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Photosynthesis

Introduction: Photosynthesis is a very complicated process at the biomolecular level. It is carried out by those organisms called producers. Plants and some bacteria fall into this category. It involves many different reactions in order to convert sunlight into the chemical energy autotrophs can use.

The driving force behind photosynthesis is sunlight (or some kind of light source). Without it, plants are unable to collect the energy they need to make food for themselves.

Photosynthesis can be summed up into the following equation:
$CO_2 +H_2O -> C_6H_12O_6 +H_2O + O_2$

or

carbon dioxide and water yields glucose, water and oxygen.

Plants then take the glucose and move it into cellular respiration, where it is broken down for energy in the form of ATP. Notice that oxygen is produced through this reaction. While many students assume that it comes from the carbon dioxide, it actually comes from the water. A series of reactions causes the hydrogen of the water molecule to be broken off, releasing the oxygen. In essence, the oxygen is the waste product of this reaction. As luck would have it, animals need that "waste" in order to survive. However, this relationship between plants and animals is very one sided. If all the animals were to disappear tomorrow, the plants would never know it. However, if all the plants were to die, the animals would soon follow.

Photosynthesis is broken into three major steps. The first is called light absorption. Just like it sounds, this is the phase when the chlorophyll inside the leaves of the plant are absorbing all the light energy they can. The next step is call the electron transport chain. Like cellular respiration, this step involves a series of reactions and energy carriers to shuttle electrons around. The final phase is called the Calvin cycle. It is here that the carbon from the carbon dioxide is fixed and transfigured into glucose.

Directions for this Lesson: Answer the practice questions and then watch the video for more details.

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