PhotosynthesisPhotosynthesis

How is energy being obtained by How is energy being obtained by the organisms in this picture?the organisms in this picture?

Autotrophs & HeterotrophsAutotrophs & Heterotrophs(Review)(Review)

Plants are able to use light energy from the sun Plants are able to use light energy from the sun to produce food. - to produce food. - AutotrophsAutotrophs

Organisms that obtain energy from the foods Organisms that obtain energy from the foods they eat .they eat . - Heterotrophs - Heterotrophs

PhotosynthesisPhotosynthesis

Definition:Definition: Photosynthesis is the Photosynthesis is the

process by which process by which light energy is light energy is converted to converted to chemical energy in chemical energy in form of glucose. form of glucose.

EnergyEnergy

Energy is the ability Energy is the ability to do work and to do work and there’s always work there’s always work to be done by the cellto be done by the cell

First Law of First Law of ThermodynamicsThermodynamics

Energy cannot be Energy cannot be created or destroyedcreated or destroyed—it can only be —it can only be changed in form.changed in form.

Energy is changed from potential energy to kinetic energy (the energy of motion)

Light energy is changed to chemical energy

Jan Van Helmont’s Jan Van Helmont’s Experiment-1600sExperiment-1600s

Question: When a Question: When a seedling with a mass seedling with a mass of only a few grams of only a few grams grows into a tree with grows into a tree with a mass of several a mass of several tons, where does the tons, where does the tree’s increase in tree’s increase in mass come from? mass come from? From the soil? The From the soil? The air? The water?air? The water?

Jan Van Helmont’s Jan Van Helmont’s ExperimentExperiment

Hypothesis: Since a Hypothesis: Since a plant’s roots are in plant’s roots are in the soil, perhaps the the soil, perhaps the tree is eating the soil tree is eating the soil and therefore, its’ and therefore, its’ mass comes from mass comes from the soil.the soil. He imagined tiny faces on the

ends of roots “eating” the soil.

Jan Van Helmont’s Jan Van Helmont’s ExperimentExperiment

Procedure: Van Procedure: Van Helmont carefully Helmont carefully found the mass of a found the mass of a pot of dry soil and a pot of dry soil and a small seedling.small seedling.

He planted the He planted the seedling in the pot of seedling in the pot of soil, watering it soil, watering it regularly for 5 years.regularly for 5 years.

Jan Van Helmont’s Jan Van Helmont’s ExperimentExperiment

Results: At the Results: At the end of 5 years, end of 5 years, the seedling the seedling had gained 75 had gained 75 kilograms.kilograms.

The soil and The soil and the pot had the pot had only decreased only decreased a few grams.a few grams.

Jan Van Helmont’s Jan Van Helmont’s ExperimentExperiment

Van Helmont’s Van Helmont’s Conclusion: He Conclusion: He concluded that most concluded that most of the mass of the of the mass of the tree must have come tree must have come from the water from the water because that was the because that was the only thing that was only thing that was added to the pot.added to the pot.

Trees are made of water??????

Van Helmont was Van Helmont was incorrect!incorrect!

Van Helmont’s Van Helmont’s experiment accounts experiment accounts for the for the hydratehydrate or or water portion of the water portion of the carbohydrate carbohydrate produced by produced by photosynthesis. But photosynthesis. But where does the where does the carbon of the carbon of the carbocarbo portion come from?portion come from? Glucose—the most common and

important carbohydrate/sugar made by plants in photosynthesis

The Rest of the Story that Van The Rest of the Story that Van Helmont didn’t know: COHelmont didn’t know: CO2 2 !!

Although Van Although Van Helmont did not Helmont did not realize it, carbon realize it, carbon dioxide in the air dioxide in the air made a major made a major contribution to the contribution to the mass of his tree. It is mass of his tree. It is the carbon in COthe carbon in CO22 that is used to make that is used to make carbohydrates. carbohydrates.

Carbon Dioxide

Joseph Priestley’s Joseph Priestley’s Experiment-1780Experiment-1780

Priestly took a candle, Priestly took a candle, placed a glass jar over it, placed a glass jar over it, and watched as the flame and watched as the flame gradually died out.gradually died out.

Something in the air was Something in the air was necessary to keep the necessary to keep the candle burning.candle burning.

Today we call that Today we call that substance oxygen.substance oxygen.

Plants Produce OxygenPlants Produce Oxygen

Priestley than found out that if he Priestley than found out that if he put a sprig of mint under the jar put a sprig of mint under the jar and allowed a few days to pass, and allowed a few days to pass, the candle could be re-lighted and the candle could be re-lighted and would remain lighted longer.would remain lighted longer.

The plant produced the substance The plant produced the substance needed for the candle to burn.needed for the candle to burn.

Later it was shown that this would Later it was shown that this would only occur if the plant was placed only occur if the plant was placed in the light.in the light.

Requirements for Requirements for PhotosynthesisPhotosynthesis

Photosynthesis Photosynthesis requires:requires:

Carbon dioxideCarbon dioxide WaterWater LightLight Pigments such as Pigments such as

chlorophyll to absorb chlorophyll to absorb the light energythe light energy

Formula For Formula For Photosynthesis:Photosynthesis:

6 CO6 CO2 + 2 + 6 H6 H22O + Sunlight O + Sunlight → C→ C66HH1212OO66 + 6 O + 6 O22

Carbon Dioxide + Water + Light→ Glucose + OxygenCarbon Dioxide + Water + Light→ Glucose + Oxygen

SunlightSunlight

Nearly all organisms Nearly all organisms on Earth depend on on Earth depend on the sun for energy.the sun for energy.

Sunlight contains Sunlight contains wavelengths of wavelengths of energy that can be energy that can be absorbed by plants.absorbed by plants.

Electromagnetic Electromagnetic SpectrumSpectrum

Energy exists Energy exists in different in different wavelengths.wavelengths.

Shorter Shorter wavelengths wavelengths have more have more energyenergy

Why are leaves green?Why are leaves green?

Leaves contain the Leaves contain the pigment chlorophyll.pigment chlorophyll.

This pigment is green This pigment is green because it absorbs all because it absorbs all other colors of light other colors of light exceptexcept green. green.

It reflects green light.It reflects green light.

Pigments Absorb Light Pigments Absorb Light EnergyEnergy

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

The most important The most important pigment is pigment is chlorophyll-a green chlorophyll-a green pigment.pigment.

Chlorophyll

Energy-Storing Energy-Storing CompoundsCompounds

Light energy that is absorbed by chlorophyll is Light energy that is absorbed by chlorophyll is transferred to ATP molecules. transferred to ATP molecules.

Photosynthesis: The Photosynthesis: The Light and Dark ReactionsLight and Dark Reactions

Photosynthesis occurs in 2 sets of reactions:Photosynthesis occurs in 2 sets of reactions: Light Reactions-trap sunlight energy and use it to make Light Reactions-trap sunlight energy and use it to make

ATP (The “photo” part of photosynthesis)ATP (The “photo” part of photosynthesis) Dark Reactions-use energy from ATP plus CODark Reactions-use energy from ATP plus CO22 and and

HH22O to build glucose. (the “synthesis” part of O to build glucose. (the “synthesis” part of

photosynthesis).photosynthesis).

Glucose

ChloroplastChloroplast

Photosynthesis Photosynthesis takes place in the takes place in the chloroplast.chloroplast.

Light energy is Light energy is trapped by trapped by chlorophyll chlorophyll molecules molecules embedded in the embedded in the membranes of membranes of the chloroplast.the chloroplast.

Draw and label all parts- color the thylakoid membranes green!

Summary of Dark Summary of Dark ReactionsReactions

Also called the Light-Also called the Light-Independent Independent Reactions.Reactions.

In these reactions In these reactions (called the Calvin (called the Calvin Cycle), COCycle), CO22 is used is used

to build glucose.to build glucose.

Overview of Overview of PhotosynthesisPhotosynthesis

In summary, light In summary, light energy is changed to energy is changed to chemical energy that chemical energy that is stored in a is stored in a molecule of glucose. molecule of glucose.

Plants and almost all Plants and almost all other organisms use other organisms use glucose to provide glucose to provide them with energy for them with energy for cellular work.cellular work.