Final answer:
Lactose and sucrose are disaccharides, composed of different monosaccharide molecules. Lactose is found naturally in milk, while sucrose is commonly known as table sugar. Both sugars have distinct compositions and occur naturally in their respective sources.
Step-by-step explanation:
Lactose and sucrose are disaccharides, which are a type of sugar made up of two monosaccharide molecules. Lactose, also known as milk sugar, is composed of one glucose molecule and one galactose molecule. Sucrose, commonly known as table sugar, is made up of one fructose molecule and one glucose molecule. Both lactose and sucrose occur naturally in their respective sources, milk and plants.