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Photosynthesis From Sunlight to Sugar What is Photosynthesis? Photosynthesis is a process that captures energy from sunlight to make sugars used as food for producers. The light energy is stored as chemical energy in the sugars. What is Photosynthesis? • Autotrophs (producers) use sunlight energy to build carbohydrates. Organisms that can perform photosynthesis: Plants, Algae and some Bacteria Where does it occur in the cell? Occurs in the Chloroplast of a cell Grana The Chloroplast • Contains Chlorophyll, a green pigment that absorbs and traps light energy from the sun. • Grana: within the chloroplast. Stacks of thylakoids. • Thylakoid: Membrane “sacs” that contain the chlorophyll. • Stroma: Fluid filled space that surrounds the grana. Chlorophyll Membranes of the thylakoids contain chlorophyll. Absorbs most light; reflects green (and yellow) light (this is why we see it as green). Plants have other photosynthetic pigments: Carotenoids These are not green so they absorb and reflect other spectrums of light. They are less abundant so they get masked by chlorophyll making leaves look green. Xanthophyll Carotene Chlorophyll Green (and yellow) light are Reflected. What is the overall Photosynthesis Reaction? (light) 6 H2O + 6 CO2 (Water + Carbon Dioxide) (chlorophyll) C6H12O6 + 6 O2 (Glucose + Oxygen) Some released into The atmosphere Taken into the leave Absorbed by the roots Transferred to all Parts of the plant http://www.youtube.com/watch?v=mYbMPwmwx88 Steps of Photosynthesis • STEP 1 is the LIGHT REACTION – The “Photo” part; Light is required – Occurs in the Thylakoid of a chloroplast. – Chlorophyll traps light energy Steps of Photosynthesis STEP 2: CALVIN CYCLE • The light Independent Reaction or “Dark Reaction”. • The “Synthesis” part of photosynthesis; Glucose is made. • Occurs in the stroma of the chloroplast. Stroma Step 1: Light Reaction Detail • Light energy causes chlorophyll electrons to get excited and gain energy. • the excited electrons lose energy which is used to perform the following: Split water: 2 H2O 2H+ + O2 Trapped as ATP: ADP + P + energy from the ePicked up by NADP (an electron carrying molecule): e- + 2H+ + NADP NADPH + H+ (The electron carrier) Step 1: Light Reaction Split water releasing e- ATP formed NADPH picking up e- http://www.youtube.com/watch?v=BK_cjd6Evcw Step 1: Light Reaction Overview: • Used: – H2O – Light Energy • Produced: – NADPH from NADP picking up free Hydrogen Ions – O2 from split H2O – ATP from energy given off by excited chlorophyll electrons Sunlight + H2O ATP + NADPH + O2 Step 2: Calvin Cycle Detail • From the Light Reaction comes hydrogen ions (from NADPH), electrons, and ATP. • Calvin Cycle: CO2 and H+ are cycled through a series of reactions with the help from ATP producing glucose (C6H12O6) which is used as food for the plant and has chemical energy stored in it. Step 2: Calvin Cycle ADP + P Carbon Molecule Complex Continues Cycle To the Light Reaction Glucose NADP Back Step 2: Calvin Cycle • ATP from the Light Reaction provides energy to drive the cycle. • Energy from ATP is stored in newly formed Carbon bonds of glucose. Step 2: Calvin Cycle Overview • No light needed • Used: – H+ carried by NADPH – ATP – CO2 • Produced: – C6H12O6 (Glucose) – ADP + P (Back to Light Reaction) – NADP+ (Back to Light reaction) ATP + NADPH + CO2 C6H12O6 Reactants diffused into the chloroplast Products leaving Chloroplast Steps of Photosynthesis (light/energy) 6 H2O + 6 CO2 (chlorophyll) C6H12O6 + 6 O2 Step 1: Light Reaction: Sunlight + H2O ATP + NADPH + O2 Step 2: Calvin Cycle (Dark Reaction): ATP + NADPH + CO2 C6H12O6 Review • What is the purpose of photosynthesis? • Write the overall balanced equation and circle the main product. Underline the waste product. Review • What is the purpose of photosynthesis? To trap light energy in sugars which are used as food for the plant. • Write the overall balanced equation and circle the main product. Underline the waste product. (light/energy) 6 H2O + 6 CO2 (chlorophyll) C6H12O6 + 6 O2 Review • What is the purpose of the light reaction? • What is the purpose of the Calvin Cycle? • What is transferred from the Light Reaction to the Calvin Cycle? Review • What is the purpose of the light reaction? To absorb light energy • What is the purpose of the Calvin Cycle? To produce simple sugar (glucose) • What is transferred from the Light Reaction to the Calvin Cycle? ATP and NADPH Review • If you put a plant in green light and blue light, what would you expect in terms of its growth? • A) Both plants will not grow since white light is necessary. • B) Plant in green would grow, plant in blue light would not. • C) Plant in green would not grow, plant in blue would grow. • D) Both would grow Review • If you put a plant in green light and blue light, what would you expect in terms of its growth? • A) Both plants will not grow since white light is necessary. • B) Plant in green would grow, plant in blue light would not. • C) Plant in green would not grow, plant in blue would grow. • D) Both would grow