Is there anything called *photorespiration*?

Question

I came across this term in a book, but couldn't find it or anything related to it in any other book. Can someone please help??
The question in the book was:
Specify two conditions in which photorespiration may take place in green plants.

I think photorespiration means -respiration by plants in the presence of sunlight.
Is that right??

please put it in a fourteen year old's language

Answer 1

Photorespiration occurs when the CO2 levels inside a leaf become low. This happens on hot dry days when a plant is forced to close its stomata to prevent excess water loss. If the plant continues to attempt to fix CO2 when its stomata are closed, the CO2 will get used up and the O2 ratio in the leaf will increase relative to CO2 concentrations.

When the CO2 levels inside the leaf drop to around 50 ppm, Rubisco starts to combine O2 with RuBP instead of CO2.

The net result of this is that instead of producing 2 3C PGA molecules, only one molecule of PGA is produced and a toxic 2C molecule called phosphoglycolateis produced.

The plant must get rid of the phosphoglycolate

First it immediately gets rid of the phosphate group, converting the molecule to glycolic acid. The glycolic acid is then transported to the peroxisome and there converted to glycine.

The glycine is then transported into a mitochondria where it is converted into serine.

The serine is then used to make other organic molecules. All these conversions cost the plant energy and results in the net loss (and ultimate death, under prolonged use) of CO2 from the plant.

To prevent this process, two specialized biochemical additions have been evolved in the plant world: C4 and CAM metabolism

Answer 2

Photorespiration is an alternate pathway for Rubisco, the main enzyme of photosynthesis (specifically, the Calvin cycle). Although Rubisco favors carbon dioxide, it can also use oxygen, producing a glycolate and a glycerate. This usually occurs when oxygen levels are high; for example, when the stomata (tiny pores on the underside of the leaf) are closed to prevent water loss on dry days. It involves chloroplast peroxisomes and mitochondria.(Ashwani)

The reaction is catalyzed by RuBP oxygenase activity:

RuBP + O2 → Phosphoglycolate + 3-Phosphoglycerate
The phosphoglycolate is salvaged by a series of reactions in the peroxisome and mitochondria whereby it is converted into serine and later glycerate and enters the Calvin cycle, at a cost of 1 ATP, by conversion to 3-phosphoglycerate within the chloroplast

Answer 3

Here is a link that covers photorespiration quite well.
http://en.wikipedia.org/wiki/Photorespiration