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Identifying the Properties of Photosynthesis Photosynthesis is: • This conversion of the Sun’s energy into chemical energy is the single most important reaction on earth, and could be called • THE REACTION OF LIFE. Photosynthesis One of the main differences between plants and animals is the ability of plants to manufacture their own food. Photosynthesis - Respiration Comparison • Photosynthesis • Respiration • Occurs only in green plants • Occurs only in green plant cells • Proceeds only in light • Food is made • Increases dry weight • CO2, H2O are used • Produces sugars and O2 • Stores energy in sugar • ATP & NADPH produced • ATP and NADPH used in sugar synthesis • Occurs in all plants and animals • Occurs in all living cells • Proceeds in light and darkness • Food is used • Decreases dry weight • Sugar and O2 are used • Produces CO2 and H2O • Releases energy • ATP produced • ATP and NADPH used for many reactions Photosynthesis • In Photosynthesis Light energy is captured by chlorophyll contained in green tissue of plants, mainly the leaves, • And is used to convert carbon dioxide CO2 from the air and water H2O from the soil & atmosphere into carbohydrates C6H12O6 which are stored in the plant for future use. Photosynthesis occurs in the chlorophyll molecule of the chloroplasts in the leaves of green plants and photosynthetic bacteria Plant Cell with Chloroplast Algae Cell with Chloroplasts. Photosynthesis • The carbohydrate is stored inside cell vacuoles until use in several metabolic processes: • Glycolysis - glucose to pyruvic acid • Respiratory metabolism • Metabolic maintenance - growth of plant cells and tissues Photosynthesis • Photosynthesis takes place in the CHLOROPLAST of the cells. The Structure of the Chloroplasts Plant Cell The Leaf & Photosynthesis Green Plant Carbon Dioxide + Water Glucose + Oxygen + Light Energy Water Requirements for Photosynthesis • 1. Healthy, living, green plant • 2. Light • 3. Carbon Dioxide (CO2) • 4. Water (H2O) Factors Affecting Photosynthesis Factors Affecting Photosynthesis • 1. Light Quality • 2. Light Intensity • 3. Light Duration • 4. Carbon Dioxide Concentration • 5. Temperature • 6. Water Availability Factors Affecting Photosynthesis • 1. Light Quality • Light is required for the process of photosynthesis • Chloroplasts contain chlorophyll capable of intercepting light and converting electromagnetic energy to chemical energy. • Chlorophyll molecules absorb mostly red (700 nm) and blue (450 nm) light and reflect green light (that is why plants look green to the human eye). Light Waves & Photosynthesis Light Spectrum Factors Affecting Photosynthesis • 2. Light Intensity • Influences the rate of photosynthesis. • Some species require high light intensity • “Sun-loving plants” • Corn, turf • Some species do not require high light intensity • “Shade-loving plants” • Forest floors, house ornamentals Factors affecting Photosynthesis • 3. Light Duration • A plants photosynthetic production is directly proportional to the length of day. • The longer the leaves receive light, the longer they photosynthesize and the faster the plant grows. Factors Affecting Photosynthesis • 4. CO2 Carbon Dioxide Concentration • Concentration of Carbon Dioxide in the air surrounding the leaves affects photosynthesis. • Normal atmospheric concentrations of CO2 are 0.03% and O2 are 21% . • Experiments have shown increases in atmospheric CO2 can increase photosynthesis rates. • Increasing CO2 to 0.1% will double the photosynthesis rate in wheat, rice, and some vegetables. The exchange of oxygen & carbon dioxide in the leaf occurs through pores called stoma Factors Affecting Photosynthesis • 5. Temperature • As a general rule, if light is not limiting, photosynthesis rates will double for each 18oF increase in temperature • Excessively high temperatures (>100o ) will reduce photosynthesis by causing stoma closure (no uptake of CO2) • 65-85oF is optimum Factors Affecting Photosynthesis • 6. Water Availability • Excessive soil moisture reduces root respiration and limits photosynthesis in leaves • Water stress conditions (low soil moisture; hot, drying winds) • Plants transpire water faster than it can be absorbed through roots • Leaves wilt and gas exchange (CO2 and O2) is restricted thus decreasing photosynthesis rates Photosynthesis - Equation General Reaction Green Plant Glucose + Water + Light EnergyOxygen Carbon Dioxide + Water Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6H2O + 6 O2 Discussing the Equation • Six molecules of carbon dioxide react with • twelve molecules of water • in the presence of light and a green plant • to produce: • one molecule of glucose (carbohydrate) • six molecules of water and • six molecule of oxygen Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 Products of Photosynthesis • Carbohydrates • Water • Oxygen Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 Photosynthesis in a Plant The Chemistry of Photosynthesis • The process of photosynthesis is stated in simple equations, but the total process is extremely complex. • The overall process is separated into two parts: • Light Reactions (Hill Reaction) • Dark Reactions (Calvin Cycle) The Light and Dark Reactions of Photosynthesis. Light Reaction (Hill Reaction) • In the Light Reaction, energy in the form of light received by chlorophyll is used to: • 1.) • 2.) Reduce (NADP+) to NADPH. Provide chemical energy through the production of adenosine triphosphate (ATP) from adenosine diphosphate (ADP). • 3.) The water molecule is split to produce O2 and H+ Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 The Z-Scheme of Photosynthesis • A chlorophyll photo-active center (PSII) in the granum is activated by light and splits the water molecule into O2 and H+. • As the Energy is passed downhill, ATP is formed. ATP is energy. • A second photo-active center (PSI) receives light, and releases energy, delivering electrons to form NADPH. Light Reaction (Z-Scheme) Increasing Energy Level Electron Acceptors Electron Transport System Electron Transport System H+ 2 e- 2 e- Light Light P 680 P 700 Photosystem I Photosystem II 2H2O 4H+ + O2 + 2e- (Photolysis) NADP+ NADPH Z-Scheme - Light Reaction Z-Scheme of the Light Reaction • 1. Light Reaction - Hill Reaction Notes: Light energy is received by chlorophyll and used to reduce NADP to NADPH.. • 2. Production of ATP • 3. The water molecule is split to produce Oxygen. Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 Light Reaction - Hill Reaction Notes: • The Hill Reaction occurs in the Granum of the Chloroplast. • Requires Light Light Reaction Hill Reaction Dark Reaction Calvin Cycle The Light Reactions of Photosynthesis stop when the sun goes down. The Dark Reaction is known as the Calvin Cycle Dark Reacton - Calvin Cycle • The Calvin Cycle is the Carbon-Fixing Cycle of Photosynthesis. It does not require light. • It may proceed in light or dark. Dark Reaction - Calvin Cycle • The Calvin Cycle takes place in the stroma of the chloroplast. Dark Reaction - Calvin Cycle • The Calvin Cycle uses NADPH and ATP from the Light Reaction to convert Carbon Dioxide to a six Carbon Sugar Molecule. Dark Reaction - Calvin Cycle • Carbon dioxide molecules from the air enter the cycle one cycle at a time, making six turns of the cycle necessary to produce one molecule of (sugar) glucose, C6H12O6. Calvin Cycle Dark Reaction (Calvin Cycle) • In the Dark Reaction of Photosynthesis, • 1. Carbon taken into the plant as CO2 from the air accepts the energy, ATP & NADPH from light reaction. • 2.This energy is used to convert carbon dioxide into carbohydrates, (Glucose). Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 Calvin Cycle Notes • Does not require light. • May proceed in light or dark. • Occurs in the Stroma of the Chloroplast. • Uses NADPH & ATP from the light reaction to convert CO2 to a 6 carbon sugar. Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 Review of Photosynthesis Photosynthesis - • Photosynthesis • Occurs only in green plants • Occurs only in green plant cells • Proceeds only in light • Food is made • Increases dry weight • CO2, H2O are used • Produces sugars and O2 • Stores energy in sugar • ATP and NADPH are produced Photosynthesis is: • The Transformation of sun’s energy (light) into useable chemical energy • The Reaction of Life Requirements for Photosynthesis • 1. Healthy, living, green plant • 2. Light • 3. Carbon Dioxide (CO2) • 4. Water (H2O) Factors Affecting Photosynthesis • Light Quality • Light Intensity • Light Duration • Carbon Dioxide • Temperature • Water Availability Photosynthesis - Equation General Reaction Green Plant 6 CO2 + 12 H2O Light Energy C6H12O6 + 6 H2O + 6 O2 The Chemistry of Photosynthesis • The process of photosynthesis is stated in simple equations, but the total process is extremely complex. The overall process is separated into two parts: • Light Reactions (Hill Reaction) • Dark Reactions (Calvin Cycle) Hill Reaction Notes: • Light energy is received by chlorophyll and used to synthesize ATP and NADPH • Requires Light • Creates Oxygen • Occurs in the Granum Calvin Cycle Notes • Does not require light • May proceed in light or dark • Occurs in the Stroma • Uses NADPH & ATP from the light reaction to convert CO2 to a 6 carbon sugar.