Overview of C4 carbon fixation

C₄ carbon fixation is a metabolic pathway found in some land plants (C4 plants). They have a competitive advantage over plants possessing the more common C3 carbon fixation pathway under conditions of drought, high temperatures and nitrogen limitation. The C₄ plants possess a characteristic leaf anatomy. Their vascular bundles are surrounded by two rings of cells. The inner ring, called Bundle Sheath Cells, contain starch-rich chloroplasts lacking grana which differ from those in mesophyll cells present as the outer ring. Hence, the chloroplasts are called dimorphic. This peculiar anatomy is called Kranz Anatomy (Kranz-Crown/Halo). The C₄ cycle allows for a spacial separation of carbon fixation from respiration, thus allowing C₄ plants to increase concentration of CO₂ within their leaves. This increases the amount of photosynthesis and decreases the chances of photorespiration, a harmful process in which organic material and energy is lost from the plant due to high concentrations of oxygen. This was proved by two Australian scientists Hatch and Slack in 1966. Therefore, it is also called Hatch-Slack pathway. It is called "C₄" because the product, oxaloacetate, contains four carbon atoms. It occurs in the mesophyll of the leaf, specifically in the mesophyll cells and the bundle sheath cells. The chemical equation is: Image File history File links HatchSlackpathway. ... Image File history File links HatchSlackpathway. ... u fuck in ua ... C3 carbon fixation is a pathway for carbon fixation in photosynthesis. ... A drought or an extreme dry periodic climate is an extended period where water availability falls below the statistical requirements for a region. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... In botany, a leaf is an above-ground plant organ specialized for photosynthesis. ... Starch is a complex carbohydrate which is insoluble in water. ... The inside of a chloroplast Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... This article is about the leaf, a plant organ. ... Carbon fixation is a process found in photosynthesis in autotrophic plants. ... Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. ... Photorespiration is an alternate pathway for Rubisco, the main enzyme of photosynthesis (specifically, the Calvin cycle). ... Organic material or organic matter is any material which originated as a living organism. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... This article is about the leaf, a plant organ. ... In botany, a leaf is an above-ground plant organ specialized for photosynthesis. ... In botany, a leaf is an above-ground plant organ specialized for photosynthesis. ...

PEP carboxylase + PEP + CO₂ → oxaloacetate

The product is usually converted to malate, a simple organic compound that gives up its CO₂ to the Calvin cycle after being shipped off to bundle sheath cells surrounding a nearby vein. After losing the CO₂, it becomes pyruvate, and can be phosphorylated into PEP at the cost of a phosphorus group and one ATP. It can then be reused in the above equation. Since every CO₂ molecule has to be fixed twice, the C₄ pathway is more energy consuming than the C₃ pathway. The C₃ pathway requires 18 ATP for the synthesis of one molecule of glucose while the C₄ pathway requires 30 ATP. But since otherwise tropical plants lose more than half of photosynthetic carbon in photorespiration, the C₄ pathway is an adaptive mechanism for minimizing the loss. Malate (-OOC-CH2-CH(OH)-COO-) is the ionized form of malic acid. ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon. ... It has been suggested that this article or section be merged with Light-independent reaction. ... In geology, a vein is a finite volume within a rock, having a distinct shape, filled with mono or poly mineralic crystal aggregates, which were precipitated from an (aqueous) fluid or melt. ... Pyruvate (CH3COCOO−) is the ionized form of pyruvic acid. ... Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule. ... Name Phosphoenolpyruvate; Phosphoenolpyruvic acid; PEP Formula C3H5O6P Mass 167. ... This article is about the chemical element. ... Adenosine 5-tripenis (ATP) is the nucleotide known in biochemistry as the molecular currency of intracellular energy transfer; that is, ATP is able to store and transport chemical energy within cells. ... Photorespiration is an alternate pathway for Rubisco, the main enzyme of photosynthesis (specifically, the Calvin cycle). ...

C4 carbon fixation has evolved on several occasions in different groups of plants, so is an example of convergent evolution. Plants which use C4 metabolism include sugarcane, maize, sorghum, Eleusine, Amaranthus, and Euphorbia. C4 plants are known only since the Cenozoic and did not became common until the Miocene. Today they represent about 5% of Earth's plant biomass. A speculatively rooted phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese. ... In evolutionary biology, convergent evolution describes the process whereby organisms not closely related independently acquire similar characteristics while evolving in separate and sometimes varying ecosystems. ... Species Saccharum arundinaceum Saccharum bengalense Saccharum edule Saccharum officinarum Saccharum procerum Saccharum ravennae Saccharum robustum Saccharum sinense Saccharum spontaneum Sugarcane or Sugar cane (Saccharum) is a genus of between 6–37 species (depending on taxonomic interpretation) of tall grasses (family Poaceae, tribe Andropogoneae), native to warm temperate to tropical regions... Binomial name Zea mays L. Maize (Zea mays ssp. ... Species About 20 species, including: Sorghum almum Sorghum bicolor Sorghum caffrorum Sorghum caudatum Sorghum cernuum Sorghum halepense Sorghum nervosum Sorghum nigricans Sorghum nitidum Sorghum propinquum Sorghum roxburghii Hybrids Sorghum × almum Sorghum × drummondii Sorghum is a genus of about 20 species of grasses, native to tropical and subtropical regions of Eastern... Species See text Amaranthus, also known by the common name pigweed, is a widely distributed genus of annual, short-living herb, occurring mostly in temperate and tropical regions, belonging to the Amaranth family (Amaranthaceae). ... This article needs cleanup. ... The Cenozoic Era (sometimes still Caenozoic in the United Kingdom) is the most recent of the four classic geological eras. ... The Miocene epoch is a period of time that extends from about 23 to 5. ...

The isotopic signature of C4 plants shows lower degree of ¹³C depletion than the signature of C3 plants. An isotopic signature (also isotopic fingerprint) is a ratio of stable or unstable isotopes of particular elements found in an investigated material. ...

See also

• Rubisco
• Crassulacean acid metabolism (CAM)