Basically the photosynthesis process is the inverse of the respiration process. In photosynthesis carbohydrates and oxygen are produced starting only from CO2 and H20 with the help of solar energy having as mediator (catalyst) chlorophyll. In respiration carbohydrates are burnt in oxygen to produce energy, CO2 and water. Therefore in photosynthesis complex molecules are produced starting from basic molecules and energy, while in respiration these complex molecules are broken into much simpler molecules to produce energy.
The two processes can both be represented by the equation:
`C_6H_12O_6 +6O_2 harr "energy" + 6CO2+ 6H2O`
For respiration the direction of the reaction is to the right, for photosynthesis the direction of the reaction is to the left.
While respiration is encountered in all living organisms (plants and animals) photosynthesis is only an attribute of plants, because it needs the presence of chlorophyll to make the reaction possible. If we refer only to plants, both respiration and photosynthesis processes are encountered, but while photosynthesis is prevalent during the daylight hours, only the respiration process is present during night. Therefore plants produce manly oxygen during day and mainly CO2 during night. (This is why is not recommended to have a plant next to your bed).
Another difference between the two processes is that respiration takes place in the cytoplasm in the living cells, while the photosynthesis takes place in the chloroplasts of plant cells.