Energy and photosynthesis
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  • 1. Energy and Life
    Without the ability to obtain and use energy, life would cease to exist.
  • 2. Chemical Energy & ATP
    Energy comes in many forms:
  • 3. When a candle burns, what is happening?
  • 4. ATP
    The principal chemical compound used for energy.
  • 5. What is ATP?
    It contains the following:
    5 – Carbon Sugar (Ribose)
    3 Phosphate Groups
    Analogy: ATP is like a ……
    The three phosphate groups are key to storing and releasing the energy of ATP.
  • 6. What is ADP?
    A battery that needs charged!!!
    It is just like ATP, but is missing a phosphate group.
    To store energy the third phosphate group is added to make ATP.
    How does ATP release its energy?
  • 7. How Do Cells Use the Energy of ATP?
    Active Transport – Pumps Na+ out of the cell and K+ into the cells to maintain ion balances.
    MotorProteins – ATP gives these proteins the energy they need to move organelles around the cell. 
    Blinkof aFirefly – ATP powers the enzymes that allow fireflies to blink
    ProteinSynthesis – Helps to bond amino acids together to make proteins..
  • 8. Why Do Cells Contain Only a Small Amount of DNA?
    Cells only have enough ATP to fuel the cells for a few seconds.
    ATP is great at transferring energy, but not at storing it.
    Glucose stores 90x more energy the ATP!!
  • 9. Photosynthesis
    Plants use the sun’s energy to convert CO2 & H2O.
  • 10. Van Helmont’s Experiment
    He planted a seedling in a measured amount of soil. After 5 years, he had a small tree, but the mass of the soil was unchanged.
    What did he conclude?
    He only added one thing to the seedling….
  • 11. Priestley’s Experiment
    He put a glass jar over a candle. What happened?
    Then he put a sprig of mint with the candle under the glass jar. What happened to the candle this time?
  • 12. Jan Ingenhousz
    He found that Priestly’s results were only valid if sunlight was present.
    The work of the three men led to what we know about photosynthesis today……it requires light, and can turn CO2 and H2O into sugars while giving off oxygen.
    Once the glucose is made, it can be converted into complex starches.
  • 13. Light and Pigments of Photosynthesis
    Pigment – light absorbing molecules found in autotrophs (absorb the energy with the light)
    Chlorophyll – plants principal pigment (chlorophyll a & b) – reflects green wavelengths of light
  • 14. Structure of a Chloroplast
    Thylakoids – sac – like photosynthetic membranes found in chloroplasts
    Grana – stacks of thylakoids
    Photosystems – clusters of pigments and proteins that absorb light energy in thylakoids
    Stroma – outside the thylakoid membrane where Calvin Cycle occurs
  • 15. Light Dependent Reactions
    Occurs only with sunlight.
    Makes ATP & NADPH
    Occurs in the Thylakoid Membrane 
  • 16. Light Independent Reactions
    Calvin Cycle
    Don’t need sunlight
    Makes the sugars (glucose)
    Occurs in the Stroma
  • 17. Electron Carrieres
    Light “excites” electrons in chlorophyll. Theses excited elections are then carried from chlorophyll to OTHER MOLECULES.
    CarrierMolecule – A compound that can accept a pair of high energy electrons and transfer the electron and their energy to another molecule.
    Ex. NADP+ - A carrier Molecule
    It becomes NADPH when it accepts electrons and their energy.
    This energy is then used to build energy rich molecules.
  • 18. The Light Dependent
  • 19. First Step
    Photosystem II Pigments absorb sunlight. That energy is absorbed by two electrons and passed to the ELECTRON TRANSPORT CHAIN. (the carriers)
  • 20. Second Step
    These excited electrons are moved to PhotosystemI (with their energy). The energy is used to transport H+ ions from the stroma to the thylakoid space.
  • 21. Third step
    In Photosystem I, its pigments absorb more light and reenergize the electrons.
    NADP+ picks up the electrons and H+ ions on the surface of the thylakoid membrane and becomes NADPH.
  • 22. Fourth step
    As the electrons are passed from chlorophyll to NADP+, H+ ions are pumped across the membrane. This makes inside the thylakoid + and the outside -. This charge difference produces energy to make ATP.
  • 23. Fifth step
    ATP Synthase in thylakoid membrane to allow H+ to pass and adds a phosphate to ADP to make ATP.
  • 24. The Calvin Cycle
    ATP and NADPH will only remain stable for a few minutes. The Calvin Cycle uses the ATP and NADPH from the light-dependent reactions to produce high-energy sugars. 
  • 25. Step 1
    3 CO2 molecules enter the cycle from the air and combine with 3, 5 carbon molecules (RuBP) .
    The result is 6,3 carbon molecules (PGA).
  • 26. Step 2
    The 6, 3-carbon PGA molecules are converted then to higher energy forms by adding a phosphate group. (energy comes from 6 ATPs and high energy electrons form NADPH)
  • 27. Step 3
    1 of the 6, 3 carbon molecules (G3P) are removed to make sugar, lipids, and other compounds. Another 3 carbon G3P molecule is need to make sugar. Hence, a repeat of the cycle.
  • 28. Step 4
    The 5 remaining 3 carbon molecules are converted into 5, 5 carbon molecules to be reused in step 1. ADP and NADP+ will be reenergized in light reactions.
  • 29. What Affect the Rate of Photosynthesis?