Cell Culture Techniques Questions and Answers

Answer: A

Cells are usually passaged before they reach full coverage, since crowding slows growth and can change their behaviour. It is judged by eye under a microscope rather than measured. Judging it consistently takes a little practice.

Answer: B

Overgrowth causes contact inhibition, altered behaviour and sometimes death, so cells are normally split at around eighty per cent coverage. Waiting longer damages the culture rather than improving it. Cells are usually split at around eighty per cent coverage.

Answer: C

Ice crystals forming inside a cell tear its membranes apart, and the cryoprotectant limits their growth. Cooling slowly and thawing quickly are both part of the same strategy. Both rates are chosen to give ice as little chance to form as possible.

Answer: D

Both are true and the reason gives the rationale for each half: the danger at both stages is ice, and the two rates are chosen to give it as little opportunity as possible to form or grow. Ice, not cold, is what actually destroys a frozen cell.

Answer: A

Correct answer: count cells in a known volume of suspension

A haemocytometer is a slide with a precisely etched grid and a chamber of known depth, so counting the cells within a defined number of squares gives a concentration directly. It remains standard because it is cheap and, with trypan blue, reports viability at the same time - dead cells take up the dye and living ones exclude it.

Answer: B

An intact membrane keeps the dye out, so blue cells are dead and clear ones alive. The test measures membrane integrity rather than any deeper notion of viability. A cell can be dying and still exclude the dye for some hours.

Answer: C

Exclusion shows only that the membrane is intact, and a cell can be committed to apoptosis while still excluding the dye. The test is a useful screen rather than a verdict on the state of the cell. Apoptotic cells commonly exclude it until quite late in the process.

Answer: D

A millilitre is ten thousand times 0.1 microlitres, so 80 becomes 800,000. Getting the volume conversion right is the whole of the calculation, and it is where most errors arise. Working the units through carefully is more important than the arithmetic.

Answer: A

Most cells from solid tissue require a surface, which is why culture vessels are treated to encourage attachment. Blood-derived lines by contrast grow perfectly well in suspension. Which behaviour a line shows follows from the tissue it came from.

Answer: B

The first two are correct. The third is the standing caveat of the whole field, since adaptation to culture changes cells in ways that may matter to the question being asked. A line is a model of the tissue rather than the tissue itself.