Essentially 100% of the energy that fuels the earth comes from the sun. To maintain a constant global average temperature, all of the sun's radiation that enters Earth's atmosphere must eventually be sent back to space. This is achieved through Earth's energy balance.
You subtract the number of protons and the mass to get the number of neutrons.
That would be called a source or head water
Mitochondria. The “powerhouses” of the cell, mitochondria are oval-shaped organelles found in most eukaryotic cells. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as ATP (adenosine triphosphate).
Food enters the stomach during the third stage of digestion, hope this helps.