The answer is Nitrification.
Fats are used for energy after they are broken into fatty acids. Protein can also be used for energy, but the first job is to help with making hormones, muscle, and other proteins. Broken down into glucose, used to supply energy to cells. Extra is stored in the liver.
density, it's a mass per unit volume
Yes and no. Everyone's heart works the same way, is made of the same type of tissue and is located in the same part of the body. However, there are people with diseases who have hearts that are in worse condition and may look different. For example, people with coronary artery disease experience plaque build up in their coronary arteries, which causes a reduction of blood flow to the heart, and in order to treat this they may get a bypass surgery in which another blood vessel from somewhere else in the body, would be used to bypass the blocked blood vessel. In this case the anatomy of that person's heart would be slightly different.
