Dictionary > C3 carbon fixation pathway

C3 carbon fixation pathway

A metabolic pathway where CO2 is converted to 3-phosphogylycerate, the first stable intermediate organic compound containing three carbon atoms.
The C3 carbon fixation pathway is in fact the initial phase of Calvin cycle. It starts with the enzyme rubisco catalyzing the carboxylation of Ribulose-1,5-bisphosphate by CO2 producing a highly unstable 6-carbon intermediate known as 3-keto-2-carboxyarabinitol 1,5-bisphosphate, which splits instantaneously into two molecules of the more stable 3-phosphogylycerate, an organic compound containing three carbon atoms (hence the name C3).
Plants that solely depend to C3 pathway for carbon fixation are faced with the negative effects of photorespiration, such as the wasteful loss of CO2. Photorespiration occurs under conditions of drought, high temperatures and low nitrogen or CO2 concentrations. These conditions cause the stomata to close in an attempt to prevent excessive water loss. The closure of stomata increases O2 levels, and the enzyme rubisco reacts with O2 instead of CO2, consequently losing CO2 instead of fixing CO2.
Word origin: from the intermediate compound, which contains three carbon atoms, hence the name C3.
Compare: C4 carbon fixation pathway, crassulacean acid metabolism.

See also: C3 plant.

You will also like...

Ecological Research Measuring & Analysis
Ecological Research: Measuring & Analysis

This lesson is about the methods used for ecological research, such as quadrat and transect sampling, canopy fogging, an..

DNA - schematic
Genetic Mutations

This tutorial looks at the mutation at the gene level and the harm it may bring. Learn about single nucleotide polymorph..

Homo Species
The Homo Species

The evolution of the species of the genus "Homo" led to the emergence of modern humans. Find out more about human evolut..

Water Cycle
The Water Cycle

The water cycle (also referred to as the hydrological cycle) is a system of continuous transfer of water from the air, s..

Digestion and Absorption of Food
Digestion and Absorption of Food

The gastrointestinal system breaks down particles of ingested food into molecular forms by enzymes through digestion and..

Flowers and tiny fruits of the pomegranate plant
Fruits, Flowers, and Seeds

This tutorial deals with the structure and function of flowers, fruits, and seeds. Also included here are the types of f..