Which one of the following microorganisms consists of only one cell?
Answer: B
Correct answer: Bacteria
Bacteria are unicellular: one cell is the whole organism. Bread mould and most fungi are multicellular, and a virus is not a cell at all.
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What type of microorganism is yeast which is used in many food preparations?
Answer: B
Correct answer: Fungi
Yeast is a single-celled fungus. It ferments sugars to alcohol and carbon dioxide, which is what makes it useful for both baking and brewing - the same process, with a different product wanted in each case.
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Which of the following is not used as a food preservative?
Answer: D
Correct answer: Methane
Methane is a gas and preserves nothing. Salt and sugar preserve by drawing water out of microbial cells osmotically, and vinegar by acidity - all three work by making the food a place where microorganisms cannot grow.
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Which of the following is a communicable disease?
Answer: B
Correct answer: Chicken pox
A communicable disease is one that spreads from person to person, and chicken pox does so readily - through droplets and through contact with the rash. Diabetes, Alzheimer’s and cancer are not caused by transmissible agents.
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The disease caused by protozoa is
Answer: D
Correct answer: malaria
Malaria is caused by Plasmodium, a protozoan, transmitted by the female Anopheles mosquito. Tuberculosis and typhoid are bacterial and polio viral.
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Which microorganism causes AIDS?
Answer: C
Correct answer: A virus
AIDS is caused by HIV, the human immunodeficiency virus - a retrovirus that infects CD4 helper T cells. Their gradual loss is what leaves the patient open to the opportunistic infections that define the disease.
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Alcohol is produced with the help of
Answer: B
Correct answer: yeast
Yeast ferments sugar to ethanol and carbon dioxide in the absence of air. It is the basis of every alcoholic drink, and the same organism, used aerobically, makes bread rise - the difference being whether the CO2 or the alcohol is the product wanted.
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While baking cakes, yeast reproduces rapidly and produces ___ gas.
Answer: C
Correct answer: carbon dioxide
Yeast ferments the sugars in the batter and releases carbon dioxide, which is trapped as bubbles and makes the cake rise. The alcohol produced alongside it evaporates in the oven.
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A common preservative used in jam and pickles is
Answer: A
Correct answer: Sodium benzoate
Sodium benzoate is the standard chemical preservative for jams, squashes and pickles. It works only in acid conditions, where it converts to benzoic acid and enters the microbial cell, disrupting its metabolism - which is why it suits acidic foods and not others. Salt and sugar preserve too, but osmotically rather than as chemical preservatives.
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Which among the following statements is not associated with food preservation?
Answer: B
Correct answer: Decreased shelf life
Preservation exists to increase shelf life, so a decrease is the opposite of what is wanted. The other three describe it correctly: preventing decay, sealing against air and organisms, and keeping food for later use.
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