Photosynthesis and cellular respiration are almost totally different from the Biochemistry perspective. In terms of the end products, they're almost exactly the opposite of each-other: photosynthesis takes carbon dioxide and water and, using energy in the form of the sun's light, strip the hydrogen from the water and combine it with the carbon dioxide to make sugar, producing oxygen gas as a waste product. Cellular respiration, on the other hand, takes oxygen gas and combines it with sugar to produce carbon dioxide and water, releasing the energy that went into making the sugar in the first place, only now the energy is ultimately tuned into heat and can't be turned back into sunlight.

Photosynthesis and cellular respiration are similar in the fact that they are both used to generate ATP, which is chemical energy, for organisms. The differences between the two processes lie in the fact that photosynthesis is carried out by mainly plants and some kinds of microorganisms to make ATP from light energy, whereas cellular respiration is mainly carried out by animals and various microorganisms to generate ATP from food. I hope this helps!