Final answer:
Protoplasm is a colloidal solution, which is a type of heterogeneous mixture with particle sizes between true solutions and suspensions. The particles do not settle upon standing, distinguishing colloids from suspensions.
Step-by-step explanation:
The protoplasm within a cell is best described as a colloidal solution. A colloidal solution, or dispersion, is a heterogeneous mixture where the particle size is intermediate between that of a true solution and a suspension. The particles are larger than those found in a true solution, but unlike suspensions, they do not settle out upon standing. Colloids include familiar substances such as milk and blood, where the particles remain dispersed throughout the liquid without settling.
By comparing with other mixtures, we can see that protoplasm is similar to a colloid. For instance, a true solution is a homogeneous mixture like saltwater, which is clear and where the solutes do not settle out. A suspension, like mud in water, consists of larger particles that can settle over time. In contrast, colloidal solutions are homogeneous on a macroscopic scale but do not settle out like true solutions.
Protoplasm, comprising large molecules and aggregates of smaller species, has properties that are consistent with colloidal behavior. It exhibits a uniform distribution on a visual scale and the ability to scatter light, which is characteristic of colloids.