Which one of the following is not a fungus?
Answer: C
Correct answer: Chickenpox
Chickenpox is caused by a virus, varicella-zoster. Bread mould, potato blight and mushrooms are all fungi or fungus-like organisms.
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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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Which of the following is the smallest?
Answer: B
Correct answer: Virus
Viruses are the smallest, typically 20-300 nanometres - far below the resolution of a light microscope, which is why they were unknown until the electron microscope. Bacteria are measured in micrometres, a thousand times larger, and fungi larger still.
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Milk, if left out of the refrigerator will quickly go sour.
Which one of the following statements is incorrect?
Answer: C
Correct answer: Viruses cause milk to go sour faster.
Milk sours because bacteria ferment its lactose to lactic acid - viruses have nothing to do with it. The other three statements are true: warmth speeds bacterial growth, bacteria are the cause, and the souring is the acid produced.
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Fungi are simple plants. Which one of the following statements about fungi is INCORRECT?
Answer: A
Correct answer: Fungi contain chlorophyll.
Fungi have no chlorophyll and cannot photosynthesise - which is why they must absorb organic nutrients, as saprotrophs or as parasites. The absence of chlorophyll is the main reason they are no longer classed as plants at all, but placed in a kingdom of their own.
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Chemicals produced by bacteria and fungi, and which treat infections caused by bacteria, are known as
Answer: B
Correct answer: antibiotics
Antibiotics are substances produced by microorganisms - moulds and soil bacteria - that kill or inhibit other microorganisms. Penicillin from Penicillium is the type case. They act on bacterial structures such as the cell wall and the 70S ribosome, which is why they are useless against viruses.
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Athlete’s foot is an example of a disease caused by a
Answer: A
Correct answer: fungus
Athlete’s foot is a fungal infection of the skin between the toes, caused by dermatophytes that thrive in the warm damp conditions of enclosed shoes. It is treated with antifungal creams, not antibiotics.
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Which one of the microorganisms below reproduces inside living cells and eventually kills the cell?
Answer: A
Correct answer: Virus
A virus takes over the host cell’s machinery to make copies of itself, and the cell is commonly destroyed as the new particles are released. That is what makes viruses so hard to treat: attacking the virus means attacking a process the cell itself is carrying out.
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Viruses are not considered living because they do not have all of the seven characteristics of living things. Which one of these characteristics do viruses have?
Answer: D
Correct answer: Reproduction
Of the seven characteristics of life, a virus shows only reproduction - and even that only inside a host cell, using the host’s machinery. It does not grow, move, feed, respire, excrete or respond to stimuli, which is why viruses sit on the border of the living and the non-living.
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Tooth decay is caused by sugars.
What feeds on sugars in the mouth to cause tooth decay?
Answer: B
Correct answer: Bacteria
Streptococcus mutans and related bacteria in dental plaque ferment sugars from food and produce acid, and it is the acid that dissolves the enamel. Sugar alone would do nothing without them, which is why brushing - removing the plaque - matters as much as avoiding sweets.
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