Photosynthesis

PHOTOSYNTHESIPHOTOSYNTHESISS

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PhotosynthesisPhotosynthesis

• Carbon dioxide (COCarbon dioxide (CO22)) requiring requiring process that uses process that uses 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

Light Dependent Reactions

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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 membranes]thylakoid membranes]

• Chlorophyll pigments Chlorophyll pigments harvest energy harvest energy (photons)(photons) by absorbing certain by absorbing certain

• wavelengths wavelengths (blue-420 nm and red-(blue-420 nm and red-660 nm660 nm are most important) are most important)

• Plants are Plants are greengreen because the because the green green wavelength is reflectedwavelength is reflected, not , not absorbedabsorbed.

Amazing Chloroplast

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Wavelength of Light (nm)Wavelength of Light (nm)

400 500 600 700

Short wave Long wave(more energy) (less energy)

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Absorption of Light by Absorption of Light by ChlorophyllChlorophyll

wavelengthwavelength

Absorption

violet blue green yellow orange red

Chlorophyll absorbs blue-violet & red Chlorophyll absorbs blue-violet & red light bestlight best

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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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How do cells obtain 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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Structure of ATPStructure of ATP

• ATP stands for adenosine triphosphate

• It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups

• The LAST phosphate group is bonded with a HIGH ENERGY chemical bond

• This bond can be BROKEN to release ENERGY for CELLS to use

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Removing a Phosphate from Removing a Phosphate from ATPATP

Breaking the LAST PHOSPHATE bond from ATP, will ---– Release ENERGY for cells to use– Form ADP– Produce a FREE PHOSPHATE

GROUP

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High Energy Phosphate High Energy Phosphate BondBond

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FREE PHOSPHATE can be re-FREE PHOSPHATE can be re-attached to ADP reforming ATPattached to ADP reforming ATP

Process called Process called PhosphorylationPhosphorylation

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Parts of Parts of PhotosynthesisPhotosynthesis

Types of Photosynthesis

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Two Parts of Two Parts of PhotosynthesisPhotosynthesis

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

1.1.Light Reaction or Light Light Reaction or Light Dependent ReactionDependent Reaction - -

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 or Light Calvin Cycle or Light Independent Independent ReactionReaction

• 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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Light Reaction (Electron Light Reaction (Electron Flow)Flow)

• Occurs in the Occurs in the Thylakoid Thylakoid membranesmembranes

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Calvin CycleCalvin Cycle• Carbon Fixation Carbon Fixation (light independent (light independent

reaction)reaction)• CC33 plants (80% of plants on earth) plants (80% of plants on earth)• Occurs in the Occurs in the stromastroma• Uses Uses ATP and NADPHATP and NADPH from light from light

reaction as energyreaction as energy• Uses Uses COCO22

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

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ChloroplastChloroplast

GranumThylakoid

STROMA– where Calvin Cycle occursOuter Membrane

Inner Membrane

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Calvin CycleCalvin Cycle

Remember: CRemember: C33 = Calvin Cycle = Calvin Cycle

C3

Glucose

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PhotorespirationPhotorespiration

• Occurs on hot, dry, bright daysOccurs on hot, dry, bright days

Stomates closeStomates close

• Fixation of OFixation of O22 instead of CO instead of CO22

• Produces Produces 2-C molecules 2-C molecules instead of 3-C sugar moleculesinstead of 3-C sugar molecules

• Produces Produces no sugarno sugar molecules molecules or or no ATPno ATP

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PhotorespirationPhotorespiration

Because of photorespiration, Because of photorespiration, plants have special plants have special adaptations to limit the effect adaptations to limit the effect of photorespiration:of photorespiration:

1.1. CC44 plants plants

2.2. CAM plantsCAM plants

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CC44 Plants Plants• Hot, moist Hot, moist

environmentsenvironments• 15% of plants 15% of plants

((grasses, corn, grasses, corn, sugarcane)sugarcane)

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CAM PlantsCAM Plants• Hot, dry environmentsHot, dry environments• 5%5% of plants (cactus and ice of plants (cactus and ice

plants)plants)• Stomates closed during dayStomates closed during day• Stomates open during the nightStomates open during the night• Light reaction - occurs during Light reaction - occurs during

the daythe day• Calvin Cycle - occurs when COCalvin Cycle - occurs when CO22

is presentis present

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Question:Question:

Why do CAM Why do CAM plants close plants close

their stomata their stomata during the day?during the day?

Cam plants Cam plants close their close their

stomata in the stomata in the hottest part hottest part of the day to of the day to

conserve conserve waterwater

What is the Difference ?• Journal in your notebooks using a

Venn diagram to discuss your comparisons between C3 and C4 Plants.

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