what is the role of water in photosynthesis?

Answer 1

Photosynthesis (photo=light, synthesis=putting together), generally, is the synthesis of sugar from light, carbon dioxide and water, with oxygen as a waste product. It is arguably the most important biochemical pathway known; nearly all life depends on it. It is an extremely complex process, comprised of many coordinated biochemical reactions. It occurs in higher plants, algae, some bacteria, and some protists, organisms collectively referred to as photoautotrophs. This article summarizes some of the major aspects of the process and provides links to more detailed articles explaining the numerous technical details, and implications, involved.

Photosynthesis uses the energy of light to make the sugar, glucose. A simplified general equation for photosynthesis follows.

6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
Carbon Dioxide + Water + Light energy → Glucose + Oxygen
Photosynthesis occurs in two stages. In the first phase light-dependent reactions or photosynthetic reactions (also called the Light reactions) capture the energy of light and use it to make high-energy molecules. During the second phase, the light-independent reactions (formerly the Dark Reactions) use the high-energy molecules to capture carbon dioxide (CO2) and make the precursors of glucose.

In the light-dependent reactions the pigment chlorophyll absorbs light and loses an electron that travels down an electron transport chain producing the high energy molecules NADPH and ATP. The chlorophyll molecule regains its electron by taking one from water, a process that releases oxygen gas.

In the Light-independent or dark reactions the enzyme RuBisCO captures CO2 from the atmosphere and in a complex process called the Calvin-Benson cycle releases 3-carbon sugars which are later combined to form glucose.

Photosynthesis may simply be defined as the conversion of light energy into chemical energy by living organisms. It is affected by its surroundings and the rate of photosynthesis is affected by the concentration of carbon dioxide, light intensity and the temperature.

Most plants are photoautotrophs, which means that they are able to synthesize food directly from inorganic compounds using light energy -for example the sun, instead of eating other organisms or relying on nutrients derived from them. This is distinct from chemoautotrophs that do not depend on light energy, but use energy from inorganic compounds.

The energy for photosynthesis ultimately comes from absorbed photons and involves a reducing agent, which is water in the case of plants, releasing oxygen as a waste product. The light energy is converted to chemical energy (known as light-dependent reactions), in the form of ATP and NADPH, which is used for synthetic reactions in photoautotrophs. Most notably plants use the chemical energy to fix carbon dioxide into carbohydrates and other organic compounds through light-independent reactions. The overall equation for carbon fixation (sometimes referred to as carbon reduction) in green plants is

n CO2 + 2n H2O + ATP + NADPH → (CH2O)n + n O2 + n H2O,
Where n is defined according to the structure of the resulting carbohydrate.
More specifically, carbon fixation produces an intermediate product, which is then converted to the final hexose carbohydrate products. These carbohydrate products are then variously used to form other organic compounds, such as the building material cellulose, as precursors for lipid and amino acid biosynthesis or as a fuel in cellular respiration. The latter not only occurs in plants, but also in animals when the energy from plants get passed through a food chain. Organisms dependent on photosynthetic and chemosynthetic organisms are called heterotrophs. In general outline, cellular respiration is the opposite of photosynthesis: glucose and other compounds are oxidised to produce carbon dioxide, water, and chemical energy. However, both processes actually take place through a different sequence of reactions and in different cellular compartments.

Plants capture light primarily using the pigment chlorophyll, which is the reason that most plants have a green color. The function of chlorophyll is often supported by other accessory pigments such as carotenes and xanthophylls. Both chlorophyll and accessory pigments are contained in organelles (compartments within the cell) called chloroplasts. Although all cells in the green parts of a plant have chloroplasts, most of the energy is captured in the leaves. The cells in the interior tissues of a leaf, called the mesophyll, contain about half a million chloroplasts for every square millimeter of leaf. The surface of the leaf is uniformly coated with a water-resistant, waxy cuticle, that protects the leaf from excessive evaporation of water and decreases the absorption of ultraviolet or blue light to reduce heating. The transparent epidermis layer allows light to pass through to the palisade mesophyll cells where most of the photosynthesis takes place.

Algae is a range from multicellular forms like kelp to microscopic, single-celled organisms. Although they are not as complex as land plants, photosynthesis takes place biochemically the same way. Very much like plants, algae have chloroplasts and chlorophyll, but various accessory pigments are present in some algae such as phycoerythrin in red algae (rhodophytes), resulting in a wide variety of colours. All algae produce oxygen, and many are autotrophic. However, some are heterotrophic, relying on materials produced by other organisms. For example, in coral reefs, there is a symbiotic relationship between zooxanthellae and the coral polyps.

Photosynthetic bacteria do not have chloroplasts (or any membrane-bound organelles), instead, photosynthesis takes place directly within the cell. Cyanobacteria contain thylakoid membranes very similar to those in chloroplasts and are the only prokaryotes that perform oxygen-generating photosynthesis, in fact chloroplasts are now considered to have evolved from an endosymbiotic bacterium, which was also an ancestor of and later gave rise to cyanobacterium. The other photosynthetic bacteria have a variety of different pigments, called bacteriochlorophylls, and do not produce oxygen. Some bacteria such as Chromatium, oxidize hydrogen sulfide instead of water for photosynthesis, producing sulfur as waste.

Water photolysis
The NADPH is the main reducing agent in chloroplasts, providing a source of energetic electrons to other reactions. Its production leaves chlorophyll with a deficit of electrons (oxidized), which must be obtained from some other reducing agent. The excited electrons lost from chlorophyll in photosystem I are replaced from the electron transport chain by plastocyanin. However, since photosystem II includes the first steps of the Z-scheme, an external source of electrons is required to reduce its oxidized chlorophyll a molecules. The source of electrons in green-plant and cyanobacterial photosynthesis is water. Two water molecules are oxidized by four successive charge-separation reactions by photosystem II to yield a molecule of diatomic oxygen and four hydrogen ions; the electron yielded in each step is transferred to a redox-active tyrosine residue that then reduces the photooxidized paired-chlorophyll a species called P680 that serves as the primary (light-driven) electron donor in the photosystem II reaction center. The oxidation of water is catalyzed in photosystem II by a redox-active structure that contains four manganese ions; this oxygen-evolving complex binds two water molecules and stores the four oxidizing equivalents that are required to drive the water-oxidizing reaction. Photosystem II is the only known biological enzyme that carries out this oxidation of water. The hydrogen ions contribute to the transmembrane chemiosmotic potential that leads to ATP synthesis. Oxygen is a waste product of light-independent reactions, but the majority of organisms on Earth use oxygen for cellular respiration, including photosynthetic organisms.

Answer 2

Photosynthesis Water

Answer 3

Water In Photosynthesis

Answer 4

Photosynthesis is a photochemical reaction in green plants. It involves the production of glucose from carbon dioxide and water, using the energy from sunlight, thus carbon dioxide is combined with water, using energy taken in from sunlight by chloroplasts. This produces oxygen as well as the plants food. Without water there is no photosynthesis and obviously no plant.

Answer 5

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what is the role of water in photosynthesis?

Answer 6

1 H2O splits apart into hydrogen and oxygen atoms.
2 The hydrogen atoms combine with carbon dioxide (CO2) to make sugar.
3 Sugar is plant food and by product is oxygen.

PHOTOSYNTHESID USES THE ENERGY OF LIGHT TO MAKE THE SUGAR, GLUCOSE. A SIMPLIFIED GENERAL EQUATION FOR PHOTO SYNTHESIS AS FOLLOWS:-

6CO2+6H2O-C6H12O6+6O2

Answer 7

In photosynthesis water is photochemically split into oxygen ,hydrogen ions and electrons in the light reation.The electrons formed are used to drive further processes and the oxygen act as the final electrons acceptor.Hence the role of water is to provide the neccessary materials required for photosynthesis to proceed.

Answer 8

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Answer 9

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