molecular energy level. (physical chemistry). One of the states of motion of nuclei and electrons in a molecule, having a definite energy, which is allowed by quantum mechanics.1  Facebook.olecular energy level. (physical chemistry). One of the states of motion of nuclei and electrons in a molecule, having a definite energy, which is allowed by quantum mechanics. 1  Facebook.
Air first enters your body through your nose or mouth, which wets and warms the air. (Cold, dry air can irritate your lungs.) The air then travels through your voice box and down your windpipe. The windpipe splits into two bronchial tubes that enter your lungs.
Therefore, air can flow into the lungs uninterrupted. In other words, normal breathing during wakefulness is like drinking the milkshake through a plastic soda straw. When we sleep, there is an increased risk for the airway behind the tongue to collapse with each breath (particularly when sleeping on our backs).