Read the passage and answer the following questions:
Yeasts, such as Saccharomyces cerevisiae, have been used for centuries to produce alcoholic beverages like wine, beer, whisky, brandy, and rum. These beverages are made through the fermentation of malted cereals and fruit juices by yeast, specifically brewer's yeast. During fermentation, yeast undergoes metabolic reactions that result in the production of ethanol, the primary alcohol in alcoholic beverages. Different types of alcoholic drinks are obtained based on the raw materials used and the processing methods employed. Wine and beer are produced without distillation, while whisky, brandy, and rum are produced by distilling the fermented mixture. On the other hand, antibiotics, which are chemical substances produced by certain microbes, are considered one of the significant discoveries of the twentieth century. They have greatly contributed to the well-being of human society. Antibiotics are capable of killing or inhibiting the growth of disease-causing microbes, thereby having a positive impact on human health.
What are antibiotics?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Chemical substances produced by certain microbes to kill or inhibit the growth of disease-causing microbes
The passage states that antibiotics are “chemical substances produced by certain microbes” that are “capable of killing or inhibiting the growth of disease-causing microbes”.
So an antibiotic has two features: it is made by a microbe, and it acts against other, disease-causing microbes. Penicillin, made by the mould Penicillium notatum, is the best-known example.
Option (1) Chemical substances produced by plants to repel insects — Incorrect. Antibiotics are not plant chemicals, and their action is on microbes, not on insects. Substances that repel insects have nothing to do with treating infections.
Option (2) Chemical substances produced by certain microbes to kill or inhibit the growth of disease-causing microbes — Correct. This option has both features: produced by certain microbes and able to kill or inhibit the growth of disease-causing microbes.
Option (3) Chemical substances used in the fermentation process to produce alcohol — Incorrect. In fermentation, yeast itself turns sugars into ethanol. No antibiotic is used to make alcohol.
Option (4) Chemical substances used to enhance the flavour of alcoholic beverages — Incorrect. The flavour of a drink comes from its raw material and processing. Antibiotics are used to treat diseases, not to flavour beverages.