A noncovalent bond between an electronegative atom (commonly oxygen or nitrogen) and a hydrogen atom covalently bonded to another electronegative atom. Particularly important in stabilizing the three-dimensional structure of proteins and formation of base pair s in nucleic acids.
Introduction[edit] The respiratory system serves three principal purposes in the human body: gaseous exchange; sound production; and assistance in compression of the abdomen. It can be divided into two structural divisions, upper and lower, as well as two functional divisions, conducting and respiratory.
The terminal bronchi and alveoli are located at the very end of the conducting zone and the beginning of the respiratory zone in the respiratory system. The bronchi (or bronchus) are the air passages into the lungs that begin at the end of the trachea.