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# Long description

Part (a) shows that the disruption of the cells produces a homogenate comprising intact organelles and resealed membranes called microsomes. In part (b), low speed centrifugation of a cell homogenate produces a pellet of larger components such as whole cells, nuclei and cytoskeleton; medium speed centrifugation produces a pellet of smaller components such as mitochondria; high speed centrifugation produces a pellet of yet smaller components such as microsomes and small vesicles; and very high speed centrifugation produces a pellet of even smaller components such as ribosomes, viruses and large macromolecules. In part (c), centrifugation of a cell homogenate in a sucrose density gradient produces a fast-sedimenting, high density band of particles low down the tube and a slow-sedimenting, low density band of particles further up the tube. The tube is pierced at the bottom and successive fractions of decreasing density are collected.