What is "photorespiration" and why it is needed by plants?

First of all pop93star, you should probobly just stick to your media, because obviously you know nothing about biology. And Erin, don't just copy and paste things you have no prior knowledge or understanding about. In order to give the truth about this matter, perhaps you people should be looking for an answer from someone who know's what they are talking about. Like myself, for example who is a Biology Major. For starts, reading the article on Wikipedia wouldn't hurt, it seems to have a somewhat decent article on the subject which could give anyone a good general overview of photorespiration.

But in order to make matters regarding RuBP and RuBisCo actually TRUTHFUL, here's what you really need to know. First of all, they are not the same thing. RuBP stands for Ribulose Bisphosphate which is a 5-Carbon organic compound already contained within the chloroplasts of plant cells. When CO2 (Carbon Dioxide) molecules go through the Calvin Cycle, RuBisCo (Ribulose Bisphosphate Carboxylase) which is an ENZYME, adds the CO2 molecules (one at a time) to RuBP, thus forming a 6-Carbon Compound which is highly unstable. As a result, this compound immediately splits into 2 SEPERATE 3-Carbon molecules called 3-Phosphoglycerates, which will then travel through the rest of the cycle ultimately yielding Glyceraldehyde-3-Phosphate (G3P).

However, in Photorespiration, instead of CO2 being added by RuBisCo to RuBP, O2 (Oxygen) is instead. This is a result of hot & dry weather in which a plant closes certain pores called stomata so that water doesn't evaporate from its cells. The outcome caused by photorespiration is thus considered wasteful because when O2 travels through the Calvin Cycle rather than CO2, the end result is a release of CO2 into the surrounding atmosphere and NO production of sugar which the plant needs as a source of energy. Not to mention, the light reactions of photosynthesis which normally produce products needed BY THE CALVIN CYCLE to convert CO2 to sugar (stored energy), are simply wasted in photorespiration because nothing essential to the cell is produced.