Controlling the synthesis of proteins is the key to controlling the chemical pathways in the cell.
This is because proteins have key roles in many chemical reactions in the cell.
The most important proteins for the chemical reactions in the cell are enzymes.
Enzymes catalyze many chemical reactions, therefore, the control of the enzyme synthesis is a direct way of controlling other chemical reactions in the cell.
B. bacteria that convert ammonia into nitrites and nitrates are found in the soil
This statement best demonstrates a way that the geo-sphere is involved in the nitrogen cycle.
A nitrogen cycle is defined as the movement of nitrogen between the atmosphere, biosphere, and geo-sphere in different forms. Ammonia is converted to nitrates by nitrifying bacteria in the soil. Then the plants absorb these nitrates from the soil and use these to build up proteins.