## **Core Concept**
The question tests the understanding of iron-containing proteins involved in gas transport in the body. Specifically, it focuses on the protein complex that binds with oxygen (O2) and carbon dioxide (CO2). This process is crucial for respiration and maintaining acid-base balance.

## **Why the Correct Answer is Right**
Hemoglobin is a protein in red blood cells that has a complex structure, including four iron-containing heme groups. Each heme group can bind one molecule of oxygen (O2), allowing hemoglobin to transport oxygen from the lungs to the body's tissues. Additionally, hemoglobin plays a role in transporting carbon dioxide (CO2) from the tissues back to the lungs for exhalation. The iron in the heme group is essential for the binding of both O2 and CO2, making hemoglobin critical for both respiratory and acid-base balance functions.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Myosin is a protein involved in muscle contraction and does not bind oxygen or carbon dioxide.
- **Option B:** Cytochrome c is a component of the electron transport chain in mitochondria and does not primarily function to transport O2 or CO2.
- **Option D:** Ferritin is a protein that stores iron in a non-toxic form but does not bind oxygen or carbon dioxide.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that alterations in hemoglobin's structure or function, such as in sickle cell disease or carbon monoxide poisoning, can significantly impact oxygen delivery and acid-base balance. Understanding the role of hemoglobin in gas transport is essential for managing various clinical conditions.

## **Correct Answer:** C. Hemoglobin.