Final answer:
Bile salts and phospholipids like lecithin keep cholesterol dissolved in bile by forming micelles, which are tiny spheres that can suspend hydrophobic substances in the watery intestinal environment, leading to their absorption.
Step-by-step explanation:
Cholesterol is kept dissolved within bile primarily through the action of bile salts and phospholipids such as lecithin. Bile salts are derived from cholesterol and help dissolve it in the form of bile salt-cholesterol particles that are eventually eliminated. Furthermore, bile salts along with lecithin enclose hydrophobic molecules like cholesterol and long-chain fatty acids within a micelle. Micelles are tiny spheres with polar (hydrophilic) ends that face the watery environment and hydrophobic tails turned inward. This structure allows the micelle to stay suspended in the watery chyme of the intestine and enables the transportation and absorption of hydrophobic substances.
In cases where there is excess cholesterol, it can precipitate and form gallstones. However, normally, cholesterol is maintained in solution in the bile due to the emulsifying actions of bile salts and phospholipids, which prevent the cholesterol from congealing into insoluble forms. This mechanism is essential for the proper digestion and absorption of dietary fats and cholesterol through the small intestine.