Structure 3 in the diagram represents where cellular respiration occurs and
ATP is produced.
The structure is known as the mitochondrion and it has an oval shape in
which series of reactions takes place to produce energy needed by the cells
of organisms.
The mitochondrion is regarded as the power house of the cell because
cellular respiration takes place which produces ATP. The ATP formed is the
usable form of energy by cells to preform their daily activities and for
optimal functioning.
Read more about cellular respiration on https://brainly.com/question/12827458
