what is it composed of?
It consists mostly of water, dissolved ions, small molecules, and large water-soluble molecules (such as proteins).
Cytosol
consists mostly of water, dissolved ions, small molecules, and large water-soluble molecules (such as proteins). 
where does the most metabolic activity in the cell occur In the cytosol. define it? It is the liquid found inside cells.
wiki:1548546
Cytosol [SEP] Properties and composition
The proportion of cell volume that is cytosol varies: for example while this compartment forms the bulk of cell structure in bacteria, in plant cells the main compartment is the large central vacuole. The cytosol consists mostly of water, dissolved ions, small molecules, and large water-soluble molecules (such as proteins). The majority of these non-protein molecules have a molecular mass of less than 300 Da. This mixture of small molecules is extraordinarily complex, as the variety of molecules that are involved in metabolism (the metabolites) is immense. For example, up to 200,000 different small molecules might be made in plants, although not all these will be present in the same species, or in a single cell.