Question Focus: Main idea - British scientists making progress toward artificial enzymes
Passage Reference: 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.
Why this is correct: This paragraph introduces the overall achievement. It tells us British chemists have made progress toward creating an artificial enzyme that can help industry.
Common Mistake: Some students choose Fast reactions due to the receptor because they see the word speed up. That is a Context shift trap because Paragraph 1 is about the achievement, not how fast reactions work.
Paraphrasing: Passage: 'come a step nearer to building an artificial enzyme' = Statement: 'achievement'
Tips: For headings, always ask: is this paragraph giving details, or just introducing the main achievement?
Key Vocabulary:
- come a step nearer = make progress
- artificial enzyme = man-made catalyst
Question Focus: Detailed description of the receptor structure
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. 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.
Why this is correct: This paragraph focuses on what the receptor looks like and how it is built. It gives physical and chemical details of the large receptor molecule.
Common Mistake: Students sometimes pick Fast reactions due to the receptor because of 60,000 times as fast. This is a Partial truth trap because speed is mentioned, but the paragraph mainly describes the molecule.
Paraphrasing: Passage: 'designed and synthesized a large cyclic receptor molecule' = Statement: 'large receptor molecule designed'
Tips: When a paragraph has many physical details, the heading is usually about design or structure.
Key Vocabulary:
- synthesized = made
- cyclic = ring-shaped
Question Focus: Explanation of a chemical reaction process
Passage Reference: 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.
Why this is correct: This paragraph explains what the Diels-Alder reaction is and how it works. It defines the reaction and its importance.
Common Mistake: Some students choose The creation of six-membered rings. That is a Paraphrase trap because ring creation is only one detail, not the main focus.
Paraphrasing: Passage: 'the so-called Diels-Alder reaction' = Statement: 'The Diels-Alder reaction'
Tips: If a paragraph defines a term, the heading usually repeats that term.
Key Vocabulary:
- mainstay = very important part
- synthesis = making chemicals
Question Focus: Cause and effect - receptor making reactions faster
Passage Reference: 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'.
Why this is correct: This paragraph explains why reactions become faster when the receptor is used. It clearly links the receptor to increased reaction speed.
Common Mistake: Students may choose The drawback of the receptor. This is a Wrong section trap because disadvantages appear later, not here.
Paraphrasing: Passage: 'allowing a fast reaction' = Statement: 'Fast reactions due to the receptor'
Tips: Look for cause words like 'therefore' or explanations of why something happens.
Key Vocabulary:
- effective concentration = how close reactants are
- reactants = chemicals that react
Question Focus: Comparison of normal products versus receptor-controlled products
Passage Reference: 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.
Why this is correct: This paragraph talks about what products are made in the reaction, and how the receptor changes the result.
Common Mistake: Some students choose The creation of six-membered rings. That is a Context shift trap because rings are not the focus here.
Paraphrasing: Passage: 'produce a mixture of two products' = Statement: 'Products produced'
Tips: If a paragraph compares results or outcomes, the heading is often about products.
Key Vocabulary:
- mixture = more than one result
- orientation = position
Question Focus: Future plans and hopes
Passage Reference: 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.
Why this is correct: This paragraph looks to the future and explains what Sanders wants to do next with the receptor.
Common Mistake: Students may choose British chemists' achievement. This is a Time/tense trap because the paragraph is about future work, not past success.
Paraphrasing: Passage: 'hopes to modify the receptor' = Statement: 'Further efforts to be made'
Tips: Words like 'hopes' and 'could lead to' signal future plans.
Key Vocabulary:
- modify = change
- synthesis = making chemicals
Question Focus: Limitation compared to enzymes
Passage Reference: 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.
Why this is correct: This paragraph explains the main disadvantage of the receptor compared to real enzymes.
Common Mistake: Some students pick Further efforts to be made on the receptor. That is a Partial truth trap because improvement is mentioned, but the focus is the drawback.
Paraphrasing: Passage: 'large quantities of the receptor are needed' = Statement: 'drawback'
Tips: If a paragraph compares weaknesses, the heading is usually about disadvantages.
Key Vocabulary:
- drawback = disadvantage
- turnover = rate of reaction
General Tips:
- Matching headings follow paragraph order - do them from Paragraph 1 to the end.
- Focus on the main idea of each paragraph, not one interesting detail.
- Ignore numbers and technical terms first - ask what the paragraph is mainly doing.
- If a paragraph talks about the future, do not choose a heading about past achievements.
