Lactose and lactase, these words sound pretty similar. Actually, they have many differences structurally and functionally. Their proximity to the sound sometimes leads to confusion. These two words are usually heard together with lactose intolerance. It is a certain health condition that some people experience due to a decreased ability to digest lactose. Today, we will be introduced with key differences between lactose and lactase. Let’s enjoy learning.



Lactose belongs to the bio-molecular group of carbohydrates. And you know carbohydrates are mainly divided into monosaccharide, disaccharide, and polysaccharide. Lactose is a disaccharide or bi-molecular, because one lactose basically is made up of two molecules. One is “Galactose” and another one is “Glucose”. It is 2 to 8 percent sugar in milk. Its molecular symbol is C12H22O11. Cow's milk contains about 4.7% lactose where human milk contains almost 7%. Basically, lactose content is high in mammalian milk. It is one of the first tastes we experience as babies. It is a carbohydrate simple polymer of two smaller sugars.


Lactose > Lactase > Galactose and Gluecose

Lactase is an enzyme which is made up of amino acids chain folding into 3D structure. Enzymes are proteins. So it is made up of proteins. In biological terms, “ase” stands for enzyme. Enzymes act as biological catalysts. A catalyst is an agent which helps or accelerates a chemical reaction without participating in it. Some folk are intolerant of lactose and allergic since they lack the enzyme lactase. People who have lactose intolerance actually are having a lack of lactase in their bodies.

Lactase is an enzyme that breaks down a substance called lactose in milk and dairy foods into one molecule of galactose and one molecule of glucose. Its main function is to break down the disaccharide (lactose) into glucose and galactose. Hence, people with lactose intolerance are unable to split the two molecules apart. So they don’t get metabolized by the body in the digest system. This is how lactose intolerance work. As disaccharides don't directly mix in the blood stream, it needs to get converted to monosaccharides in order to mix with the blood. The body’s function is designed that way. [1]


  • Lactose is a carbohydrate sugar whereas lactase is enzyme.
  • Lactose is disaccharide carbohydrates ; Lactase acts like a catalyst to break down the disaccharide (lactose).
  • Lactose works as an energy source for the body ; lactase doesn’t work as an energy source.
  • Lactose is taken from the outside of the body where lactase is naturally produced inside the body.
  • Lactose is made up of two different sugars ; but lactase is made up of amino acids.


[1] Between Mates, Lactose and Lactase Retrieved From : on 207

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