Cytosol Definition
Cytosol is the liquid found inside cells. It is a water-based solution in which organelles, proteins, and other cell structures float.
The cytosol of any cell is a complex solution, whose properties allow the functions of life to take place. Cytosol contains proteins, amino acids, mRNA, ribosomes, sugars, ions, messenger molecules, and more!
Though once thought to be a simple solution, scientists are increasingly discovered that cytosol can have structure and organization. For example, some cells use gradients of ions or messenger particles to contain important information that is necessary for later growth.
Some species use the organization of their cytoplasm to direct the growth of embryos from the fertilized egg cell. In these species, messenger molecules are distributed differently throughout the cytoplasm of the egg cell.
When the egg cell divides after fertilization, this results in different daughter cells receiving different messenger molecules – and subsequently developing into different tissue types.
This principle shows the importance and complexity of the cytoplasm, which was once thought to be mere salt water!
Membrane-bound organelles float in the cytosol, but their interiors are not considered to be part of it. Chloroplasts, mitochondria, nuclei, and other closed, self-contained membranes within cells have their own internal fluid and chemistry that is separate from the cytosol.
Function of Cytosol
Cytosol serves as the medium for intracellular processes. This means it must be containing the proper proteins, ions, and other ingredients for cytosolic activities.
Activities that take place in, or involve the cytosol include:
1. Enzyme activities. Enzymes often require certain salt concentrations, pH levels, and other environmental conditions to work properly.
2. Signal transduction. Messenger molecules may diffuse through the cytosol to change the functioning of enzymes, organelles, or even DNA transcription. These may be messengers from outside the cell, or messengers from one part of the cell to another.
3. Structural support of the cell and organelles. Most cells rely on the volume of the cytosol to create its shape and create space for chemicals to move within the cell.
4. In prokaryotes which lack membrane-bound organelles, virtually all functions of life including DNA transcription and replication, glycolysis, etc., happen in the cytosol.
