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.
Alveoli (round part of flask) that do not receive a good blood flow (i.e., perfusion) do not receive a good supply of carbon dioxide. Respiratory bronchioles connected to such alveoli are narrow. This adaptation of the air passages to the blood flow is called 'ventilation-perfusion coupling.'.entilation, breathing, and external respiration all mean the same thing; the movement of air into and out of the lungs.