In order to make proteins, plants and cells need nitrogen, in what form do they absorb nitrogen from the soil?

Lightning also converts nitrogen gas to nitrate compounds. The Haber process converts nitrogen gas into ammonia used in fertilizers. Ammonia is converted to nitrates by nitrifying bacteria in the soil. Plants absorb nitrates from the soil and use these to build up proteins.

Well,what i learned was that unlike many other  endothermic  reactions,  photosynthesis  does not absorb energy as heat. instead, during plants absorb energy from sunlight to turn carbon dioxide and water into oxygen and glucose, which is a type of sugar molecule. the energy is stored in the glucose molecules, ready to be used when needed.