Q.21 In ABO blood group system, antigenic determinants are
- (A) nucleic acid
- (B) carbohydrate
- (C) lipid
- (D) protein
In ABO blood group system, antigenic determinants are carbohydrates attached to glycoproteins and glycolipids on red blood cell surfaces. This SEO-optimized article answers the MCQ: In ABO blood group system, antigenic determinants are (A) nucleic acid, (B) carbohydrate, (C) lipid, (D) protein—essential for biotechnology, immunology, and medical students studying blood compatibility and transfusion science.
Correct Answer: Option (B) Carbohydrate
ABO antigens are oligosaccharide chains (carbohydrates) extending from membrane glycoproteins/glycolipids. A antigen adds N-acetylgalactosamine to H antigen; B adds galactose. These terminal sugars create immunodominant epitopes recognized by anti-A/anti-B antibodies.
Glycosyltransferases encoded by ABO locus on chromosome 9 determine blood type: A enzyme adds GalNAc, B adds Gal, O produces inactive enzyme leaving H antigen exposed.
Explanation of All Options
ABO specificity derives from carbohydrate epitopes, not other biomolecules:
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(A) Nucleic acid: Incorrect. DNA/RNA don’t form cell surface antigens; genetic but not antigenic.
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(B) Carbohydrate: Correct. Specific sugar sequences (GalNAcα1-3(Fucα1-2)Galβ- for A antigen) trigger immune recognition.
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(C) Lipid: Incorrect. While glycolipids carry ABO antigens, lipid portions identical across types—carbohydrate confers specificity.
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(D) Protein: Incorrect. Glycoprotein protein cores universal; carbohydrate chains determine A/B/O specificity.
Option Biomolecule Forms ABO Epitope? Blood Group Specificity (A) Nucleic acid DNA/RNA No Genetic information (B) Carbohydrate Oligosaccharides Yes Immunodominant sugars (C) Lipid Ceramide/sphingosine No Membrane anchor only (D) Protein Glycoprotein core No Structural scaffold Biotechnology Relevance
Carbohydrate engineering produces universal donor blood (enzymatic conversion O→H), supports your N-glycosylation research (Q.13), and enables synthetic blood substitutes. ABO compatibility testing prevents transfusion reactions costing millions annually.
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