Selected Notes1 Flashcards
What are Light-Dependent Reactions?
Light energy is used to split water to produce energy-storing molecules: ATP (PSI) & NADPH (PSII). Oxygen is released as a byproduct and takes place in the thylakoid membrane.
What occurs in Photosystem II?
- Energy is absorbed by chlorophyll, electrons are energized. Water splits producing H+ protons, electrons, and O2. 2. Electrons move through the electron transport chain, losing energy as they pass through a series of electron acceptors. Protons accumulate in the thylakoid lumen. ATP Synthase combines ADP and phosphate to create ATP.
What occurs in Photosystem I?
Chlorophyll uses light to excite an electron to its own primary acceptor. This electron, along with a proton, catalyzes a reaction to form NADPH from NADP. Final products: NADPH, ATP, Oxygen.
What are Light-Independent Reactions?
Energy from Light-Dependent Reactions is used to produce glucose in the Calvin Cycle, which takes place in the stroma.
What are the steps in the Calvin Cycle?
- Carbon Fixation: RuBisCO catalyzes 3 CO2 & 3 RuBP into an unstable 6-carbon compound that splits into 2 3-PGA. 2. Reduction: NADH donates electrons to make G3P from 3-PGA using ATP and NADPH. 3. Regeneration: G3P molecules are used to make glucose or recycled to regenerate RuBP, requiring ATP.
What is RuBP carboxylase Oxygenase?
Photorespiration occurs when RuBisCO acts as an oxygenase, which has no apparent benefit due to plants evolving when atmospheric O2 levels were very low.
What is C4 Photosynthesis?
An alternate carbon fixation pathway that incorporates CO2 into 4-Carbon Acids, delivering CO2 to bundle sheath cells, creating high concentrations around RuBisCO, resulting in higher efficiency and lower photorespiration compared to C3 plants.
What are C4 Plants?
Evolved in hot-moist or arid non-saline habitats, C4 plants are more efficient in high temperatures where water and nitrogen are limiting.
What are C3 plants?
C3 plants make up 95% of plants and are more efficient in low temperatures with shade.
What is CAM photosynthesis?
Common in succulents, CAM photosynthesis is an adaptation to cope with extreme water limitation where plants open stomata at night to take in CO2 and store it for use during the day.
What are the 3 fates of glucose in plants?
- Respiration: #1 priority for energy production (ATP). 2. Excess: conversion to sucrose or starch for storage. 3. Building macromolecules using ATP from respiration, such as cellulose, lignin, DNA, amino acids, and proteins.
What is Cellular Respiration?
The conversion of oxygen and glucose to carbon dioxide and water, with the purpose of yielding ATP energy (up to 38). It does not require sunlight and consists of glycolysis and the Krebs cycle.
What is Glycolysis?
The initial stage of cellular respiration that breaks glucose down into pyruvate, investing ATP to create more ATP. It occurs in the cytoplasm and has a net gain of 2 ATP.
What occurs in the Krebs cycle?
Occurs in the mitochondria with inputs of Acetyl-CoA (oxidized pyruvate) and oxaloacetate, producing 2 CO2, 3 NADH, and 1 FADH2.
What are the respiration priorities?
- Maintenance respiration: associated with protein and membrane turnover. 2. Growth respiration: associated with synthesis of new structures in growth, nutrient uptake, and phloem loading.
What is the carbon balance in plants?
Carbon must ‘break even’ for plants to stay alive, and a positive carbon balance must occur for growth to happen.
What is the light compensation point?
The light level where photosynthesis carbon input offsets loss from respiration. It is important for carbon balances because if more carbon is used up than produced, the plant will struggle to grow or die.
What are the effects of temperature on plants?
Light levels above the light compensation point usually result in a positive carbon balance. Higher temperatures rapidly increase respiration rates.
Why is water important for plants?
Water is crucial for plant growth and distribution and is a reactant in many chemical reactions, including photosynthesis.
What is turgor pressure?
Water inflates leaves and stems, necessary for cell enlargement, growth, and maintenance. It regulates stomatal opening/closing.
What is osmotic potential?
The presence of dissolved solutes in water lowers osmotic potential when solute dissolves in water.
What is cohesion in plants?
Cohesion refers to water sticking to water.