Where Do The Electrons Come From In Photosynthesis

Where Do The Electrons Come From In Photosynthesis?

In (a) photosystem II the electron comes from the splitting of water which releases oxygen as a waste product. In (b) photosystem I the electron comes from the chloroplast electron transport chain. The two photosystems absorb light energy through proteins containing pigments such as chlorophyll.In (a) photosystem I

photosystem I
Photosystem I (PSI or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae plants and cyanobacteria. … The combined action of the entire photosynthetic electron transport chain also produces a proton-motive force that is used to generate ATP.

How are electrons created in photosynthesis?

The light reactions of photosynthesis use energy from photons to generate high-energy electrons (Figure 19.2). These electrons are used directly to reduce NADP+ to NADPH and are used indirectly through an electron-transport chain to generate a proton-motive force across a membrane.

What is the source of electrons for photosynthesis in plants?


The source of energized electrons flowing in the ETC during photosynthesis is sunlight.

Where do electrons come from in cellular respiration?

All of the electrons that enter the transport chain come from NADH and FADH 2​start subscript 2 end subscript molecules produced during earlier stages of cellular respiration: glycolysis pyruvate oxidation and the citric acid cycle.

Where do the electrons entering photosystem II come from?

Photosystem II obtains replacement electrons from water molecules resulting in their split into hydrogen ions (H+) and oxygen atoms. The oxygen atoms combine to form molecular oxygen (O2) which is released into the atmosphere. The hydrogen ions are released into the lumen.

What is the source of electrons?

Electrons are present in all matter but in an electrical circuit there must be a source of high-energy electrons. This source is often a) dry cell wet cell or battery from which the high-energy electrons can flow and then be returned after their energy is used.

Where do plants get electrons from?

Light reactions occur when plants synthesize food from carbon dioxide and water referring specifically to the part of energy production that requires light and water to generate electrons needed for further synthesis. Water provides the electrons by splitting into hydrogen and oxygen atoms.

What does photosynthesis produce?

Photosynthesis is the process by which plants use sunlight water and carbon dioxide to create oxygen and energy in the form of sugar.

What are electron carriers in photosynthesis?

Electron carrier molecules are arranged in electron transport chains that produce ATP and NADPH which temporarily store chemical energy. The light reactions capture energy from sunlight which they change to chemical energy that is stored in molecules of NADPH and ATP.

What is electron transport in photosynthesis?

Photosynthetic electron transport is the first stage of photosynthesis that produces chemically stored energy and uses solar photons to drive electron transport against a thermodynamic gradient.

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Where do the protons and electrons come from that are used in the electron transport chain?

Figure 1. The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen. In the process protons are pumped from the mitochondrial matrix to the intermembrane space and oxygen is reduced to form water.

What is produced in photosystem 2?

Photosystem II is the first membrane protein complex in oxygenic photosynthetic organisms in nature. It produces atmospheric oxygen to catalyze the photo-oxidation of water by using light energy. It oxidizes two molecules of water into one molecule of molecular oxygen.

Where do replacement electrons come from in the light reactions?

When light energy is absorbed by pigments and passed inward to the reaction center the electron in P700 is boosted to a very high energy level and transferred to an acceptor molecule. The special pair’s missing electron is replaced by an electron from PSII (arriving via the electron transport chain).

What is produced in photosystem 2 quizlet?

Photosystem II produces a proton gradient that drives the synthesis of ATP.

What is the thermionic electron source?

Thermionic emission of electron

Thermionic sources rely on heat to generate electrons similar to how light is produced by incandescent lightbulbs. … Just like a tungsten filament these crystals are heated by an applied current until there is enough energy to emit electrons.

What is the source of electrons in electron microscope?

The electron gun and condenser system

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The source of electrons the cathode is a heated V-shaped tungsten filament or in high-performance instruments a sharply pointed rod of a material such as lanthanum hexaboride.

What is the thermionic source used in TEM for electrons?

LaB6 is the only thermionic source used in modern TEMs so we’ll just describe these. The LaB6 crystal is used as the cathode in a triode gun shown in Figure 5.1. In addition to the cathode there is a grid called a Wehnelt cylinder and an anode at earth potential with a hole in its center.

What is photosynthesis explain the process of photosynthesis in the plants?

photosynthesis the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants light energy is captured and used to convert water carbon dioxide and minerals into oxygen and energy-rich organic compounds.

How does photosynthesis start?

Photosynthesis begins when light strikes Photosystem I pigments and excites their electrons. The energy passes rapidly from molecule to molecule until it reaches a special chlorophyll molecule called P700 so named because it absorbs light in the red region of the spectrum at wavelengths of 700 nanometers.

How does photosynthesis occur in plants?

Photosynthesis takes place inside plant cells in small objects called chloroplasts . Chloroplasts contain a green substance called chlorophyll . This absorbs the light energy needed to make photosynthesis happen. … Plants get carbon dioxide from the air through their leaves and water from the ground through their roots.

How do you make photosynthesis?

To perform photosynthesis plants need three things: carbon dioxide water and sunlight. for photosynthesis. Carbon dioxide enters through tiny holes in a plant’s leaves flowers branches stems and roots. Plants also require water to make their food.

What is produced in cyclic electron flow?

In cyclic electron flow (CEF) electrons are recycled around photosystem I. As a result a transthylakoid proton gradient (ΔpH) is generated leading to the production of ATP without concomitant production of NADPH thus increasing the ATP/NADPH ratio within the chloroplast.

What is the role of electrons in photosynthesis?

Electron transport helps establish a proton gradient that powers ATP production and also stores energy in the reduced coenzyme NADPH. … This energy is used to power the Calvin Cycle to produce sugar and other carbohydrates.

Where does the electron transport chain take place?


The electron transport chain is a series of four protein complexes that couple redox reactions creating an electrochemical gradient that leads to the creation of ATP in a complete system named oxidative phosphorylation. It occurs in mitochondria in both cellular respiration and photosynthesis.

How many electrons are transferred in photosynthesis?

The total number of quanta required therefore to transfer the four electrons that result in the formation of one molecule of oxygen via the two light reactions should be four times two or eight. It appears however that additional light is absorbed and used to form ATP by a cyclic photophosphorylation pathway.

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Where did these electron acceptor molecules come from?

The electron acceptor molecules come from glycolysis the link reaction and krebs cycle.

What is the source of electrons for the chloroplast electron transport chain?

What is the initial source of electrons for the chloroplast electron transport chain? Water is the initial source. The reaction center contains a pair of chlorophyll a molecules with a special property.

How are the protons H +) from #7 produced where?

How are the protons (H+) from #7 produced? … In most cases the proton-motive force is generated by an electron transport chain which acts as a proton pump using the Gibbs free energy of redox reactions to pump protons (hydrogen ions) out across the membrane separating the charge across the membrane.

Where do photosystem 1 electrons come from?

Photosystem I receives electrons from plastocyanin or cytochrome c6 on the lumenal side of the thylakoid membrane and uses light energy to transfer them across the membrane to ferredoxin on the stromal side. It can also function in a cyclic electron transport pathway.

Where is o2 produced in photosynthesis?

The chloroplast is involved in both stages of photosynthesis. The light reactions take place in the thylakoid. There water (H2O) is oxidized and oxygen (O2) is released. The electrons that freed from the water are transferred to ATP and NADPH.

What is the produced in the Calvin cycle?

Products. The immediate products of one turn of the Calvin cycle are 2 glyceraldehyde-3-phosphate (G3P) molecules 3 ADP and 2 NADP+. (ADP and NADP+ are not really “products”. They are regenerated and later used again in the Light-dependent reactions).

Which of the following is produced during light phase of photosynthesis?

Light reactions need light to produce organic energy molecules. They are initiated by colored pigments mainly green colored chlorophylls. Light reaction occurs inside thylakoids. The function of this phase is to produce NADPH and energy-rich ATP molecules.

Where does the light independent reaction of photosynthesis occur what is produced?

The light-independent reactions of photosynthesis take place within the stroma. It contains enzymes that work with ATP and NADPH to “fix” carbon from carbon dioxide into molecules that can be used to build glucose.

Where do the light dependent reactions of photosynthesis occur in the chloroplast?

Light-dependent reactions happen in the thylakoid membrane of the chloroplasts and occur in the presence of sunlight. The sunlight is converted to chemical energy during these reactions. The chlorophyll in the plants absorb sunlight and transfers to the photosystem which are responsible for photosynthesis.

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