Background information before Photosynthesis

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Background informationbefore Photosynthesis

• ATP cycle
• Redox reactions
• Electron Transport Chain (ETC)
• Coenzymes (NADP)

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ATP Cycle

• Adenosine Triphosphate is an energy carrying
  molecule.
• Adenosine Phosphate Phosphate Phosphate
• When there is a demand for energy in our cells,
  enzymes break the last bond () releasing useable
  energy, producing
• Adenosine Phosphate Phosphate Phosphate
• (ADP Phosphate energy release)
• Dephosphorylation Exergonic reaction

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ATP Cycle

• After cellular respiration, a lot of energy is
  release from the break down of glucose.
• This energy can be used to attach free phosphates
  to ADP to produce ATP. In fact there is enough
  energy released to require the formation of 36
  ATP molecules.
• Phosphorylation- attachment of a phosphate group
• Phosphorylation - Endergonic
• This breaking down and building up of ATP is
  called the ATP cycle
• Other reactions where ATP is formed Glycolysis
  and the Light Reaction of photosynthesis

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ATP Cycle
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ATP Cycle

• What is ATP?
• ATP cartoon

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Redox Reactions

• Reduction is gaining electrons/hydrogen (and
  usually some energy)
• Oxidation is losing electrons/hydrogen (and
  usually some energy.
• OIL RIG
• During most chemical reactions, electrons are
  being lost or gained by atoms that make up
  molecules.
• Molecules that gain electrons are said to be
  reduced and molecules that lose electrons are
  said to be oxidized

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Electron Transport Chain

• - a series of redox reactions that transport
  electrons
• 2e-
  
  
  

Energy
Coe
ADP P ATP
Coe
Coe
Coe
Coenzyme
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Electron Transport Chain

• When a coenzyme grabs 2 electrons, it has been
  reduced.
• When the coenzyme releases the electrons, it has
  been oxidized, and energy is released.
• Using this energy to attach a phosphate to ADP is
  called Oxidative Phosphorylation.
• If some protons are waiting at the bottom of the
  ETC, they join with the electrons to form
  Hydrogen atoms

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Coenzymes

• Coenzymes are organic molecules that act as
  electron carriers, or Hydrogen carriers.
• The coenzyme that functions in photosynthesis is
  Nicotinamideadeninedinucleotidephosphate
• Ok, it is really 4 words, and we can call it NADP
• NADP 2H NADPH2

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Photosynthesis

• Divided into 2 stages, the Light Reaction and the
  Dark Reaction
• Balanced chemical equation
• 6 CO2 12 H2O Light C6H12O6 6O2 6H2O
• DR LR DR
  LR DR

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Chloroplast
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Light Reaction

• Can only take place in the presence of light
  energy
• Happens in the thylakoid disks
• Consists of 3 reactions that are happening at the
  same time and are interdependent.
• Photosystem 1 (PS1)
• Photosystem 2 (PS2)
• Photolysis

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Electromagnetic Spectrum
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Products of the Light Reaction

• The Light Reaction is considered the power
  phase
• The products of the Light Reaction are
• ATP provide a source of energy for the Dark
  Reaction (and some phosphates)
• NADPH2 provide H for the Dark Reaction (and a
  little energy)

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Photosystem 1

• Chlorophyll of PS1 absorbs energy and becomes
  excited (EM spectrum?)
• Chlorophyll loses 4 electrons
• This creates a problem chlorophyll aint
  chlorophyll no more
• PS2 to the rescue!

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Photosystem 2

• Chlorophyll of PS2 absorbs light energy
• Chlorophyll loses 4 electrons
• These electrons move along an ETC and replace the
  electrons lost in PS1
• As they move along the ETC, energy is given off
  and used to produce ATP.
• For every pair of electrons moved, enough energy
  is released to synthesize 1 ATP, therefore .
• One problem solved.
• One problem created

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PS2 continued

• Chlorophyll of PS1 has been restored
• Chlorophyll of PS2 is missing electrons
• Have no fear!
• Photolysis to the rescue!

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Photolysis

• - breakdown of water, in the presence of
  sunlight.
• 2 H2O sunlight 4 Hydrogen atoms 2 oxygen
  atoms.
• 4 H separate into 4 electrons (-) and 4 protons
  ()
• 2 O join to form O2 (atmospheric oxygen gas)

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What happens to the products of Photolysis?

• 4 electrons replace those lost from PS2
• 4 protons - join with the original electrons
  lost from PS1 to form 4 hydrogen atoms
• O2 is released into the atmosphere
• The 4 hydrogen atoms are picked up by the
  coenzyme (hydrogen carrier) NADP
• 2 NADP 4 H 2NADPH2
• 2NADPH2 carry hydrogen atoms to the Dark Reaction

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How many ATP are produced in the Light Reaction?

• 2 ATP come from the ETC
• A third ATP is produced when sunlight provides
  the energy needed to attach a phosphate to an ADP
  molecule..this is called
• Photophosphorylation

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End products of the Light Reaction

• 2 NADPH2 carry hydrogen atoms to the Dark
  Reaction (and some energy)
• 3 ATP provide energy for the Dark Reaction
  (and some phosphates)

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Light Reaction Summary