Living systems are open systems, they constantly receive substances from the outside that are necessary for life, and unnecessary substances exit into the environment. This is one of the properties of living systems. Due to the substances entering the body, its own substances (proteins, lipids, carbohydrates, nucleic acids) are built. Without this, the existence of any living organism is impossible.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.