The first stage of cellular respiration is glycolysis. It does not require oxygen. During glycolysis, one glucose molecule is split into two pyruvate molecules, using 2 ATP while producing 4 ATP and 2 NADH molecules.
The bile is produced by the liver and the gallblader only serves as storage between meals. The main stimulus for the release of bile from the gallblader comes from the nervous system,after food is put in the mouth.
<span>Hiking in the morning, assuming you have not eaten anything prior to the hike, results in your body having to perform work with lowered glucose levels, thus causing the body to feel out of breath.</span>