The thylakoid membrane function in a cell is the site that captures sunlight that is needed for photosynthesis. The structure of the thylakoid helps in accomplishing this role.

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A thylakoid is a sheet-like membrane-bound organelle in chloroplasts and cyanobacteria that is the site of light-dependent photosynthesis reactions

Thylakoids are membrane-bound compartments found within chloroplasts and cyanobacteria. They are the location for light-dependent reactions in photosynthesis.

Thylakoids are made up of a thylakoid membrane that surrounds a thylakoid lumen. It is the location where chlorophyll is found, which is used to absorb light and used in biochemical reactions. Thylakoid is derived from the Greek word thylakos, which means pouch or sac. “Thylakoid” means “pouch-like” with the -oid suffix.

Thylakoids are also known as lamellae, though this term can refer to the portion of a thylakoid that connects grana.

The thylakoids are the site for light-dependent reactions in photosynthesis. Therefore, the functions of the thylakoids membrane include light-driven water oxidation and oxygen evolution, proton pumping across thylakoid membranes coupled with the electron transport chain of the photosystems, and cytochrome complex. Another function of the thylakoid is ATP synthesis by the ATP synthase using the generated proton gradient.

The first step in the function of the thylakoid membrane is water photolysis, which occurs on the thylakoid membrane’s lumen site. In this step, light energy is used to reduce or split water. This reaction generates electrons, which are required by electron transport chains and protons. The electrons are pumped into the lumen to create a proton gradient. The proton gradient created across the thylakoid membrane produces oxygen. Despite the fact that oxygen is required for cellular respiration, the gas produced by this reaction is released into the atmosphere.

The electrons produced by photolysis are directed to the photosystems of the electron transport chains. The photosystems contain an antenna complex that collects light at various wavelengths by using chlorophyll and related pigments. The localization of the thylakoid membrane electron transport chains ensures that the energy released can be used to establish an H+ ion gradient.

Photosystem I converts NADP+ to NADPH + H+ using light energy and is involved in both noncyclic and cyclic electron transport. The energized electron is passed down a chain in cyclic mode, eventually returning it (in its base state) to the chlorophyll that energized it.

Photosystem II is only active in noncyclic transport and uses light energy to oxidize water molecules, producing electrons (e–), protons (H+), and molecular oxygen (O2). Electrons are not conserved in this system, but rather enter from oxidized 2H2O (O2 + 4 H+ + 4 e–) and exit with NADP+ when it is finally reduced to NADPH.

During photosynthesis, two types of electron transport are used namely Noncyclic electron transport, also known as noncyclic photophosphorylation, which generates NADPH + H+ and ATP. The other type of electron transport used is cyclic electron transport or cyclic photophosphorylation which generates only ATP.

The noncyclic electron flow is dependent on both photosystems, whereas the cyclic electron flow is dependent on only photosystem I.

The establishment of chemiosmotic potential is a critical function of the thylakoid membrane and its associated photosystems. The carriers in the electron transport chain actively transport protons from the thylakoid membrane and stroma to the lumen by utilizing some of the electron’s energy. During the process of photosynthesis, the lumen becomes acidic, with a pH as low as 4, compared to the stroma’s pH of 8. Chemiosmosis in thylakoid membrane represents a 10,000-fold gradient in proton concentration across the thylakoid membrane.

Protons in the lumen are derived from three primary sources.

The consumption of protons in the stroma to produce NADPH from NADP+ at the NADP reductase also contributes to the proton gradient.

The molecular mechanism of ATP (Adenosine triphosphate) generation in chloroplasts is similar to that of mitochondria, and the required energy is derived from the proton motive force (PMF). The PMF is the product of a proton chemical potential (as determined by the proton concentration gradient) and a transmembrane electrical potential (given by charge separation across the membrane). Unlike mitochondrial inner membranes, which have a significantly higher membrane potential due to charge separation, thylakoid membranes do not have a charge gradient.

To compensate for the lack of a charge gradient, the 10,000 fold gradient in proton concentration across the thylakoid membrane is much higher than the 10 fold gradient across the inner membrane of mitochondria. The resulting chemiosmotic potential between lumen and stroma is sufficient to drive ATP synthesis via ATP synthase. ADP + Pi are combined into ATP as protons travel back down the gradient through channels in ATP synthase. The light dependent reactions in the thylakoid membrane are thus linked to the synthesis of ATP via the proton gradient.

The above-mentioned make up the structure of thylakoid membrane.

The membrane is the site of the light-dependent reactions of photosynthesis, with photosynthetic pigments embedded directly in it. The membrane consists of an alternating pattern of dark and light bands, each measuring 1 nanometre. The thylakoid membrane has lipid bilayer like acidic lipids. These lipids are also found in cyanobacteria, and other photosynthetic bacteria and play a role in the functional integrity of photosystems.

Higher plant thylakoid membranes are primarily made up of phospholipids and galactolipids that are arranged asymmetrically along and across the membranes. Thylakoid membranes are richer in galactolipids than phospholipids, and they are primarily composed of hexagonal phase II lipids that form monogalacotosyl diglyceride lipids. Despite their distinct composition, plant thylakoid membranes have been shown to be primarily made of lipid-bilayer that is dynamically organized.

The lipids that make up the thylakoid membranes, which are rich in high-fluidity linolenic acid, are synthesized in a complex pathway that involves the exchange of lipid precursors between the endoplasmic reticulum and the inner membrane of the plastid envelope and are then transported from the inner membrane to the thylakoids via vesicles.

The thylakoid lumen is a continuous aqueous phase that is surrounded by the thylakoid membrane. It is essential for photophosphorylation during photosynthesis. Protons are pumped across the thylakoid membrane into the lumen during the light-dependent reaction, making it acidic in the region of a pH of 4.

Thylakoids in higher plants are organized into a granum-stroma membrane assembly. A granum (plural grana) is a thylakoid disc stack. Chloroplasts can have between 10 and 100 grana. Grana contribute to the high surface area to volume ratio of chloroplasts.

Stroma thylakoids, also known as intergranal thylakoids or lamellae, connect grana. The distinguishing factor between grana thylakoids and stroma thylakoids is their protein composition.

At the granal interface, the stroma lamellae are organized in wide sheets perpendicular to the grana stack axis, forming multiple right-handed helical surfaces.

The thylakoid membrane location in plant cells is the chloroplasts.

Photosynthesis occurs in chloroplasts, which contain chlorophyll. The chloroplasts in plant cells are surrounded by a double membrane and have a third inner membrane known as the thylakoid membrane, which forms long folds within the organelle. Thylakoid membranes appear like coins stacked together in electron micrographs, despite the fact that the compartments they form are connected like a maze of chambers. The green pigment chlorophyll which plants use to absorb light for photosynthesis is found within the thylakoid membrane.

The thylakoid membrane in photosynthesis houses photosynthetic pigments (such as chlorophyll). These pigments are embedded in the thylakoid membrane. The thylakoid membrane chlorophyll is the site of the light-dependent reactions of photosynthesis. The shape of the grana’s stacked coil provides the chloroplast with a high surface area to volume ratio, which aids photosynthesis efficiency.

During photosynthesis, the thylakoid lumen is used for photophosphorylation. Protons are pumped into the lumen by light-dependent reactions in the membrane, lowering its pH to 4.

Cyanobacteria are photosynthetic prokaryotes with complex membrane systems. They have an internal thylakoid membrane system that houses the fully functional electron transfer chains of photosynthesis and respiration. The presence of multiple membrane systems gives these bacteria cells a distinct level of complexity.

Cyanobacteria must be able to reorganize membranes, synthesize new membrane lipids, and target proteins to the appropriate membrane system. The cyanobacterial cell’s outer membrane, plasma membrane, and thylakoid membrane all serve specific functions.

In contrast to the thylakoid network of algae and higher plants, which is divided into grana and stroma lamellae, cyanobacteria’s thylakoids are organized into multiple concentric shells that split and fuse to form a highly connected network. This produces a continuous network that encloses a single lumen (as seen in the chloroplasts of higher plants) and allows water-soluble and lipid-soluble molecules to diffuse through the entire membrane network.

Besides that, perforations are frequently seen within the parallel thylakoid sheets. These gaps in the membrane allow particles of various sizes, such as ribosomes, glycogen granules, and lipid bodies, to move throughout the cell. The relatively large distance between the thylakoids allows for the phycobilisomes, which are external light-harvesting antennae. This macrostructure, like that of higher plants, exhibits some flexibility in response to changes in the physicochemical environment.

Many integral and peripheral membrane proteins, as well as lumenal proteins, are found in thylakoids. The thylakoid is made up of at least 335 different proteins. 89 of these are in the lumen, 116 are integral membrane proteins, 62 are stroma-side peripheral proteins, and 68 are lumen-side peripheral proteins.

Integral membrane proteins in thylakoid membranes play an important role in light-harvesting and photosynthesis’s light-dependent reactions. The thylakoid membrane contains four major protein complexes namely photosystems I and II, cytochrome b6f complex, and ATP synthase.

Photosystem II is mostly found in the grana thylakoids, while photosystem I and ATP synthase are mostly found in the stroma thylakoids and the grana’s outer layers. The cytochrome b6f complex is evenly distributed across thylakoid membranes.

Because the two photosystems in thylakoid membrane are located separately in the thylakoid membrane system, mobile electron carriers are required to shuttle electrons between them. Therefore, these mobile electron carriers are plastoquinone and plastocyanin. Plastoquinone transports electrons from the photosystem II complex to the cytochrome b6f complex, whereas plastocyanin transports electrons from the cytochrome b6f complex to the photosystem I complex.

Light energy is used by these proteins to drive electron transport chains, which generate a chemiosmotic potential across the thylakoid membrane and NADPH, a product of the terminal redox reaction. During photophosphorylation, the ATP synthase uses chemiosmotic potential to produce ATP.

These photosystems are light-driven redox centers comprised of an antenna complex that harvests light at various wavelengths using chlorophylls and accessory photosynthetic pigments such as carotenoids and phycobiliproteins. Each antenna complex contains between 250 and 400 pigment molecules, and the energy they absorb is transferred to a specialized chlorophyll a at the reaction center of each photosystem via resonance energy transfer. When either of the 2 chlorophyll a molecules at the reaction center absorbs 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 absorbs light at a maximum wavelength of 700 nm. Photosystem II contains P680 chlorophyll, which absorbs light best at 680 nm.

To fully understand the abbreviations, the letter P stands for pigment, and the number represents the specific absorption peak in nanometers for chlorophyll molecules in each reaction center.

The cytochrome b6f complex is a component of the thylakoid electron transport chain that links electron transfer to proton pumping into the thylakoid lumen. It is located between the two photosystems and transfers electrons from photosystem II-plastoquinone to plastocyanin-photosystem I.

The CF1FO-ATP synthase is a thylakoid ATP synthase that is similar to the mitochondrial ATPase. The CF1-part sticks into the stroma and is integrated into the thylakoid membrane. Thus, ATP synthesis occurs on the stromal side of the thylakoids, where ATP is required for light-independent photosynthesis reactions.

Based on their targeting signals, luminal proteins can be predicted computationally. Out of the predicted lumenal proteins containing the Tat signal in Arabidopsis, the largest groups with known functions are 19% involved in protein processing (proteolysis and folding), 18% in photosynthesis, 11% in metabolism, and 7% in redox carriers and defense.

Chloroplasts have their own genome that encodes several thylakoid proteins. However, extensive gene transfer from the chloroplast genome to the cell nucleus occurred during plastid evolution from their cyanobacterial endosymbiotic ancestors. As a result, the four major thylakoid protein complexes are encoded partially by the chloroplast genome and partially by the nuclear genome.

To ensure proper stoichiometry and assembly of these protein complexes, plants have developed several mechanisms to co-regulate the expression of the different subunits encoded in the two different organelles.

For example, regulation of the transcription of nuclear genes encoding components of the photosynthetic apparatus is done by light. Whereas, phosphorylation via redox-sensitive kinases in thylakoid membranes regulates the biogenesis, stability, and turnover of thylakoid protein complexes.

The presence or absence of assembly partners influences the translation rate of chloroplast-encoded proteins (controlled by epistasy of synthesis). This mechanism involves negative feedback via excess protein binding to the 5′ untranslated region of chloroplast mRNA.

Chloroplasts must also balance the photosystem I and II ratios for the electron transfer chain. The redox state of the electron carrier plastoquinone in the thylakoid membrane has a direct effect on the transcription of chloroplast genes encoding proteins of the photosystems’ reaction centers, thus balancing the electron transfer chain.

The region of the chloroplast between the inner membrane and the thylakoid membrane is called the lumen.

Chlorophyll a, chlorophyll b, and carotenoids are the light-harvesting molecules found in thylakoid membranes.

The formation of a proton gradient across the thylakoid layer is caused by the accumulation of protons on the internal side of the lumen and the decrease of protons in the stroma.

The thylakoid membrane is located between the stroma and the aqueous lumen of the chloroplast.

It is the location where chlorophyll is found, which is used to absorb light, which they use in biochemical reactions.

Platoquinol—plastocyanin reductase proton pump is an enzyme related to Complex III that is found in the thylakoid membrane of chloroplasts of plants, cyanobacteria, and green algae. Electron transport drives this proton pump, which catalyzes the transfer of electrons from plastoquinol to plastocyanin.

The thylakoid membrane is the site for oxygenic photosynthesis using photochemical and electron transport reactions. This also answers the question of what is a thylakoid membrane.

Photosystem II (PSII), cytochrome b6/f complex, photosystem I (PSI), and ATP synthase are thylakoid membrane protein complexes or series.

The thylakoid membrane is a saclike membrane in plant chloroplasts that are often arranged in stacks called grana and serves as the site of photosynthesis light reactions.

The part of photosynthesis that does not occur in the thylakoid membrane is the light-independent photosynthesis otherwise known as the Calvin cycle.

Because it helps in the transfer of electrons during photosynthesis from photosystem I to NADPH. 

The transfer of electrons from one protein pump to another protein pump happens.

The three molecular complexes contained in the thylakoid membrane are photosystem II (PSII), cytochrome b6f (cytb6f), and photosystem I (PSI),

The pigments in thylakoid membrane are chlorophyll and carotenoids.

It is required to synthesize ATP.

Yes, the thylakoid membrane contains a protein called ATP synthase.

The thylakoid membrane is located in the chloroplasts.

Yes, the ATP synthase is found in the thylakoid membrane.

The thylakoid membrane is stacked into the grana.

Embedded inside the thylakoid membrane are chlorophyll molecules.

This is the reaction that occurs in the thylakoid membrane in the presence of sunlight.

The damage will affect the thylakoid membrane mitochondria electron flow and the splitting of the water molecule would be affected if the thylakoid was damaged.

The flow of H+ ions across the thylakoid membrane through the ATP synthase produces ATP

The lumen proteins especially plastocyanin moves through the thylakoid membrane.

When the number of protons in the stroma decreases, protons accumulate, and the pH value in the lumen decreases, the proton gradient across the thylakoid membrane is created and it increases.

The relationship is such that the membrane is critical in chloroplasts, where it replaces the inner mitochondrial membrane in electron transport and chemiosmotic ATP generation.

The thylakoid membrane is used to absorb light that is used in biochemical reactions. This is because the membrane is where chlorophyll is found.

Embedded in the thylakoid membrane are two photosystems, named photosystem I and photosystem II.

PSII and energy from PSI pump protons from the stroma to the lumen.

The thylakoid membrane function as the site for light-dependent photosynthesis reactions.

The thylakoid is made up of membrane, lumen, granum and stroma lamellae.This is also the thylakoid membrane structure and function in light dependent reactions.

Both organelles are involved in energy transformation and they both have multiple membranes that separate their interiors into compartments.

The electron transport chain components are embedded in the thylakoid membrane.

Chemiosmosis in the thylakoid membrane is directly responsible for the formation of molecules of ATP, which are used for the formation of sugar molecules in the second stage of photosynthesis.

Protons pumped across the thylakoid membrane are essential for the synthesis of ATP.

In order to trace what events occur in the thylakoid membrane during the light-dependent reactions, one has to view the whole stages of photosynthesis. In the first stage, light dependent reactions happen in the thylakoid membrane where light energy is captured and stored as ATP.

Protons are pumped across the thylakoid membrane of the chloroplast during the electron-transport process.

The clusters are known as photosystems.

A proton gradient across the thylakoid membrane is established, with a higher concentration of protons and lower pH in the thylakoid lumen.

The purpose of the thylakoid membrane is to absorb light for photosynthesis.

They are called antenna complexes; LH or LHC

The specialized structures of photosystem I (PSI) and photosystem II (PSII), are found in the thylakoid membrane systems of cyanobacteria, as well as plant and algal chloroplasts (PSII),

They are called light-harvesting molecules.

In thylakoid membranes, chlorophyll pigments are found in packets called quantasomes.

The thylakoid membrane houses the pigments that are needed for the light reaction of photosynthesis.

The thylakoid lumen will not be intact in the punctured thylakoid, so the H+concentration ions will not be developed. As a result, ATP synthase will not function and no ATP will be synthesized.

Light-dependent reactions occur in the chloroplast thylakoid membrane.

The thylakoid membrane in an animal cell is not present.

A class of pigments that are present in the thylakoid membrane is chlorophylls.

The creation of proton gradient across the thylakoid membrane is caused by the accumulation of protons on the internal side of the lumen and the decrease of protons in the stroma.

Light-induced -proton gradients are required for ATP synthesis.

A series of carriers that pass electrons in thylakoid membrane are called photosystems.

Yes, it is possible.

The pH inside the thylakoid membrane is less than the pH of the stroma.