Photoautotrophs absorb and convert light energy into the stored energy of chemical bonds in organic molecules through a process called photosynthesis.
Plants, algae, and cyanobacteria are known as oxygenic photoautotrophs because they synthesize organic molecules from inorganic materials, convert light energy into chemical energy, use water as an electron source, and generate oxygen as an end product of photosynthesis.
Oxygenic photosynthesis is composed of two stages: the light-dependent reactions and the light-independent reactions.
The light-independent reactions use the ATP and NADPH from the light-dependent reactions to reduce carbon dioxide and convert the energy to the chemical bond energy in carbohydrates such as glucose.
The light-independent reactions can be summarized as follows: 12 NADPH + 18 ATP + 6 CO2 yields C6H12O6 (glucose) + 12 NADP+ + 18 ADP + 18 Pi + 6 H2O.
Most plants use the Calvin cycle to fix CO2. To begin the Calvin cycle, a molecule of CO2 reacts with a five-carbon compound called ribulose bisphosphate (RuBP) producing an unstable six-carbon intermediate which immediately breaks down into two molecules of the three-carbon compound phosphoglycerate (PGA).
The energy from ATP and the reducing power of NADPH (both produced during the light-dependent reactions) is now used to convert the molecules of PGA to glyceraldehyde-3-phosphate (G3P), another three-carbon compound.
Most of the G3P produced during the Calvin cycle are used to regenerate the RuBP so that the cycle may continue, however, some of the molecules of G3P, however, are used to synthesize glucose and other organic molecules.
The light-dependent reactions convert light energy into chemical energy, producing ATP and NADPH. The light-dependent reactions can be summarized as follows: 12 H2O + 12 NADP+ + 18 ADP + 18 Pi + light and chlorophyll yields 6 O2 + 12 NADPH + 18 ATP.
The light-independent reaction in such detail as to show that: carbon dioxide reacts with ribulose bisphosphate (RuBP) to form two molecules of glycerate 3-phosphate (GP). This reaction is catalysed by the enzyme rubisco. ATP and reduced NADP from the light-dependent reaction are used to reduce GP to triose phosphate.
Photosynthesis occurs in the chloroplasts, the light-dependent reactions are located on the innermost membrane of chloroplasts called thylakoid membrane and light-independent reactions occur in the cytoplasm of the chloroplasts called stroma [17].
The light-dependent reactions release oxygen as a byproduct as water is broken apart. In the Calvin cycle, which takes place in the stroma, the chemical energy derived from the light-dependent reactions drives both the capture of carbon in carbon dioxide molecules and the subsequent assembly of sugar molecules.
Krebs cycle and electron transport cannot proceed, and glycolysis produces just 2 ATP molecules per glucose molecule. Under aerobic conditions, the Krebs cycle and electron transport enable the cell to produce 34 more ATP molecules per glucose molecule.
The light-independent reactions can be summarized as follows: 12 NADPH + 18 ATP + 6 CO2 yields C6H12O6 (glucose) + 12 NADP+ + 18 ADP + 18 Pi + 6 H2O. Most plants use the Calvin cycle to fix CO2.
In the stroma, in addition to CO2, two other components are present to initiate the light-independent reactions: an enzyme called ribulose bisphosphate carboxylase (RuBisCO), and three molecules of ribulose bisphosphate (RuBP), as shown in Figure 2. RuBP has five atoms of carbon, flanked by two phosphates.
AKA Calvin cycle. A dark reaction (does not need light energy as long as it has ATP and NADPH) in the chloroplasts of plants using carbon dioxide to convert carbon dioxide (CO2) into organic molecules called carbohydrates.
The Calvin cycle refers to the light-independent reactions in photosynthesis that take place in three key steps. Although the Calvin Cycle is not directly dependent on light, it is indirectly dependent on light since the necessary energy carriers ( ATP and NADPH) are products of light-dependent reactions.
The light reactions of photosynthesis describe the pathway in which electrons are removed from water and transferred to NADP+ or ferredoxin to generate reduced cofactors for biosynthetic metabolism (reviewed in Nelson and Ben-Shem, 2004).
The standard photosynthetic pathway is C3 photosynthesis named after the first stable compound produced after fixation of CO2 by RubisCO, the three-carbon organic acid 3-phosphoglyceric acid (3PGS), which is then reduced to carbohydrate in the Calvin cycle.
In the light-dependent reactions, energy absorbed by sunlight is stored by two types of energy-carrier molecules: ATP and NADPH. The energy that these molecules carry is stored in a bond that holds a single atom to the molecule. For ATP, it is a phosphate atom, and for NADPH, it is a hydrogen atom.
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. The chloroplast's own genetic material (separate from that of the cell) is also stored in the stroma.
The light-independent reactions of photosynthesis, also known as the Calvin cycle, mainly produce organic sugar molecules. These reactions use ATP and NADPH generated from the light-dependent reactions to convert carbon dioxide (CO2) into these sugars.
In a process called non-cyclic photophosphorylation (the "standard" form of the light-dependent reactions), electrons are removed from water and passed through PSII and PSI before ending up in NADPH. This process requires light to be absorbed twice, once in each photosystem, and it makes ATP .
The Light Reactions of Photosynthesis. Light is absorbed and the energy is used to drive electrons from water to generate NADPH and to drive protons across a membrane. These protons return through ATP synthase to make ATP.
During the process of photosynthesis, light penetrates the cell and passes into the chloroplast. The light energy is intercepted by chlorophyll molecules on the granal stacks. Some of the light energy is converted to chemical energy. During this process, a phosphate is added to a molecule to cause the formation of ATP.
In Dark Reaction, 6 ATPs are required for converting 6 molecules of phosphoglycerate into 6 molecules of Bisphosphoglycerate. Since 2 Dark Reactions take place to produce one glucose molecule, therefore 12 ATPs are required in Dark Reaction to produce 1 glucose molecule.
Introduction: My name is Chrissy Homenick, I am a tender, funny, determined, tender, glorious, fancy, enthusiastic person who loves writing and wants to share my knowledge and understanding with you.
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