Biology 9700 · AS & A Level · Cells as the basic units of living organisms

Cells as the basic units of living organisms — practice question

A scientist performed an experiment to separate the organelles in an animal cell according to mass. The cells were combined with a buffer solution that had the same water potential as the cells. A blender was used to break the cells open and release the organelles. The resulting mixture was filtered and then placed in a centrifuge at high speed so that the heaviest type of organelle could be separated. These organelles settled at the bottom, creating solid pellet 1. The liquid above pellet 1 was transferred to a clean centrifuge tube and spun in the centrifuge at a higher speed to separate the next heaviest type of organelle. These organelles settled at the bottom, creating solid pellet 2. This process was repeated twice more to produce pellet 3 and pellet 4, each containing one type of organelle only. What is the main function of the type of organelle obtained in pellet 2?

  • Adigestion of old organelles
  • Bproduction of ATP
  • Cproduction of mRNA
  • Dsynthesis of protein

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