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A roughly spherical group of large molecules that come together in a colloid. For example, a molecule of soap or detergent has a hydrophilic ("water-loving") polar head and a long hydrophobic ("water-hating") nonpolar tail. When soaps or detergents dissolve in water, the molecules clump together to form micelles with the nonpolar tails at the center, surrounded by a sphere of polar heads linked to water molecules. Bile salt in the intestine make the product of fat digestion form micelles, which are thereby more easily absorbed.

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