Plasma transports materials needed by cells and materials that must be removed from cells.
If one takes a sample of blood, treats it with an agent to prevent clotting, and spins it in a centrifuge,
- the red cells settle to the bottom
- the white cells settle on top of them forming the "buffy coat".
- The fraction occupied by the red cells is called the haematocrit. Normally it is approximately 45%
- The plasma contains fibrinogen which is involved in clotting
| Component | Percent |
| Water | ~92 |
| Proteins | 6-8 |
| Salts | 0.8 |
| Lipids (fats) | 0.6 |
| Glucose (blood sugar) | 0.1 |
