PHOTOSYNTHESIS

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PHOTOSYNTHESIS
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PLANTS PROVIDE THE WORLDS ORGANISMS WITH FOOD

• Plants produce carbohydrates by converting light
  energy into chemical energy
• Photosynthesis is the process by which this
  conversion takes place

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THE BIG PICTURE
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THE REACTIONS OF PHOTOSYNTHESIS
Overall Rxn
12 H2O 6 CO2
6 O2 C6H12O6 6 H2O
LIGHT
CARBON DIOXIDE
OXYGEN
WATER
GLUCOSE
WATER
Net Rxn 6 CO2 6 H2O light? C6H12O6 6
O2 Simplest form CO2 H2O light? CH2O
O2
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PLANT ANATOMY

• Leaves
• Major organs of photosynthesis
• Mesophyll
• Tissue in interior of leaves

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photosynthetic cells
upper surface of leaf
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PLANT ANATOMY

• Stomata
• Tiny pores that allow gas exchange

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Leaf surfaces contain stomata
18 µm
Pore
Guard cells
Stoma
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Carbon dioxide diffuse into leaves through stomata
H2O
H2O
Leaf cross-section
CO2
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PLANT ANATOMY

• Chloroplasts
• Organelles in plant cells
• Site of photosynthesis

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Leaves contain millions of chloroplasts
Leaf cross-section
Cells containing chloroplasts
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Chloroplasts are highly structured, membrane-rich
organelles.
Outermembrane
Innermembrane
Thylakoids
Granum
Stroma

• Stroma (Not To Be Confused With Stomata!!!)
• Dense fluid within surrounding thylakiod

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ENERGY FROM LIGHT IS CAPTURED AND CONVERTED IN
CHLOROPLASTS

• Energy from light is passed through an ETC (in
  chloroplasts) that converts it into a usable
  chemical form

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LIGHT DARK REACTIONS

• Transformation of solar energy into chemical
  energy occurs through 2 metabolic pathways
• Light Reactions
• Convert solar energy into cellular energy
• Calvin Cycle
• Reduce CO2 to CH2O

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LIGHT REACTIONS

• Light Rxns
• Occur in thylakoid
• Use light (photo) to make chem. energy in form of
  ATP NADPH
• Produce oxygen as by product

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PROPERTIES OF LIGHT

• Light
• Form of energy called EM radiation
• Travels in waves
• Behaves as if composed of matter

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PHOTONS

• Photons
• Are not tangible matter
• Are units of energy
• Have fixed quantity of energy
• Photon energy is inversely related to wavelength
• Shorter wavelength greater photon energy

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400-nanometer wavelength
750-nanometer wavelength
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WAVELEGNTH

• Different types of light have characteristic
  wavelengths associated with them
• Wavelength
• Distance between two sequential peaks
• Measured in nanometers (nm) 10 9 meters

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ELECTROMAGNETIC (EM) SPECTRUM

• EM Spectrum
• The entire range of
• EM radiation
• Visible Light Spectrum
• Consists of narrow band of light detectable to
  the human eye
• 380-750 nm
• Light that drives photosynthesis

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THE VISIBLE LIGHT SPECTRUM
1013
Radiowaves
Visiblelight
1011
750
Lowerenergy
Higherwavelength
109
700
Micro-waves
107
105
Infrared
Wavelengths (nm)
600
103
Ultra-violet
101
500
10-1
X rays
10-3
Gammarays
Lowerwavelength
Higherenergy
400
10-5
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PROPERTIES OF LIGHT

• As Light Meets Matter It May Be
• Reflected
• Transmitted
• Absorbed

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WAVELEGNTH COLOR

• We perceive waves of EM radiation (visible light
  spectrum) as different colors
• We see objects as the color that correspond to
  the wavelength those objects transmit/reflect