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PHOTOSYNTHESISPHOTOSYNTHESIS
Providing Energy for LifeProviding Energy for Life
Do you remember food web Do you remember food web terminology?terminology?
Autotrophs = producersAutotrophs = producers PhotoautotrophsPhotoautotrophs ChemoautotrophsChemoautotrophs
Heterotrophs = consumersHeterotrophs = consumers Primary consumers, secondary consumers, etcPrimary consumers, secondary consumers, etc decomposersdecomposers
PhotosynthesisPhotosynthesis
Photoautotrophic cells contain pigments that Photoautotrophic cells contain pigments that absorb visible lightabsorb visible light This is their source of ENERGYThis is their source of ENERGY
Where does photosynthesis Where does photosynthesis occur?occur?
Leaf: cross sectionLeaf: cross section
PhotosynthesisPhotosynthesis
Most occurs in the mesophyll layer of the leafMost occurs in the mesophyll layer of the leaf Each mesophyll cell contains 30 - 40 chloroplastsEach mesophyll cell contains 30 - 40 chloroplasts
CHLOROPLASTCHLOROPLAST
CHLOROPLASTCHLOROPLAST
CHLOROPLASTCHLOROPLAST
CHLOROPLASTCHLOROPLAST
Light-absorbing pigments are embedded in Light-absorbing pigments are embedded in thylakoid membranesthylakoid membranes
A stack of thylakoids is called a A stack of thylakoids is called a granumgranum Plural = Plural = granagrana
Grana have a large surface area to allow Grana have a large surface area to allow greater diffusion of materialsgreater diffusion of materials
CHLOROPLASTCHLOROPLAST
STROMASTROMA Surrounds the thylakoid membranesSurrounds the thylakoid membranes Contains enzymes, DNA, RNAContains enzymes, DNA, RNA
Electromagnetic SpectrumElectromagnetic Spectrum
Electromagnetic spectrumElectromagnetic spectrum
Visible light drives photosynthesisVisible light drives photosynthesis Substances that absorb visible light are called Substances that absorb visible light are called
pigmentspigments Pigments appear different colors because they Pigments appear different colors because they
reflect different wavelengths (and thus absorb reflect different wavelengths (and thus absorb different wavelengths)different wavelengths)
Spectrophotometer measures the ability of a Spectrophotometer measures the ability of a pigment to absorb different wavelengths of lightpigment to absorb different wavelengths of light
CHLOROPLAST PIGMENTSCHLOROPLAST PIGMENTS
CHLOROPHYLL = green pigmentCHLOROPHYLL = green pigment Two forms of chlorophyllTwo forms of chlorophyll
Chlorophyll aChlorophyll a Chlorophyll bChlorophyll b
Chlorophyll absorbs light energy in the Chlorophyll absorbs light energy in the violet/blue and orange/red rangesviolet/blue and orange/red ranges REFLECTS in the green rangeREFLECTS in the green range
ChlorophyllChlorophyll
The color that we see is the color that is The color that we see is the color that is REFLECTED, not absorbedREFLECTED, not absorbed Therefore, chlorophyll appears GREEN, because Therefore, chlorophyll appears GREEN, because
green wavelength light is reflectedgreen wavelength light is reflected
Other Pigments in ChloroplastsOther Pigments in Chloroplasts
Xanthophyll: yellowXanthophyll: yellow Carotene: orangeCarotene: orange Different colors indicate that they absorb (and Different colors indicate that they absorb (and
therefore reflect) energy at different therefore reflect) energy at different wavelengthswavelengths
Absorption SpectraAbsorption Spectra
Plant PigmentsPlant Pigments
Located in the thylakoid membraneLocated in the thylakoid membrane Absorption spectrum tells us which Absorption spectrum tells us which
wavelengths are absorbed bestwavelengths are absorbed best Why is this important? HINT: it has to do with Why is this important? HINT: it has to do with
amount of energy absorbed!amount of energy absorbed!
PHOTOSYNTHESISPHOTOSYNTHESISOverviewOverview
Photosynthesis involves 3 energy conversionsPhotosynthesis involves 3 energy conversions 1. 1. absorptionabsorption of light energy of light energy 2. 2. conversionconversion of light energy into chemical energy of light energy into chemical energy 3. 3. storagestorage of chemical energy as sugars (carbon- of chemical energy as sugars (carbon-
containing compounds)containing compounds)
Law of Conservation of EnergyLaw of Conservation of Energy
REMEMBER!!!REMEMBER!!!
Energy cannot be created or destroyed, only Energy cannot be created or destroyed, only converted into different formsconverted into different forms
PHOTOSYNTHESISPHOTOSYNTHESISoverall summaryoverall summary
KNOW THIS!!!!!KNOW THIS!!!!!
Carbon dioxide gas combines with water in Carbon dioxide gas combines with water in the presence of light energy and the presence of light energy and chlorophyll to form sugar and oxygen gaschlorophyll to form sugar and oxygen gas
PHOTOSYNTHESISPHOTOSYNTHESIS
PHOTOSYNTHESISPHOTOSYNTHESIS
Photosynthesis occurs in 2 groups of reactionsPhotosynthesis occurs in 2 groups of reactions LIGHT REACTIONSLIGHT REACTIONS CALVIN CYCLE OR DARK REACTIONSCALVIN CYCLE OR DARK REACTIONS
PHOTOSYNTHESISPHOTOSYNTHESIS
I’M NOT GONNA DENY IT….THIS IS I’M NOT GONNA DENY IT….THIS IS GOING TO INVOLVE GOING TO INVOLVE MEMORIZATION!!MEMORIZATION!!
LIGHT REACTIONSLIGHT REACTIONS
Pigment molecules in the thylakoids absorb Pigment molecules in the thylakoids absorb light energylight energy
Light energy is converted to short-lived Light energy is converted to short-lived chemical energy in carrier moleculeschemical energy in carrier molecules Conversion to chemical energy has to do with Conversion to chemical energy has to do with
transfer of transfer of electronselectrons from one molecule to anotherfrom one molecule to another Remember Remember Oxidation-ReductionOxidation-Reduction reactions???? reactions????
Light ReactionsLight Reactions
Light ReactionsLight Reactions
CALVIN CYCLECALVIN CYCLE
Energy molecules from the light reactions are Energy molecules from the light reactions are used to make sugarused to make sugar
Also known as the DARK REACTIONSAlso known as the DARK REACTIONS
Calvin CycleCalvin Cycle
PHOTOSYNTHESIS: SUMMARYPHOTOSYNTHESIS: SUMMARY
AssignmentAssignment
Define/describe a PHOTOSYSTEMDefine/describe a PHOTOSYSTEM Diagram (and label) the light reactions of Diagram (and label) the light reactions of
photosynthesisphotosynthesis Diagram the dark reaction of photosynthesisDiagram the dark reaction of photosynthesis