Photosynthesis Overview - rgreenbergscience.ppt by pptfiles


           Essential Questions:
How does the process of photosynthesis store
   What are the steps of Photosynthesis?
 Why is photosynthesis important for life on
    Match the seed to its plant

                     2            C

The sequoia is the largest living thing on Earth!

But it starts as a TINY seed…

        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
  – 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
   – 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
                  • The Chloroplast is
                    the cell organelle
                    where photosynthesis
                  • In the chloroplasts are
                    pigments that
                    absorb wavelengths
                    of light.
Where are the

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
• 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.)
           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
   – Otherwise the dark reaction could
     not occur!
                                                                     • The Calvin cycle
                                                                       uses the ATP and
                                                                       NADPH from the
                                                                       light dependent
                                                                       reaction to create
                                                                     • Reactant:
                                                                       Carbon Dioxide
                                                                     • Product:
                                                                       a 6 Carbon Sugar
                                                                         Calvin’s in the
                                                                         Dark about
          What’s the big deal about
• 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!
     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
• Make sure to write
  down further
  questions you have!
• Turn it into the box
  before you leave
  class today!

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