Physical Nature

The cytoplasm is somewhat of a mystery as it serves both the purpose of mobility and structure for the cell. It allows organelles to move throughout the cell while ensuring that the cell itself has a solid structure. Flow in and out of the cell, known as cytoplasmic flow plays a crucial part in numerous cellular functions. However, this flow is dependent on the type of cell and the permeability it allows within its cytoplasm. For instance, many cellular processes and functions involve the diffusion of cell components across the cell membrane. Cell signaling is one of those processes. Larger structures and molecules often need help when moving throughout the cytoplasm whereas the smaller ones such as calcium ions have no issues diffusing in and out of the cell cytoplasm.

As a sol-gel

Sometimes, the cytoplasm is known to behave similarly to that of a sol-gel. A sol-gel is a mixture of molecules that sometimes act like a collusion solution or a liquid (sol) and other times acts like a solid (gel) integrated network.

As a glass

It has also been observed that cytoplasms sometimes have glass-like behavior as well. This is when the cytoplasm acts as though it is approaching the glass transition as a glass-forming liquid. This comes off the theory that sometimes that cytoplasm may contain many solid components and hence the cytosol needs to act as glass and hold the solid components together so that they do not move excessively. This behavior still allows however for the movement of organelles and other inclusions across the cytoplasm and membrane if needed. This ability of the cytoplasm to somewhat “freeze” everything in place actually becomes very handy as a self-defense mechanism. This frozen stature would prevent harmful physical effects to the cell while still allowing cellular activities to take place whenever the goes back to a more fluid state.

Other perspectives

Some other research has questioned whether the constituents of the cytoplasm move separately from the cytoplasmic entity itself. These are theorized to be channeled by motor proteins which assist with this non-Brownian motion within the cells versus actually having random forces causing the movements.