Photosynthesis Essential Questions: How does the process of photosynthesis store energy? What are the steps of Photosynthesis? Why is photosynthesis important for life on Earth? Match the seed to its plant 3 1 2 C A B The sequoia is the largest living thing on Earth! But it starts as a TINY seed… http://www.youtube.com/watch?v=vTx9 XHMG68Q&feature=PlayList&p=CED208 A405CBC700&index=1 How does this happen? Where does the mass of a tree come from? Brainstorm your idea and write it down! Recap: Where does our energy come from? • We know that the source of all energy comes from the SUN! • Since we can’t eat sunshine to get our energy, we must rely on plants via a process called photosynthesis. – We can obtain their energy by directly eating the plant. – Or we can get energy indirectly Is photosynthesis exothermic or endothermic? by eating other animals who got their energy from eating plants. Endothermic: Stores Energy! Photosynthesis Overview • Photo = light • Synthesis = putting together • Photosynthesis is the process that plants use to trap the sun’s energy and build carbohydrates (called glucose) that store energy • Happens in 2 phases: – 1) The Light (light-dependent) reaction creates ATP, releases Oxygen. – 2) The Dark (light-independent) reaction uses those ATP molecules (from the light reaction) to make glucose. Overview of Photosynthesis In which organ does photosynthesis take The LEAF! place? Root, Stem, Leaf, Flower or Fruit? Where does photosynthesis occur? • The top of the leaf is where photosynthesis occurs. • The Chloroplast is the cell organelle where photosynthesis occurs. • In the chloroplasts are pigments that absorb wavelengths of light. Where are the chloroplasts? Thinking about where a chloroplast lives is like giving directions to where you live in your hometown. The Chloroplast You Leaf State Mesophyll Cell County Chloroplast City Granum Neighborhood Thylakoid House on Street • Sunlight is made up of ALL the colors together. – Pigments reflect the color of light that we see. – They absorb the other colors. • Look at the graph. Where is absorption the lowest? • Where is it the highest? Chlorophyll (a and b) absorb all colors except green so it is reflected! That means chlorophyll absorbs a lot more light than it reflects, which is a good thing! Why do leaves change color in the fall? In Fall, trees reabsorb chlorophyll • Remember- chlorophyll is leaving the other the pigment that captures pigments visible! sunlight and what gives plants their green color. • In order for chlorophyll to be produced, sunlight is needed. • Year round, many different color pigments are present, but the green from the chlorophyll prevents those colors from showing through. CLICK HERE TO WATCH A TIME-LAPSE OF A LEAF CHANGING COLOR! Light-Dependent Reactions 1:2 • 1st stage of photosynthesis requires light. (Light dependent) • Light energizes electrons and are passed from the chlorophyll to the electron transport chain. • The Electrons come from splitting molecules of water. • This process is called photolysis: – Each water molecule supplies… • ½ molecule of Oxygen gas • 2 Hydrogen ions • 2 Electrons • ETC = series of proteins embedded in the thylakoid I’m free to membrane of the chloroplast. leave out • As the electron passes on the of the chain between chlorophyll stomata! molecules, it loses a bit of energy at each protein. Light-Dependent Reactions 2:2 • After the electron has passed through the first chain, it enters a second electron chain so any e- (light) energy isn’t wasted. • A carrier molecule called NADP+ is used (when with an electron it binds with a Hydrogen ion and becomes Haha! NADPH.) What am I? • Binds to the electron and stores the energy from the electron in a chemical form. • NADPH plays a role in the formation of Carbohydrates. • Summary: Converts ADP and NADP+ into ATP and NADPH with Oxygen gas. What happens to plants when there is no sunlight? • Chlorophyll is “turned off.” • Plants produce lots of glucose--enough to last them through the night and several cloudy days. • However, plants cannot store excess glucose. – Instead, plants convert the excess glucose to starch. – Starches are long term energy storage molecules and make the cellular components of plants. • like cellulose for their cell walls! • When they need glucose for energy they convert the starch back to glucose. Light-Independent Reactions • Does not need light! (Also called the “Dark Reaction.”) – Called the Calvin Cycle. • Uses CO2 to form 6 Carbon Sugars. (Carbohydrates) • Takes place in the stroma of the chloroplast. • Called a Cycle because the end products can be used again to initiate the process. • Uses the NADPH and ATP produced in the earlier light reactions. – Otherwise the dark reaction could not occur! http://www.tracy.k12.ca.us/thsadvbio/animations/Photosynthesis.swf Calvin Cycle • The Calvin cycle uses the ATP and NADPH from the light dependent reaction to create sugar. • Reactant: Carbon Dioxide • Product: a 6 Carbon Sugar Calvin’s in the Dark about Photosynthesis! What’s the big deal about Photosynthesis? • The Calvin Cycle removes Carbon Dioxide from the Earth’s atmosphere and creates sugars. • Plants can use those sugars for food or to make larger molecules like cellulose for growth and development. • When we eat plants (or herbivores) eat plants, we use the energy stored in the carbohydrates. • A byproduct of our breathing is Carbon Dioxide, which is used by plants for photosynthesis. It is also a greenhouse gas contributing to global warming. • Without plants to harvest the sun’s energy, there would be no life for animals on Earth! • Photosynthesis Song! http://www.youtube.com/watch?v=R_17euLU_EM&feature=related So, back to the CLICK HERE TO WATCH original question…. THEM GROW! • Where does the mass of a tree come from? • Revisit your original thought… – Were you right? – Are you surprised by the answer? Answer: The Mass of a tree comes from the Carbon from atmospheric CO2 taken in during photosynthesis! Gets converted into cellulose! Activity: Photosynthesis Exit Ticket • Complete the exit ticket so I can assess your understanding of Photosynthesis. • Make sure to write down further questions you have! • Turn it into the box before you leave class today!
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