Question

Lactose is made up of:
A. Galactose and glucose unit
B. Glucose unit and fructose
C. Both glucose units
D. Glucose and arabinose unit

Answer 1

Hint: Lactose is basically a reducing sugar, it is known as milk sugar, because it is found to occur in the milk of cows and also in other mammals. Lactose is found to be lowest in sweetness among all others found in nature.

Step by step solution:
-Structure of lactose is found as:

-When lactose undergoes acid hydrolysis then two monosaccharides are formed, one molecule of D-glucose and one molecule of D-galactose.
- They are found to be joined by a $\beta -1,4-\text{ }gly\cos idic$ bond , the bond from the anomeric carbon of the first monosaccharide unit is in upward direction.
- This process also involves the catalytic action of enzyme lactase.
- Hence, we can conclude that the option (a)is correct that lactose is made up of galactose and glucose units.

Additional information:
- We can see that there is lactose intolerance found in most adults. Lactose intolerance means when a body is not able to digest the lactose which is found in milk and various dairy products.
- There are various symptoms of lactose intolerance depending on the amount of lactose that our body can make. Some of them are like: gas, pain or cramps and mostly diarrhoea.
- It is found that the reason for lactose intolerance is when the small intestine can’t produce sufficient enzymes that are called lactose. Our body basically needs lactose to digest lactose.
- Those people who are lactose intolerant should eat calcium rich food that can make their bones healthy.

Note:
- Galactose and glucose both have the same chemical formula that is ${{C}_{6}}{{H}_{12}}{{O}_{6}}$. Also, both of them have the same structure but the difference is only in the position of one hydroxyl group.