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.
1 The upper respiratory tract includes the mouth, nose, throat, larynx (voice box), and trachea (windpipe). 2  Upper respiratory infections are often referred to as  colds 3  .. The lower respiratory tract includes the bronchial tubes and the lungs.4  Bronchitis and pneumonia are infections of the lower respiratory tract. The upper respiratory tract includes the mouth, nose, throat, larynx (voice box), and trachea (windpipe). 2  Upper respiratory infections are often referred to as  colds 3  .. The lower respiratory tract includes the bronchial tubes and the lungs.