Sugars

[Medgen]

I am a bit confused on carbohydrate terminology.
What is the difference between a glycosidic linkage and a glucosidic linkage? My study material indicates that amylose has alpha 1-4 glucosidic linkages but that mannose and maltose have alpha 1,1' glycosidic linkages and 1,4 glycosidic linkages respectively. I can't really seem to figure out the difference between the two types.

Also- what differentiates the Beta 1-4 glucosidic linkage in cellulose from the Beta 1-4 galactosidic linkage in lactose? Why can we digest one and not the other?

Thanks!

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[Catburr]

I am a bit confused on carbohydrate terminology.
What is the difference between a glycosidic linkage and a glucosidic linkage? My study material indicates that amylose has alpha 1-4 glucosidic linkages but that mannose and maltose have alpha 1,1' glycosidic linkages and 1,4 glycosidic linkages respectively. I can't really seem to figure out the difference between the two types.

Also- what differentiates the Beta 1-4 glucosidic linkage in cellulose from the Beta 1-4 galactosidic linkage in lactose? Why can we digest one and not the other?

Thanks!

Mannose is a monomer, so I'm not sure what your material is referring to there. But the difference between a 1,1 and a 1,4 linkage is just how it sounds. 1,1 is between the number 1 carbons on each molecule. 1,4 is between the number 1 carbon on the first molecule, and the number 4 carbon on the other. Can you be more specific about why you can't find the difference? Look up trehalose (1,1 bond) and maltose (1,4 bond) - build them with a model set if you have one. You should be able to see the differences.

I've never heard the term "glucosidic linkage," but it seems (just from googling) like it's a not-too-common term for a glycosidic linkage in which at least one of the monomers is glucose. That's just from brief searching though, take it or leave it.

Lactose and cellulose both have beta 1,4 linkages, sure. But the similarity stops there - cellulose is a polysaccharide, made up of only glucose monomers. Lactose is a disaccharide, made up of glucose and galactose. So the enzyme (lactase) that can recognize lactose and break it into monosaccharides doesn't recognize cellulose. Enzyme-substrate specificity is based on more than just one bond in the substrate.