The key difference between haemoglobin and blood is that haemoglobin is a specific protein found within red blood cells, while blood is a complex fluid that contains red blood cells (and thus haemoglobin), along with many other components.
Blood is a vital fluid circulating throughout the body. It is composed of several different elements, including:
- Plasma: The liquid portion, making up about 55% of blood volume. It consists mostly of water, along with proteins, glucose, ions, hormones, and waste products.
- Blood Cells: These make up the remaining 45% of blood volume and include:
- Red Blood Cells (Erythrocytes)
- White Blood Cells (Leukocytes)
- Platelets (Thrombocytes)
Understanding Haemoglobin
As stated in the reference, Haemoglobin (Hb) is the protein contained in red blood cells that is responsible for delivery of oxygen to the tissues. It is a critical molecule that binds to oxygen in the lungs and transports it to the body's tissues, releasing it where needed. Haemoglobin also helps transport carbon dioxide back to the lungs.
To ensure adequate tissue oxygenation, a sufficient hemoglobin level must be maintained. The amount of hemoglobin in whole blood is expressed in grams per deciliter (g/dl). This measurement indicates the concentration of haemoglobin protein present within a specific volume of blood.
The Relationship
Think of blood as a mixture or a complete system, and haemoglobin as a specific, very important part within that system, specifically residing inside one type of blood cell (red blood cells).
- Blood is the medium that carries oxygen, nutrients, waste, hormones, and much more throughout the body.
- Haemoglobin is the primary molecule within red blood cells that performs the essential task of oxygen transport.
Key Differences Summarized
Here is a comparison to highlight the distinctions:
| Feature | Blood | Haemoglobin |
|---|---|---|
| Nature | A complex fluid tissue | A specific protein molecule |
| Location | Circulates throughout the body | Primarily found inside red blood cells |
| Composition | Plasma, red cells, white cells, platelets | Protein responsible for binding oxygen and CO2 |
| Function | Transports oxygen, nutrients, waste, etc. | Primarily transports oxygen (and some CO2) |
| Measurement | Measured in various ways (volume, cell counts) | Measured as concentration in whole blood (g/dL) |
In essence, blood is the carrier, while haemoglobin is the specific oxygen-carrying component contained within the red blood cells that are part of the blood.
