Lactose vs Galactose: what is the difference?
Lactose is milk sugar, glucose and galactose joined together, while galactose is a single sugar, one of the two halves lactase splits lactose into.
Sources and notes
- The sentence under the titlefrom sourceMoleculeFinder comparison notesThe pair's answer line.
- The two drawingscomputedMoleculeFinder rule (RDKit MCS)Drawn the same way round on the skeleton they share. Aligned; 11 atoms differ, too many to mark as one group.
- Structural similaritycomputedRDKit Morgan/Tanimoto0.61 of 1, a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.
Side by side
| Lactose | Galactose | |
|---|---|---|
| Molecular weightCalculated PubChem | 342.3 g/molC12H22O11 | 180.16 g/molC6H12O6 |
| Hydrogen-bond donorsCalculated PubChem | 8 | 5 |
| SweetnessMeasured HSDB via PubChem; Weber et al. 2025 | 0.17× sugar | 0.32× sugar |
| Against table sugar, which is 1. | ||
| Where each turns upEditorial MoleculeFinder food and product lists | Not on our lists | |
| FamilyEditorial MoleculeFinder curated | Sugars | Sugars |
| Everyday groupEditorial MoleculeFinder curated | Sweetener | Sweetener |
| Chemical groupsCalculated Found by rule (RDKit) | Alcohols, Ethers | Alcohols, Ethers |
| Hazard labelReported ECHA via PubChem | Not recorded | Warning |
| The supplier-filed hazard label's signal word, not a statement about ordinary use. | ||
Sources and notes
- Molecular weightcomputedPubChemComputed from the structure; the formula is under each weight.
- Hydrogen-bond donorscomputedPubChemThe hydrogens on nitrogen or oxygen that each molecule can lend to a hydrogen bond, counted from its structure.
- Sweetnessfrom sourceHSDB via PubChem; Weber et al. 2025
- Where each turns upfrom sourceMoleculeFinder food and product listsEach amount is an editorial figure from our lists, not a measurement of any one product. Each mark is set by hand on the list, never inferred.
- Familyfrom sourceMoleculeFinder curated
- Everyday groupfrom sourceMoleculeFinder curated
- Chemical groupscomputedFound by rule (RDKit)Each group is found in the structure by a chemical pattern.
- Hazard labelfrom sourceECHA via PubChem
- ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
- Identifiersfrom sourcePubChemPubChem CID 6134 (Lactose) and 6036 (Galactose).
In more detail
This pair is a molecule and its component rather than two competitors. Lactose is glucose joined to galactose at 342.3; splitting it needs the enzyme lactase, and most adults worldwide stop making enough lactase after childhood, which is what lactose intolerance is. Galactose alone is 180.16 and has the same formula as glucose, differing only in the orientation of one hydroxyl group. Babies handle both easily, and a rare inherited inability to process galactose is screened for at birth in many countries. Neither is especially sweet: lactose is one of the least sweet common sugars, which is why milk does not taste sugary.
Sources and notes
- The paragraphfrom sourceMoleculeFinder comparison notes
Questions
- What is the difference between Lactose and Galactose?
- Lactose is milk sugar, glucose and galactose joined together, while galactose is a single sugar, one of the two halves lactase splits lactose into.
- Is Lactose bigger than Galactose?
- Lactose is the heavier molecule, 342.3 g/mol against 180.16 g/mol for Galactose. Lactose is C12H22O11 and Galactose is C6H12O6.
- Is Lactose sweeter than Galactose?
- Galactose is the sweeter of the two, about 0.32 times as sweet as table sugar against about 0.17 times for Lactose. Sweetness here is measured against sucrose, which is defined as 1.
Sources and notes
- The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.