What is structure of lactose? [closed]

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

• – Anubhav Goel Aug 13 '17 at 22:40

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.