Sterols are an important class of organic molecules. They occur naturally in plants, animals and fungi, with the most familiar type of animal sterol being cholesterol. Cholesterol is vital to cellular function, and a precursor to fat-soluble vitamins and steroid hormones. Types of sterols Sterols of plants are called phytosterols and sterols of animals are called zoosterols. Important zoosterols are cholesterol and some steroid hormones; notable phytosterols include campesterol, sitosterol, an… (More on Sterols)