**Core Concept**
Gamma carboxylation is a post-translational modification that involves the addition of a carboxyl group (-COOH) to specific amino acids, enabling them to bind calcium ions. This process is crucial for the activation of certain proteins, such as clotting factors and osteocalcin. Vitamin K plays a vital role in this process by serving as a cofactor for the enzyme gamma-glutamyl carboxylase.

**Why the Correct Answer is Right**
Gamma-glutamyl carboxylation specifically targets glutamic acid residues in proteins, converting them into gamma-carboxyglutamic acid (Gla). This modification is essential for the proper functioning of proteins involved in blood coagulation, bone mineralization, and other physiological processes. Vitamin K is necessary for this reaction to occur, as it is a critical cofactor for the enzyme gamma-glutamyl carboxylase. The vitamin K-dependent gamma-glutamyl carboxylase enzyme catalyzes the carboxylation of glutamic acid residues, which then bind calcium ions, enabling the activation of target proteins.

**Why Each Wrong Option is Incorrect**
**Option A:** Glutamine is not the target of gamma carboxylation; it is an amino acid involved in various other biochemical processes, including protein synthesis and nitrogen transport.
**Option C:** Glycine is not directly involved in gamma carboxylation; it is a non-essential amino acid that plays a role in protein synthesis and the biosynthesis of certain compounds, such as creatine.
**Option D:** Aspartate is not the target of gamma carboxylation; it is an amino acid involved in various biochemical processes, including protein synthesis and the citric acid cycle.

**Clinical Pearl / High-Yield Fact**
Vitamin K-dependent gamma-glutamyl carboxylation is essential for the activation of clotting factors II, VII, IX, and X, which are critical for blood coagulation. Warfarin, a commonly used anticoagulant, inhibits vitamin K-dependent gamma-glutamyl carboxylation, leading to impaired blood clotting.

✓ Correct Answer: B. Glutamic Acid