Photosynthesis: The world's quickest overview.
VBS Home page, Photosynthesis Navigator, Previous Page, Next Page
 
 
 

Photosynthesis is the process by which living certain organisms take carbon dioxide and water and convert these compounds into carbohydrates and oxygen via the action of light. The summarized chemical equation for photosynthesis is shown in the figure.
Photosynthesis involves two big parts. In the first part, called the light reactions, the photosynthetic organism converts the light energy into energy carried by electrons. The analogy is with solar cells converting sunlight into electricity which can do work. In photosynthesis the electrons are picked up by electron transport systems which use the energy in the electrons to make an energy carrying compound called ATP and a second compound, NADPH. The ATP and the NADPH are used for the next big part, theCalvin cycle,or "dark reactions. 

In the Calvin cycle, carbon dioxide is first incorporated into a five carbon molecule called ribulose biphosphate or RuBP. Then in a series of chemical reactions, hydrogens and electrons from the NADPH are progressively added to form a simple, energy rich, phosphorylated carbohydrate called PGAL.  In turn the PGAL is used to make glucose and other carbohydrates for use by the plant.

We'll discuss what really goes on. But first you need some concepts related to energy and light. 
 pgd revised 02/18/00