Option A is wrong because it is the respiratory pigment of plant body, wether option D is correct.

Respiratory Pigment in the Human Body is Hemoglobin

Respiratory pigments are specialized proteins that are responsible for carrying oxygen from the respiratory system to the body's tissues. In humans, the respiratory pigment is called hemoglobin, not chlorophyll. Chlorophyll is a pigment found in plants and is responsible for capturing sunlight for photosynthesis.

Hemoglobin, on the other hand, is an iron-containing protein found in red blood cells. It plays a crucial role in the transport of oxygen throughout the body and helps in the exchange of carbon dioxide. Let's explore the details of why hemoglobin is the correct answer.

1. Structure of Hemoglobin:
- Hemoglobin is made up of four protein subunits, each containing a heme group.
- The heme group contains an iron ion, which is responsible for binding oxygen molecules.
- The structure of hemoglobin allows it to bind and carry oxygen efficiently.

2. Oxygen Binding:
- Hemoglobin binds to oxygen in the lungs, where the oxygen concentration is high.
- The iron ions in the heme groups bind to the oxygen molecules, forming an oxygenated form of hemoglobin.
- This oxygenated hemoglobin is bright red in color.

3. Oxygen Release:
- Hemoglobin releases oxygen in the body's tissues, where the oxygen concentration is lower.
- As the oxygenated hemoglobin reaches the tissues, it encounters a lower oxygen concentration, causing the heme groups to release oxygen molecules.
- The released oxygen can then be utilized by the cells for various metabolic processes.

4. Carbon Dioxide Transport:
- Hemoglobin also plays a role in the transport of carbon dioxide, a waste product of cellular respiration.
- Carbon dioxide diffuses from the tissues into the blood and is converted into bicarbonate ions (HCO3-) inside red blood cells.
- The formation of bicarbonate ions helps in maintaining the pH balance of the blood.
- Hemoglobin also binds to a small portion of the carbon dioxide directly, aiding in its transport.

Conclusion:
In conclusion, the correct answer to the question regarding the respiratory pigment in the human body is hemoglobin, not chlorophyll. Hemoglobin, a protein found in red blood cells, is responsible for carrying oxygen from the lungs to the body's tissues and facilitating the exchange of carbon dioxide. Understanding the structure and function of hemoglobin is essential in comprehending the process of oxygen transport in the human body.