Carbon dioxide is transported in blood mainly as:
**Core Concept**
Carbon dioxide transport in blood is a critical aspect of maintaining acid-base balance. The body's primary mechanism for CO2 transport is through bicarbonate ions (HCO3-), which are formed in the presence of carbonic anhydrase enzyme.
**Why the Correct Answer is Right**
Carbon dioxide reacts with water in the blood to form carbonic acid, which is then rapidly converted into bicarbonate ions and hydrogen ions by the enzyme carbonic anhydrase. This reaction occurs mainly in the red blood cells and is facilitated by the enzyme's high affinity for CO2. The bicarbonate ions are then transported to the lungs, where they are converted back into CO2 and exhaled. This process is essential for maintaining the body's acid-base balance.
**Why Each Wrong Option is Incorrect**
**Option A:** Carbon dioxide is not primarily transported as dissolved gas in the blood plasma, although a small amount is present in this form.
**Option B:** While carbon dioxide does react with hemoglobin to form carbaminohemoglobin, this is not the primary mechanism of CO2 transport in the blood.
**Option C:** Free fatty acids and other lipids do not play a significant role in the transport of carbon dioxide in the blood.
**Clinical Pearl / High-Yield Fact**
The bicarbonate buffering system is a critical component of the body's acid-base balance, and alterations in this system can lead to acidosis or alkalosis. Understanding the mechanisms of CO2 transport is essential for diagnosing and managing acid-base disorders.
**Correct Answer:** C.