Lesson 6b- 4.2 Fixing Carbon Dioxide The Light-Independent Rxns PDF

Light Independent Reaction  The chemical energy stored in the high-energy bonds of ATP and NADPH are produced then used in the STROMA of the chloroplast.  This is where the Light – Independent or Dark Stage of photosynthesis occurs.  This is also called Carbon Fixation or The Cal...

Light Independent Reaction  The chemical energy stored in the high-energy bonds of ATP and NADPH are produced then used in the STROMA of the chloroplast.  This is where the Light – Independent or Dark Stage of photosynthesis occurs.  This is also called Carbon Fixation or The Calvin Cycle.  conversion of inorganic carbon, in the form of carbon dioxide from the atmosphere, into organic carbon, in the form of the three-carbon organic molecule glyceraldehyde- 3-phosphate (G3P)  Can occur in the absence or presence of light; also called the dark reactions and the Calvin-Benson cycle The Calvin Cycle The process of carbon fixation was worked out by Melvin Calvin (1960’s) A series of reactions takes place in the stroma of the chloroplasts. These reactions convert carbon dioxide into carbohydrates. The Calvin cycle is divided into three phases: Carbon fixation Reduction reactions Ribulose 1, 5 – bisphosphate (RuBP) regeneration Can be divided into 3 Phases: 1. Fixing Carbon Dioxide  chemical bonding of the carbon atom in carbon dioxide to a ribulose-1,5- bisphosphate (RuBP)in the stroma. The resulting six-carbon compound is unstable and breaks down into two identical three-carbon compounds called 3- phosphoglycerate (PGA).  This reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase(rubisco). 2. Reduction  three-carbon compounds are in a low-energy state. To convert them into a higher-energy state, they are first activated by ATP and then reduced by NADPH. The result of these reactions is molecules of glyceraldehyde-3- phosphate (G3P). In their reduced (higher-energy) state, some of the G3P molecules leave the cycle and may be used to make glucose and other carbohydrates. 3. Regenerating RuBP  Most of the reduced G3P molecules are used to re-make more RuBP. Energy, supplied by ATP, is required to break and reform the chemical bonds to make the five-carbon RuBP from G3P. Net Equation: 6CO2 + 18 ATP +12 NADPH + water →2 G3P (glucose) + 16 Pi + 18 ADP + 12 NADP+ The Calvin Cycle Overall Equations of Calvin Cycle  Aerobic Respiration compared with Photosynthesis. Respiration Photosynthesis Reactants Organic molecules Carbon dioxide and water e.g. glucose + O₂ Products Carbon dioxide and Organic molecules water e.g. glucose + O₂ Energy Released as ATP Required-stored as chemical potential energy Electron source Organic intermediates Water, chlorophyll ETC electron source NADH, FADH₂(electron Chlorophyll carriers) Final electron Oxygen NADP⁺ acceptor Products of ETC Water NADPH(electron carrier) Chemiosmotic Yes Yes coupling ATP synthase used Yes Yes Organelle Mitochondrion Chloroplast H⁺ reservoir Inner membrane space Thylakoid lumen ATP synthesis Fluid matrix Stroma Equation Waste products Water and carbon Oxygen dioxide Helpful Links  https://www.youtube.com/watch?v=c2ZTumtpHrs  https://www.youtube.com/watch?v=l12GClqoI10 Textbook Work  Rd. pg. 166-170  Do: Learning Check pg. 167 13-18  Pg. 171 Q 1, 3, 6, 7, 14