You answer is here:
http://cosperscience.wikispaces.com/file/view/Life+processes.pdfBut just to tell you plants get CO2 from the air and togeather with H20 (water) and sunlight energy they create O2 (oxygen) which gets released and they keep Glucose as their energy. This process is Photosynthesis.
The sugar and other organic molecules are transported through the plant by means of a special layer of tissue called phloem. Phloem is composed of living cells that transport a water solution of sugars that we commonly call sap. This movement is modeled by the pressure-flow theory, a part of which is that the sugar-containing fluid is moved through sieve tubes by fluid pressure. By this means, nutrients can be moved from the photosynthetic site (the source) to the place where the sugar is being used (the sink) whether it is up or down the stem of the plant.
The energy can be stored in cells the chloroplasts or even mitochondria in some plants.
Humans breath Oxygen get into the alveoli in the lungs and exchanges it with CO2 (the waste product of body cells). Then the cells uses 02 and glucose with some other stuff to create ATP which is energy in the body. This is created in the Mitochondria and can be stored there for later usage. All you have to do it keep breathing and eating.
And as I said the waste product of this is CO2 which gets exhaled out.