Hemiacetal formation is the mechanism by which pentoses and hexoses assume their cyclic forms. Nucleophilic attack by typically the #4 or #5 carbon's hydroxyl group onto the carbonyl group (the anomeric carbon) of the noncyclic form leads to hemiacetal formation. Another nucleophile can act out the second part of the acetal formation mechanism upon the anomeric carbon forming a mixed acetal, termed a glycoside. The nucleophile may be adenine, guanine, cytosine, thymine, or uracil, in which case the glycoside product is a nucleoside, a fundamental building block of the nucleic acids DNA and RNA. If the nucleophile is another sugar, the process leads to the formation of a disaccharide (or polysaccharide). In other words, disaccharides are glycosides with the nucleophile being another sugar molecule.












The WikiPremed MCAT Course is a comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum. Please read our policies on Privacy and Shipping & Returns.  Contact Us. MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course. WikiPremed offers the customers of our publications or our teaching services no guarantees regarding eventual performance on the MCAT.


Creative Commons License
WikiPremed is a trademark of Wisebridge Learning Systems LLC. The work of WikiPremed is published under a Creative Commons Attribution NonCommercial ShareAlike License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions.