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Chapter 8:Photosynthesis - Coggle Diagram
Chapter 8:Photosynthesis
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Photosynthesis: is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process takes place in chloroplasts, specialized organelles containing chlorophyll, a pigment that captures light energy.
steps in photosynthesis:
Light Absorption: Light energy is absorbed by chlorophyll, primarily found in the chloroplasts of plant cells. This light absorption initiates the process of photosynthesis.
Water Splitting (Photolysis): In the presence of light, water molecules are split into oxygen, protons (H+ ions), and electrons. This reaction occurs in the thylakoid membrane of the chloroplasts.
Formation of ATP and NADPH:
The electrons generated during water splitting are used to create energy-rich molecules, adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide phosphate (NADPH).
Carbon Fixation (Calvin Cycle):
In the stroma of the chloroplasts, the Calvin Cycle incorporates carbon dioxide from the atmosphere into organic molecules.ATP and NADPH, produced in the earlier stages, provide the energy and reducing power needed for this process.
Glucose Synthesis: The organic molecules produced in the Calvin Cycle are used to synthesize glucose and other carbohydrates. Glucose serves as an energy storage molecule for the plant.
Oxygen Release: As a byproduct of water splitting, oxygen is released into the atmosphere. This oxygen is crucial for the respiration of many living organisms.
C3 and C4 plants are two different types of plants based on the pathway they use for photosynthesis.
C3 Plants:
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First Stable Product: The first stable product of carbon fixation is a three-carbon compound, 3-phosphoglyceric acid (PGA).
Efficiency: C3 plants are generally less efficient in photosynthesis under high-temperature and arid conditions due to a process called photorespiration.
Examples: Most plants, including rice, wheat, and soybeans, are C3 plants.
C4 Plants:
Pathway: C4 plants use a modified pathway for carbon fixation, involving the Calvin cycle and an additional step in the mesophyll cells, forming a four-carbon compound (oxaloacetate).
First Stable Product: The first stable product of carbon fixation is a four-carbon compound, usually malate or aspartate.
Efficiency: C4 plants are more efficient in photosynthesis under high-temperature and arid conditions compared to C3 plants. They have a higher CO2 concentration around the enzyme responsible for initial carbon fixation, which reduces photorespiration.
Examples: Examples of C4 plants include corn (maize), sugarcane, and certain grasses.
There are two main types of photosystems, Photosystem I (PSI) and Photosystem II (PSII)
Photosystem II (PSII):
Reaction Center Chlorophyll: PSII contains a pair of special chlorophyll molecules known as P680 chlorophylls. These chlorophylls absorb light with a wavelength of 680 nanometers.
Protein Complexes: PSII is composed of several protein complexes, including the core complex (D1 and D2 proteins), the oxygen-evolving complex (OEC), and several peripheral antenna complexes.
Water Splitting (Oxygen-Evolving Complex): PSII is responsible for the photolysis of water molecules into oxygen, protons, and electrons. The oxygen-evolving complex (OEC) is critical for this process.
Electron Transport Chain: PSII is part of the electron transport chain in the thylakoid membrane. After absorbing light, P680 chlorophylls donate electrons to the primary electron acceptor, initiating the flow of electrons through the electron transport chain.
Photosystem I (PSI):
Reaction Center Chlorophyll:
PSI contains a pair of chlorophyll molecules known as P700 chlorophylls. These chlorophylls absorb light with a wavelength of 700 [nanometers.
Protein Complexes: PSI consists of several protein complexes, including the core complex (PsaA and PsaB proteins) and peripheral antenna complexes.
Electron Transport Chain: The electrons that flow through the electron transport chain from PSII are ultimately accepted by PSI. PSI is responsible for reducing NADP+ to NADPH, a key molecule in the production of carbohydrates during the Calvin cycle.
Ferredoxin and NADP+ Reductase: PSI transfers electrons to ferredoxin, and then ferredoxin passes electrons to NADP+ through the enzyme NADP+ reductase. This results in the production of NADPH.