Sucrose vs Lactose
Sucrose and lactose are categorized as carbohydrates. Carbohydrates are a group of compounds which are defined as “polyhydroxy aldehydes and ketones or substances that hydrolyze to yield polyhydroxy aldehydes and ketones.” Carbohydrates are the most abundant type of organic molecules on earth. They are the source of chemical energy for living organisms. Not only this, they serve as important constituents of tissues. Carbohydrate can be again categorized into three as monosaccharide, disaccharides and polysaccharides. Monosaccharides are the simplest carbohydrate type. Glucose, galactose, and fructose are monosaccharides. Disaccharides are formed by combining two monosaccharide molecules. This is a condensation reaction where a water molecule is eliminated. Sucrose, lactose, and maltose are few examples for disaccharides. Both disaccharides and monosaccharides are sweet in taste. They are soluble in water. Both are reducing sugars (except sucrose). When more than two monosaccharide molecules are joined they form oligosaccharides and if they have a larger molecular weight (more than 10000), these are known as polysaccharides.
Sucrose is a disaccharide. It is made up of combining glucose (aldose sugar) and fructose (ketose sugar) molecules via a glycosidic bond. During this reaction, a water molecule is eliminated from the two molecules. Sucrose can be hydrolyzed back into the starting molecules when needed. Sucrose has the following structure.
This is a disaccharide that we find commonly in plants. Glucose, which is produced from the photosynthesis in leaves, should be distributed to other growing and storing parts of the plant. And sucrose is the form of transporting. Therefore, in plants, glucose is converted to sucrose in order to distribute them. We are familiar with sucrose in our day to day lives, as we are using this as table sugar. Industrially, sugar cane and beet is used to produce table sugar. Sucrose is a white crystalline solid. It has a sweet taste, and it is readily soluble in water.
Lactose is the disaccharide made from joining the monosaccharides, glucose and galactose via a glycosidic bond. It has the following structure.
This is the disaccharide that is found in milk. Depending on individuals and species, the amount of lactose in milk varies. In infants, there is an enzyme called lactase to digest lactose in milk. Therefore, in the digestive system it breaks down into glucose and lactose again, and these simple sugars are absorbed into the body. Lactose intolerance is the disease condition caused due to the inability to digest lactose. Lactose is important in producing dairy products. When producing curd, cheese and yoghurt naturally, lactose is important.
What is the difference between Sucrose and Lactose?
• Sucrose is produced from a glucose and a fructose molecule. Lactose is produced from a glucose and a galactose molecule.
• Sucrose is the abundant sugar in fruits and vegetables, whereas lactose is abundant in milk.
• Lactose is a reducing sugar, whereas sucrose is not.
• Therefore, sucrose doesn’t answer to the Benedict’s test o Fehling’s test. But if sucrose solution is initially treated with dilute acid and then tested using these tests, it gives a positive result