Final answer:
Albumin's primary role in water balance is to maintain blood osmotic pressure by preventing the leakage of water into body tissues.
Step-by-step explanation:
The role of albumin in water balance is primarily to maintain blood osmotic pressure. Albumin, being the most abundant plasma protein, contributes to the osmotic balance that controls the movement of water between cells and their environment. It helps to keep the water in the blood vessels, thus preventing it from leaking into the body tissues; this is crucial to avoid conditions such as oedema. Deficiency of albumin can lead to an imbalance, causing excessive fluid accumulation in tissues.
Through its capacity to bind various biological molecules, albumin also plays a part in the transport of fatty acids and hormones, although these functions are secondary to its primary role in water balance.