Light Dependent Reactions In Chloroplasts Of A Plant

Light intensity is a key component in photosynthesis, amongst carbon dioxide and water to sustain a suitable rate of photosynthesis. Chlorophyll absorbs the light, causing photoexcitation and the formation of NADPH and ATP with production of O2 as a by-product. The Calvin Cycle takes the NADPH and ATP to reduce CO2 into sugars (CH2O), and return NADP+ and ADP + Pi to the light reactions. The process will then repeat. (Reece, et al, 2015)

Photosynthesis is the process by which plants use light to synthesize food from H2O and CO2 within the thylakoid and the stroma of the cells. In order for photosynthesis to occur, light must be present. Light reactions occur within the thylakoids of the chloroplasts by absorbing light and H2O and producing oxygen gas, ATP, or Adenosine triphosphate, and NADPH, or nicotinamide adenine dinucleotide phosphate. The oxygen gas is released back into the atmosphere while ATP and NADPH are inputs of the Calvin Cycle within the stroma. The Calvin Cycle uses these two molecules, in addition to carbon dioxide gas, to produce ADP, or Adenosine diphosphate, NADP+, and glucose molecules. Photosynthesis is represented by the following equation:

The effects of light intensity and light wavelength on photosynthesis was observed in two different experiments and closer study of different pigments in spinach was observed. For the experiment where the effects of light was observed, it was found that a light intensity of 30 cm, wavelengths of blue and red lights show the greatest photosynthetic activity. The different pigments present is spinach were also observed and it was noted that though chlorophyll is the most abundant in plants, there are other pigments present as well.

The process of photosynthesis, by which light energy is used to convert inorganic compounds into organic substances with the release of oxygen, may be the most important biological event sustaining life (Keir et al. 2017). In the light-dependent reactions, the chloroplasts of a plant use the pigment chlorophyll to convert light energy into chemical energy. This energy is used to split water and produce oxygen (Eller et al. 2015). The energy is later used in the light independent reactions, where carbon dioxide (CO2) undergoes carbon fixation with the aid of enzyme rubisco, because it catalyses both carboxylation and oxygenation reactions and most of responses of photosynthesis to light, CO2, and temperature (John Evans 2013).

In light reactions, light is absorbed by chlorophyll in the thylakoid membrane and energizes the electrons. ATP is created from ADP and P. NADP accepts electrons and turns in to NADPH, which is energy. Once the light reactions have taken place, the light-independent, or ‘dark’ reaction occurs in the stroma, where CO2 is converted to sugar. The

The process of photosynthesis needs light in its reactions as well as the Calvin cycle

The light dependent reactions in a cell uses the suns energy to produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate) for the Calvin cycle. The process starts when light strikes an electron in the absorption pigments in the leaves of the plant. The electron jumps away onto the electron transport chain, and the absorption pigment is left with a positive charge. This pulls electrons off of the hydrogen atoms in water in the nearby lumen. This causes an imbalance in the concentration of positive ions between the lumen and the stroma, causing the protons to leave the lumen and move into the stroma.

This light is then converted into a chemical energy by the chlorophyll and other pigments within the plant. This energy is used for the process of photosynthesis. During photosynthesis, water molecules split apart, releasing electrons and hydrogen ions and producing oxygen gas. These electrons and hydrogen ions are then used to generate ATP and NADPH. Both ATP and NADPH are also used in the light independent reaction, which is the second part of photosynthesis. This reaction occurs in the stroma of the chloroplasts. In contrast to the light dependent reaction, this type of reaction can occur without light. During the light independent reactions of photosynthesis ATP and NADPH are required to form glucose. Adenosine triphosphate, often called ATP, is used to construct organic molecules from carbon dioxide and water. Nicotinamide adenine dinucleotide phosphate, often called NADPH, reduces carbon dioxide and produces monosaccharides for use by the plant.

During photosynthesis, the section that is light dependent stage is in the thylakoids in the Mitochondria of a plant cell, while the light independent stage is in the stroma of the Mitochondria of a plant cell, specifically named the Calvin cycle. The light dependent and light independent stage work together to perform photosynthesis. The light independent gives ATP and NADPH to the light independent stage. In return, the light independent stage gives the light dependent stage NADP+ and ADP. The light dependent stage works in the thylakoids of the Mitochondria in a plant cell. It starts off by light energy being absorbed by photosystem II,

This is known as the light dependent reaction of photosynthesis. The goal of photophosphorylation is to take the energy from sunlight and convert it into chemical energy for the Calvin cycle. The Calvin cycle then takes this chemical energy and uses it to make glucose. Photophosphorylation begins when a photon (packet of light) is absorbed by a pigment (light absorbing molecule), which is attached to a protein along the thylakoid membrane of the chloroplast. The energy from the photon creates resonance (electron passing from one pigment to the next), which eventually reaches a special reaction center. The reactions center is a protein that houses a special pair of chlorophyll molecules capable of releasing electrons. When the chlorophyll molecules get excited, they release two electrons. These two electrons then move along the membrane through a series of specialized protein releasing energy as they go. This action creates an H+ gradient inside the lumen of the chloroplast. Eventually the electrons reach the end of the chain and attach onto electron carriers. The H+ flow across the ATP Synthase protein where they meet up with ADP (andesine diphosphate) and Pi (phosphate group) to from ATP. The chemical energy created can then be used in the Calvin

The main source of energy in photosynthesis is light energy, which is converted to glucose sugar, and later converted into ATP to provide energy to the cells. In the first phase, photons of sunlight hit the thylakoid membrane, exciting chloroplast molecules, inducing the transport of the electrons extracted from water splitting to form oxygen, down an electron transport chain, much like the one in cellular respiration. In this electron transport chain, the final electron acceptor is NADP+, which is reduced to NADPH to be used later in the Calvin cycle. Much like in cellular respiration, a proton gradient builds up within the thylakoid, and protons are passively transported from the thylakoid lumen to the chloroplast stroma through the enzyme, ATP synthase which phosphorylates ADP to make ATP. This type of chemiosmosis of protons to create ATP energy is uniquely called photophosphorylation. In photosynthesis, carbon dioxide is taken up from the atmosphere from the plants’ stomata, ultimately to create glucose molecules. The oxygen released from water splitting by photosystem II is crucial for almost all life. Overall, the process of photosynthesis is anabolic, as it builds up a large molecule, glucose from less complex smaller molecules, while requiring energy to do so.

Most enzymes in the important process of photosynthesis are usually embedded in the stroma in thylakoid membranes. The stroma is filled with fluid surrounding the grana and also has a part in the syntheses of organic molecules from water and carbon dioxide. After that production of the starch or sugar moves out into the stroma. That is where the enzymes take carbon from carbon dioxide then mixes it with oxygen and hydrogen to make a carbohydrate molecule. The function is generally known as the Light-independent reactions or the dark reactions.

The system that converts light energy to chemical energy is through the function thylakoid system. The fluid that is inside the membrane envelope and the outside of the thylakoid is called the stroma. The chloroplast has mainly two steps in the process of photosynthesis in plant cells. The first one is energy transferring known as the light dependent or light reactions. the second step is carbon fixation reactions known as the dark reactions.

     Photosynthesis has a two-stage performance before plants produce the two products they are known to produce. These stages are Photosystem I and II. Photosystem II is dependant on light reactions for energy which causes the electrons to be react and be transferred to Photosystem II. The electrons are transported through the Photosystem II electron transport system, however some energy is used to drive ATP synthesis. Meanwhile, light is being absorbed by the Photosystem I, which causes the electrons to react. This process sends the electrons to the Photosystem I transport system where some energy is released as electrons travel through the electron transport system and is captured as NADPH. When this process is completed oxygen is released from the plant and glucose has been

     To metabolic pathways involved in photosynthesis are light reaction and dark reaction. The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. Light absorbed by chlorophyll or other photosynthetic pigments is used to drive a transfer of electrons and hydrogen from water to and acceptor called NADP , reducing it to the form of NADPH by adding a pair of electrons and a single proton. The water or some other donor molecule is split in the process. The light reaction also generates ADP, a process called photophosphorylation. ATP is a versatile source of chemical energy used in most biological processes. The light reaction produces no carbohydrates such as sugars.