PHOTOSYNTHESIPHOTOSYNTHESISS

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PhotosynthesisPhotosynthesis

• Process that requires carbon Process that requires carbon dioxide (COdioxide (CO22)), , light energy light energy (photons),(photons), and and water (Hwater (H22O)O) to to produce produce organic macromolecules organic macromolecules (glucose).(glucose).

6CO2 + 6H2O C6H12O6 + 6O2glucoseglucose

SUNphotonsphotons

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Question:Question:

Where does Where does photosynthesiphotosynthesis take place?s take place?

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PlantsPlants• Autotrophs Autotrophs – produce their own – produce their own

food food (glucose)(glucose)• Process called Process called photosynthesisphotosynthesis• Mainly occurs in the Mainly occurs in the leaves:leaves:

a.a.stoma - poresstoma - pores

b.b.mesophyll cellsmesophyll cells

StomaMesophyllCell

Chloroplast

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Stomata (stoma)Stomata (stoma)PoresPores in a plant’s cuticle in a plant’s cuticle

through which through which water vaporwater vapor and and gasesgases (CO(CO22 & O & O22)) are are exchanged between the plant exchanged between the plant and the atmosphere.and the atmosphere.

Guard CellGuard CellCarbon Dioxide (CO2)

Oxygen (O2)

Found on the underside of Found on the underside of leavesleaves

StomStomaa

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Mesophyll Cell of LeafMesophyll Cell of Leaf

Cell WallNucleusNucleus

Chloroplast

Central Vacuole

Photosynthesis occurs in these Photosynthesis occurs in these cells!cells!

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ChloroplastChloroplast

OrganelleOrganelle where photosynthesisphotosynthesis takes place.

GranumThylakoid

Stroma

Outer Membrane

Inner Membrane

Thylakoid stacks are connected Thylakoid stacks are connected togethertogether

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ThylakoidThylakoid

Thylakoid Membrane

Thylakoid SpaceGranum

Grana make up the inner Grana make up the inner membranemembrane

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Question:Question:

Why are Why are plants plants green?green?

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Chlorophyll MoleculesChlorophyll Molecules

• Located in the Located in the thylakoid thylakoid membranesmembranes

• Plants are Plants are greengreen because the because the green wavelength is reflectedgreen wavelength is reflected, , not absorbednot absorbed.

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Question:Question:

During the fall, During the fall, what causes what causes the leaves to the leaves to

change colors?change colors?

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Fall ColorsFall Colors• In addition to the chlorophyll In addition to the chlorophyll

pigments, there are pigments, there are other other pigmentspigments present present

• During the fall, the During the fall, the green green chlorophyll pigments are chlorophyll pigments are greatly reducedgreatly reduced revealing the revealing the other pigmentsother pigments

• CarotenoidsCarotenoids are pigments that are pigments that are either are either redred, , orangeorange, or , or yellowyellow

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Question:Question:

What do What do cells use cells use

for for energy?energy?

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Energy for Life on EarthEnergy for Life on Earth

•Sunlight is the ULTIMATE energy for all life on Earth

•Plants store energy in the chemical bonds of sugars

•Chemical energy is released as ATP during cellular respiration

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High Energy Phosphate High Energy Phosphate BondBond

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Parts of Parts of PhotosynthesisPhotosynthesis

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Two Parts of Two Parts of PhotosynthesisPhotosynthesis

Two reactions make up Two reactions make up photosynthesis:photosynthesis:

1.1.Light ReactionsLight Reactions- -

Produces energy from solar Produces energy from solar power (photons) in the form power (photons) in the form of ATP and NADPH.of ATP and NADPH.

SUNSUN

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Two Parts of Two Parts of PhotosynthesisPhotosynthesis

2. 2. Calvin Cycle Calvin Cycle

• Uses energy (Uses energy (ATP and ATP and NADPHNADPH) from light ) from light reaction to make sugar reaction to make sugar (glucose).(glucose).

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Stage 1: Light ReactionsStage 1: Light Reactions

• Where do they occur?Where do they occur?

Thylakoid membranesThylakoid membranes• What is the starting molecule?What is the starting molecule?

WaterWater

• What are the end products?What are the end products?

Oxygen, ATP, NADPHOxygen, ATP, NADPH• This stage requires light!This stage requires light!

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Calvin Cycle FYICalvin Cycle FYI• Occurs in the Occurs in the stromastroma• Uses Uses ATP and NADPHATP and NADPH from from

light reaction as energylight reaction as energy• Uses Uses COCO2 2

• To produce To produce glucoseglucose: it takes : it takes 6 turns and uses 18 ATP and 6 turns and uses 18 ATP and 12 NADPH. 12 NADPH.

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Stage 2: Calvin CyclesStage 2: Calvin Cycles

• Where do they occur?Where do they occur? StromaStroma

• What is the starting molecule?What is the starting molecule?

Carbon dioxide (COCarbon dioxide (CO22), ATP, and ), ATP, and NADPHNADPH

• What are the end products?What are the end products? GlucoseGlucose

• This stage This stage doesdoes notnot require require light!light!

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ChloroplastChloroplast

GranumThylakoid

STROMA– where Calvin Cycle occursOuter Membrane

Inner Membrane

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The overall equation for The overall equation for PhotosynthesisPhotosynthesis

• 6CO6CO22 + 6H + 6H22O + light energy O + light energy C C66HH1212OO66 + +

6O6O22

• In words:In words:• Carbon dioxide + water + light Carbon dioxide + water + light

energy energy Glucose + oxygenGlucose + oxygen

Photosynthesis