A cell is like a plastic bag filled with fluid. The bag itself is the cell membrane and the fluid it contains is the cytosol. The cytosol is a complex mixture of water, various ions, small molecules and proteins. Some proteins have a definite structure and are arranged to form a type of scaffolding, which can change shape as required. The living cell is not, therefore, an amorphous bag of fluid, it has a definite, but continually changing structure.

The cytosol is the site of intermediary metabolism, the sequence of chemical reactions by which the cell generates and forms the precursors necessary for biosynthesis of the larger molecules used as the building blocks for cell growth and function.

CITY STREETS / OPEN SPACES

Rather like the cytosol of a cell, the streets, markets and parks of a city are where the people who live in the city meet and perform their interactions. This is where trade takes place. Obviously, running through these spaces are the transport systems and sited within the spaces are the factories and recycling units.

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