These molecules - proteins, lipids, carbohydrates, and nucleic acids - make up every component in living things. Lipids are used as energy and form making membranes that all living things have. Carbohydrates are the primary source of energy for many living things. Proteins are used to build tissues or enzymes. Nucleic acids are used for the genetic material to be transferred to offspring.
The α-amino group of many amino acids is transferred to α-ketoglutarate to form glutamate, which is then oxidatively deaminated to yield ammonium ion (NH4+).
