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What is energy? The capacity to do work Work Kinetic Energy The energy of moving objects A capacity to do work that results from the location or position of an object First Law of Thermodynamics Energy can never be created or destroyed. Second Law of Thermodynamics Every conversion of energy includes the transformation of some energy into heat. Energy Conversions Only ~1% of the energy released by the sun that earth receives is captured and converted by plants. • Converted into chemical bond energy ATP Recycling in the Cell ADP + phosphate group + energy = ATP How do cells regulate the speed of reactions? • Enzymes • protein catalysts • speed up reactions • not consumed • Require energy to initiate breaking of existing bonds & begin reaction (activation energy) = energy barrier Cellular Respiration catabolism: breaking down organic molecules to extract energy Two Catabolic Pathways 1) Fermentation (anaerobic) 2) Cellular Respiration (aerobic) Cellular Respiration Requires fuel and oxygen Potential energy stored in chemical bonds of sugar, protein, and fat molecules. Breaks bonds to release the high-energy electrons captured in ATP. Oxygen is electron magnet. Note locations Cellular Respiration The big picture Three-Step Process Biggest ATP “payoff” (90%) occurs during the electron transport chain. 1st Step Glycolysis Study Slide Four Main Steps in Cellular Respiration 1) Glycolysis (“sugar breaking”) - location = cytoplasm - each glucose breaks into 2 molecules of pyruvic acid (pyruvate) - 2 ATP’s used in reaction - 4 ATP’s generated - net gain = 2 ATP + 2 NADH NADH (nicotinamide adenine dinucleotide) - carries H atoms (e-) & ultimately loses e- The Preparatory Phase to the Krebs Cycle 2nd Step Getting Ready for the Krebs Cycle Four Main Steps in Cellular Respiration 2) Formation of acetyl coenzyme A - occurs in mitochondria (of eukaryotes) - pyruvic acid loses e-; given to NAD+ - 1 C atom removed & leaves as CO2 - coenzyme A is added to modified pyruvic acid Result of last reaction = acetyl coenyme A (Acetyl CoA) = high energy fuel that is now ready to enter the next step 3rd Step Four Main Steps in Cellular Respiration 3) Krebs (Citric Acid) Cycle - location = matrix of mitochondria For each turn in the cycle: 2 CO2 leave 3 NADH made 1 FADH2 made 1 ATP made FADH2 = (flavin adenine dinucleotide) same function as NADH = hydrogen (e-) carrier Study Slide 4th Step Follow the Electrons #2) This proton concentration gradient represents a significant source of potential energy! Four Main Steps in Cellular Respiration 4) Electron Transport Chain - NADH & FADH2 transported to mitochondria cristae - electron carriers = membrane proteins Four Main Steps in Cellular Respiration 4) Electron Transport Chain - chemiosmosis - cascading effect – protons travel down an energy gradient - 32-34 ATP generated How Does Electron Transport Chain Work? + - • NADH & FADH2 lose e- (H+ by-product) • H+ gradient results in electrical gradient • Flow of H+ through ATP synthase = ATP Study Slide Anaerobic Conditions (Fermentation) Alcoholic (Glycolysis) 2 ATP’s 2 Ethanol Lactic Acid (Glycolysis) 2 ATP’s 2 Lactic Acid 4.17 Eating a complete diet: cells can run on protein and fat as well as on glucose. “Photo” and “Synthesis” 3 inputs 2 products Photosynthesis = plants make food from CO2 & H2O with the aid of solar energy Chloroplast - thylakoid - granum (grana) - stroma A Closer Look at Chloroplasts Two Processes 1) Light Reactions (“Photo”) (Light Energy to Chemical Energy) - location = granum (a) / thylakoid - Produce O2 as waste - Light energy used to generate ATP & NADPH (H carrier = e- source) Two Processes 2) Calvin Cycle (“Synthesis”) (CO2 to Sugar) - location = stroma - NADPH provides e- ATP powers the Cycle Light Reactions What is Sunlight? - energy = radiation or electromagnetic energy - travels in waves - also travels as particles of energy = photons = kinetic energy Photosynthetic pigments: 1) chlorophyll a (impt in light reactions) 2) chlorophyll b 3) carotene 4) xanthophyll How Do the Light Reactions Work? - Photosynthetic pigments absorb photons - One of the pigment’s e- gain this energy How Do the Light Reactions Work? - High-energy e- is lost to a primary e- acceptor - e- shuttled through an e- transport chain, thereby generating ATP - Final e- acceptor = NADP+ Light Reactions The “Photo” Part Sunlight ATP A high-energy electron carrier Electrons That Leave the Photosystem Are Replenished Where does oxygen come from? An Electron Transport Chain Connects the two photosystems The Second Photosystem Follow the electrons Study Slide How Do the Light Reactions Work? ** ATP & NADPH now ready to enter the Calvin Cycle Calvin Cycle carbon fixation: convert CO2 into organic compound (sugar) What are the Ingredients? What are the Products? What is the Price? - The Calvin Cycle Series of chemical reactions Occurs in stroma Involves enzyme The Processes in the Calvin Cycle Occur in Three Steps: Study Slide