What is the function of mitochondria in muscle fibers?

During strenuous exercise, the rate of energy use in skeletal muscles can increase by more than 100-fold almost instantly. To meet this energy demand, muscle cells contain mitochondria. These organelles, commonly referred to as the cell's “power plants,” convert nutrients into the molecule ATP, which stores energy.

what's the

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.