Protein from plants:
Animals that get all their nutrition from grass and other plants are called herbivores. Herbivores are capable of something that humans aren’t: digesting cellulose. Cellulose is a type of carbohydrate that helps make up plant cell walls. These cell walls are rigid and hard to break down, making them difficult to digest, even for herbivores. Herbivores have digestive systems that contain bacteria that have the enzymes necessary to break down cellulose. Once the cells are broken down they can access proteins, sugar and fat locked inside plant cells.