Question

soluble lewis antigens in secretions are synthesized to:

type 1 chains.
type 3 chains.
type 4 chains.
type 2 chains.

Explanation:

Identify the core biochemical structure of Lewis antigens

Using the Lewis Antigen Biosynthesis knowledge point

Soluble Lewis antigens found in secretions (such as saliva) and plasma are synthesized on Type 1 precursor chains. Type 1 chains are characterized by a \(\beta(1
ightarrow3)\) linkage between galactose and N-acetylglucosamine, which is the specific substrate for the fucosyltransferases encoded by the Le (\(FUT3\)) and Se (\(FUT2\)) genes.

Differentiate from other precursor chains

Using the Lewis Antigen Biosynthesis knowledge point

In contrast, Type 2 precursor chains possess a \(\beta(1
ightarrow4)\) linkage and serve as the primary backbone for ABH antigens on red blood cell membranes. Type 3 and Type 4 chains are also structurally distinct and are not the substrates for soluble Lewis antigen synthesis in secretions.

Answer:

• Type 1 chains. (Correct answer)
• Type 3 chains.
• Type 4 chains.
• Type 2 chains.