PhotosynthesisPhotosynthesis

Stored EnergyStored Energy

What is Photosynthesis?What is Photosynthesis?

plants convert the energy of sunlight into plants convert the energy of sunlight into the energy in the chemical bonds of the energy in the chemical bonds of carbohydrates – sugars and starches. carbohydrates – sugars and starches.

Requirements for Requirements for PhotosynthesisPhotosynthesis

Carbon Dioxide - COCarbon Dioxide - CO22

Water - HWater - H22OO

Energy – In the form of sunlightEnergy – In the form of sunlight

3 Main Stages3 Main Stages

1. Energy is captured from sunlight.1. Energy is captured from sunlight. 2. Light energy is converted to chemical 2. Light energy is converted to chemical

energy (ATP & NADPH)energy (ATP & NADPH) 3. ATP and NADPH power the synthesis 3. ATP and NADPH power the synthesis

of organic molecules, using carbon from of organic molecules, using carbon from carbon dioxide.carbon dioxide.

Where does Where does Photosynthesis occur?Photosynthesis occur?

Inside plant cells – specifically Inside plant cells – specifically chloroplastschloroplasts

1.  DNA

2.  Ribosomes

3. & 6.  Outer Membrane

4. Grana

5.  Stroma

7.  Starch Grain

ChloroplastChloroplast

Thylakoid – flattened, Thylakoid – flattened, membrane bound membrane bound sacsac

Grana – stacks of Grana – stacks of thylakoidsthylakoids

Stroma – fluid matrixStroma – fluid matrix

Light EnergyLight Energy(Energy is captured by (Energy is captured by

sunlight)sunlight) Radiant Energy – Radiant Energy –

energy that is energy that is transmitted in waves transmitted in waves that can travel that can travel through a vacuum.through a vacuum.

Electromagnetic Electromagnetic spectrum – complete spectrum – complete range of radiant range of radiant energy. energy.

Electromagnetic Spectrum

PHOTONS!PHOTONS!

Tiny packets of radiant energyTiny packets of radiant energy

When Photons strike a When Photons strike a surface…..surface…..

1 – reflected1 – reflected

2 – absorbed2 – absorbed

3 – transmitted 3 – transmitted

• Green plants are green because they absorb all of the colors of the visible spectrum except the green color (aka the green wavelengths).

Pigments Pigments

Molecules containingMolecules containing

atoms that enable atoms that enable

it to absorb light.it to absorb light.

Types of PigmentsTypes of Pigments

Chlorophyll – the Chlorophyll – the primary light-primary light-absorbing agent for absorbing agent for photosynthesisphotosynthesis

Carotenoids – yellow Carotenoids – yellow & orange pigments& orange pigments

Phycoerythrin – red Phycoerythrin – red and blueand blue

Photosytems- Photosytems- molecule clusters molecule clusters of pigments found in the thylakoid of pigments found in the thylakoid membranesmembranes

Photosytem IPhotosytem I boost boost electrons by electrons by absorbing absorbing light with a light with a wavelength of wavelength of 700 nm700 nm

Photosystem IIPhotosystem II – boosts – boosts electrons by electrons by absorbing light absorbing light with a slightly with a slightly shorter shorter wavelength wavelength than 680 nmthan 680 nm

Stage 2 Stage 2 Light energy is converted to Light energy is converted to

chemical energy… a.k.a.chemical energy… a.k.a.

Light – Dependent Light – Dependent ReactionsReactions

Electron CarriersElectron Carriers Excited electrons – high energyExcited electrons – high energy Special carriers – electron carriersSpecial carriers – electron carriers

Electron transport chainElectron transport chain

NADPNADP++ - - accepts and holds 2 high energy accepts and holds 2 high energy electrons along with a hydrogen ion (electrons along with a hydrogen ion (HH ++))

NADPNADP++ + H + H + + = NADPH= NADPH

Light-Dependent Light-Dependent ReactionReaction

4 Basic Processes4 Basic Processes Light absorptionLight absorption Electron transportElectron transport OO22 production production

ATP formationATP formation

Light-Dependent Light-Dependent ReactionReaction

cont.cont. 1. Photons of radiant energy strike PSII1. Photons of radiant energy strike PSII Energy is passes to the chlorophyll moleculeEnergy is passes to the chlorophyll molecule Excited electron (eExcited electron (e--) is boosted to….) is boosted to….

2. A thylakoid membrane protein where… 2. A thylakoid membrane protein where… the ethe e- - is passed along a series of electron is passed along a series of electron carriers called …carriers called … the electron transport chainthe electron transport chain

3. At the end of the ETC, an ATP is 3. At the end of the ETC, an ATP is released into the stromareleased into the stroma

4. PS I gets the e4. PS I gets the e-- from PS II. It gets from PS II. It gets boosted to….boosted to….

5. Thylakoid membrane protein where…5. Thylakoid membrane protein where… The eThe e-- is passed to the ETC… is passed to the ETC…

6. The ETC passes the e6. The ETC passes the e-- to the electron to the electron carrier NADPcarrier NADP+ + and is converted to and is converted to NADPHNADPH

7. As e7. As e-- move from chlorophyll to NADP move from chlorophyll to NADP++, , more Hmore H++ ions are pumped across the ions are pumped across the membranemembrane

8. The inside of the thylakoid membrane 8. The inside of the thylakoid membrane builds up with + chargebuilds up with + charge

9. Outside the thylakoid is – charged.9. Outside the thylakoid is – charged. 10. H10. H++ ions cannot exit without help. They ions cannot exit without help. They

use ATP synthase.use ATP synthase. 11. Protein channel rotates.11. Protein channel rotates. 12. As it rotates, ADP binds 12. As it rotates, ADP binds

with a phosphate to make with a phosphate to make ATPATP

Why doesn’t the Why doesn’t the chlorophyll run out of echlorophyll run out of e-- ? ? Enzymes on the Enzymes on the

inner side of the inner side of the thylakoids break up thylakoids break up water molecules water molecules into 2 electrons, into 2 electrons, HH + + ions , and 1 ions , and 1 oxygen atom! oxygen atom!

Light-Dependent Light-Dependent ReactionReaction

UsesUses WaterWater ADPADP NADPNADP++

ProducesProduces OxygenOxygen ATPATP NADPH NADPH

The Calvin Cycle – The Calvin Cycle – sometimes called Light sometimes called Light Independent ReactionsIndependent Reactions

Plants use the energy that ATP and Plants use the energy that ATP and NADPH contain to build high-energy NADPH contain to build high-energy compounds that can be stored for a long compounds that can be stored for a long time. Uses ATP and NADPH from the time. Uses ATP and NADPH from the light dependent reactions to produce light dependent reactions to produce high-energy sugars.high-energy sugars.

Steps to the Calvin CycleSteps to the Calvin Cycle

6 CO6 CO22 molecules enter the cycle from the molecules enter the cycle from the

atmosphereatmosphere These combine with 6, 5 - carbon These combine with 6, 5 - carbon

molecules to make 12, 3 - carbon molecules to make 12, 3 - carbon moleculesmolecules

The 12 are converted into higher-energy The 12 are converted into higher-energy forms (Energy from ATP & NADPH)forms (Energy from ATP & NADPH)

Calvin Cycle cont.Calvin Cycle cont.

2 of the 12, 3 – carbon molecules are 2 of the 12, 3 – carbon molecules are removed from the cycle to make sugars, removed from the cycle to make sugars, lipids, amino acids or other compoundslipids, amino acids or other compounds

The remaining 10, 3 – carbon molecules The remaining 10, 3 – carbon molecules are converted back to 6, 5 – carbon are converted back to 6, 5 – carbon molecules.molecules.