Supramolecular Chemistry, UAF, 2005. Photosynthesis Where does the energy come from that sustains all life? The Sun!! Well most of it anyway……

Supramolecular Chemistry, UAF, 2005


PhotosynthesisPhotosynthesisWhere does the energy come from that

sustains all life?

The Sun!!The Sun!!Well most of it anyway……


What is photosynthesis?What is photosynthesis?

In the process of photosynthesis, plants In the process of photosynthesis, plants convert the energy of sunlight into the convert the energy of sunlight into the energy in the chemical bonds of energy in the chemical bonds of carbohydrates-sugars and starches.carbohydrates-sugars and starches.


Discovery of the process:Discovery of the process:

For many years, people wondered how a few For many years, people wondered how a few seedlings could develop into a large tree. seedlings could develop into a large tree. The mass of seedlings are only a few grams, The mass of seedlings are only a few grams, where as the mass of a tree is several tons. where as the mass of a tree is several tons. Dutch physician Jan Van Helmont devised an Dutch physician Jan Van Helmont devised an experiment. experiment. He concluded that the mass grew from the He concluded that the mass grew from the water, because that was the only thing he had water, because that was the only thing he had added to the pot. added to the pot. This was just one of the things needed for This was just one of the things needed for photosynthesis to occur.photosynthesis to occur.


What makes photosynthesis complete?What makes photosynthesis complete?

Helmont did not realize that Helmont did not realize that carbon dioxidecarbon dioxide in the air also plays a major role in the in the air also plays a major role in the contribution of mass growth. contribution of mass growth.

The carbon in carbon dioxide is what is The carbon in carbon dioxide is what is used to make used to make carbohydratescarbohydrates in in photosynthesis.photosynthesis.


Later on, scientist Joseph Priestly Later on, scientist Joseph Priestly performed an experiment that would give performed an experiment that would give rise to rise to why oxygen is releasedwhy oxygen is released in in photosynthesis, and why photosynthesis, and why sunlight is sunlight is neededneeded for it to photosynthesize. for it to photosynthesize.

Priestly placed a candle in a jar along with Priestly placed a candle in a jar along with a mint plant. a mint plant.

He then realized that the candle could only He then realized that the candle could only stay lit when the mint plan was present. stay lit when the mint plan was present.

This would mean that the plant was This would mean that the plant was releasing releasing oxygenoxygen. .


Why is Photosynthesis important?Why is Photosynthesis important?

Through experiments, it was realized that Through experiments, it was realized that in the presence of light, plants transform in the presence of light, plants transform carbon dioxide and water into carbon dioxide and water into carbohydrates and release oxygen. carbohydrates and release oxygen. Plants that are able to use a source of Plants that are able to use a source of energy, such as sunlight, to provide food energy, such as sunlight, to provide food directly from simple inorganic molecules directly from simple inorganic molecules are known as are known as autotrophsautotrophs. . This is made possible through This is made possible through photosynthesis.photosynthesis.


WHAT IS THE WHAT IS THE DIFFERENCE BETWEEN A DIFFERENCE BETWEEN A

HETEROTROPH & AN HETEROTROPH & AN AUTOTROPH?AUTOTROPH?


the equation for photosynthesis is:the equation for photosynthesis is:


6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O

The sugars that result from photosynthesis are

produced by adding the hydrogen ions and electrons

from water to carbon dioxide, NOT by splitting CO2 and

adding water!

oxidized

reduced

H+ and e-


Bromothymol BlueBromothymol Blue

Used to test for the presence of carbon Used to test for the presence of carbon dioxide (COdioxide (CO22))

If COIf CO22 is present it is a is present it is a yellowyellow color color

If COIf CO22 is is NOTNOT present it is a present it is a blueblue color color



Light Absorption & Light EnergyLight Absorption & Light Energy

The actual process of photosynthesis The actual process of photosynthesis begins when light is absorbed by pigments begins when light is absorbed by pigments in the plant cell. in the plant cell.

The principal pigment in plants is The principal pigment in plants is chlorophyllchlorophyll which gives the plant its green which gives the plant its green color.color.


internal leaf structure

chloroplastsouter membrane

inner membrane

thylakoid

Plant PhotosynthesisPlant Photosynthesis


Photosystems use some wavelengths of light but reflect Photosystems use some wavelengths of light but reflect others…others…


Another way in which light energy is Another way in which light energy is trapped in chemical form involves trapped in chemical form involves adenosine triphosphate or ATPadenosine triphosphate or ATP. . During photosynthesis, green plants During photosynthesis, green plants produce ATP, which is the energy storing produce ATP, which is the energy storing compound used by every living cell. compound used by every living cell. The energy is released by means of The energy is released by means of breaking the phosphate bondsbreaking the phosphate bonds which which make up the ATP cycle. make up the ATP cycle. The energy is used in almost all cellular The energy is used in almost all cellular activities.activities.


Respiration vs. PhotosynthesisRespiration vs. Photosynthesis


Photosynthesis and respiration are Photosynthesis and respiration are complementarycomplementary processes in the living world. processes in the living world. Photosynthesis uses the energy of sunlight to Photosynthesis uses the energy of sunlight to produce produce sugarssugars and other organic molecules. and other organic molecules. These molecules in turn serve as food. These molecules in turn serve as food. Respiration is a process that uses O2 and forms CO2 from Respiration is a process that uses O2 and forms CO2 from the same carbon atoms that had been taken up as CO2 and the same carbon atoms that had been taken up as CO2 and converted into sugars by photosynthesis. converted into sugars by photosynthesis. In respiration, organisms obtain the energy that they need to In respiration, organisms obtain the energy that they need to survive. survive. Photosynthesis Photosynthesis precededpreceded respiration on the earth for respiration on the earth for probably billions of years before enough O2 was released to probably billions of years before enough O2 was released to create an atmosphere rich in oxygen. create an atmosphere rich in oxygen. (The earth's atmosphere presently contains 20% O2.)(The earth's atmosphere presently contains 20% O2.)


Self-Evaluation QuestionsSelf-Evaluation Questions1. In the process of photosynthesis, plants convert 1. In the process of photosynthesis, plants convert

the energy of sunlight into what?the energy of sunlight into what?2. When Helmont devised an experiment, he 2. When Helmont devised an experiment, he

concluded that the mass grew from the_____, concluded that the mass grew from the_____, which was the only thing he had added to the soil.which was the only thing he had added to the soil.

3. What scientist gave rise to the explanation of 3. What scientist gave rise to the explanation of plants giving off oxygen, and the reason sunlight is plants giving off oxygen, and the reason sunlight is needed in order for plants to photosynthesize?needed in order for plants to photosynthesize?

4. Fill in the missing part of the equation for 4. Fill in the missing part of the equation for photosynthesis--Carbon dioxide + water yields photosynthesis--Carbon dioxide + water yields what? (two things)what? (two things)

5. What do you call plants that obtain their nutrients 5. What do you call plants that obtain their nutrients in organic molecules through photosynthesis?in organic molecules through photosynthesis?

Supramolecular Chemistry, UAF, 2005. Photosynthesis Where does the energy come from that sustains all life? The Sun!! Well most of it anyway……

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