Final answer:
Disaccharides are carbohydrates composed of two monosaccharides linked by a glycosidic bond. Cellulose and starch are classified as polysaccharides. Lactose, a disaccharide found in milk, is formed by glucose and galactose.
Step-by-step explanation:
Disaccharides are a type of carbohydrate that are formed by the joining of two monosaccharides. These monosaccharides are linked by a glycosidic bond, which is the result of a dehydration synthesis process. Three important disaccharides to humans are: sucrose (table sugar), lactose (milk sugar), and maltose (malt sugar). Before these disaccharides can be utilized by the body as an energy source, they must be split into their monosaccharide components through the process of hydrolysis in the digestive tract.
In response to the student's questions:
- Cellulose and starch are examples of polysaccharides.
- Lactose is a disaccharide composed of glucose and galactose, joined by a glycosidic bond.