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Warm-up. For thought: How do you get something as big as an oak tree from an acorn?. 1. Mesophyll. 1. Mesophyll. A layer of cells that contain & are responsible for most of the plant’s photosynthesis. chloroplasts. Page 2. Page 2. O 2. CO 2. 2. Stomata.
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Warm-up For thought: How do you get something as big as an oak tree from an acorn?
1. Mesophyll 1. Mesophyll A layer of cells that contain & are responsible for most of the plant’s photosynthesis chloroplasts Page 2
Page 2 O2 CO2 2. Stomata Openings in plant leaves that allow for to occur gas exchange Carbon Dioxide (CO2) passes in and (O2) passes out. Oxygen
Mesophyll Cell Chloroplast The site of Photosynthesis Double-membrane bound organelle Outer membrane Inner membrane Page 2
8. Grana 6. Stroma 7. Thylakoid resides in these membranes Chlorophyll 8. Grana Page 2
Photosynthesis: Discoveries Experiment: 1 Seedling in dry soil Only added water for five years Results: Plant gained 75 kg Conclusion: Plant mass comes from water. Jan Van Helmont Page 3
Page 3 Photosynthesis: Discoveries Joseph Priestly Jan Ingenhousz
Page 3 Photosynthesis: Discoveries Microbiologist who observed: Purple sulfur bacteriaunderwent photosynthesis, but there was a big difference: H2S + CO2 C6H12O6 + S2 Cornelius Van Niel
Page 3 Photosynthesis: Discoveries • Van Niel theorized: H2O is the source of Oxygen in Photosynthesis. • How was his theory proven? H2O + CO2 C6H12O6 + O2 O O H2O + CO2 C6H12O6 + O2 O O
Page 4 Pathway of Photosynthesis On your own, balance this equation: CO2 + H2O + (Light) C6H12O6 + O2 Reactants must equal Products 6 6 1 6 6 6 Carbon Hydrogen Oxygen Carbon Hydrogen Oxygen 12 12 18 18
Label the image in your notes, and fill in the notes provided Thylakoid Page 4
Photosynthesis: The Light Reaction Chloroplasts • are chemical factories powered by the sun. • Their thylakoids transform light energy into the energy of and . NADPH ATP Page 5
The Nature of Light Page 5
The Nature of Light • In addition to the wave-like nature of light, light consists of discrete particles called . photons Page 5
Page 5 Why are leaves green?Substances that absorb light are called pigments Carotenoids Chlorophyll a Chlorophyll b Chlorophyll absorbs and light, reflecting red blue green
How do plants keep from losing all of this energy? • A complex of proteins and other organic molecules called photosystems
Photosystems: Harvest Light Photon Primary Electron Acceptor Electron Transfer Reaction Center Chlorophyll Transfer of Energy Antenna pigment molecules
NADPH making enzyme Protein complex
Mechanical analogy for the light reactions • Photon excites an electron • In Photosystem II • ATP is produced during this stage • The electron moves on to Photosystem I • An electron is excited by another photon • NADPH is produced
ATP Synthetase • An enzyme embedded in the • Hydrogen ionsbuild up here: • ADP & Picombine to form ATP here: thylakoid membrane thylakoid lumen Thylakoid membrane stroma
ProteinComplex Enzyme
NADP+ NADPH + + 4e- 2e- + + + + + + + + + + + + + + + + + + + + + + + + + ATP ADP Pi
To the “Dark Reaction” – or the Calvin Cycle • The Plant’s Dilemma: The Calvin Cycle uses more ATP than NADPH. How would you create more ATP, and no additional NADPH?
Cyclic Electron Flow Protein complex
Dark Reaction:An Overview • The General Formula for Photosynthesis is: CO2 + H2O + (Light ) C6H12O6 +O2 • Which of these reactants has not been accounted for so far?
ATP ATP & NADPH are used to convert CO2 into sugar NADPH CO2 This is done in a three-phase cycle… Sugar!
STEP 1: Carbon fixation 5-Carbon Sugar (RuBP) + CO2 + the help of Rubisco (An enzyme) 2 3-Carbon Compounds (PGA) RuBP PGA
ATP adds a phosphate NADPH donatesan electron & removes aphosphate PGAL is the product PGAL
That doesn’t add up • Glucose is a 6-Carbon sugar. • PGAL is a 3-Carbon sugar. • How many times must a chloroplast undergo the Calvin Cycle to create one glucose molecule?
PGA PGAL