Explain why a satellite in polar orbit can take pictures of all parts of the earth over time.

Best A satellite in a polar orbit passes over both poles, but the earth rotates beneath it. The time taken for each orbit of the earth depends on the height of thsatellitete. If the satellite is in a circular orbit 260 kilometers above the surface it will have an orbital period of two hours.

The light is great source of energy

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.