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Chapter 5 Photosynthesis and Cellular Respiration Energy & Living Things Directly or Indirectly almost all of the energy comes from the SUN Metabolism Using energy to build molecules Breaking down molecules where energy is stored Building Molecules That Store Energy Photosynthesis – is the process by which light energy is converted to chemical energy Autotrophs – organisms that use the sun to convert inorganic substances into organic substances Breaking Down Food For Energy Heterotrophs – must eat food to get energy Cellular Respiration – process by which cells produce energy from carbohydrates O2 + C6H12O6 H2O + CO2 Releases energy to make ATP Transfer of Energy to ATP Energy is released in a series of enzyme assisted chemical reactions Food Breaks down into 1) Heat Energy 2) Portable Energy (ATP) ATP drives most cellular activity Adenosine Triphosphate 3 Phosphate Groups 5 Carbon Sugar (Ribose) Phosphate Tail is negatively charged Energy is released when phosphate bonds are broken H2O + ATP ADP + P + energy Energy released powers metabolism Section 1 Review 1. What is the primary source of energy that flows through most living systems? 2. Organisms that can make their own food using energy from the sun are called ___________. 3. How is energy released from ATP? Photosynthesis Stage 1: Energy is captured from sunlight Stage 2: Light energy is converted to chemical energy, which is temporarily stored in ATP and the energy carrier molecule NADPH Stage 3: ATP & NADPH powers the formation of organic compounds using CO2 Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2 Important for life processes Sugars form starch Starch is broken down to produce ATP Sugar fragments form Proteins, Nucleic Acids & other molecules Stage 1: Absorption of Light Energy “Light Dependent Stage” Require Sun Light Pigments – light absorbing substances Carotenoids & Chlorophyll –a and b Pigments in plants Enables plants to absorb more light Located in the Thylakoids of a chloroplast Production of Oxygen Electrons get “excited” Electrons leave the chlorophyll Replaced by e- from split H2O molecules H electron replaces excited electron Leaving H+ ions & O2 (oxygen gas) Electrons are used to power the 2nd stage of Photosynthesis Stage 2: Conversion of Light Energy Excited e- are used to make ATP Electron Transport Chains 1st Located b/t 2 chlorophyll pigments Contains a protein that acts as a membrane pump Excited e- pass through the protein Electrons lose energy Energy is used to pump H+ into the thylakoid 1st Electron Transport Chain H+ ions are also produced when H2O molecules split H+ are highly concentrated inside H+ diffuse out of the thylakoid – down the concentration gradient through carrier proteins Carrier Proteins – act as an Ion Channel & Enzyme 1st Electron Transport Chain 1. 2. 3. 4. 5. H+ pass through the channel The protein catalyzes a reaction A Phosphate group is added to ADP ATP is made ATP is used to power Stage 3 2nd Electron Transport Chain Provides energy to make NADPH NADPH – is an electron carrier that provides the high energy e- needed to make C-H bonds in stage 3 NADP – is and electron acceptor E- + H ions + NADP+ NADPH Light Dependent Stages Summary (Stages 1 & 2) 1) Pigment molecules in the thylakoid absorb light 2) E- are excited by light & move through 2 Electron Transport Chains 3) Excited e- leaving the thylakoid are replaced by e- from H20 that is split by an enzyme 4) O atoms combine and form O2 5) H+ accumulate inside the thylakoid setting up a concentration gradient that provides the energy to make ATP Stage 3: Storage of Energy Light Independent Stage Carbon atoms are used to make organic compounds to store chemical energy CARBON DIOXIDE FIXATION The Calvin Cycle A series of enzyme-assisted chemical reactions that produce a 3-C sugar Calvin Cycle Melvin Calvin Step 1: Enzymes add CO2 to a 5-C compound Step 2: The 6-C compound splits into two 3-C compounds P groups form ATP Electrons form NADPH Both are added forming 3-C sugars Calvin Cycle Step 3: One 3-C sugar is used to make organic compounds Step 4: Other 3-C sugars are used to regenerate the initial 5-C compound The organic compounds provide the organism with energy for growth & metabolism Factors that Affect Photosynthesis #1 – Light #2 – Carbon Dioxide #3 – Temperature Section 2 Review 1. T/F Chloroplasts are found within the thylakoid membrane. 2. T/F Carbon Dioxide fixation takes place during the Calvin Cycle. 3. The electron transport chain converts light energy to chemical energy during the __ stage of photosynthesis. 4. During photosynthesis, plants store energy in this… Section 3: Cellular Respiration Energy is stored in proteins, carbohydrates and fats Cells transfer the energy in organic compound to ATP through CELLULAR RESPIRATION Metabolism describes the sum of all chemical reactions Aerobic = Requires Oxygen Anaerobic = Does NOT require Oxygen Cellular Respiration C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY Takes place in the Mitochondria Stage 1: Glucose is converted to Pyruvate, producing small amounts of ATP and NADH Stage 2: Aerobic Respiration – Pyruvate & NADH make large amounts of ATP Anaerobic Respiration – Pyruvate is converted into Lactic Acid or Ethanol & CO2 Stage 1: Breakdown of Glucose Fuel – Glucose Glucose is broken down in the cytoplasm during GLYCOLYSIS Glycolysis – is an enzyme assisted anaerobic process that breaks down one 6-C molecules into two 3-C pyruvate ions Stage 1: Breakdown of Glucose Pyruvate – is the ion of a 3-C organic acid called pyruvic acid Broken down glucose transfers H+ ions to NAD+ forming NADH NAD + is an electron acceptor NADH is an electron carrier NADH donates electrons to organic compounds turning back into NAD Summary of Stage 1 1. Phosphate groups from 2 ATP molecules are transferred to glucose (3 reactions) 2. 6-C compound is broken into two 3-C compounds, each with a Phosphate group (2 reactions) 3. 2 NADH molecules are produced, 1 phosphate group is transferred to a 3-C compound 4. Each 3-C compound is converted into a 3-C pyruvate, producing 4 ATP molecules Stage 1 to Stage 2 Glycolyisis uses 2 ATP molecules to make 4 ATP molecules – 2 net ATPs Pyruvate produced in glycolysis enters the mitochondria and is converted into a 2-C compound 1 – CO2 1 – NADH 1 – acetyl-CoA Stage 2: Production of ATP Acetyl-CoA enters a series of enzyme assisted reactions called the KREBS CYCLE Step 1: Acetyl-CoA combines with a 4-C compound forming a 6-C compound & releasing Coenzyme A Step 2: CO2 is released from the 6-C compound forming a 5-C compound Electrons + NAD NADH Stage 2: Production of ATP Step 3: CO2 is released from the 5-C compound resulting in a 4-C compound Step 4: 4-C compound is converted to a new 4-C compound ATP & NADH is made Electrons are transferred from FAD to FADH2 Step 5: The new 4-C compound is converted to the 4-C compound that began the cycle Another NADH molecule is produced After the Krebs Cycle NADH & FADH2 contain much of the energy previously stored in glucose & pyruvate Donated electrons from NADH & FADH2 enter the Electron Transport Chain in the mitochondria membrane Electrons are used to help move H+ ions ATP & O2 is produced Anaerobic Respiration Electron Chain does NOT function NAD+ has to be recycled in another way Recycling NAD+ using an organic H acceptor is called FERMENTATION 1. Lactic Acid – exhausted muscles, yogurt & cheese 2. Alcoholic Fermentation – releases CO2 – making bread, beer & wine Production of ATP After Glycolysis 1 of 2 paths: 1. Oxygen Present Krebs Cycle 2. Oxygen Absent Fermentation ATP Produced Fermentation – None Krebs Cycle – 2 Electron Transport Chain 34 ATP