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
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$\begingroup$ Related How do we assign alpha/beta status in polysaccharides? $\endgroup$– Anubhav GoelCommented Aug 13, 2017 at 22:40
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1 Answer
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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.
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$\begingroup$ Sorry, can you please focus on OH group at carbon 1.. $\endgroup$ Commented Aug 13, 2017 at 22:06
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$\begingroup$ 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 $\endgroup$ Commented Aug 13, 2017 at 22:08
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$\begingroup$ Sorry again, anomeric carbon please. $\endgroup$ Commented Aug 13, 2017 at 22:11
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$\begingroup$ @AnubhavGoel I edited my answer to include this difference $\endgroup$ Commented Aug 13, 2017 at 22:17
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$\begingroup$ But both show beta glycosidic bonds? $\endgroup$ Commented Aug 13, 2017 at 22:20