Photorespiration

Photorespiration (pronounced: pho·to·res·pi·ra·tion) is a process in plant physiology that occurs in plants, particularly under high light intensities and oxygen concentrations, and high temperatures.

Etymology

The term "photorespiration" is derived from the Greek words "photo-", meaning "light", and "respiration", meaning "breathing". It refers to a process that is somewhat similar to respiration in animals, but is triggered by light and occurs in plants.

Definition

Photorespiration is a metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output. It generally occurs when the CO2 levels inside a leaf become low. This happens on hot dry days when a plant closes its stomata to prevent water loss.

Process

The process begins in the chloroplasts, where oxygen is combined with RuBP, a five-carbon compound, to form a two-carbon compound and a three-carbon compound. The two-carbon compound is then transported to the peroxisome, where it is converted into a three-carbon compound. This compound is then transported to the mitochondria, where it is converted back into a three-carbon compound, which is then transported back to the chloroplasts.

Related Terms

RuBisCO: The enzyme that catalyzes the first major step of carbon fixation, a process by which the atmospheric carbon dioxide is converted by plants to energy-rich molecules such as glucose.
Stomata: Tiny openings or pores in plant tissue that allow for gas exchange.
Chloroplasts: Organelles found in plant cells and eukaryotic algae that conduct photosynthesis.
Peroxisome: A type of organelle known for its role in the oxidation of specific biomolecules.
Mitochondria: An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.

External links

Medical encyclopedia article on Photorespiration
Wikipedia's article - Photorespiration

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Photorespiration