Summary
The covalent link between sugar units formed by condensation, alpha in starch and beta in cellulose.
In depth
A glycosidic bond joins the anomeric carbon of one sugar to a hydroxyl of another. Alpha 1-4 links create coiled chains (starch, glycogen), alpha 1-6 creates branches and beta 1-4 produces straight chains (cellulose).
Human enzymes cut alpha but not beta linkages, which is why we cannot digest cellulose.
The orientation matters: alpha linkages (as in starch) are hydrolysed by human amylase, but beta linkages (as in cellulose) are not, since the enzyme's active site does not fit. Termites and ruminants depend on microbes that supply cellulase.
Glycosidic bonds also occur in nucleotides (N-glycosidic bonds join base to sugar), in glycoproteins and in drugs such as the heart medicine digoxin, a glycoside. Numbering such as 1-4 means carbon 1 of one sugar joined to carbon 4 of the next.
Key idea: a tiny difference in bond geometry produces large differences in digestibility and structure.
Frequently asked questions
What is Glycosidic Bond?
The covalent link between sugar units formed by condensation, alpha in starch and beta in cellulose.
Which area of biology covers Glycosidic Bond, and how advanced is it?
Glycosidic Bond is one of the 51 topics in Biomolecules & Biochemistry. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Disaccharides, Condensation and Hydrolysis, Polysaccharides.
Can you give an example of Glycosidic Bond?
Ruminants rely on microbes that make cellulase.
What should I learn before Glycosidic Bond?
Work through the Beginner topics in Biomolecules & Biochemistry first, such as Water Properties, Carbon Chemistry, Carbohydrates, then return to Glycosidic Bond. Intermediate topics assume the Beginner vocabulary.
What topics are related to Glycosidic Bond?
The closest topics to Glycosidic Bond are Disaccharides, Condensation and Hydrolysis, Polysaccharides, Macromolecules. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Glycosidic Bond?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Glycosidic Bond. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Glycosidic Bond different from Disaccharides?
Glycosidic Bond: The covalent link between sugar units formed by condensation, alpha in starch and beta in cellulose. Disaccharides: Two monosaccharides joined by a glycosidic bond, for example sucrose, lactose and maltose. Read both side by side and note what each one explains.
How should I study Glycosidic Bond step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Disaccharides and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.