Lesson Overview

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Lesson Overview

• 8.2 Photosynthesis An Overview

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Light

• Energy from the sun travels to Earth in the form
  of light.
• Sunlight is a mixture of different wavelengths,
  many of which are visible to our eyes and make up
  the visible spectrum.

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Pigments

• Plants gather the suns energy with
  light-absorbing molecules called pigments.
• The plants principal pigment is chlorophyll.

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Pigments
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Chloroplasts

• Chloroplasts contain saclike photosynthetic
  membranes called thylakoids, which are
  interconnected and arranged in stacks known as
  grana.
• The fluid portion outside of the thylakoids is
  known as the stroma.

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Energy Collection

• When chlorophyll absorbs light, a large fraction
  of the light energy is transferred to electrons.
  These high-energy electrons make photosynthesis
  work.

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High-Energy Electrons

• The high-energy electrons produced by chlorophyll
  are highly reactive and require a special
  carrier.
• Think of a high-energy electron as being similar
  to a hot potato. If you wanted to move the potato
  from one place to another, you would use an oven
  mitt a carrierto transport it.
• Plants use electron carriers to transport
  high-energy electrons from chlorophyll to other
  molecules.

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High-Energy Electrons

• NADP (nicotinamide adenine dinucleotide
  phosphate) is a carrier molecule.
• NADP accepts and holds two high-energy
  electrons, along with a hydrogen ion (H). In
  this way, it is converted into NADPH.
• The NADPH can then carry the high-energy
  electrons to chemical reactions elsewhere in the
  cell.

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An Overview of Photosynthesis

• Photosynthesis uses the energy of sunlight to
  convert water and carbon dioxide into high-energy
  sugars and oxygen.
• In symbols
• 6 CO2 6 H2O ? C6H12O6 6 O2
• In words
• Carbon dioxide Water ? Sugars Oxygen

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An Overview of Photosynthesis

• Plants use the sugars generated by
  photosynthesis to produce complex carbohydrates
  such as starches, and to provide energy for the
  synthesis of other compounds, including proteins
  and lipids.

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Light-Dependent Reactions

• Photosynthesis involves two sets of reactions.
• The first set of reactions is known as the
  light-dependent reactions because they require
  the direct involvement of light and
  light-absorbing pigments.

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Light-Dependent Reactions

• The light-dependent reactions use energy from
  sunlight to produce ATP and NADPH.
• These reactions take place within the thylakoid
  membranes of the chloroplast.
• Water is required as a source of electrons and
  hydrogen ions. Oxygen is released as a byproduct.

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Light-Independent Reactions

• During light-independent reactions, ATP and
  NADPH molecules produced in the light-dependent
  reactions are used to produce high-energy sugars
  from carbon dioxide.
• No light is required to power the
  light-independent reactions.
• The light-independent reactions take place
  outside the thylakoids, in the stroma.

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Questions

• In the process of photosynthesis, plants convert
  the energy of sunlight into chemical energy
  stored in the bonds of _________.
• Carbohydrates
• Photosynthetic organisms capture energy from
  sunlight with ________.
• Pigment
• The plants principal pigment is _______.
• Chlorophyll
• Photosynthesis takes place in ___________.
• Chloroplasts
• T or F - Chloroplasts contain an abundance of
  saclike photosynthetic membranes called
  thylakoids.
• TRUE
• T or F - The fluid portion of the chloroplast,
  outside of the thylakoids, is known as the
  matirx.
• FALSE - STROMA
• Raising the energy levels of electrons on the
  chlorophyll molecule, light energy can produce a
  steady supply of _______________electrons, which
  is what makes photosynthesis work.
• High Energy

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Questions

• 8. An electron _________is a compound that can
  accept a pair of high-energy electrons and
  transfer them, along with most of their energy,
  to another molecule.
• Carrier
• 9. NADP is converted to ______________as it
  accepts and transfers electrons to chemical
  reactions elsewhere in the cell.
• NADPH
• 10. What is the overall equation of
  photosynthesis?
• 6CO2 6H2O light ? C6H12O6 6O2
• 11. The light- ______________reactions produce
  ATP and NADPH from sunlight in the thylakoid
  membranes.
• Dependent
• 12. The light-______________t reaction in the
  stroma, sugars are created from carbon dioxide
  using the ATP and NAPH from the light-dependent
  reactions.
• Independent

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Photosynthesis REVIEW
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Photosynthesis REVIEW
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Photosynthesis REVIEW
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Journal

• What is the equation for photosynthesis?