Photosynthesis chemical reactionPhotosynthesis chemical reaction(Remember… conservation of matter (Remember… conservation of matter

and energy)and energy)

Light + 6Light + 6 CO2 CO2 + 6 + 6 H2O H2O C6C6H12H12O6O6 + 6 + 6 O2 O2 + Heat + Heat

**Remember to look for the flow of hydrogens.

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Purpose of each portion for Purpose of each portion for photosynthesisphotosynthesis

ReactantsReactantsLight = Original source of energyLight = Original source of energyCO2 = gains hydrogens to become glucose (sugar)CO2 = gains hydrogens to become glucose (sugar)H20 = break water to release hydrogens to provide electrons, H20 = break water to release hydrogens to provide electrons, release oxygen as byproductrelease oxygen as byproduct

ProductsProductsC6H12O6 (glucose) = sugar (food). C6H12O6 (glucose) = sugar (food). O2 = byproduct (not used)O2 = byproduct (not used)Heat = imperfect energy conversion (2Heat = imperfect energy conversion (2ndnd law of law of thermodynamics)thermodynamics)

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Photosynthesis - Photosynthesis - Method of converting sun’s Method of converting sun’s

energy into chemical energy usable by cellsenergy into chemical energy usable by cells

AutotrophsAutotrophs: self feeders, organisms capable of : self feeders, organisms capable of making their own foodmaking their own food PhotoautotrophsPhotoautotrophs: use sun’s energy e.g. plants : use sun’s energy e.g. plants

photosynthesis-makes organic compounds (glucose) photosynthesis-makes organic compounds (glucose) from lightfrom light

ChemoautotrophsChemoautotrophs: use chemical energy e.g. : use chemical energy e.g. bacteria that use sulfide or methane bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methanechemical energy contained in sulfide or methane

**** Photosynthesis does not give plants energy. It provides **** Photosynthesis does not give plants energy. It provides them with the food (glucose) that mitochondria can then use them with the food (glucose) that mitochondria can then use to create energy (ATP). to create energy (ATP).

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Autotroph - PlantsAutotroph - Plants

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Autotroph - AlgaeAutotroph - Algae

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Autotroph - PhytoplanktonAutotroph - Phytoplankton

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Autotroph - BacteriaAutotroph - Bacteria

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PhotosynthesisPhotosynthesis

PhotosynthesisPhotosynthesis takes place in specialized takes place in specialized structures inside plant cells called structures inside plant cells called chloroplasts. chloroplasts. Chloroplasts are located in the Chloroplasts are located in the leaves of plants (so that’s where leaves of plants (so that’s where photosynthesis occurs).photosynthesis occurs).

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Leaf and Leaf and ChloroplastChloroplast structure structure

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Light absorbing pigments in Light absorbing pigments in chloroplastchloroplast

Chlorophyll IS NOT the only light absorbing Chlorophyll IS NOT the only light absorbing pigment in plants. It is just the most abundant pigment in plants. It is just the most abundant (which is why chloroplasts (and thus plants) are (which is why chloroplasts (and thus plants) are green).green).

Different pigments are responsible for absorbing Different pigments are responsible for absorbing different wavelengths of light. Remember different wavelengths of light. Remember ROYGBIV.ROYGBIV.

Pigments include chlorophyll a, chlorophyll b, Pigments include chlorophyll a, chlorophyll b, carotenoid, among others. carotenoid, among others.

If chlorophyll are green, what colors of light do they absorb?If chlorophyll are green, what colors of light do they absorb?

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Chloroplast structureChloroplast structure

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Overall ReactionOverall Reaction **** Cellular Respiration Equation is exact opposite **** Cellular Respiration Equation is exact opposite

of photosynthesis equation of photosynthesis equation (minus the sunlight)(minus the sunlight)

6CO6CO2 2 + 6 H+ 6 H22O + light energy O + light energy →→ C C66HH1212OO6 6 + 6O+ 6O22

Carbohydrate made is glucoseCarbohydrate made is glucose Water is split as a source of electrons from hydrogen atoms releasing OWater is split as a source of electrons from hydrogen atoms releasing O22 as a byproduct as a byproduct Electrons increase potential energy when moved from water to sugar therefore energy is Electrons increase potential energy when moved from water to sugar therefore energy is

required required Why does it take 6 carbon dioxide and 6 waters to make 1 glucose (and release 6 oxygen)??Why does it take 6 carbon dioxide and 6 waters to make 1 glucose (and release 6 oxygen)?? ****To remember this equation, think “what does a plant need and what does it ****To remember this equation, think “what does a plant need and what does it

make”make” **** It “needs” **** It “needs” COCO22to turn into glucose, water for electrons, and sunlight. Energy to turn into glucose, water for electrons, and sunlight. Energy

from sunlight breaks water. Hfrom sunlight breaks water. H++ are taken from water and given to CO are taken from water and given to CO22. . **** It makes glucose for food and oxygen as a byproduct (waste). Adding H**** It makes glucose for food and oxygen as a byproduct (waste). Adding H++ to to

COCO22 generates glucose and taking H+ from water generates oxygen. generates glucose and taking H+ from water generates oxygen.

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ChloroplastChloroplastSee the See the green light green light being being

reflectedreflected

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Chlorophyll absorbs the Chlorophyll absorbs the blueblue but reflects the but reflects the green.green.

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Light Reactions Overview:***H20 + Light energy O2 + ATP + NADPH**This part makes the “batteries” (ATP and NADPH) for making sugar in the next step**** Note that this is where we use water and light as well as make oxygen. What other parts of the photosynthesis equation are not used / made here (so they have to be in next step)?

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****ELECTRON TRANSPORT CHAIN pumps H+ ions into the thylakoid space and CHEMIOSMOSIS uses this to

make ATP using ATP Synthetase

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Pumping the H+ (protons) into a confined space to build up potential energy.

See the similarity in structure and function?

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Calvin Cycle (light independent or “dark” Calvin Cycle (light independent or “dark” reactions) – occurs in stromareactions) – occurs in stroma

ATP and NADPH generated in light reactions used to fuel the ATP and NADPH generated in light reactions used to fuel the reactions which take COreactions which take CO22 and break it apart, then reassemble and break it apart, then reassemble

the carbons into glucose.the carbons into glucose. (Underline this on handout) (Underline this on handout) Called Called carbon fixationcarbon fixation: taking : taking

carbon from an inorganic molecule (atmospheric COcarbon from an inorganic molecule (atmospheric CO22) and ) and

making an organic molecule out of it (glucose)making an organic molecule out of it (glucose) **** Basically, Calvin Cycle uses products from light **** Basically, Calvin Cycle uses products from light

reactions to make glucose. reactions to make glucose. **** Even though this is called the “dark reactions” they **** Even though this is called the “dark reactions” they

still occur mostly during the day. Why?still occur mostly during the day. Why?

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Calvin Cycle Overview:**** 6 CO2 + ATP + NADPH C6H12O6 (glucose) + ADP (P) + NADP+

**** Note that ATP and NADPH are not in overall equation because they are constantly recycled (ATP ADP + P and NADPH NADP+)

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