Final answer:
The compound in arterial fluid that decreases molecular cohesion and reduces surface tension is a surfactant.
Step-by-step explanation:
The component of arterial fluid designed to decrease the molecular cohesion at the surface of a liquid is known as a surfactant. Surfactants are compounds that reduce surface tension by disrupting the cohesive forces between water molecules at the surface of a liquid. They are commonly found in soaps and detergents. Surface tension itself is a result of cohesive forces causing the surface of a liquid to minimize its area. In the context of arterial fluids, surfactants play an important role in the prevention of clotting, by keeping the liquid state consistent and aiding with smooth flow within the arteries.