Chapter 8 Photosynthesis by 36FgQS

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									Chapter 8 Photosynthesis

   8-1 Energy and Life

   8-2 Photosynthesis: An Overview

   8-3 The Reactions of Photosynthesis
     8-1 Energy and Life
   Key Concepts:
    – Where do plants get the energy they need to
      produce food?
    – What is the role of ATP in cellular activities?
   Vocabulary:
    – Autotroph
    – Heterotroph
    – Adenosine triphosphate (ATP)
   Autotrophs: (auto = “self”)
    – Organisms that make their own food
      (energy). (plants and some bacteria)
   Heterotrophs: (hetero = other)
    – Obtain energy from food they consume.
   Chemical Energy and ATP
    – Energy can be stored in many forms:
       Light

       Heat

       Electricity

       Chemical      Compounds (BONDS!)
   ATP
    – Adenosine TriPhosphate
          Adenine (N)
          5-Carbon Sugar (Ribose)
          3-phosphate groups

   ADP
    – Adenosine DiPhosphate
          Adenine (N)
          5-Carbon Sugar (Ribose)
          2-phosphate groups
           ATP and Energy
   ATP- stores energy in living things
     – JUST ENOUGH energy…….

    The   characteristics of ATP make it an
    exceptionally useful molecule that is used
    by all types of cells as their BASIC
    energy source.
   Energy is released when ATP is converted
    to ADP
   Energy is stored when a phosphate group
    is added to ADP
•Please draw the molecular structure of ATP in your notes
                                           to power
                                            the cell

Energy is stored when a    Energy is released when
phosphate group is added   ATP is converted to ADP
to ADP
•Is this ATP or

•Is it ready to
release or store
           Use of ATP
Ways cells use ATP:
 Active transport (Sodium/Potassium
 Movement in the cell
  – Organelles moving along the cytoskeleton
    use energy in the form of ATP
   ATP:
    – Efficient in transferring energy
    – Not very good for storing large amounts
      of energy long term.
        Useful for a few seconds

    – A single molecule of sugar (glucose)
      stores more than 90 times the chemical
      energy of a molecule of ATP
        Cells regenerate ATP by using the
         energy in carbs like glucose……so
         more efficient for the cell to keep a
         small supply of ATP on hand.
Review…with the person
  sitting next to you…

   What is the difference between ADP and
   What happens when a phosphate group is
    removed from ATP?

   Is ATP for short term or long term storage of
    energy (why?) How do the cells regenerate
      8-2 Photosynthesis
   Key Concepts:
    – What did the experiments of van Helmont,
      Priestley, and Ingenhousz reveal about how
      plants grow?
    – What is the overall reaction for photosynthesis?
    – What is the role of light and chlorophyll in
   Vocabulary:
    – Photosynthesis
    – Pigment
    – chlorophyll
    8-2 Photosynthesis: An Overview

   Photosynthesis:
    – Plants use the energy of sunlight to
      convert water and carbon dioxide into
      oxygen and high energy carbohydrates
      (sugars and starches).

H2O + CO2 + Sunlight      O2 + Carbohydrates
   3 different scientists helped identify the
    components of the photosynthesis
    – Van Helmont
    – Priestley
    – Ingenhousz
Jan Baptiste Van
         The Von Helmont Problem

  QUESTION: Do plants grow by taking material
  out of the soil?

• He put a 2.3 kg. (5 lb.) willow tree in 90.8 kg
  (200 lbs). of soil.
• The tree received only rainwater for five years.
• After 5 years, Von Helmont found that the soil
  only weighed 57 g less than when the
  experiment began.
• The willow tree now weighed 76.8 kg (169 lbs. 3
What did Helmont conclude was
responsible for most of the tree
weight gain?

Is this the only thing responsible?
Joseph Priestley
   In 1772 another Englishman, Joseph
    Priestly (1733-1804), reported the results of
    an important experiment.
   He found that a sprig of mint would not die
    when placed in air that had been “spent”
    (used) by burning a candle in it.
   To the contrary, in such air the plant would
    grow and the air would then, to his
    astonishment, again support a candle flame.
   Priestly inferred that the mint produced a
    substance that was required for burning.

   What is that substance?
J. Ingenhousz
 The  Dutch physician, Jan
  Ingenhousz, published
  Experiments on Vegetables, which
  supplied experimental evidence
  stating that the effect observed by
  Priestly occurred only in sunlight.
 He showed that only the green
  parts of plants, especially the
  leaves, have this capacity.
Review…with the person
  sitting next to you…

   What were the contributions of…
    – Van Helmont?
    – Priestly?
    – Ingenhousz?
(Before the REAL fun begins!)

6H2O + 6CO2 ----------> C6H12O6+ 6O2

 •Photosynthesis uses the energy of
 sunlight to convert water and carbon
 dioxide into oxygen and high energy
 •C6H12O6 = sugar
 •Plants use the sugars to produce
 complex carbohydrates such as
         Light & Pigment

   In addition to water and carbon dioxide,
    plants need light and chlorophyll
   The sun’s energy travels to earth as light
    – Colors we see= visible spectrum
    – Different wavelengths= different colors
   Chlorophyll=pigment (molecule) in plants
         Light & Pigment
   White light is actually a mixture of different
    wavelengths of light.
   Plants gather the sun’s energy with light
    absorbing molecules called PIGMENTS.
   The plant’s principle pigment is chlorophyll
    and there are 2 main types: “a” and “b.”
    – Plants also contain red and orange pigments
      such as carotene which absorbs light in other
      areas of the spectrum.
   Energy absorbed by chlorophyll is
    transferred directly to electrons in the
    chlorophyll molecule. These high energy
    electrons make photosynthesis work.
  So why are leaves green?

•Look at the
wavelengths of
light that
absorbs & uses in
•The colors that
are left are
reflected back
and that is what
you see.
 Chlorophyll absorbs mostly red and
  blue wavelengths of light
 Since light= energy
    – Chlorophyll absorbs energy, which is
      transferred to electrons that can do work
 Review…with the person
   sitting next to you…

 What is the photosynthesis equation?
 What is the function of chlorophyll?

 Would a plant grow well in green light?
    8-3 The Reactions of
   Key Concepts
    – What happens in the light-dependent reactions?
            LIGHT REACTIONS
    – What happens in the light-independent
            DARK REACTIONS
   Vocabulary
    –   NADP+ / NADPH
    –   ADP / ATP
    –   Chlorophyll
    –   Chloroplast
    –   Glucose
    –   Light Reactions
    –   Dark Reactions
   In the last section, we learned
    – Pigments, such as chlorophyll absorb sunlight
    – Pigments are found in leaf cells
    – Plant leaves have openings (called stomata)
      where Carbon Dioxide enters

    – Water is brought into a plant by the roots
6H2O + 6CO2 ----------> C6H12O6+ 6O2

This is where photosynthesis occurs…
   Thylakoid= cluster of proteins and
    pigments tha capture the sun’s energy
    – In stacks called grana

   Stroma= space on the interior of a
     Before we get to the
         hard stuff…
   When the sun excites electrons, they
    increase in energy
   They are so “hot” that they need an electron
    – Ex: Hot coals
   An electron carrier moves high energy
    electrons from chlorophyll to other
    molecules (without using much energy itslef)
    – In photosynthesis, this electron carrier is NADPH
    – Empty dump truck (NAD+) vs. full dump truck
To simplify the very complex process
of photosynthesis, we are going to set
up the 2 reactions (Light and Dark) as
a chart in our notes.
 H20                      CO2

   Light               “Dark”      Glucose
 Reactions            Reactions

Thylakoids            Stroma

  O2                      H20
              ADP        (waste)
       Equation for

6H2O + 6CO2 ----------> C6H12O6+ 6O2
The Light Reactions:
USE                    PRODUCE
Water                  Oxygen (O2)
ADP                    ATP
NADP+                  NADPH
Light Energy                           Write
                                     this info
                                      in your
The Dark Reactions:
USE                    PRODUCE
Carbon Dioxide (CO2)   Glucose
ATP                    ADP
NADPH                  NADP+
       Factors Affecting
   Water supply
   Temperature
    – Some of the enzymes function best
      between 0-35 degrees Celsius.
   Intensity of light
    – As light intensity increases, so does the
      rate of photosynthesis (to a point)
   Which reaction is “light independent”?
   What is the name of the electron carrier in
   What are the 3 things needed for the Dark
    Reaction to occur?
   What is the main product of photosynthesis?
   What 2 things are “recycled” back to the
    light reaction?

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