Write NO MORE THAN THREE WORDS/AND OR A NUMBERfrom the passage for each answer.
A Giant Step for Artificial Enzymes
1. Chemists in Britain have come a step nearer to building an “artificial enzyme” — a molecule which could speed up some reactions that are useful to industry.
2. Jeremy Sanders and his colleagues at the University of Cambridge have designed and synthesized a large cyclic “receptor” molecule, which makes one such reaction proceed almost 60,000 times as fast as usual. The receptor is similar to another built last year by the same team (New Scientist, Science, 1 February 1992). It consists of a ring of three porphyrin molecules kinked by bridging chemical groups. Each porphyrin molecule contains a zincion at its centre. The central cavity of the new receptor is slightly smaller than before, and the researchers have also anchored pyridine groups to two of the zincions to act as bonding sites.
3. Sanders and his colleagues have used their receptor to speed up and control the products of the so-called Diels-Alder reaction, a mainstay of chemical synthesis. The reaction occurs between two molecules — a “diene”, which has two carbon-carbon bonds separated by a single bond, and a diene-seeking molecule, or “dienophile”. In the right conditions, these two molecules transfer the elections involved in their double bonds from atom to atom to form new bonds that complete a ring of six carbon atoms with a single double bond. The creation of such six-membered rings is the crucial first step in making many pharmaceuticals and agrochemical.
4. Some Diels-Alder reactions are too slow to be useful industrially. The researchers, therefore, designed their receptor so that it would hold the diene and dienophile, via the pyridine (Py) groups, in the right positions to react quickly. According to Sanders, the receptor acts like a “molecular reaction vessel in which the effective concentration of reactants can be increased dramatically, so allowing a fast reaction”.
5. Normally, Diels-Alder reactions produce a mixture of two products. But because in the receptor the reactants are forced into a specific orientation relative to each other, only one of the two possible products can form.
6. Sanders hopes to modify the receptor to bring together in the cavity two molecules that do not normally react. This could lead to be the synthesis of compounds which everyday synthetic chemistry cannot make.
7. The receptor differs from an enzyme or other catalyst in one important respect. Only a tiny amount of an enzyme is needed to make a reaction thousands of times faster, but large quantities of the receptor are needed to make a significant difference to the speed of a reaction. However, Sanders is confident that in the future his team will be able to increase the turnover or able to increase the turnover of reactants by designing new features into the receptor. This would reduce the amount of receptor needed to speed up a reaction by a given amount. The researchers report further details of their results in the latest issue of Journal of the Chemical Society, Chemical Communications.
How fast can the receptor molecule make reactions proceed?
What is the mainstay of chemical synthesis?
What is crucial to making many pharmaceuticals and agrochemicals?
AI explanationShows the answer. Tap to open.
Question Focus: Synonym match - the question asks about speed, and the passage gives a numerical comparison
Correct Answer: 60,000 times
Why this is correct: The passage clearly says the reaction proceeds almost 60,000 times as fast as usual. The question asks how fast the receptor can make reactions proceed, so 60,000 times directly answers this.
Passage Reference: Jeremy Sanders and his colleagues at the University of Cambridge have designed and synthesized a large cyclic 'receptor' molecule, which makes one such reaction proceed almost 60,000 times as fast as usual.
Common Mistake: Some students write very fast or much faster, but those words are not in the passage. You must copy the exact wording or number. This is a synonym trap.
Paraphrasing: Passage: 'almost 60,000 times as fast as usual' = Question: 'How fast can the receptor molecule make reactions proceed?'
Tips: When you see numbers in the passage, copy them carefully and check the word limit.
Key Vocabulary:
- proceed = happen
- synthesized = made
Question Focus: Direct definition - the passage directly names the mainstay
Correct Answer: Diels-Alder reaction
Passage Reference: Sanders and his colleagues at the University of Cambridge have designed and synthesized a large cyclic 'receptor' molecule, which makes one such reaction proceed almost 60,000 times as fast as usual. The receptor is similar to another built last year by the same team (New Scientist, Science, 1 February 1992). It consists of a ring of three porphyrin molecules kinked by bridging chemical groups. Each porphyrin molecule contains a zincion at its centre. The central cavity of the new receptor is slightly smaller than before, and the researchers have also anchored pyridine groups to two of the zincions to act as bonding sites. 3. Sanders and his colleagues have used their receptor to speed up and control the products of the so-called Diels-Alder reaction, a mainstay of chemical synthesis.
Why this is correct: The passage explicitly states that the Diels-Alder reaction is a mainstay of chemical synthesis. The question repeats this idea using the same wording.
Common Mistake: Students sometimes write just Diels-Alder and forget reaction. That makes the answer incomplete. This is a partial truth trap.
Paraphrasing: Passage: 'a mainstay of chemical synthesis' = Question: 'What is the mainstay of chemical synthesis?'
Tips: If the question repeats the same wording as the passage, look for a direct copy answer.
Key Vocabulary:
- mainstay = most important part
- synthesis = making chemicals
Question Focus: Synonym match - the question asks what is crucial, and the passage explains the key step
Correct Answer: six-membered rings
Passage Reference: The creation of such six-membered rings is the crucial first step in making many pharmaceuticals and agrochemical.
Why this is correct: The passage says the creation of such six-membered rings is the crucial first step in making many pharmaceuticals and agrochemicals. The core idea is six-membered rings, which fits the word limit.
Common Mistake: Many students copy creation of six-membered rings, but that is more than two words. This is a word limit trap.
Paraphrasing: Passage: 'the creation of such six-membered rings is the crucial first step' = Question: 'What is crucial to making many pharmaceuticals and agrochemicals?'
Tips: If the full phrase is too long, choose the key noun that carries the main meaning.
Key Vocabulary:
- crucial = very important
- agrochemicals = farm chemicals
General Tips:
- Summary and note completion questions follow passage order. Find the first answer, then scan forward.
- Always check the word limit. Even a correct idea is wrong if it has too many words.
- Copy words exactly from the passage. Do not change spelling, form, or number.
- Look for definition phrases like 'is a mainstay of' or 'is the crucial first step'.
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