Why is the 1,6 linkage in Amylopentin an alpha link and not a Beta link? [closed]

The alpha link as I have understood it means that the $$\ce{OH}$$ molecules which make up the glycosidic bond lie on the same side of(above/ below) the plane and for beta, one lies above the plane and the other below it.

For the 1,6 linkage in Amylopectin, one $$\ce{OH}$$ group lies below the plane and the $$\ce{CH3OH}$$ group lies below the plane. Then why is the 1,6 link in amylopectin not an alpha linkage?

• Your question is unclear to me and in danger of being closed. Amylopectin has alpha linkages. If the linkage were beta, amylopectin would not be digestible by humans. – user55119 Jul 17 '20 at 15:42
• The 1,6 bond in amylopectin is labeled as alpha link and it looks similar to the Beta links of cellulose. (One OH below the plane and one OH above the plane. I am talking of those OH condensed to make the glycosidic link.) So i am unable to understand how the 1,6 link in amylopectin is labelled as alpha as it very much resembles the Beta nature. – the.eleventh.letter Jul 17 '20 at 16:06
• "OH molecule"? Amylopentin? is 1,6 link is? I understand that articles are difficult if you don´t come from a indoeuropean language, but this is embarassing. The effort people put into their answers is usually directly proportional to the effort you put into writing up your question! – Karl Jul 17 '20 at 19:03
• The title and body of the question contradict each other, making it difficult to take it seriously. – Gwyn Jul 17 '20 at 21:30
• Actually I didnt understand the meaning of alpha link correctly previously. I now undertsand that when two alpha anomers make up a link its called alpha link ; same for beta; and if alpha and beta make up the link its called alpha - beta. Although i previously knew what alpha anomer means i was confusing it with the meaning of what alpha link means. Anyways i have got it cleared up now. – the.eleventh.letter Jul 18 '20 at 6:01

1 Answer

You seem to be having trouble with the terms alpha and beta and how to recognize these terms in carbohydrates. Here is an easy way to recognize them. In a Fischer projection of glucopyranose, the hydroxyl group in the beta anomer is on the left; the alpha anomer is on the right. [Notice that the italicized terms have fewer letters than the bold terms!] In the Haworth projection and the chair conformation of glucopyranose the terms beta, top and up have fewer letters than their respective terms alpha, bottom and down in the other anomer.

Amateur sailors use the same mnemonic to remember that the port is on the left (red light) side of the boat and that the starboard is on the right (green light).

• Actually I didnt understand the meaning of alpha link correctly previously. I now undertsand that when two alpha anomers make up a link its called alpha link ; same for beta; and if alpha and beta make up the link its called alpha - beta. Although i previously knew what alpha anomer means i was confusing it with the meaning of what alpha link means. Thanks. – the.eleventh.letter Jul 18 '20 at 6:00