It all begins at the roots. Plants get nutrients from two different systems — one begins in the leaves and is responsible for photosynthesis. The other begins at the roots and moves water filled with dissolved ions up through the plant. Protein is one of the nutrients that begin at the roots and work their way upward.
Plants Are Autotrophs
Plants are autotrophs. Unlike animals, which must get their food from outside sources such as plants and other animals, plants are able to manufacture their own. Plants take basic elements from the outside world and bring them into their bodies, where they are converted to starches and proteins that can be used by the plant or by the animal that eats it.
Nitrogen and Bacteria
Protein is made from nitrate, a form of nitrogen that has been fixed by microorganisms. Plants cannot use nitrogen directly, so they rely on bacteria to convert the nitrogen into a form they can use. These bacteria reside near the roots of the plants or in special structures on the roots called nodules. The bacteria in nodules have formed a symbiotic relationship with the plants where they exchange usable nitrogen for sugar from the plant.
Nitrates and Amino Acids
Nitrates taken into the plant through the roots are pulled into the plant, where they are converted into 20 different kinds of amino acids. These amino acids are turned into proteins in special structures in the cells called ribosomes. These structures reside in four places in the plant. Some float free in the cytoplasm of cells, while others are attached to the surface of the endoplasmic reticulum, the mitochondria and the chloroplasts.
From the ribosomes contained in the endoplasmic reticulum, the proteins are sent into the golgi apparatus. The golgi apparatus sorts those proteins for distribution throughout the plant, where they will be used to form new structures for further nutrient transport, as well as basic metabolic processes.