[Campbell Biology P.146] A researcher is performing cell fractionation using differential ce... | Practice Question

A researcher is performing cell fractionation using differential centrifugation to isolate mitochondria from a eukaryotic cell culture. Based on the principles described, what would be the most effective approach to obtain a pellet rich in mitochondria?

  • A: Spin the disrupted cells at very high speeds, as mitochondria are very small components.
  • B: Begin with a very slow spin to remove larger components, then gradually increase the speed to pellet successively smaller components, including mitochondria.
  • C: Perform only a single, very high-speed spin to ensure all cellular components, including mitochondria, are pelleted at once.
  • D: Use a specific stain that targets mitochondria, then centrifuge at any speed to isolate them.

Explanation

The text describes differential centrifugation as a process involving "a series of increasing speeds." It states, "At lower speeds, the pellet consists of larger components, and higher speeds result in a pellet with smaller components." To isolate mitochondria, which are smaller than nuclei but larger than ribosomes, a stepwise increase in speed is necessary. This method allows for the collection of different cellular components in successive pellets, enriching for mitochondria at an intermediate speed after larger components have been removed.