Photosynthesis Photosynthesis Materials needed: Carbon dioxide WaterProduct: Sugar (glucose) Oxygen (waste product) Energy source:  Light

Photosynthesis  Autotrophs Self feeders Self feeders Make their own food Make their own food  Heterotrophs feed on autotrophs feed on autotrophs each other & each other & organic waste organic waste  Photosynthesis occurs in the chloroplast 2 main reactions: 2 main reactions: Light reactionLight reaction Calvin cycleCalvin cycle

 Photosynthesis Organisms use light energy to make sugar from carbon dioxide and water Organisms use light energy to make sugar from carbon dioxide and water In the process they also make Oxygen In the process they also make Oxygen  6CO 2 + 6H 2 O  + C 6 H 12 O 6 + 6O 2  Carbon dioxide + water yields sugar (glucose) + oxygen Plants make O 2 by splitting water Plants make O 2 by splitting water

Light Dependent Reaction  Convert light energy to chemical energy O 2 gas produced as a waste product O 2 gas produced as a waste product  Occurs in the thylakoid membranes Light energy absorbed by cholorphyll Light energy absorbed by cholorphyll 1. Reactants: water, sun, ADP, NADP + 2. Products: O 2, ATP, NADPH

 Photosystem Light harvesting pigments absorb light energy and pass the energy from molecule to molecule until it reaches the reaction center Light harvesting pigments absorb light energy and pass the energy from molecule to molecule until it reaches the reaction center The primary electron acceptor captures the light excited electron from the reaction center chlorophyll and passes it to the electron transport chain The primary electron acceptor captures the light excited electron from the reaction center chlorophyll and passes it to the electron transport chain

Light dependent reaction Light dependent reaction  Requires light energy energy  Chlorophyll absorbs all wave length’s except green.  Photosystem II 1. Energy from the light is absorbed by electrons, increasing their energy level. 2. Electrons enter the electron transport chain which generates ATP 3. Water molecules are broken apart into – 2 electrons, 2 H + ions and 1 oxygen. Electron supplyElectron supply  Use light energy to break water apart and forms ATP and oxygen.

Light Dependent Reaction (Continued)  Photosystem I Light energy excites electron in the reaction center Light energy excites electron in the reaction center Electron raised energy level, electrons from the bottom of the electron transport chain supply electrons Electron raised energy level, electrons from the bottom of the electron transport chain supply electrons Electrons pass through a short ETC producing NADPH Electrons pass through a short ETC producing NADPH NADP+  NADPHNADP+  NADPH

Energy from the light reactions drive the Dark reactions

Light-independent reaction Calvin cycle Light-independent reaction Calvin cycle  Does not require light  Uses the energy from ATP and NADPH.  Carbon dioxide enters the cycle. (attaches to RuBP)  Carbon dioxide molecule is broken apart.  Oxygen is released.  Carbon molecules start a cycle (six times)  Use 6 molecules of carbon dioxide to produce a single 6 –carbon sugar molecule (glucose)

Calvin Cycle ChloropIast CO 2 Enters the Cycle Energy Input 5-Carbon Molecules Regenerated Sugars and other compounds 6-Carbon Sugar Produced Go to Section: