Plant NutritionPlant Nutrition

Biology Chapter 17Biology Chapter 17

(Science Content Standards for California Public Schools, Grades 9-12, Biology/Life Sciences: 1a-b, 1d-j)

One of the largest differences One of the largest differences between plants and animals is that between plants and animals is that

plants . . .plants . . .

MAKE THEIR OWN FOOD!MAKE THEIR OWN FOOD!

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•Early 1600s.Early 1600s.•Flemish Flemish physician Jan physician Jan van Helmont.van Helmont.•Concluded that Concluded that new plant new plant material came material came directly from directly from water.water.

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•1770s.1770s.•Joseph Priestley Joseph Priestley found that plants found that plants could grow in could grow in “damaged” air.“damaged” air.

•By early 1800s By early 1800s scientists knew scientists knew plants need COplants need CO22, ,

water and light.water and light.

PhotosynthesisPhotosynthesis

Process of capturing and Process of capturing and transforming the energy of sunlight transforming the energy of sunlight into chemical energy.into chemical energy.

Requires Requires lightlight energy. Visible light is energy. Visible light is part of the part of the electromagnetic spectrumelectromagnetic spectrum..

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LightLight Travels as waves, but acts as Travels as waves, but acts as

particles. Particles called particles. Particles called photonsphotons..

Photons can excite electrons of an Photons can excite electrons of an atom. When eatom. When e-- return to ground state, return to ground state, heat and light emitted.heat and light emitted.

This is what happens to the pigment This is what happens to the pigment chlorophyllchlorophyll in plants. in plants.

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17-117-1In photosynthesis, this energy is captured to make sugars (reduced carbon).

Sunlight

Watercarbohydrates

SugarsSugars

+

+

+

+

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Inputs and outputs from Inputs and outputs from Photosynthesis:Photosynthesis:

Sunlight (430, 670 nm)Sunlight (430, 670 nm) Carbon dioxideCarbon dioxide WaterWater

SugarsSugars CarbohydratesCarbohydrates OxygenOxygen

InputsInputs OutputsOutputs

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6CO6CO22 + 6H + 6H22O CO C66HH1212OO66 + 6O + 6O22

+ energy from sunlight

The big pictureThe big picture

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PhotosynthesisPhotosynthesis

There are 2 parts:There are 2 parts:

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and

Light-independent reactions

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Light-dependent reactionsLight-dependent reactions

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4.24.2

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ATP millATP mill

Driven by chemiosmosisDriven by chemiosmosis

Cellular respirationCellular respiration

Used with permission from: http://student.ccbc.cc.md.us/biotutorials/photosyn/atpasep.html

Energyfrom

sunlight

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Used with permission from: http://student.ccbc.cc.md.us/biotutorials/photosyn/atpasep.html 17-217-2

LookFamiliar?

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Adapted from: http://138.192.68.68/bio/Courses/biochem2/Photosynthesis/Photosystem1.html17-217-2

Light-independent Light-independent reactions (dark reactions)reactions (dark reactions)

Calvin cycleCalvin cycleATP and NADPH from light reactions are used to “fix” or reduce carbon (CO2) into sugars.

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Most Most abundant abundant protein on protein on earth!earth!

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CC44 Photosynthesis Photosynthesis COCO22 incorporated into incorporated into 4-carbon 4-carbon

compound*compound* prior to the Calvin cycle. prior to the Calvin cycle. Examples: sugar cane, cornExamples: sugar cane, corn

• *PEP Carboxylase vs. RUBISCO *PEP Carboxylase vs. RUBISCO CAM PhotosynthesisCAM Photosynthesis

COCO22 incorporated into 4-carbon incorporated into 4-carbon compound compound at night at night when water loss is when water loss is minimized.minimized.

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Q: How do these alternate PS pathways allow these types of plants to save water?

It is estimated that photosynthesis makes It is estimated that photosynthesis makes about 160 billion metric tons of about 160 billion metric tons of

carbohydrate per year (a metric ton is carbohydrate per year (a metric ton is 1,000 kg, about 1.1 tons). That’s organic 1,000 kg, about 1.1 tons). That’s organic matter equivalent to a stack of about 60 matter equivalent to a stack of about 60

trillion copies of this textbook--17 stacks of trillion copies of this textbook--17 stacks of books reaching from Earth to the sun! No books reaching from Earth to the sun! No other chemical process on the planet can other chemical process on the planet can match the output of photosynthesis. And match the output of photosynthesis. And

no process is more important than no process is more important than photosynthesis to the welfare of life on photosynthesis to the welfare of life on

Earth.Earth.

Respiration vs. PhotosynthesisRespiration vs. PhotosynthesisSame Different

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