced in the laboratory. Some paleobiologists believe similar sequences could have been formed and accumulated on the surfaces of clay particles.
1
It is apparent that amino acids had an important role in the development of the larger and more complex molecules that were necessary for the development of early life on Earth. They are the chief components of proteins. Two environmental circumstances in the early years of Earth history may have been important in the natural synthesis of amino acids. Prior to the accumulation of the ozone layer in Earth’s upper atmosphere, ultraviolet rays bathed Earth’s surface. Ultraviolet radiation is capable of separating the atoms in mixtures of water, ammonia, and hydrocarbons and of recombining those atoms into amino acids. A second form of energy capable of accomplishing this feat is electrical discharge in the form of lightning. Either together or separately, lightning and ultraviolet radiation may have stimulated the production of amino acids at shallow depths in lakes or oceans.
The word “components” in the passage is closest in meaning to
Asources
Bcompanions
Cingredients
Dreceivers
2
It is apparent that amino acids had an important role in the development of the larger and more complex molecules that were necessary for the development of early life on Earth. They are the chief components of proteins. Two environmental circumstances in the early years of Earth history may have been important in the natural synthesis of amino acids. Prior to the accumulation of the ozone layer in Earth’s upper atmosphere, ultraviolet rays bathed Earth’s surface. Ultraviolet radiation is capable of separating the atoms in mixtures of water, ammonia, and hydrocarbons and of recombining those atoms into amino acids. A second form of energy capable of accomplishing this feat is electrical discharge in the form of lightning. Either together or separately, lightning and ultraviolet radiation may have stimulated the production of amino acids at shallow depths in lakes or oceans.
It can be inferred from paragraph 1 that ultraviolet radiation
Acontains more energy than lightning does
Bis blocked by Earth’s upper-atmosphere ozone layer
Ccannot penetrate water
Dmust be present for the production of amino acids
3
Researchers have sought to test whether amino acids could be created from the chemicals of a primitive Earth. Scientists in the mid-nineteenth century had succeeded in manufacturing some relatively simple organic compounds in the laboratory. However. it was not until 1953 that the laboratory synthesis of amino acids and other molecules of roughly similar complexity was announced Stanley Miller, at the suggestion of Harold Urey. performed the now-famous experiment. He created an atmosphere in an apparatus that at that time was thought to be like Earth’s earliest atmosphere. It was a methane, ammonia, hydrogen, and water vapor atmosphere As the mixture was circulated through the glass tubes, sparks of electricity (simulated lightning) were introduced into the mixture. At the end of only eight days, the condensed water in the apparatus had become turbid and deep red. Analysis of the crimson liquid showed that it contained a large quantity of amino acids as well as somewhat more complicated organic compounds that enter into the composition of all living things.
It can be inferred from paragraph 1 that ultraviolet radiation
Acontains more energy than lightning does
Bis blocked by Earth’s upper-atmosphere ozone layer
Ccannot penetrate water
Dmust be present for the production of amino acids
4
In additional experiments by other biochemists, it was shown that similar organic compounds could also be produced from gases (carbon dioxide, nitrogen, and water vapor) of the preoxygenic atmosphere. The main requirement for the success of the experiments seemed to be the lack, or near absence, of free oxygen (oxygen not combined with any other element). To the experimenters, it now seemed almost inevitable that amino acids would have developed in Earth’s pre-life environment. Because amino acids are relatively stable, they probably increased gradually to levels of abundance that would enhance their abilities to join together into more-complex molecules leading to proteins.
The word “inevitable” in the passage is closest in meaning to
Acritical
Bincredible
Cpredictable
Dcertain
5
In additional experiments by other biochemists, it was shown that similar organic compounds could also be produced from gases (carbon dioxide, nitrogen, and water vapor) of the preoxygenic atmosphere. The main requirement for the success of the experiments seemed to be the lack, or near absence, of free oxygen (oxygen not combined with any other element). To the experimenters, it now seemed almost inevitable that amino acids would have developed in Earth’s pre-life environment. Because amino acids are relatively stable, they probably increased gradually to levels of abundance that would enhance their abilities to join together into more-complex molecules leading to proteins.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information
AAmino acids’ stability probably let them build up until they joined into more-complex molecules that, in turn, formed proteins
BProteins are formed from complex molecules that are made up of amino acids that have increased abilities to join together.
CBecause of their stability, amino acids are usually more abundant than proteins, which require more-complex molecules.
DThe abundance and complexity of molecules formed from combinations of amino acids are probably due to the stability of the amino acids.
6
To come together and form protein-like molecules, amino acids must lose water. This loss can be accomplished by heating concentrations of amino acids to temperatures of at least 140°℃. Volcanic activity on the primitive crust would be capable of providing such temperatures. However, the biochemist S. W. Fox discovered that the reaction also occurred at temperatures as low as 70°C if phosphoric acid was present. Fox and his co-workers were able to produce protein-like chains from a mixture of eighteen common amino acids. They called these structures proteinoids and reasoned that billions of years ago, they were the transitional structures leading to true proteins. This was not a wild guess, for Fox was able to find proteinoids similar to those he created in his laboratory among the lavas and cinders adjacent to the vents of Hawaiian volcanoes. Apparently, amino acids formed in the volcanic vapors and were combined into proteinoids by the heat of escaping gases.
According to paragraph 4, amino acids cannot come together to form protein-like molecules without
Athe presence of volcanic activity
Bbeing exposed to phosphoric acid
Cgetting rid of some water first
Dexperiencing temperatures lower than 70℃
7
To come together and form protein-like molecules, amino acids must lose water. This loss can be accomplished by heating concentrations of amino acids to temperatures of at least 140°℃. Volcanic activity on the primitive crust would be capable of providing such temperatures. However, the biochemist S. W. Fox discovered that the reaction also occurred at temperatures as low as 70°C if phosphoric acid was present. Fox and his co-workers were able to produce protein-like chains from a mixture of eighteen common amino acids. They called these structures proteinoids and reasoned that billions of years ago, they were the transitional structures leading to true proteins. This was not a wild guess, for Fox was able to find proteinoids similar to those he created in his laboratory among the lavas and cinders adjacent to the vents of Hawaiian volcanoes. Apparently, amino acids formed in the volcanic vapors and were combined into proteinoids by the heat of escaping gases.
The author mentions “Hawaiian volcanoes” in order to
Aprovide evidence for the claim that proteinoids led to the formation of true proteins early in Earth’s history
Bindicate where volcanic activity on the primitive crust of Earth mainly took place
Cillustrate the difference between proteinoids created in the laboratory and those found in nature
Didentify the source of amino acids used by Fox in his laboratory experiments
8
Hot, water-based solutions of proteinoids will, on cooling, form into tiny spheres that show many characteristics common to living cells. These proteinoid microspheres, as they are called, have a film-like outer wall through which liquids can move; exhibit budding as do yeast organisms; and can be observed to divide into “daughter” microspheres. They occasionally cluster together in lines to form filaments, as in some bacteria. and they exhibit a streaming movement of internal particles similar to that observed in living cells Although complete long-chain nucleic acids (e.q., DNA) have not been experimentally produced under pre-life conditions, short stretches of ordered sequences of nucleic acid components have now been produced in the laboratory. Some paleobiologists believe similar sequences could have been formed and accumulated on the surfaces of clay particles.
Why does the author mention that proteinoid microspheres “exhibit budding”?
ATo explain how proteinoid microspheres are able to develop a film-like outer wall
BTo point out a characteristic that proteinoid microspheres share with living organisms
CTo point out an effect of warm temperatures on proteinoid microspheres
DTo help explain how proteinoid microspheres divide
9
It is apparent that amino acids had an important role in the development of the larger and more complex molecules that were necessary for the development of early life on Earth. They are the chief components of proteins.■ Two environmental circumstances in the early years of Earth history may have been important in the natural synthesis of amino acids. ■Prior to the accumulation of the ozone layer in Earth’s upper atmosphere, ultraviolet rays bathed Earth’s surface. ■ Ultraviolet radiation is capable of separating the atoms in mixtures of water, ammonia, and hydrocarbons and of recombining those atoms into amino acids. ■ A second form of energy capable of accomplishing this feat is electrical discharge in the form of lightning. Either together or separately, lightning and ultraviolet radiation may have stimulated the production of amino acids at shallow depths in lakes or oceans.
Look at the four squaresthat indicate where the following sentence could be added to the passage
But how did they first form on Earth?
Where would the sentence best fit？Click on a square sentence to the passage.
10
Amino acids, the building blocks of proteins, must have been present for life to have begun on Earth.
AExperiments have confirmed that the formation of amino acids and other organic compounds on early Earth may have been caused by energy from ultraviolet radiation or lightning
BThe atmosphere of early Earth was originally thought to contain only water, ammonia, and hydrocarbons but was later shown to contain methane and nitrogen as well.
CThe fact that proteinoid microspheres share some features with living cells supports the idea that proteinoids played a role in the eventual rise of life.
DIt is thought that the formation of the ozone layer increased production of amino acids, a development that enhanced the ability o amino acids to join together into more complex molecules.
ES. W. Fox showed that protein-like chains of amino acids form as a result of volcanic activity and theorized that these chains could have been transitional forms leading to true proteins
FScientists have shown that long-chain nucleic acids could not have formed under pre-life conditions although short sequences of DNA might have
