C1.3 Photosynthesis HL Flashcards
Photosystems
Complexes of pigments and proteins in photosynthetic membranes that absorb light and generate excited electrons.
Advantage of Pigment Arrays
Arrays allow absorption of light across a broader range of wavelengths, enhancing the efficiency of photosynthesis.
Reaction Centre
A specific chlorophyll molecule in a photosystem where a photochemical reaction occurs, emitting an excited electron
Photolysis of Water
Process in photosystem II where water is split to replace lost electrons, producing oxygen as a waste product.
Chlorophyll a and b
Primary pigments in photosystems; chlorophyll a is at the reaction centre, and both pigments absorb light of different wavelengths.
Photosystem I vs. Photosystem II
PS I is most sensitive to 700 nm light; PS II is most sensitive to 680 nm light and is the first activated in the light-dependent reactions.
Oxygen Generation in Photosynthesis
Oxygen is produced as a by-product during the photolysis of water in photosystem II, contributing to the light-dependent reactions.
Chemiosmosis
Process in thylakoids producing ATP from ADP during photosynthesis, driven by a proton gradient across the thylakoid membrane
Cyclic Photophosphorylation
A type of photophosphorylation where electrons from photosystem I return to it after ATP production, not producing NADPH
Non-Cyclic Photophosphorylation
Photophosphorylation process involving both photosystems, producing ATP and NADPH by transferring electrons to NADP+.
Reduction of NADP in Photosynthesis
Process where NADP+ accepts electrons and H+ ions to become NADPH, catalyzed by photosystem I
Role of Thylakoid in Photolysis
Thylakoids provide space for water splitting, releasing oxygen and providing electrons for the light-dependent reactions
Importance of Thylakoid Membrane
Houses photosystems, electron transport chain, and ATP synthase; essential for chemiosmosis and ATP production
Photophosphorylation
The process of converting ADP to ATP using light energy during photosynthesis, occurring in thylakoids
Rubisco in Carbon Fixation
Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes the fixation of atmospheric CO2 by adding it to RuBP, forming two molecules of glycerate 3-phosphate (GP). It’s a crucial step in the Calvin cycle.
Glycerate 3-Phosphate to Triose Phosphate
Glycerate 3-phosphate (GP) is converted to triose phosphate using ATP for energy and reduced NADP for adding hydrogen. This step is critical for synthesizing glucose.
Regeneration of RuBP
In the Calvin cycle, RuBP is regenerated from triose phosphate, using the energy of ATP. This step is essential for the cycle’s continuation.
Importance of Rubisco
Rubisco is significant because it initiates the process of carbon fixation in the Calvin cycle, leading to the production of carbohydrates in photosynthetic organisms.
Role of ATP in Calvin Cycle
ATP provides the necessary energy for synthesizing triose phosphate from GP and for regenerating RuBP from triose phosphate.
Role of Reduced NADP
Reduced NADP is used in the Calvin cycle to add hydrogen to GP, converting it into triose phosphate, an important step in glucose synthesis.
Calvin Cycle Efficiency
The Calvin cycle requires a high concentration of Rubisco due to its slow nature and high energy requirement, making it relatively inefficient at low CO2 concentrations.
Triose Phosphate
A product of the Calvin cycle, triose phosphate is the basis for synthesizing various carbon compounds in plants, such as carbohydrates, amino acids, and fatty acids.
Calvin Cycle Role in Carbon Compound Synthesis
The Calvin cycle synthesizes carbohydrates, amino acids, fatty acids, and nucleotides in plants. Each compound follows its specific metabolic pathway.
Calvin Cycle’s Connection to Nucleotides
The Calvin cycle contributes to nucleotide synthesis by providing ribose sugar, derived from triose phosphate. Nucleotides are crucial for DNA and RNA formation.
Light-Dependent Reactions’ Products
The light-dependent reactions of photosynthesis produce ATP and reduced NADP, which are essential for driving the light-independent reactions.
Light-Independent Reactions’ Dependency
Light-independent reactions depend on the products of light-dependent reactions (ATP and reduced NADP) and cannot continue in the absence of light.
Interdependence of Photosynthesis Reactions
Light-dependent reactions require NADP and ADP, while light-independent reactions need ATP and reduced NADP, illustrating their mutual dependency.
Impact of CO2 on Light-Dependent Reactions
A lack of CO2, halting light-independent reactions, can severely impede the light-dependent reactions due to reduced availability of NADP and ADP.
