Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors. Conditions like these are found deep within the Earth or where tectonic plates meet.
Because amino acids can be arranged in many different combinations, it's possible for your body to make thousands of different kinds of proteins from just the same 21 amino acids. You may see books that say there are only 20 amino acids.
