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Warm-up What is the equation below? 6CO2 + 6H2O + light energy → C6H12O6 + 6O2 Where Do We Get Our Energy? •From the air we breathe? •From the water we drink? •From the food we eat? Where does our food get its energy? • Steak = cows get their energy by grazing on grass • But how does grass get its energy???? Where Does Our Food Get Its Energy? • Chicken = chickens get their energy by eating grain • Grain usually comes from corn or wheat • Where do corn and wheat get their energy??? Where Does Our Food Get Its Energy? • Many vegetarians eat TOFU which comes from soybeans • Soybeans are produced by a plant • Where do soybeans get their energy??? So almost all living things get their energy from: THE SUN!!! Autotrophic vs. Heterotrophic • Autotrophs are • Heterotrophs are “self-feeders” “other feeders” • They can make • These organisms their own food! cannot make their own food • Usually they use photosynthesis to • They must eat food make food made by others Plants are autotrophs!! • They undergo photosynthesis to make food for themselves…and for us!! Thank you plants! Extra Credit Opportunity • Someone explain why leaves change color? What happens to the chloroplasts? Tell me about it tomorrow before class and be willing to share your findings with the class! AUTOTROPHS You will now see some pictures of autotrophic organisms... Algae Some bacteria The tree, not the person… So what do Autotrophic organisms have in common? They can make their own food!! Autotrophic = “self-feeder” HETEROTROPHS Can’t make their own food, so they eat food made by other organisms! You will now see some pictures of heterotrophic organisms... Animals are heterotrophs Sleepy baby sloths are heterotrophs Where is this fungus getting its nutrition? Sharks are very hungry heterotrophs Mold in Blue Cheese Gangrene – decay of tissue from a bacterial infection (the bacteria is the heterotroph) Ewwww… So what do Heterotrophic organisms have in common? They get their food from some other source! Heterotrophic = “other-feeder” Now that the review is over, let’s get down to the nitty gritty of photosynthesis! Photosynthesis Carbon dioxide + water + light Glucose + oxygen Where does photosynthesis occur in plants? • You should already know the answer to this question! • It occurs in the chloroplasts of plant cells The structure of a chloroplast Outer membrane Inner membrane Thylakoid membrane Stroma (fluid) Key Molecules in photosynthesis: 1) ATP (adenosine tri-phosphate) = energy that the cell can use • ADP is the low energy form (only has two phosphates) • ATP is high energy (it has three phosphates) 2) NADPH = temporarily stores electrons for the cell • NADP+ stores no electrons, NADPH stores two electrons Once sunlight is captured, its energy is trapped in the chemical bonds of sugars such as Glucose That is photosynthesis in a nutshell Photosynthesis occurs in two steps: Step 1: The light reactions: light is required for this step!! Step 2: The Calvin cycle (also known as the light-independent reactions) The Light Reactions • Location: the thylakoid membrane of the chloroplast • Purpose: to generate ATP and NADPH (energy storing compounds) that will be used in the Calvin cycle Key Molecules in photosynthesis: 1) ATP (adenosine tri-phosphate) = energy that the cell can use • ADP is the low energy form (only has two phosphates) • ATP is high energy (it has three phosphates) 2) NADPH = temporarily stores electrons for the cell • NADP+ stores no electrons, NADPH stores two electrons Here’s what happens in the light reactions: 1) Light is absorbed by chlorophyll ***chlorophyll is a green pigment that absorbs light Here’s what happens in the light reactions: 2) Chlorophyll then releases electrons to a series of proteins in the thylakoid membranes ***these proteins are called electron carriers ****these electron carriers pass the electrons from one to another along an electron transport chain ****at the end of the chain, the electrons are passed to NADP+ making it into NADPH The electron transport chain Electron carrier Electrons (from Chlorophyll) H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ Phospholipids NADP+ + e- = NADPH OUTSIDE THE MEMBRANE Here’s what happens in the light reactions: 3) As the electron carriers pass the electrons down the electron transport chain, they also pump H+ ions inside the thylakoid membrane ***the inside of the membrane becomes + charged ***the outside of the membrane becomes – charged ***this difference in charge is a source of energy ATP synthase uses this energy to make ATP!!!!! Here’s what happens in the light reactions: 4) Oxygen is produced when water splits to donate its electrons to chlorophyll • this replaces the electrons donated by chlorophyll to the electron transport chain • This is the reaction when water splits: 2H2O 4 H+ + O2 • We benefit from this oxygen production…take a deep breath!!! Summary of the Light Reactions Reactants Products *Water *ATP *Sunlight *NADPH *NADP+ *ADP *Oxygen The second step of photosynthesis is called the…. •Step 1 = the Light Reactions •Step 2 = the Calvin Cycle Here’s what happens in the Calvin Cycle CO2 2 ATP *Rubisco 2 ADP 2 NADPH 2 NADP+ Glucose (+ Lipids & Amino Acids) The Calvin Cycle • Location = the stroma of the chloroplast • Does not require light to work! (unlike the light reactions) • Does require ATP, NADPH and CO2 • Does require Rubisco to bring in CO2 A Summary of Photosynthesis Light + H2O + CO2 Light Reactions Calvin Cycle Oxygen + Glucose