Respiratory System Drugs — MCQs

Q: Vitamin K is involved in the post-translational modification of which amino acid?

Glutamate. **Explanation:** **1. Why Glutamate is Correct:** Vitamin K acts as a vital cofactor for the enzyme **gamma-glutamyl carboxylase**. This enzyme is responsible for the post-translational modification of specific **glutamate (Glu)** residues on certain proteins, converting them into **gamma-carboxyglutamate (Gla)** residues. This carboxylation adds a second negative charge to the glutamate side chain, which is essential for the protein's ability to bind **calcium ions (Ca²⁺)**. In the context of coagulation, this calcium binding allows clotting factors to anchor to phospholipid membranes, a critical step in the coagulation cascade. **2. Why Other Options are Incorrect:** * **Aspartate:** While chemically similar to glutamate, aspartate is not a substrate for Vitamin K-dependent carboxylation. * **Glycine:** This is the simplest amino acid and lacks the carboxyl side chain required for this specific modification. * **GABA (Gamma-Aminobutyric Acid):** GABA is an inhibitory neurotransmitter derived from glutamate via decarboxylation, not a target for Vitamin K-mediated post-translational modification. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vitamin K-Dependent Factors:** Factors **II, VII, IX, X**, and anticoagulant proteins **C and S**. * **Mechanism of Warfarin:** Warfarin inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K and thus inhibiting the gamma-carboxylation of glutamate residues. * **Osteocalcin:** Beyond clotting, Vitamin K is also required for the carboxylation of osteocalcin in bones, which is necessary for bone mineralization. * **Laboratory Marker:** Deficiency or Warfarin use leads to the production of **PIVKA** (Proteins Induced by Vitamin K Absence/Antagonism), which are functionally inactive factors.

Practice by Chapter

Bronchodilators

Practice Questions

Corticosteroids in Respiratory Disorders

Practice Questions

Anti-inflammatory Respiratory Agents

Practice Questions

Mast Cell Stabilizers

Practice Questions

Leukotriene Modifiers

Practice Questions

Antitussives and Expectorants

Practice Questions

Nasal Decongestants

Practice Questions

Pulmonary Surfactants

Practice Questions

Drugs for Pulmonary Hypertension

Practice Questions

Oxygen Therapy

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Scan to download app