The process of conversion of sugar into alcohol by yeast is called
Answer: A
Correct answer: Fermentation
Converting sugar to alcohol and carbon dioxide by yeast, in the absence of air, is fermentation. Pasteurisation is a heat treatment that kills microorganisms, and alcoholism is a disease of dependence - neither is a chemical process.
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Agar is placed in a petri dish and some soil is sprinkled on the agar. The lid is placed on the petri dish, and it is incubated for two days. After two days, areas of bacteria and fungi are visible on the agar.
What is the name for these areas?
Answer: D
Correct answer: Colonies
Each visible patch is a colony - the descendants of a single cell that landed on the agar and multiplied until the mass became visible. Counting colonies is how bacteria are counted, on the assumption that one colony grew from one organism.
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The type of microorganism used to make yoghurt is
Answer: A
Correct answer: bacteria
Yoghurt is made with bacteria - Lactobacillus bulgaricus and Streptococcus thermophilus - which ferment lactose to lactic acid. The acid coagulates the milk protein and gives yoghurt its texture and its sharp taste.
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Spirogyra is a type of
Answer: C
Correct answer: Algae
Spirogyra is a filamentous green alga of fresh water, named for the spiral chloroplasts that wind through each cell. Being photosynthetic, it makes its own food.
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Which of the following diseases can be cured using antibiotics?
Answer: C
Correct answer: Typhoid
Typhoid is caused by a bacterium, Salmonella typhi, and so responds to antibiotics. AIDS and dengue are viral and malaria protozoal - antibiotics act on bacterial structures that none of those possess.
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Lactobacillus is commonly found in
Answer: B
Correct answer: Curd
Lactobacillus ferments the lactose of milk to lactic acid, which coagulates the casein and sets the curd. Bread and cake are raised by yeast, a fungus, not by lactobacilli.
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Litmus, used as an indicator for acids and bases, is extracted from
Answer: A
Correct answer: Lichens
Litmus is extracted from lichens, chiefly Roccella species. It turns red in acid and blue in alkali, and was one of the earliest chemical indicators - used long before anyone understood why it worked.
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Which organisms are microscopic and dependent on host organisms for reproduction?
Answer: C
Correct answer: Viruses
Viruses are microscopic and can reproduce only inside a living host cell: they have no ribosomes and no metabolism of their own, so they must use the host’s. Bacteria, protozoa and algae are cells and multiply on their own.
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Vaccines are made up of:
Answer: B
Correct answer: Weak microorganisms
A vaccine contains the pathogen in a form that cannot cause disease - weakened (attenuated) or killed organisms, or just a part of one such as a surface protein or an inactivated toxin. The immune system responds and retains memory cells, so a later encounter with the real organism is dealt with at once.
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Which cannot fix atmospheric nitrogen in the soil?
Answer: D
Correct answer: Penicillium
Penicillium is a mould, and it fixes no nitrogen - it is famous for producing penicillin. Rhizobium fixes nitrogen symbiotically in root nodules, while Azotobacter and Clostridium do so free-living in the soil.
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