Muscle cells contract using ATP. There is little ATP in your blood stream. How do your muscle cells get ATP they need to contract and move you? 1. ADP enters the cells from the bloodstream and it turns into ATP by adding a phosphate group in the nucleus
2. glucose from the bloodstream enters the cells and the mitochondria turns it into ATP
3. amino acids in the muscle tissue are broken down into ATP in the nucleus
4. glycogen from the bloodstream is turned directly into ATP by using enzyme glycanase