Chapter 8: Photosynthesis

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Chapter 8 Photosynthesis

• Section 3 Process of Photosynthesis

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A. General Formula

• Reactants Carbon Dioxide and Water
• Products Glucose (Food) and Oxygen
• During Photosynthesis, the Suns energy will be
  converted through a series of chemical reactions
  to glucose. This requires an input of CO2 and
  produces O2 as a waste product!

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1. Two Sets of Chemical Reactions

• The Light Dependents Reactions (Light Reactions)
• Require Light (hence the name)
• These reactions take place in chlorophyll
• Utilize water and sunlight
• Produce ATP (Energy) and NADPH (Energy Storing
  Electron Carrier) to be used later on!!
• The Light Independent Reactions (Dark Reactions
  or Calvin Cycle)
• Do not require light (Hence the Dark Part)
• Take place in the Stroma
• Utilize ATP, NADPH, and CO2 from the atmosphere
• Produce Glucose and O2 by using the energy
  gained from light reactions

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2. Light Reactions

• Steps in the Process
• 1. Photosystem II collection of chloroplast
  molecules
• Absorbs light energy (photons)
• Breaks down water into 3 things
• - an Oxygen atom (Which is ½ of O2)
• - 2 Hydrogen ions (Important Later)
• - 2 Electrons that have absorbed suns
  energy (Crazy, Mad Important!)

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2. Electron Transport Chain A collection of
molecules on the thylakoid membrane As
electrons travel down this chain they lose
energy That
energy is used to make ATP! 3. Photosystem I
Captures energy from the sun to re- energize
those two electrons
So they dont lose energy they need to be stored
in a molecules called NADP

When NADP stores those electrons it is called
NADPH- This is another form of energy!
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Inputs Water, Sunlight Outputs ATP, and NADPH
(Both forms of energy for the next step)
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• Dark Reactions/Calvin Cycle

Take Place in the stroma Use energy from light
reactions to turn CO2 from the atmosphere into
Glucose! This an enzyme catalyzed
reaction Rubisco is the most abundant protein on
the planet!!!
Input ATP, NADPH (both from Light Reactions)
CO2 from the atmosphere Output Glucose-
Food for plants (this was the purpose)
ADP, NADP Left over after their energy was
used Return to Light Reactions to get more
energy Oxygen
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Review
General Formula
What are the inputs of the Light reactions?
What are the inputs of the Calvin cycle?
1. H2O (Water)
1. Energy (ATP and NADPH)
2. Sunlight
2. CO2 (from Atmosphere)
What are the outputs of the Light reactions?
What are the outputs?

1. ATP

1. Glucose (Food)

2. NADPH
2. ADP and NADP (To go get more energy from
light reactions
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Factors Effecting Photosynthesis

• Temperature
• Enzymes for Photosynthesis work best between 0
  and 95 degrees Fahrenheit
• Above this we get DENATURATION of Enzymes

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• Light Intensity
• The brighter the light, the greater the rate
  of photosynthesis.
• (Unless it is too hot!)
• Water Availability
• No waterNo photosynthesis

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How do Plants in Extreme Conditions Survive!

• C4 Plants such as corn and sugar cane
• Open stomata at night to let CO2 in when temps
  are low- prevents evaporation of water!
• CAM Plants such as cacti and pineapples
• also only open their stomata at night and
  store CO2 as something else. When light is
  available to produce ATP and NADPH- PS continues

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Sugar Cane C4 Plant Grows in Tropical
climates- Very hot, lots of sunlight (Dominica
n Republic, Costa Rica, Hawaii)
Organ Pipe Cactus CAM Plant Grows in
deserts (Southwestern US, Mexico)