Chloroplasts and Photosynthesis Flashcards

Chloroplasts and Photosynthesis

• Chloroplasts convert light energy into chemical energy through photosynthesis.
• Chlorophyll is the green pigment located inside the thylakoid membrane that traps light energy.
• Carotenoids are orange and yellow pigments that absorb light and transfer energy to chlorophyll a.
• Chloroplast membranes consist of an inner membrane, outer membrane with pores, and thylakoid membrane enclosing the thylakoid lumen.
• The stroma is a fluid-filled space in the chloroplast that contains enzymes and the internal thylakoid membrane system; comparable to the mitochondrial matrix.
• The thylakoid lumen is the innermost compartment of chloroplasts, filled with fluid.
• Photosynthesis transforms light energy into chemical energy, creating carbohydrates and oxygen.
• The overall photosynthesis reaction is: 6 CO2 + H2O → glucose + 6 O2; CO2 is reduced in this process.
• Chloroplasts are primarily found in mesophyll cells of leaves, which contain air spaces and water vapor.
• The thylakoid membrane organizes into stacks called grana, where pigments and electron acceptors are embedded.
• Thylakoids are disc-like sacs suspended in the stroma, interconnected for efficient functioning.
• Grana refer to the stacked structures of thylakoid sacs.
• The thylakoid membrane encloses the thylakoids and is crucial for ATP synthesis.
• Pigments absorb light at distinct wavelengths and play key roles in photosynthesis.
• Chlorophyll is structured with a porphyrin ring that absorbs light and contains magnesium, with a long hydrocarbon side chain for membrane anchoring.
• Chlorophyll A and B differ by their terminal group: A has a methyl group and appears bright green, while B has a carbonyl group and appears green/yellow.
• P680+ is the strongest biological oxidizing agent, while P700, activated by light, is the strongest biological reducing agent.
• Antenna complexes, made of chlorophyll and other pigments, act like "satellite dishes" for trapping photons, located in the thylakoid membrane with a reaction center at their core.
• Resonance transfer occurs in the reaction center, where energy from absorbed photons is passed among pigments until reaching the reaction center.
• The reaction center consists of a special chlorophyll pair, absorbing at the longest wavelengths and promoting an electron to a higher energy state for donation to an electron acceptor.
• Photosystems I and II are connected via the electron transport chain (ETC).
• Electrons entering the ETC originate from P680 molecules in the reaction center of photosystem II.
• A proton gradient exists across the thylakoid membrane, with pH in the thylakoid lumen at 5 and in the stroma at 8.
• The ETC is coupled with proton movement across the thylakoid membrane, as energy released by electrons is used to pump protons into the thylakoid lumen.
• ATP production occurs in the stroma, utilizing ATP synthase activity.
• The Calvin cycle, responsible for carbon fixation, takes place in the stroma.
• Photolysis is the process where light energy splits water into an oxygen molecule and two protons, aiding proton gradient maintenance.
• ATP synthase activity in photosynthesis is driven by the proton motive force and its projection into the stroma.