**Question:** In starvation, nitrogen is carried from muscle to liver and kidney by

A. Glucose
B. Fat
C. Amino acids
D. Protein

**Correct Answer:** **C. Amino acids**

**Core Concept:** In starvation, the body undergoes catabolic processes to conserve energy and maintain essential functions. Nitrogen, a key component of amino acids, is released from muscle proteins to be used as a source of nitrogen for the synthesis of new molecules like nucleic acids, proteins, and other essential compounds in the liver and kidneys.

**Why the Correct Answer is Right:** In starvation, the body switches to using stored glycogen for energy as carbohydrate sources become limited. This leads to breakdown of proteins, specifically muscle proteins, to release amino acids, which are essential for maintaining nitrogen balance and supporting essential physiological functions. Amino acids are transported to the liver and kidneys for utilization in the synthesis of new molecules.

**Why Each Wrong Option is Incorrect:**

A. Glucose (A) is the primary fuel source during starvation, not the primary source of amino acids.
B. Fat (B) is stored energy and not a direct carrier of amino acids.
D. Protein (D) is a broader term that includes amino acids, but the correct option is C as amino acids are specifically responsible for carrying nitrogen between tissues during starvation.

**Clinical Pearl:** Understanding the role of amino acids in nitrogen transport during starvation is crucial for medical students and physicians, as it highlights the body's adaptive responses to limited energy resources and demonstrates the importance of maintaining proper nutrition to support protein synthesis and overall organ function.