Question

Heparin is an anticoagulant because of its overall

• A. Positive charge
• B. Negative charge
• C. Net Zero charge
• D. Lipid molecule

Hint:

Heparin: Highly sulfated Glycosaminoglycan (GAG) with strongest physiological NEGATIVE charge. Neutralized therapeutically by positively charged Protamine Sulfate.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Heparin is a glycosaminoglycan with the highest negative charge density of any known biological macromolecule, binding electrostatically to antithrombin III.
Key Formula or Approach:
\[ \text{Heparin (Poly-Anionic } -\text{SO}_3^- / -\text{COO}^-) + \text{Antithrombin III (Cationic Lys/Arg)} \longrightarrow 1000\times \text{ Acceleration of Thrombin Inactivation} \]

Step 2: Detailed Explanation:
Structure and mechanism of Heparin:
- Heparin is a sulfated glycosaminoglycan (GAG) consisting of repeating disaccharide units of sulfated D-glucosamine and D-glucuronic L-iduronic acid.
- Abundant negatively charged sulfate ($-O-SO_3^-, -NH-SO_3^-$) and carboxylate ($-COO^-$) groups give heparin the highest net negative charge density of any known biological macromolecule.
- This intense negative charge enables tight electrostatic binding to basic, positively charged lysine and arginine residues on Antithrombin III (AT-III), inducing a conformational activation that accelerates AT-III's inhibition of thrombin (Factor IIa) and Factor Xa by over 1,000-fold.

Step 3: Final Answer:
Hence, Heparin acts as an anticoagulant due to its overall Negative charge, matching option (B).