PhotosynthesisPhotosynthesisBiology 1114

Autotrophs “Self Feeders” Autotrophs “Self Feeders” PhotosynthesizePhotosynthesize

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

Photosynthesis “The conversion of light Photosynthesis “The conversion of light energy from the sun into chemical energy from the sun into chemical

energy”energy”

• Light Energy is converted into Chemical Energy

• Organisms trap the Sun’s Energy to Build Carbohydrates

chlorophyll

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

Photosynthesis Photosynthesis Enables Societies Enables Societies to Function and to Function and is the Sole Means is the Sole Means of Sustaining of Sustaining LifeLife

Utilization of Photosynthetic Utilization of Photosynthetic SugarsSugars

• Wood

• Fibers

• Stored Carbohydrates

• Amino Acids

• Clothing

• Shelter

• Food

Photosynthesis Photosynthesis Provides Provides Consumers with Consumers with Energy Through Energy Through the Ingestion of the Ingestion of ProducersProducers

Ozone Protects us Ozone Protects us from UV Radiation from UV Radiation from the Sunfrom the Sun

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.

Skin Cancer

Scientists say ozone layer recovery may not be detectable

for as many as 45 years.

Fossil FuelsFossil Fuels

PhotosynthesisPhotosynthesis

chlorophyll

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

enzymes

PhotosynthesisPhotosynthesis

• 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

PhotosynthesisPhotosynthesis

chlorophyll

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

enzymes

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

Von Helmont Von Helmont ExperimentExperiment

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.

Where Does Photosynthesis Occur?

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

This Chemical Energy is Stored in ATP and NADPHThis 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 Light Independent Reactions Do Not Reactions Do Not Require SunlightRequire Sunlight

They Assemble They Assemble Sugars by Using Sugars by Using ATP and NADPHATP and NADPH

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

Necessary Molecules of MatterNecessary Molecules of Matter

• Carbon Dioxide– .035%– Diffuses through

Stomata– Removed by

Photosynthesis– Returned by

Respiration

Necessary Molecules of MatterNecessary Molecules of Matter

• Water– Taken up through Roots – <1% used by Photosynthesis– >99% lost via Transpiration

LightLight• Exhibits Properties of Both waves and Particles of

Energy• Electromagnetic Spectrum• Visible Light is Involved in Photosynthesis

High Energy Low Energy

Electromagnetic SpectrumElectromagnetic Spectrum

High EnergyHigh Energy Gamma Rays Short WavelengthShort Wavelength

X-Rays

Ultra Violet

Visible Light

Infrared

Microwaves

Low EnergyLow Energy Radio Waves Long WavelengthLong Wavelength

Visible Light (Roy G. Biv)Visible Light (Roy G. Biv)

High EnergyHigh Energy Violet Short WavelengthShort Wavelength

Indigo

Blue

Green

Yellow

Orange

Low EnergyLow Energy Red Long WavelengthLong Wavelength

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

The Reactions of PhotosynthesisThe Reactions of Photosynthesis

1. Photosynthesis begins with the light-dependent reactions.

2. Light-dependent reactions are followed by light-independent reactions

Essentials and General OverviewEssentials and General Overview

Summation of Light Dependent RxnSummation of Light Dependent Rxn

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 P + ADP ATPATP

OO22 is Released 2H2H++ and NADPHNADPH For Use in the Light-For Use in the Light-Independent Independent ReactionReaction

Light Independent Reactions or Light Independent Reactions or Calvin CycleCalvin Cycle

• Stroma

• Light or Dark

• Requires1. Carbon Dioxide

2. Hydrogen Protons and Electrons

3. ATP

4. Enzymes

5. RUBP

Do What?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 PhosphorylationNote: The two reactions (Light and Dark) are complementary to one another.

Essentials of PhotosynthesisEssentials 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 PhotosynthesisEssentials 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.