Myofibrils are the building blocks or contractile unit of each muscle fiber. The tiniest functional unit of skeletal muscle, the sarcomere, is found in the myofibrils and is made up of protein filaments: actin (thin) and myosin (thick).
Yes. Indirectly, through plants. Without plants using photosynthesis, and therefore, creating oxygen, we wouldn't have enough breathable air.
I think its free nitrogen
