Why it is better to add a preassembled block of 14 sugar residues to a protein in the endoplasmic reticulum (ER), rather than making the sugar chains step-by-step on the surface of the protein by individual enzymes. Concept introduction: Chemical modifications of the proteins take place once it enters to the ER lumen. Most of the proteins that enter to the ER lumen are converted to glycoprotein by the process of glycosylation. These glycoproteins are formed by the covalent attachment of the short-branched oligosaccharide side chains composed of multiple sugars. The oligosaccharide side chain is linked as a preassembled block and is not added one-by-one.

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Chapter 15, Problem 6Q

Summary Introduction

To explain: Why it is better to add a preassembled block of 14 sugar residues to a protein in the endoplasmic reticulum (ER), rather than making the sugar chains step-by-step on the surface of the protein by individual enzymes.

Concept introduction:

Chemical modifications of the proteins take place once it enters to the ER lumen. Most of the proteins that enter to the ER lumen are converted to glycoprotein by the process of glycosylation. These glycoproteins are formed by the covalent attachment of the short-branched oligosaccharide side chains composed of multiple sugars. The oligosaccharide side chain is linked as a preassembled block and is not added one-by-one.

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