enter image description here enter image description here Please look at stereochemistry of anomeric carbon or carbon no. 1 of glucose unit. Which among two is correct structure of lactose?

If, both are correct, then how?

Note : Image 1 is from Harper biochemistry


1 Answer 1


Both of the images are lactose. The first image is $\alpha$-lactose and the second is $\beta$-lactose. The difference between $\alpha$ and $\beta$ lactose is the orientation of the most right hydroxy (OH) group in the pictures.

  • $\begingroup$ Sorry, can you please focus on OH group at carbon 1.. $\endgroup$ Aug 13, 2017 at 22:06
  • $\begingroup$ When you say carbon 1, I assume you are refering to the carbon next the red "1". There is no OH group at this particular carbon. The four bonds to this carbons is -O-, -O-, -C- and -H $\endgroup$ Aug 13, 2017 at 22:08
  • $\begingroup$ Sorry again, anomeric carbon please. $\endgroup$ Aug 13, 2017 at 22:11
  • $\begingroup$ @AnubhavGoel I edited my answer to include this difference $\endgroup$ Aug 13, 2017 at 22:17
  • $\begingroup$ But both show beta glycosidic bonds? $\endgroup$ Aug 13, 2017 at 22:20

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