Glycogen Alpha Linkage Carbons

[altitude]

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In some pictures of the structure of glycogen there appears to be extra carbons in the alpha linkages (surrounding the oxygen), like in the following:

But in the following picture, those carbons are not there:

Why is there a difference in these two pictures of the structure of glycogen?

 

[chiddler]

that's just convention, or something. those aren't carbons those are just the sigma bonds to the oxygen from the carbon.

you should understand that for glucose, there can't be a carbon in that position anyway.

 

[Morsetlis]

Those are not carbons in the top picture.

 

[MedPR]

that's just convention, or something. those aren't carbons those are just the sigma bonds to the oxygen from the carbon.

you should understand that for glucose, there can't be a carbon in that position anyway.

Yup. You should get familiar enough with glucose to know how many carbons there are.

 

[EnginrTheFuture]

I think I know what you are having trouble with.

There are two different linkages in glycogen... there is the chain link and the branching link.

The chain link is from the O on carbon 4 to the anomeric carbon to the left of it

The branch link is from the O on carbon 6 to the anomeric carbon to the left of it


The "extra" carbon is always there... there are just two different links happening in glycogen that are similar enough that they look the same, but then upon looking further there seems to be an extra carbon. Look a tad bit further and you'll realize that it's on a different part of the glucose all together for those branch links.

NOTE, the squared bends in the non branch links of top picture are NOT carbons. That is convention for alpha rather than beta links.

Check out this picture, it is much clearer.

As you can see there are branch links which have the "extra" carbon because it is an alpha (1,6) linkage and there are the "chain" links which don't have the "extra" carbon because it is an alpha(1,4) linkage. The ones without the "extra" carbon do have the carbon, that carbon is in the ring. And that carbon 6, the "extra" carbon is on every single one of those glucoses... but there isn't a branch being formed off of every glucose.

 

[MedPR]

I think I know what you are having trouble with.

There are two different linkages in glycogen... there is the chain link and the branching link.

The chain link is from the O on carbon 4 to the anomeric carbon to the left of it

The branch link is from the O on carbon 6 to the anomeric carbon to the left of it


The "extra" carbon is always there... there are just two different links happening in glycogen that are similar enough that they look the same, but then upon looking further there seems to be an extra carbon. Look a tad bit further and you'll realize that it's on a different part of the glucose all together for those branch links.

NOTE, the squared bends in the non branch links of top picture are NOT carbons. That is convention for alpha rather than beta links.

Check out this picture, it is much clearer.

As you can see there are branch links which have the "extra" carbon because it is an alpha (1,6) linkage and there are the "chain" links which don't have the "extra" carbon because it is an alpha(1,4) linkage. The ones without the "extra" carbon do have the carbon, that carbon is in the ring. And that carbon 6, the "extra" carbon is on every single one of those glucoses... but there isn't a branch being formed off of every glucose.

Maybe I'm misunderstanding you, but I think the OP believes there is a carbon in the alpha-linkages where the oxygen is joined by an "L" shaped bond and a mirror image "L" to the adjacent glucose.

There is no extra carbon.

 

[EnginrTheFuture]

Maybe I'm misunderstanding you, but I think the OP believes there is a carbon in the alpha-linkages where the oxygen is joined by an "L" shaped bond and a mirror image "L" to the adjacent glucose.

There is no extra carbon.

In my explanation I said to note that the bend was not a carbon, just convention for alpha rather than beta linkage.


What I'm trying to point out is that...

I think where his true misunderstanding is that there is not only the deceiving bend (which isn't a carbon but can be interpreted as one) but that the alpha(1,6) branching linkages have a carbon that is reinforcing that belief. The carbon in the branching linkages look like they are a part of the glycosidic linkage, morso that the analogous carbon 4. This is what I believe is causing the confusion on top of that stupid bend

 

[MedPR]

In my explanation I said to note that the bend was not a carbon, just convention for alpha rather than beta linkage.


What I'm trying to point out is that...

I think where his true misunderstanding is that there is not only the deceiving bend (which isn't a carbon but can be interpreted as one) but that the alpha(1,6) branching linkages have a carbon that is reinforcing that belief. The carbon in the branching linkages look like they are a part of the glycosidic linkage, morso that the analogous carbon 4. This is what I believe is causing the confusion on top of that stupid bend

The "extra" carbon is always there... there are just two different links happening in glycogen that are similar enough that they look the same, but then upon looking further there seems to be an extra carbon. Look a tad bit further and you'll realize that it's on a different part of the glucose all together for those branch links.

Then what is this extra carbon you are saying is always there? Glucose always has the same number of carbons.

Are you saying that what the OP thinks is an extra carbon is actually just a bond, and that the bond is the same regardless of how it is drawn?

 

[altitude]

Thank you for the explanations. It was actually those L-shaped bends that were causing the confusion because it "contradicts" what basic knowledge I have on standard notion of carbon chains/backbones (usually this would represent a carbon, but I guess here that is not the case). But, either way, thank you for the additional info on glucose, glycogen, etc.