How the carbon cycle and nitrogen cycle contribute to the usable supplies of these macromolecules?

Four classes of compounds: carbohydrates, lipids, protein, and nucleic acids. Plants interconnect the carbon and nitrogen cycles, as they fix carbon into carbohydrates and inorganic nitrogen into amino acids and proteins.

During the process of the carbon cycle (nitrogen cycle also) carbon is exchanged between the living organisms and their environment. It describes the movement of carbon (nitrogen) as it is recycled and reused. Carbon is the main component of biological compounds, so it is very important to be taken from the atmosphere by photosynthetic organisms (in the form of CO2) and used to make organic molecules (carbohydrates, lipids, protein, and nucleic acids) and again released as CO2 in respiration. On the other hand, nitrogen can’t be absorbed by plants in the form of atmospheric gas N2. Bacteria convert it in the process of nitrogen fixation into ammonia (NH3), a form of nitrogen usable by plants. When animals eat the plants, they acquire usable nitrogen compounds. Nitrogen is found in all proteins and DNA.