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 conducting system exists both outside (nose to bronchi) and within (bronchi and bronchioles) the lungs. To prevent collapse upon inspiration the walls of the conducting tubes are supported by cartilage. To strain, warm (or cool), and humidify the air the tubes are lined by a mucus membrane.