# What monosaccharides make up lactose?

Jun 27, 2015

The monosaccharides that make up lactose are galactose and glucose.

#### Explanation:

The structure of galactose, ${\text{C"_6"H"_12"O}}_{6}$, is

The structure of glucose, ${\text{C"_6"H"_12"O}}_{6}$, is

The $\text{OH}$ on $\text{C-1}$ of galactose can combine with the $\text{OH}$ on $\text{C-4}$ of glucose to form lactose

We could write the equation for the formation of lactose as

 underbrace("C"_6"H"_12"O"_6)_color(red)("galactose") + underbrace("C"_6"H"_12"O"_6)_color(red)("glucose") → underbrace("C"_12"H"_22"O"_11)_color(red)("lactose") + "H"_2"O"