Photosynthesis: Light-Dependent Reactions (PDF)

Light independent reactions of photosynthesis take place in the thylakoid membranes A stack of thylakoid membranes are called grana. The pigment that is responsible for capturing light energy during photosynthesis is chlorophyll Photosynthesis occurs in the chloroplasts Thylako...

Light independent reactions of photosynthesis take place in the thylakoid membranes A stack of thylakoid membranes are called grana. The pigment that is responsible for capturing light energy during photosynthesis is chlorophyll Photosynthesis occurs in the chloroplasts Thylakoid is a membrane structure that takes place in the chloroplasts. The primary role of the xylem plant is transporting water and nutrients from the roots Phloem brings sugars (glucose) produced by photosynthesis and brings it to different plant parts. Photosynthesis captures sunlight and converts it into co2 and water into glucose. The plant tissue that transports nutrients such as glucose is called phloem. Stoma allows gas exchange. During the light dependent reactions, ATP and Oxygen are produced as a result of sunlight being converted into chemical energy. ATP is used as an energy source to be utilized during the synthesis of glucose in the light independent reactions. Glucose’s primary function is to serve as energy storage. The substances that are reactants required for the light dependent reactions are water and sunlight. Glucose has more stored energy compared to ATP. Glycogen is the polymer form of glucose used for energy storage in animals not plants. ATP is the main energy carrying molecule. Light dependent reactions convert light energy into chemical energy, Glucose is the primary energy source for many organisms. ATP is the energy currency in the cell Stored energy is the energy formed in chemical bonds. Stomata lets the water and carbon dioxide/co2 enter the plant cell. Chemosynthesis occurs in certain bacteria. The process of breaking water a part using the sun’s energy is called photolysis. The thylakoids are important because thats the location where the light dependent reactions of photosynthesis occur. Xylem transports water and dissolved nutrients to the cells. Mesophyl is the primary site of photosynthesis Pholem transports glucose and other organic nutrients. In photosynthesis carbon goes from co2 to glucose The main role of light energy in photosynthesis is to convert light energy into chemical energy. NADPH is the energy carrying molecule formed in light reactions. Carotenoids are pigments that capture sunlight energy. Chlorophyll A is the main pigment in photosystems. Chlorophyll B is the accessory pigment for capturing light. NADP+ gains electrons and is a reduced form of NADPH (transforms) into NADPH during the light dependent reactions. The gas that is produced during the photolysis of water is oxygen. During the light reactions of photosynthesis water is split which results in hydrogen ions and oxygen gas. Autotrophs and Heterotrophs Autotrophs produce their own food using photosynthesis or chemosynthesis. Heterotrophs consume other organisms for energy. Food Chains Autotrophs are the primary producers. Herbivores are primary consumers. Carnivores are secondary consumers. Scavengers and decomposers consume other consumers. Photosynthesis in Chloroplasts Photosynthesis occurs in chloroplasts. Light-dependent reactions happen in thylakoid membranes. Light-independent reactions (Calvin cycle) occur in stroma. Thylakoids are stacks called grana. Photosynthesis Location in the Leaf Photosynthesis happens in the stoma and mesophyll of the leaf. Xylem brings water, phloem brings glucose. Pigments and Photosynthesis Pigments absorb light energy for photosynthesis. Chlorophyll absorbs blue/violet and red wavelengths. Green light is not absorbed but reflected, which is why plants appear green. Glucose and ATP Glucose stores energy. ATP is an energy-carrying molecule. Light-Dependent Reactions Light energy is converted into chemical energy. Water molecules split (photolysis), creating hydrogen ions and oxygen. NADP+ converts to NADPH and ADP to ATP. Light-Independent Reactions (Calvin Cycle) Carbon dioxide is converted to glucose. Reactants: CO2, NADPH, ATP; Products: Glucose, NADP+, ADP. Vocabulary Autotroph: Organism that makes its own food. Heterotroph: Organism that consumes other organisms. Detrivore: Organisms that break down dead organisms. Photosynthesis: Process of creating glucose from CO2. Cellular Respiration: Process of turning glucose into CO2. Chemosynthesis: Energy creation by some bacteria using chemical processes. ATP: Energy carrying molecule. ADP: Not energy carrying molecule. NADPH: Energy carrying molecule. NADP+: De-energized energy molecule. Chloroplast: Organelle where photosynthesis takes place. Thylakoid: Site of light-dependent reactions. Stroma: Site of the Calvin cycle. Carotenoids: Pigments capturing sunlight energy. Chlorophyll: Pigment in plants that captures sunlight. Stoma: Tiny openings for gas exchange. Carbon Fixation Process involving C3, C4, and CAM pathways. Carbon from CO2 is incorporated into glucose. Other Important Terms Glucose: Carbohydrate used for energy storage. Glycogen: Polymer of glucose. Phosphate: Form of phosphoric acid. CO2: Carbon dioxide, gas used in photosynthesis. O2: Oxygen gas released during photosynthesis. Electron Transport Chain: Movement of energized electrons. Enzyme: Molecules speeding up reactions. Rubisco: Example of an enzyme in photosynthesis. Xylem: Transports water to plant cells. Phloem: Transports dissolved glucose. Epidermis: Outer layer of plant leaves. Stomata: Pores to exchange gas in leaves. Guard Cells: Regulate stomata opening. Mesophyll: Part of leaf where photosynthesis mostly occurs. Organelle: Part of the cell with a specific function. Photolysis Water breaking apart due to sunlight energy. Photosynthesis Equation 6 CO2 + 6 H2O + light energy → 6 O2 + C6H12O6 (glucose) Chlorophyll location is the Chlorophyll is within the thylakoid membranes Grana function Grana are stacks of thylakoids where light-dependent reactions take place. Stoma Pores in leaves that allow gas exchange (CO2 in, O2 out). Mesophyll Photosynthetic tissue in leaves. ATP vs. Glucose ATP is used for immediate energy, glucose stores energy for later use Glucose Energy is Glucose contains more stored energy than ATP Light-Dependent Reactions Reactions in photosynthesis using light energy Photosynthesis Reactants Water and light energy are used in photosynthesis. Photosynthesis Products Sugars(glucose) and Oxygen are produced. Photolysis The breaking down of water into hydrogen ions and oxygen during photosynthesis. NADPH Energized form of NADP+ in photosynthesis. ATP Energized form of ADP storing energy in plants. Autotrophs Organisms that make their own food. Cellular Respiration Process of turning glucose to CO2. Thylakoid Hint Part of chloroplast. Back Site of light-dependent reactions in chloroplasts. Memory Tip Light-dependent reactions Front Glucose Hint Think sugar. Back A carbohydrate monomer used for energy storage. Memory Tip Energy source Front Enzyme Hint Think catalyst. Back A protein that speeds up chemical reactions. Memory Tip Reaction helper Front Chloroplast Hint Think the factory of photosynthesis. Back Plant cell organelle where photosynthesis occurs. Memory Tip Food making factory Autotrophs and Heterotrophs Definitions and Characteristics Autotrophs: Organisms that produce their own food through processes like photosynthesis or chemosynthesis, utilizing sunlight or chemical energy respectively. Heterotrophs: Organisms that cannot synthesize their own food and rely on consuming other organisms for energy, including plants, animals, and decomposers. Types of Autotrophs Photosynthetic Autotrophs: Use sunlight to convert carbon dioxide and water into glucose and oxygen, primarily through photosynthesis. Chemosynthetic Autotrophs: Typically found in extreme environments, these organisms derive energy from chemical reactions, often involving inorganic substances. Types of Heterotrophs Herbivores: Primary consumers that feed exclusively on plants, playing a crucial role in the food chain. Carnivores: Secondary consumers that prey on herbivores or other carnivores, contributing to population control. Scavengers: Organisms that consume dead animals, aiding in nutrient recycling. Decomposers: Break down dead organic matter, returning nutrients to the soil. Food Chains and Ecosystem Dynamics Structure of Food Chains Primary Producers: Autotrophs that form the base of the food chain, converting solar energy into chemical energy. Primary Consumers: Herbivores that directly consume primary producers, transferring energy up the chain. Secondary Consumers: Carnivores that eat primary consumers, further transferring energy. Tertiary Consumers: Higher-level carnivores that may eat secondary consumers. Energy Flow in Ecosystems Energy decreases as it moves up the food chain due to the second law of thermodynamics, where energy is lost as heat. Trophic Levels: Each step in a food chain represents a different level of energy transfer, with producers at the base and apex predators at the top. Case Study: Trophic Cascades A trophic cascade occurs when changes in one trophic level affect multiple levels below it, such as the reintroduction of wolves in Yellowstone National Park leading to increased vegetation and biodiversity. Photosynthesis Process Overview of Photosynthesis Photosynthesis is the process by which autotrophs convert light energy into chemical energy stored in glucose. The general equation for photosynthesis is: 6 CO2 + 6 H2O + light energy → 6 O2 + C6H12O6. Light-Dependent Reactions Occur in the thylakoid membranes of chloroplasts, where light energy is captured and converted into chemical energy. Water molecules undergo photolysis, splitting into oxygen, hydrogen ions, and electrons, which are used to form ATP and NADPH. Light-Independent Reactions (Calvin Cycle) Occur in the stroma of chloroplasts, utilizing ATP and NADPH produced in the light-dependent reactions to convert CO2 into glucose. Key reactants include CO2, NADPH, and ATP, while products are glucose, NADP+, and ADP. Key Components and Vocabulary Important Terms in Photosynthesis Chloroplast: Organelle where photosynthesis occurs, containing thylakoids and stroma. Thylakoid: Membrane-bound structure where light-dependent reactions take place, organized into stacks called grana. Stroma: Fluid-filled space in chloroplasts where the Calvin cycle occurs. Pigments and Their Role Chlorophyll: The primary pigment in plants that absorbs blue/violet and red light, reflecting green light, which is why plants appear green. Carotenoids: Accessory pigments that capture additional light energy and provide protection against photo-damage. Carbon Fixation Pathways C3 Pathway: The most common form of photosynthesis, where CO2 is directly fixed into a 3-carbon compound. C4 Pathway: An adaptation to hot, dry environments that minimizes water loss by fixing CO2 into a 4-carbon compound before entering the Calvin cycle. CAM Pathway: A strategy used by some plants to fix CO2 at night, reducing water loss during the day.