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Photosynthesis. Biology 1114. Autotrophs “Self Feeders” Photosynthesize. Plants. Algae / Protists. Some Bacteria. A Large Proportion of Photosynthesis (40%-50%) Takes Place in the Oceans of the World and is Carried Out by Plankton.

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Biology 1114

autotrophs self feeders photosynthesize
Autotrophs “Self Feeders” Photosynthesize


Algae / Protists

Some Bacteria


A Large Proportion of Photosynthesis (40%-50%) Takes Place in the Oceans of the World and is Carried Out by Plankton

photosynthesis the conversion of light energy from the sun into chemical energy
Photosynthesis “The conversion of light energy from the sun into chemical energy”
  • Light Energy is converted into Chemical Energy
  • Organisms trap the Sun’s Energy to Build Carbohydrates


6CO2 + 12 H2O + Light Energy------------------------> C6H12O6 + 6O2 + 6 H2O


utilization of photosynthetic sugars
Utilization of Photosynthetic Sugars
  • Wood
  • Fibers
  • Stored Carbohydrates
  • Amino Acids
  • Clothing
  • Shelter
  • Food

As you know, the increase in UV radiation due to ozone loss is very damaging to complex molecules, which are an essential ingredient for life as we know it.



6CO2 + 12 H2O + Light Energy------------------------> C6H12O6 + 6O2 + 6 H2O


  • Energy of the sun is transformed into chemical energy stored in food
  • Not 100% efficient
  • Not all sunlight falls on producers
  • Some absorbed energy is subsequently released and lost


6CO2 + 12 H2O + Light Energy------------------------> C6H12O6 + 6O2 + 6 H2O


Photosynthesis changes two low energy molecules (Carbon Dioxide and Water) into a high energy molecule (Sugar).

von helmont experiment

Jon Baptista von Helmont, a 17th century Flemish physician started getting a handle on what happens when plants grow in the soil with his "tree experiment." He was trying to measure how soil matter was displaced when plants grow. To do this, he planted a willow tree in a large earthen tub. He planted a 5-pound sprig into 200 pounds of soil. The tub was then covered except for a small hole for the tree trunk and one for watering.

Five years later, the tree weighed 164 pounds. Von Helmont reasoned if the tree had picked up the difference between 5 pounds and 164 pounds, then the soil in the tub should weigh only 41 pounds. The results proved him wrong! After oven drying the soil, he'found the 200 pounds of soil had only lost 2 ounces.

Von Helmont Experiment

Light Dependent Reactions Require Sunlight to Convert Light Energy into Chemical Energy

This Chemical Energy is Stored in ATP and NADPH

The Thylakoid Membranes contain all the pigments and all the enzymes necessary for the light phase of photosynthesis.


Light Independent Reactions Do Not Require Sunlight

They Assemble Sugars by Using ATP and NADPH

The fluid in the stroma contains most of the enzymes necessary for the dark phase of photosynthesis

necessary molecules of matter
Necessary Molecules of Matter
  • Carbon Dioxide
    • .035%
    • Diffuses through Stomata
    • Removed by Photosynthesis
    • Returned by Respiration
necessary molecules of matter1
Necessary Molecules of Matter
  • Water
    • Taken up through Roots
    • <1% used by Photosynthesis
    • >99% lost via Transpiration
  • Exhibits Properties of Both waves and Particles of Energy
  • Electromagnetic Spectrum
  • Visible Light is Involved in Photosynthesis

High Energy Low Energy

electromagnetic spectrum
Electromagnetic Spectrum

High Energy Gamma RaysShort Wavelength


Ultra Violet

Visible Light



Low Energy Radio Waves Long Wavelength

visible light roy g biv
Visible Light (Roy G. Biv)

High Energy VioletShort Wavelength






Low Energy Red Long Wavelength


Light Energy is Absorbed by Pigment Molecules Each Pigment Has a Characteristic Absorption Spectrum

the reactions of photosynthesis
The Reactions of Photosynthesis
  • Photosynthesis begins with the light-dependent reactions.
  • Light-dependent reactions are followed by light-independent reactions
do what
Do What?
  • During the light-dependent reactions

1. Light Energy is Absorbed

2. Water is Split

3. ATP and NADPH is Formed

Note: At this point Carbon Dioxide has not been used and no sugars have been produced.


Light Energy from the Sun is Transferred to Chlorophyll in Plants

Chlorophyll Passes Energy Down Through the Electron Transport Chain Providing Energy to do Two Things

Split Water


O2 is Released

2H+ and NADPH

For Use in the Light-Independent Reaction

light independent reactions or calvin cycle
Light Independent Reactions or Calvin Cycle
  • Stroma
  • Light or Dark
  • Requires

1. Carbon Dioxide

2. Hydrogen Protons and Electrons

3. ATP

4. Enzymes


do what1
Do What?
  • During the light-independent reactions

1. Carbon Dioxide and Hydrogen

Combine to Make Sugar

2. Sugar Contains High Energy Bonds

3. Process Occurs by Phosphorylation

Note: The two reactions (Light and Dark) are complementary to one another.

essentials of photosynthesis
Essentials of Photosynthesis
  • Two Reactions Complete the Process
  • Carbon Dioxide Combines with Hydrogen Atoms from Water to Make Sugar Molecules
  • Some of the energy that was initially absorbed by the plant in the form of sunlight, and which was temporarily stored in the bonds of ATP (and NADPH) ends up stored in the bonds of the sugar molecules. Since it utilizes the chemical energy in ATP and NADPH, it does not require sunlight
essentials of photosynthesis1
Essentials of Photosynthesis
  • This is a complex cycle of mostly adding or removing phosphate (phosphorylation) and moving electrons in chemical reactions.
  • The two reactions (Light and Dark) are complementary of one another.