What is a cell line?
Answer: D
Correct answer: Sub culturing of primary culture
A cell line arises when a primary culture is subcultured and continues to grow. A finite cell line divides a limited number of times before senescence; a continuous cell line has been transformed and divides indefinitely, HeLa being the famous example.
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Which of the following is correct?
Answer: A
Correct answer: ECL can be established in suspension cultures whereas it is exceptional for primary cell lines (PCL)
Established lines are commonly anchorage independent, so they can be grown in suspension - which is what makes large-scale culture in stirred bioreactors possible. Primary lines are almost always anchorage dependent and must be grown on a surface, so suspension culture is exceptional for them.
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pH of culture medium is initially controlled by
Answer: B
Correct answer: presence of bicarbonate buffer
The pH of culture medium is held by the bicarbonate/CO2 buffer, exactly as blood is: dissolved CO2 and bicarbonate in equilibrium. That is why cultures are kept in an incubator with a controlled CO2 atmosphere - take the flask out, CO2 escapes, and the medium turns alkaline.
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Selective media facilitate growth of only one kind of organism. Saboraud medium is used to selectively isolate
Answer: C
Correct answer: yeasts
Sabouraud’s medium has a low pH (about 5.6) and a high sugar concentration, both of which suit fungi and yeasts while suppressing most bacteria. Chloramphenicol is often added to suppress the rest.
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Which of the following is not a source of energy in active muscle cells?
Answer: C
Correct answer: Lactic acid
In the classical account, lactic acid is the waste product of anaerobic glycolysis in muscle, not a fuel - it is carried to the liver and reconverted to glucose in the Cori cycle. The energy sources are ATP itself, creatine phosphate for the first few seconds, and glucose thereafter. (Modern work shows lactate can be oxidised as a fuel by heart and by resting muscle, but that is not the sense intended here.)
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What is animal tissue culture?
Answer: A
Correct answer: Growth and maintenance of animal cells
Animal tissue culture is the growth and maintenance of animal cells outside the organism, in a controlled sterile environment. Both halves matter: cells must be kept alive and healthy as well as multiplied, which means feeding, subculturing and controlling pH, temperature and gas.
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For the selection of lactobacilli present in cheddar cheese, the pH of the medium is maintained at
Answer: B
Correct answer: 5.35
Lactobacilli tolerate acid far better than most organisms, so setting the medium at about pH 5.35 selects for them: they grow while the competing flora of the cheese are held back.
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To prevent the accumulation of lactate
Answer: C
Correct answer: low glucose concentration is required
Lactate comes from glucose, and cells ferment more of it the more there is - even when oxygen is plentiful. Keeping the glucose concentration low, by feeding it gradually rather than supplying it all at once, forces the cells to oxidise what they get and so limits lactate. That is the principle of fed-batch culture.
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Specific oxygen consumption rates for mammalian cells are in the range of (where n and prepresents to nano and pico respectively)
Answer: C
Correct answer: 0.05-5 pmol of O2/cell/h
Mammalian cells consume oxygen at about 0.05-5 picomoles per cell per hour. It is a small figure per cell but a demanding one in aggregate: oxygen is poorly soluble in water, so at high cell densities supplying it becomes the limiting factor in bioreactor design.
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Cells which have undergone transformation frequently become
Answer: A
Correct answer: anchorage independent
A transformed cell loses its need for a surface to attach to, becoming anchorage independent - it will grow in suspension or in soft agar. That property is one of the standard laboratory tests for malignant transformation, because it corresponds to the ability of a tumour cell to survive away from its tissue of origin.
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