What is the difference between photosynthesis and respiration?

There are many differences between respiration and photosynthesis. The principal difference, however, between photosynthesis and respiration is that photosynthesis utilizes carbon dioxide and water in the presence of light to produce glucose and oxygen, whereas respiration uses oxygen and glucose to power the activities of the cell. Respiration then releases carbon dioxide and water as a byproduct. 

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This question deserves  several "answers" aimed at different levels.

For elementary-school students, it is important to know that photosynthesis is how green plant cells trap sunlight to make sugar, and respiration is how all plant cells (and most other cells) break sugar down to release and use that stored energy.

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This question deserves  several "answers" aimed at different levels.

For elementary-school students, it is important to know that photosynthesis is how green plant cells trap sunlight to make sugar, and respiration is how all plant cells (and most other cells) break sugar down to release and use that stored energy.

At the high school level, we can add the understanding that all cells break down fuel molecules but only certain cells can use sun energy to create fuel molecules.  Also, although the summary equations are sort of "the reverse of each other", the processes are not just "the same but completed in reverse", but involve enzymes and chemical reactions that are specific to the process of either photosynthesis or respiration. 

In terms of ecological implications of deforestation as they relate to photosynthesis, it is not the lack of oxygen production that concerns us, because marine algae release much more oxygen per year than trees do.  Our concern is that a lot of carbon, stored in wood, is released as carbon dioxide when wood is burned, adding to the impact of "greenhouse gases" on global average temperature.

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The biggest difference between photosynthesis and respiration is that photosynthesis only occurs in plants and some bacteria while respiration occurs in all living organisms. They do share one big similarity and that is that the process of photosynthesis is actually the same process only it is completed in reverse.

Photosynthesis is Carbon Dioxide and Water that, through the process, yield Glucose and Oxygen.

Respiration is Glucose and Oxygen that, through the process of respiration, yield Carbon Dioxide and Water.

The two work well together because living organisms supply plants and some bacteria with the carbon dioxide needed to undergo photosynthesis, and plants and some bacteria give off oxygen which living organisms need to breathe or respire.

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There are a number of differences between the processes of photosynthesis and respiration.

Photosynthesis takes place in green plants, cyanobacteria, and algae. In this process, carbon dioxide and water, in the presence of sunlight, are converted to glucose and oxygen. In other words, the process causes the conversion of light energy to chemical energy. Since the energy is stored in the form of glucose molecules in photosynthesis, this process can be considered to be endothermic in nature. Photosynthesis can be summarized by the following chemical reaction:

`6CO_2 + 6H_2O + sunlight -> C_6H_12O_6 + 6O_2`

Respiration, on the other hand, takes place in all living organisms. This process can be considered to be the "reverse" of photosynthesis, since the reactants in this process are glucose and oxygen, while the products are carbon dioxide and water. Since energy is released in this process (in the form of ATP molecules), this process is exothermic. The process of respiration can be summarized by the following chemical reaction:

`C_6H_12O_6 + 6O_2 -> 6CO_2 + 6H_2O + ATP`

(Here, ATP simply refers to the energy that is released during the process of respiration. The actual number of ATP molecules released during respiration will be dependent on a number of factors, including presence or absence of oxygen, etc.)

Also note that while photosynthesis takes place only in the presence of sunlight, the process of respiration takes place continuously throughout the lifetime of living organisms. 

Hope this helps.

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