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Encyclopedia > Thylakoid
Thylakoids (green) inside a chloroplast
Thylakoids (green) inside a chloroplast
Thylakoids (green) inside a cyanobacterium (Synechocystis)
Thylakoids (green) inside a cyanobacterium (Synechocystis)

A Thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. The word "thylakoid" is derived from the Greek thylakos, meaning "sac". Thylakoids consists of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as "grana" (singular: granum). "Grana" is Latin for "stacks of coins". Grana are connected by intergrana or stroma thylakoids, which join granum stacks together as a single functional compartment. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Cyanobacteria (Greek: cyanos = blue) are a phylum of aquatic bacteria that obtain their energy through photosynthesis. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ... The leaf is the primary site of photosynthesis in plants. ...

Contents

Thylakoid structure

Thylakoid structures
Thylakoid structures

Thylakoids are membrane-bound structures embedded into the chloroplast stroma. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Stroma can refer to: The connective supportive framework of a biological cell, tissue, or organ. ...


Membrane

The thylakoid membrane is the site of the light-dependent reactions of photosynthesis with the photosynthetic pigments embedded directly in the membrane. The thylakoid lipid bilayer shares characteristic features with prokaryotic membranes and the inner chloroplast membrane. For example, acidic lipids can be found in thylakoid membranes, cyanobacteria and other photosynthetic bacteria and are involved in the functional integrity of the photosystems.[1] The thylakoid membranes of higher plants are composed primarily of galactolipids that are asymmetrically arranged along and across the membranes.[2] The lipids for the thylakoid membranes are synthesized in a complex pathway involving exchange of lipid precursors between the endoplasmic reticulum and inner membrane of the plastid envelope and transported from the inner membrane to the thylakoids via vesicles.[3] The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ... It has been suggested that Photosynthetic Pigments be merged into this article or section. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ...


Granum

A granum (plural grana) is a stack of thylakoid discs. Chloroplasts can have from 10 to 100 grana. Grana are connected by stroma thylakoids, also called intergrana thylakoids or lamellae. Grana thylakoids and stroma thylakoids can be distinguished by their different protein composition.


Thylakoid formation

Chloroplasts develop from proplastids when seedlings emerge from the ground. Thylakoid formation requires light. In the plant embryo and in the absence of light, proplastids develop into etioplasts that contain semicrystalline membrane structures called prolamellar bodies. When exposed to light, these prolamellar bodies develop into thylakoids. This does not happen in seedlings grown in the dark, which undergo etiolation. An underexposure to light can cause the thylakoids to fail. This causes the chloroplasts to fail resulting in the death of the plant. Plastids are major organelles uouououuoououououofound only in plants and algae. ... Sunflower seedlings, just three days after germination In a botanical sense, germination is the process of emergence of growth from a resting stage. ... An etioplast is a chloroplast that has not been exposed to light. ... Etiolation is a plant response to stimuli. ...


Thylakoid formation requires the action of vesicle-inducing protein in plastids 1 (VIPP1). Plants cannot survive without this protein, and reduced VIPP1 levels lead to slower growth and paler plants with reduced ability to photosynthesize. VIPP1 appears to be required for basic thylakoid membrane formation, but not for the assembly of protein complexes of the thylakoid membrane.[4] It is conserved in all organisms containing thylakoids, including cyanobacteria,[5] green algae, such as Chlamydomonas,[6] and higher plants, such as Arabidopsis.[7] Species See text. ... Species See text. ...


Thylakoid isolation and fractionation

Thylakoids can be purified from plant cells using a combination of differential and gradient centrifugation.[8] Disruption of isolated thylakoids, for example by mechanical shearing, releases the lumenal fraction. Peripheral and integral membrane fractions can be extracted from the remaining membrane fraction. Treatment with sodium carbonate (Na2CO3) detaches peripheral membrane proteins, whereas treatment with detergents and organic solvents solubilizes integral membrane proteins. Centrifugation is a process that involves the use of the centrifugal force for the separation of mixtures. ... Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid. ... Peripheral membrane proteins are proteins that adhere only temporarily to the biological membrane with which they are associated. ... Laundry detergents are just one of many possible uses for detergents Detergent is a compound, or a mixture of compounds, intended to assist cleaning. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. ...


Thylakoid proteins

Thylakoid disc with embedded and associated proteins
Thylakoid disc with embedded and associated proteins

Thylakoids contain many integral and peripheral membrane proteins, as well as lumenal proteins. Recent proteomics studies of thylakoid fractions have provided further details on the protein composition of the thylakoids.[9] These data have been summarized in several plastid protein databases that are available online.[10][11] Image File history File links Size of this preview: 800 × 258 pixelsFull resolution (854 × 275 pixel, file size: 52 KB, MIME type: image/png) Schematic representation of a thylakoid disc with embedded and associated proteins. ... Image File history File links Size of this preview: 800 × 258 pixelsFull resolution (854 × 275 pixel, file size: 52 KB, MIME type: image/png) Schematic representation of a thylakoid disc with embedded and associated proteins. ... For the journal Proteomics, see Proteomics (journal). ...


According to these studies, the thylakoid proteome consists of at least 335 different proteins. Out of these, 89 are in the lumen, 116 are integral membrane proteins, 62 are peripheral proteins on the stroma side, and 68 peripheral proteins on the lumenal side. Additional low-abundance lumenal proteins can be predicted through computational methods.[12][8] Of the thylakoid proteins with known functions, 42% are involved in photosynthesis. The next largest functional groups include proteins involved in protein targeting, processing and folding with 11%, oxidative stress response (9%) and translation (8%).[10] The term proteome was coined by Mark Wilkins in 1995 (1) and is used to describe the entire complement of proteins in a given biological organism or system at a given time, i. ... Protein targeting a. ... Typically, processing describes the act of taking something through an established and usually routine set of procedures to convert it from one form to another, as a manufacturing procedure (processing milk into cheese) or administrative procedure (processing paperwork to grant a mortgage loan). ... Protein folding is the process by which a protein assumes its characteristic functional shape or tertiary structure, also known as the native state. ... Oxidative stress is a medical term for damage to animal or plant cells (and thereby the organs and tissues composed of those cells) caused by reactive oxygen species, which include (but are not limited to) superoxide, singlet oxygen, peroxynitrite or hydrogen peroxide. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...


Integral membrane proteins

Thylakoid membranes contain integral membrane proteins which play an important role in light harvesting and the light-dependent reactions of photosynthesis. There are four major protein complexes in the thylakoid membrane: An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. ...

Photosystem II is located mostly in the grana thylakoids, whereas photosystem I and ATP synthase are mostly located in the stroma thylakoids and the outer layers of grana. The cytochrome b6f complex is distributed evenly throughout thylakoid membranes. Due to the separate location of the two photosystems in the thylakoid membrane system, mobile electron carriers are required to shuttle electrons between them. These carriers are plastoquinone and plastocyanin. Plastoquinone shuttles electrons from photosystem II to the cytochrome b6f complex, whereas plastocyanin carries electrons from the cytochrome b6f complex to photosystem I. REDIRECT [[In the process of photosynthesis, light is absorbed by a photosystem (ancient Greek: phos = light and systema = assembly) to begin an energy-producing reaction. ... The cytochrome b6f complex (plastoquinol—plastocyanin reductase; EC 1. ... An ATP synthase (EC 3. ...


Together, these proteins make use of light energy to drive electron transport chains that generate a chemiosmotic potential across the thylakoid membrane and NADPH, a product of the terminal redox reaction. The ATP synthase uses the chemiosmotic potential to make ATP during photophosphorylation. The Electron Transport Chain. ... Electrochemical potential is a thermodynamic measure that reflects energy from entropy and electrostatics and is typically invoked in molecular processes that involve diffusion. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... An ATP synthase (EC 3. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... The production of ATP using the energy of sunlight is called photophosphorylation. ...


Photosystems

Main article: Photosystem

These photosystems are light-driven redox centers, each consisting of an antenna complex that uses chlorophylls and accessory photosynthetic pigments such as carotenoids and phycobiliproteins to harvest light at a variety of wavelengths. Each antenna complex has between 250 and 400 pigment molecules and the energy they absorb is shuttled by resonance energy transfer to a specialized chlorophyll a at the reaction center of each photosystem. When either of the two chlorophyll a molecules at the reaction center absorb energy, an electron is excited and transferred to an electron-acceptor molecule. Photosystem I contains a pair of chlorophyll a molecules, designated P700, at its reaction center that maximally absorbs 700 nm light. Photosystem II contains P680 chlorophyll that absorbs 680 nm light best (note that these wavelengths correspond to deep red - see the visible spectrum). The P is short for pigment and the number is the specific absorption peak in nanometers for the chlorophyll molecules in each reaction center. REDIRECT [[In the process of photosynthesis, light is absorbed by a photosystem (ancient Greek: phos = light and systema = assembly) to begin an energy-producing reaction. ... The antenna complex is an array of chlorophyll molecules embedded in the thylakoid membrane that transfer energy to a pair of chlorophyll a molecules at the reaction center of a photosystem. ... Chlorophyll gives leaves their green color Space-filling model of the chlorophyll molecule Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. ... It has been suggested that Photosynthetic Pigments be merged into this article or section. ... Carotenoids are organic pigments naturally occurring in plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria. ... Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae (rhodophytes, cryptomonads, glaucocystophytes) that capture light energy which is then passed on to chlorophylls during photosynthesis. ... P700 is the reaction-center chlorophyll a molecule associated with photosystem I. Its absorption spectrum peaks at 700 nm. ... P680 is the reaction-center chlorophyll a molecule associated with photosystem II. Its absorption spectrum peaks at 680 nm, which is in the red part of the spectrum. ... “Visible light” redirects here. ...


Cytochrome b6f complex

The cytochrome b6f complex is part of the thylakoid electron transport chain and couples electron transfer to the pumping of protons into the thylakoid lumen. Energetically, it is situated between the two photosystems and transfers electrons from photosystem II-plastoquinone to plastocyanin-photosystem I. The cytochrome b6f complex (plastoquinol—plastocyanin reductase; EC 1. ...


ATP synthase

Main article: ATP synthase

The thylakoid ATP synthase is a CF1FO-ATP synthase similar to the mitochondrial ATPase. It is integrated into the thylakoid membrane with the CF1-part sticking into stroma. Thus, ATP synthesis occurs on the stromal side of the thylakoids where the ATP is needed for the light-independent reactions of photosynthesis. An ATP synthase (EC 3. ... Overview of the Calvin cycle and carbon fixation In photosynthesis, the light-independent reactions, also somewhat misleadingly called the dark reactions (they dont require darkness, but they do require the products of the light reactions), are chemical reactions that convert carbon dioxide and other compounds into glucose. ...


Thylakoid lumen proteins

The electron transport protein plastocyanin is present in the lumen and shuttles electrons from the cytochrome b6f protein complex to photosystem I. While plastoquinones are lipid-soluble and therefore move within the thylakoid membrane, plastocyanin moves through the thylakoid lumen. Plastocyanin is a single strand protein of the thylakoid membrane, (molecular weight 10,500), that plays an integral part in photosynthesis. ...


The lumen of the thylakoids is also the site of water oxidation by the oxygen evolving complex associated with the lumenal side of photosystem II. Oxygen evolving complex. ...


Lumenal proteins can be predicted computationally based on their targeting signals. In Arabidopsis, out of the predicted lumenal proteins possessing the "TAT" signal, the largest groups with known functions are 19% involved in protein processing (proteolysis and folding), 18% in photosynthesis, 11% in metabolism, and 7% redox carriers and defense.[8]


Thylakoid protein expression

Chloroplasts have their own genome, which encodes a number of thylakoid proteins. However, during the course of plastid evolution from their cyanobacterial endosymbiotic ancestors, extensive gene transfer from the chloroplast genome to the cell nucleus took place. This results in the four major thylakoid protein complexes being encoded in part by the chloroplast genome and in part by the nuclear genome. Plants have developed several mechanisms to co-regulate the expression of the different subunits encoded in the two different organelles to assure the proper stoichiometry and assembly of these protein complexes. For example, transcription of nuclear genes encoding parts of the photosynthetic apparatus is regulated by light. Biogenesis, stability and turnover of thylakoid protein complexes is regulated by phosphorylation via redox-sensitive kinases in the thylakoid membranes.[13] The translation rate of chloroplast-encoded proteins is controlled by the presence or absence of assembly partners (control by epistasy of synthesis).[14] This mechanism involves negative feedback through binding of excess protein to the 5' untranslated region of the chloroplast mRNA.[15] Chloroplasts also need to balance the ratios of photosystem I and II for the electron transfer chain. The redox state of the electron carrier plastoquinone in the thylakoid membrane directly affects the transcription of chloroplast genes encoding proteins of the reaction centers of the photosystems, thus counteracting imbalances in the electron transfer chain.[16] In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... An endosymbiont is any organism that lives within the body or cells of another organism, i. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry) is the calculation of quantitative (measurable) relationships of the reactants and products in chemical reactions (chemical equations). ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... This article does not cite any references or sources. ... A phosphorylated serine residue Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule or the introduction of a phosphate group into an organic molecule. ... In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules (substrates); the process is termed phosphorylation. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... This article does not cite any references or sources. ... The interaction of mRNA in a eukaryote cell. ...


Protein targeting to the thylakoids

Schematic representation of thylakoid protein targeting pathways.
Schematic representation of thylakoid protein targeting pathways.

Thylakoid proteins are targeted to their destination via signal peptides and prokaryotic-type secretory pathways inside the chloroplast. Most thylakoid proteins encoded by a plant's nuclear genome need two targeting signals for proper localization: An N-terminal chloroplast targeting peptide (shown in yellow in the figure), followed by a thylakoid targeting peptide (shown in blue). Proteins are imported through the translocon of outer and inner membrane (Toc and Tic) complexes. After entering the chloroplast, the first targeting peptide is cleaved off by a protease processing imported proteins. This unmasks the second targeting signal and the protein is exported from the stroma into the thylakoid in a second targeting step. This second step requires the action of protein translocation components of the thylakoids and is energy-dependent. Proteins are inserted into the membrane via the SRP-dependent pathway (1), the Tat-dependent pathway (2), or spontaneously via their transmembrane domains (not shown in figure). Lumenal proteins are exported across the thylakoid membrane into the lumen by either the Tat-dependent pathway (2) or the Sec-dependent pathway (3) and released by cleavage from the thylakoid targeting signal. The different pathways utilize different signals and energy sources. The Sec (secretory) pathway requires ATP as energy source and consists of SecA, which binds to the imported protein, and a Sec membrane complex to shuttle the protein across. Proteins with a twin arginine motif in their thylakoid signal peptide are shuttled through the Tat (twin arginine translocation) pathway, which requires a membrane-bound Tat complex and the pH gradient as an energy source. Some other proteins are inserted into the membrane via the SRP (signal recognition particle) pathway. The chloroplast SRP can interact with its target proteins either post-translationally or co-translationally, thus transporting imported proteins as well as those that are translated inside the chloroplast. The SRP pathway requires GTP and the pH gradient as energy sources. Some transmembrane proteins may also spontaneously insert into the membrane from the stromal side without energy requirement.[17] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A signal peptide is a short (15-60 amino acids long) peptide chain that directs the post transrational transport of a protein. ... A secretory pathway is a term used to describe different methods that cells use to transport material to the outside, usually from the endoplasmic reticulum via the Golgi apparatus. ... The twin-arginine translocation, or Tat, pathway is a protein export, or secretion pathway found in plants, bacteria, and archaea. ... Arginine (symbol Arg or R) is an α-amino acid. ... The signal recognition particle (SRP) is a protein-RNA complex that recognizes and transports specific proteins to the endoplasmic reticulum in eukaryotes and the plasma membrane in prokaryotes. ...


Thylakoid function

Light-dependent reactions of photosynthesis at the thylakoid membrane

The thylakoids are the site of the light-dependent reactions of photosynthesis. These include light-driven water oxidation and oxygen evolution, the pumping of protons across the thylakoid membranes coupled with the electron transport chain of the photosystems and cytochrome b6f complex, and ATP synthesis by the ATP synthase utilizing the generated proton gradient. Image File history File links Size of this preview: 800 × 456 pixel Image in higher resolution (905 × 516 pixel, file size: 82 KB, MIME type: image/png) Light-dependent reactions of photosynthesis at the thylakoid membrane. ... Image File history File links Size of this preview: 800 × 456 pixel Image in higher resolution (905 × 516 pixel, file size: 82 KB, MIME type: image/png) Light-dependent reactions of photosynthesis at the thylakoid membrane. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ... Oxygen evolution is the process of generating molecular oxygen through chemical reaction. ...


Water photolysis

Main article: photolysis

The first step in photosynthesis is the light-driven oxidation (splitting) of water to provide the electrons for the photosynthetic electron transport chains as well as protons for the establishment of a proton gradient. The water-splitting reaction occurs on the lumenal side of the thylakoid membrane and is driven by the light energy captured by the photosystems. It is interesting to note that this oxidation of water conveniently produces the waste product O2 that is vital for cellular respiration. The molecular oxygen formed by the reaction is released into the atmosphere. Photolysis refers to any chemical reaction in which a compound is broken down by light. ... Cellular respiration was discovered by mad scientist Mr. ...


Electron transport chains

Two different variations of electron transport are used during photosynthesis: The Electron Transport Chain. ...

  • Noncyclic electron transport or Non-cyclic photophosphorylation produces NADPH + H+ and ATP.
  • Cyclic electron transport or Cyclic photophosphorylation produces only ATP.

The noncyclic variety involves the participation of both photosystems, while the cyclic electron flow is dependent on only photosystem I.

  • Photosystem I uses light energy to reduce NADP+ to NADPH + H+, and is active in both noncyclic and cyclic electron transport. In cyclic mode, the energized electron is passed down a chain that ultimately returns it (in its base state) to the chlorophyll that energized it.
  • Photosystem II uses light energy to oxidize water molecules, producing electrons (e-), protons (H+), and molecular oxygen (O2), and is only active in noncyclic transport. Electrons in this system are not conserved, but are rather continually entering from oxidized 2H2O (O2 + 4 H+ + 4 e-) and exiting with NADP+ when it is finally reduced to NADPH.

Chemiosmosis

Main article: chemiosmosis

A major function of the thylakoid membrane and its integral photosystems is the establishment of chemiosmotic potential. The carriers in the electron transport chain use some of the electron's energy to actively transport protons from the stroma to the lumen. During photosynthesis, the lumen becomes acidic, as low as pH 4, compared to pH 8 in the stroma. This represents a 10,000 fold concentration gradient for protons across the thylakoid membrane. Chemiosmosis is the diffusion of ions across a membrane. ... Stroma can refer to: The connective supportive framework of a biological cell, tissue, or organ. ... The thylakoid lumen is the compartment in the chloroplast bounded by the thylakoid membrane. ... For alternative meanings see acid (disambiguation). ... Stroma can refer to: The connective supportive framework of a biological cell, tissue, or organ. ... For other uses, see Proton (disambiguation). ...


Source of proton gradient

The protons in the lumen come from three primary sources.

  • Photolysis by photosystem II oxidises water to oxygen, protons and electrons in the lumen.
  • The transfer of electrons from photosystem II to plastoquinone during non-cyclic electron transport consumes two protons from the stroma. These are released in the lumen when the reduced plastoquinol is oxidized by the cytochrome b6f protein complex on the lumen side of the thylakoid membrane. From the plastoquinone pool, electrons passs through the cytochrome b6f complex. This integral membrane assembly resembles cytochrome bc1.
  • The reduction of plastoquinone by ferredoxin during cyclic electron transport also transfers two protons from the stroma to the lumen.

The proton gradient is also caused by the consumption of protons in the stroma to make NADPH from NADP+ at the NADP reductase. Photolysis refers to any chemical reaction in which a compound is broken down by light. ... In the process of photosynthesis, light is absorbed by a photosystem (ancient Greek: phos = light and systema = assembly) to begin an energy-producing reaction. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... For other uses, see Electron (disambiguation). ... Plastoquinone Plastoquinone, often abbreviated pq, is a molecule used in the electron transport chain in the light-dependent reactions of photosynthesis. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ... Plastoquinone Plastoquinone, often abbreviated pq, is a molecule used in the electron transport chain in the light-dependent reactions of photosynthesis. ... Ferredoxin is an electron receptor used in both Cyclic and Non cyclic photophosphorylation. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ...


ATP generation

The molecular mechanism of ATP generation in chloroplasts is similar to that in mitochondria and takes the required energy from the proton motive force (PMF). However, chloroplasts rely more on the chemical potential of the PMF to generate the potential energy required for ATP synthesis. The PMF is the sum of a proton chemical potential (given by the proton concentration gradient) and a transmembrane electrical potential (given by charge separation across the membrane). Compared to the inner membranes of mitochondria, which have a significantly higher membrane potential due to charge separation, thylakoid membranes lack a charge gradient. To compensate for this, the 10,000 fold proton concentration gradient across the thylakoid membrane is much higher compared to a 10 fold gradient across the inner membrane of mitochondria. The resulting chemiosmotic potential between the lumen and stroma is high enough to drive ATP synthesis using the ATP synthase. As the protons travel back down the gradient through channels in ATP synthase, ADP + Pi is combined into ATP. In this manner, the light-dependent reactions are coupled to the synthesis of ATP via the proton gradient. In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Electrochemical gradients in cellular biology refers to the electrical and chemical properties across a membrane. ... In thermodynamics and chemistry, chemical potential, symbolized by μ, is a term introduced in 1876 by the American mathematical physicist Willard Gibbs, which he defined as follows: Gibbs noted also that for the purposes of this definition, any chemical element or combination of elements in given proportions may be considered a... Electrical potential is the potential energy per unit charge associated with a static (time-invariant) electric field, also called the electrostatic potential or the electric potential, typically measured in volts. ... Membrane potential (or transmembrane potential or transmembrane potential difference or transmembrane potential gradient), is the electrical potential difference (voltage) across a cells plasma membrane. ... Electrochemical potential is a thermodynamic measure that reflects energy from entropy and electrostatics and is typically invoked in molecular processes that involve diffusion. ... Stroma can refer to: The connective supportive framework of a biological cell, tissue, or organ. ... An ATP synthase (EC 3. ... An ATP synthase (EC 3. ... The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. ...


Thylakoid Membranes in Cyanobacteria

Cyanobacteria are photosynthetic prokaryotes with highly differentiated membrane systems. Cyanobacteria have an internal system of thylakoid membranes where the fully functional electron transfer chains of photosynthesis and respiration reside. The presence of different membrane systems lends these cells a unique complexity among bacteria. Cyanobacteria must be able to reorganize the membranes, synthesize new membrane lipids, and properly target proteins to the correct membrane system. The outer membrane, plasma membrane, and thylakoid membranes each have specialized roles in the cyanobacterial cell. Understanding the organization, functionality, protein composition and dynamics of the membrane systems remains a great challenge in cyanobacterial cell biology.[18] Orders The taxonomy of the Cyanobacteria is currently under revision. ... The leaf is the primary site of photosynthesis in plants. ... Respiration is a term used for the words in both biochemistry and physiology, and may refer to: Cellular respiration, the process in the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Mitochondria structure : 1) Inner membrane 2) Outer membrane 3) Crista 4) Matrix The outer membrane refers to the outside membranes of Gram-negative bacteria, the chloroplast, or the mitochondria. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ...


See also

Chemiosmosis is the diffusion of ions across a membrane. ... Electrochemical potential is a thermodynamic measure that reflects energy from entropy and electrostatics and is typically invoked in molecular processes that involve diffusion. ... An endosymbiont (also known as intracellular symbiont) is any organism that lives within cells of another organism, i. ... Oxygen evolution is the process of generating molecular oxygen through chemical reaction. ... The leaf is the primary site of photosynthesis in plants. ...

References

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  12. ^ Peltier J, Friso G, Kalume D, Roepstorff P, Nilsson F, Adamska I, van Wijk K (2000). "Proteomics of the chloroplast: systematic identification and targeting analysis of lumenal and peripheral thylakoid proteins". Plant Cell 12 (3): 319-41. PMID 10715320. 
  13. ^ Vener AV, Ohad I, Andersson B (1998). "Protein phosphorylation and redox sensing in chloroplast thylakoids". Curr Opin Plant Biol 1 (3): 217-23. PMID 10066592. 
  14. ^ Choquet Y, Wostrikoff K, Rimbault B, Zito F, Girard-Bascou J, Drapier D, Wollman F (2001). "Assembly-controlled regulation of chloroplast gene translation". Biochem Soc Trans 29 (Pt 4): 421-6. PMID 11498001. 
  15. ^ Minai L, Wostrikoff K, Wollman F, Choquet Y (2006). "Chloroplast biogenesis of photosystem II cores involves a series of assembly-controlled steps that regulate translation". Plant Cell 18 (1): 159-75. PMID 16339851. 
  16. ^ Allen J, Pfannschmidt T (2000). "Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts". Philos Trans R Soc Lond B Biol Sci 355 (1402): 1351-9. PMID 11127990. 
  17. ^ Gutensohn M, Fan E, Frielingsdorf S, Hanner P, Hou B, Hust B, Klösgen R (2006). "Toc, Tic, Tat et al.: structure and function of protein transport machineries in chloroplasts". J. Plant Physiol. 163 (3): 333-47. PMID 16386331. 
  18. ^ Herrero A and Flores E (editor). (2008). The Cyanobacteria: Molecular Biology, Genomics and Evolution, 1st ed., Caister Academic Press. ISBN 978-1-904455-15-8 . 

Textbook sources

  • Heller, H. Craig; Orians, Gordan H.; Purves, William K.; & Sadava, David (2004). LIFE: The Science of Biology (seventh edition). Sinauer Associates, Inc.. ISBN 0-7167-9856-5. 
  • Raven, Peter H.; Ray F. Evert, Susan E. Eichhorn (2005). Biology of Plants, 7th Edition. New York: W.H. Freeman and Company Publishers, 115-127. ISBN 0-7167-1007-2. 
  • Herrero A and Flores E (editors). (2008). The Cyanobacteria: Molecular Biology, Genomics and Evolution, 1st ed., Caister Academic Press. ISBN 978-1-904455-15-8. 

  Results from FactBites:
 
What is "Thylakoid"? (305 words)
It is stored in the form of compounds called ATP and NADPH.
The light reaction takes place inside the chloroplast, in a double membrane fold called the thylakoid.
On the surface of this microscopic tissue, in every cell in every leaf of every green plant on Earth, biology is working away to ensure that the sun's light will be converted into food for the plant, and, by natural extrapolation, the animal kingdom as well.
  More results at FactBites »

 
 

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