C3 carbon fixation
Encyclopedia
carbon fixation is a metabolic pathway
for carbon fixation
in photosynthesis
. This process converts carbon dioxide
and ribulose bisphosphate (RuBP, a 5-carbon sugar) into 3-phosphoglycerate through the following reaction:
This reaction occurs in all plants as the first step of the Calvin-Benson cycle. In
plants, carbon dioxide is drawn out of malate
and into this reaction rather than directly from the air.
Plant
s that survive solely on fixation ( plants) tend to thrive in areas where sunlight
intensity is moderate, temperature
s are moderate, carbon dioxide
concentrations are around 200 ppm or higher, and ground water is plentiful. The plants, originating during Mesozoic
and Paleozoic
eras, predate the
plants and still represent approximately 95% of Earth's plant biomass. plants lose 97% of the water taken up through their roots to transpiration. Examples include rice and barley.
plants cannot grow in hot areas because RuBisCO
incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration
, which leads to a net loss of carbon and nitrogen from the plant and can, therefore, limit growth. In dry areas, plants shut their stomata to reduce water loss, but this stops from entering the leaves and, therefore, reduces the concentration of in the leaves. This lowers the :O2 ratio and, therefore, also increases photorespiration. and CAM
plants have adaptations that allow them to survive in hot and dry areas, and they can, therefore, outcompete plants.
The isotopic signature
of plants shows higher degree of 13C depletion than the plants.
Metabolic pathway
In biochemistry, metabolic pathways are series of chemical reactions occurring within a cell. In each pathway, a principal chemical is modified by a series of chemical reactions. Enzymes catalyze these reactions, and often require dietary minerals, vitamins, and other cofactors in order to function...
for carbon fixation
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...
in photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. This process converts carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and ribulose bisphosphate (RuBP, a 5-carbon sugar) into 3-phosphoglycerate through the following reaction:
- CO2 + RuBP → (2) 3-phosphoglycerate
This reaction occurs in all plants as the first step of the Calvin-Benson cycle. In
C4 carbon fixation
C4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...
plants, carbon dioxide is drawn out of malate
Malate
Malate is the ionized form of malic acid. It is an important chemical compound in biochemistry. In the C4 carbon fixation process, malate is a source of CO2 in the Calvin cycle....
and into this reaction rather than directly from the air.
Plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s that survive solely on fixation ( plants) tend to thrive in areas where sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
intensity is moderate, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s are moderate, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
concentrations are around 200 ppm or higher, and ground water is plentiful. The plants, originating during Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
and Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
eras, predate the
C4 carbon fixation
C4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...
plants and still represent approximately 95% of Earth's plant biomass. plants lose 97% of the water taken up through their roots to transpiration. Examples include rice and barley.
plants cannot grow in hot areas because RuBisCO
RuBisCO
Ribulose-1,5-bisphosphate carboxylase oxygenase, commonly known by the shorter name RuBisCO, is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants to energy-rich molecules such as glucose. RuBisCo is an abbreviation...
incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration
Photorespiration
Photorespiration, or "'photo-respiration'", is a process in plant metabolism by which RuBP has oxygen added to it by the enzyme , instead of carbon dioxide during normal photosynthesis. This is the beginning step of the Calvin-Benson cycle...
, which leads to a net loss of carbon and nitrogen from the plant and can, therefore, limit growth. In dry areas, plants shut their stomata to reduce water loss, but this stops from entering the leaves and, therefore, reduces the concentration of in the leaves. This lowers the :O2 ratio and, therefore, also increases photorespiration. and CAM
Crassulacean acid metabolism
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide...
plants have adaptations that allow them to survive in hot and dry areas, and they can, therefore, outcompete plants.
The isotopic signature
Isotopic signature
An isotopic signature is a ratio of stable or unstable isotopes of particular elements found in an investigated material...
of plants shows higher degree of 13C depletion than the plants.