Compare Photosynthesis and cellular respiration

During respiration, energy is released from sugar when electrons associated with hydrogen are transported by carriers to oxygen, forming water as a by-product. The electrons lose potential energy as they are pulled down the electron transport chain to electronegative oxygen, and the mitochondrion uses the energy to synthesize ATP.

In photosynthesis, which is also a redox process like cellular respiration, it reverses the direction of electron flow. Water is split, and electrons transferred along the hydrogen ions from the water to carbon dioxide, reducing it to sugar. The electrons increase in potential energy as they move from water to sugar. The required energy boost is provided by light.


SOURCES: CAMPBELL BOOK, Thoughtchalk.com, emc.edu