2 Photosynthesis Outline LT’s 1-3: Energy and Old Dead DudesLT’s 4 & 5: Light and Structures of PSLT’s 6-8: Reactions and Factors of PS
3 ENERGY All living things need energy to live! LT 1ENERGYAll living things need energy to live!Heterotrophs-get their food by eating other organisms and turning them into energy(Ex: herbivores, carnivore, decomposers, etc)Autotrophs-get their energy by converting light or chemical energy into sugar, and then converting that into energy(Ex: plants, bacteria, and some protists)
4 ENERGY The cell will store energy in molecules like sugars and ATP Most cells have small stores of ATP that only last a few seconds, but cannot store energy there long-term.Cells will store it long term in carbohydrates/sugarsSugar energy > ATP energy90x greater
5 ENERGY What are the uses for ATP in biochemical reactions? Active TransportEnergy to move cell organellesMaking proteins or nucleic acidsPHOTOSYNTHESIS!!!
6 Understanding Photosynthesis LT 2Understanding PhotosynthesisVan Helmont**Water and CO2are needed tomake plantsgrow**Do plants grow by taking material out of the soil?Thought most of it came from the water absorbedDid not know that the bulk of the mass came from CO2 absorbed from the air.Priestley**O2 is madefrom PS **Put a flame under a jar and watched it burn out.Found there was something in the air that caused the flame to burnPut a mint plant in the jar and found it produced something flames needed.Ingenhousz**Plants needlight for PS**Found that Priestley’s experiment needed light to occur.
7 Photosynthesis Reaction LT 3Photosynthesis Reaction6 CO H2O light C6H12O O2Made in the dark rxnMade in the light rxnFrom the rootsFrom the sunFrom the airWill be made into ATP later in Cellular Respiration
8 Light and Pigments Photosynthesis starts with SUNLIGHT! LT 4Light and Pigments6 CO H2O light C6H12O O2Photosynthesis starts with SUNLIGHT!The light that comes from the sun is WHITE LIGHT or ROYGBIV (R O Y G B I V)The red end is lowerenergy and longerwavelengthThe violet end hashigher energy andsmaller wavelength
9 Light and Pigments? If plants use visible light, are all colors/wavelengths/energies equally valuable to PS? Let’s see… Read the results of the experiment from Thomas Engelmann in 1803
10 Light and Pigments Most plants are GREEN. This means that ROY BIV is absorbed and G is reflected.This means that if ROY and BIV are absorbed these are the colors of light that power PSPigment – any substance that absorbs lightChlorophyll a – the main pigment in plantsthat absorbs the sun’s light to power PS
12 Light and PigmentsThere are also other pigments, beside chlorophyll a, called ACCESSORY PIGMENTSchlorophyll b and carotenoidsEach pigment has its optimal portion of ROYGBIV for absorption and to fuel PSChlorophyll a is the main pigment for PS, while the accessory pigments help chlorophyll a by expanding the portion of ROYGBIV it can use!
13 Light and PigmentsChlorophyll a best absorption occurs around 425nm AND 660nmChlorophyll b best absorption occurs around 475nm AND 640nmCarotenoids best absorption occurs around 450nm AND 490nmTherefore, the accessory pigments expand the absorption from about 425nm (V) to nm (V-B) AND from 660nm (R) to nm (O-R). More light absorbed = More PSing!!
14 Why do leaves change color in the fall? What are the three kinds of pigments?What two factors cause the color to change?What three factors will give good fall color, especially reds?
15 Why do leaves change color in the fall? Remember…leaves get their colors from their pigmentsPIGMENTCOLORWHEN ACTIVEChlorophyllgreenPresent all yearCarotenoidsyellow, oranges, and brownsPresent all year but covered by chlorophyll in summerAnthocyaninsredOnly produced in autumn under certain conditions
16 Why do leaves change color in the fall? So how do they know to change color??Fewer hours of sunlight/days are shorterTrees produce less and less chlorophyllNow carotenoids (already in leaf) can show throughDrop in temperature
17 Why do leaves change color in the fall? But what about the anthocyanins?This is dependent upon…Temperature and cloud coverWarm days and cool nights = good redsHelp plants get all the remaining sugar out of the leaves before they fall offSo for good fall leaf color…A warm, wet summerA summer that is not too hot or dryA fall with many warm days and cool nights
18 Cell Structures We Already Know…. LT 5Cell Structures We Already Know….Cell MembraneA phospholipid bilayer embedded with proteinsSelectively permeableMaintains homeostasis for the cell viaPASSIVE (diffusion, osmosis, or facilitated diffusion)ACTIVE TRANSPORT (active transport, endocytosis or exocytosis)Now…The Leaf and ChloroplastsThe structures plants use for PS
19 The LeafCuticle- the waxy outer covering of a leaf that prevents water lossPalisdade Layer-layer of long cells where chloroplasts are found and where most of PS occursSpongy Mesophyll-random collection of cells with large spaces in between them. Some PS occurs here, but mostly this is where the gases taken in & given off by PS are exchanged between palisade layer and stoma
20 The Leaf (cont.)Guard Cells-the cells on either side of the stoma that open/close them to let gases in or out OR to keep gases inStoma- openings on the underside of leaves that allow for gas exchange between the leaf and atmosphere.
21 The Chloroplast Let’s see this Organelle responsible for PHOTOSYNTHESIS!Disc-like in shapeGreen due to the presence of the pigment Chlorophyll aFound mostly within the palisade layer, but some are in the mesophyll too.Internal structures includeThylakoidsStRomaGranum (sing.) or Grana (pl.)LumenLet’s see this
22 The Chloroplast (cont.) 1 of 2 membranes that surround the organelleFluid between the thylakoids where the dark rxn occursDisc where the pigments of PS are. Where the light rxn occurs
23 How Photosynthesis Occurs LT’s6 & 7How Photosynthesis Occurs? So what about the rest of the PS equation; like CO2, Water, Glucose and O2 ?6 CO H2O light C6H12O O2PS occurs in 2 partsLight Dependent (or Light Reaction)This part of the rxn requires LIGHT, H2O, and gives off O2Light Independent (or Dark Reaction)This part of the rxn requires CO2 and produces the sugar or glucose
25 The Light Reaction “I’m So Excited!” e- LT 6 electron carriers receivechlorophyll’s electrons the excited e-’s and pass get very excited from the them along to other sun’s energy molecules. These e-’s carriers molecules arecalled theELECTRON TRANSPORT CHAIN
26 The Light Reaction NADP+ ATP NADP+ + 2e- + 1H+ NADPH Examples of a Carrier Molecule:NADP+Takes 2e-’s from chlorophyll and 1H+ from waterNADP e H NADPHTakes energy with it to other cell rxnsThink of it like a UPS truck, picking up “packages” and dropping them offATP
27 The Light Reaction: Key Concepts Occurs in the thylakoid membrane of the chloroplastIncludes Photosystem II and Photosystem INeeds Light and H2O to startProduces O2, NADPH and ATPWaste!
28 The Light Reaction: Photosystem II PS II - In the Thylakoid Membrane (TM)1. e- absorb sun’s energy and get highly energized2. The proteins in the TM split a water (hydrolysis) to makeH+’s , e-’s , and O23. e-’s go to ETC (a series of protein carriers)4. Energy from the e-’s pumps H+’s into the TM, changing the [H+] ions (low to high-active transport)
29 The Light Reaction: Photosystem I PS I - In the Thylakoid Membrane (TM)5. Light is energized again6. e-’s move to the final e- acceptor which adds them to NADP+ to make NADPH7. High [H+] (left over from hydrolysis) diffuse through the enzyme protein ATP synthase to make ATP form ADP (H+ give energy to add a phosphate to ADP)Let’s See This
32 The Light Reaction: The Thylakoid Membrane A Little Quiz:Put a #1 where there is a higher concentration of H+Draw a squiggly line between PSII and PSIPut a #2 on the thylakoid membranePut a #3 in the stromaPut a #4 where the e-’s are first energizedPut a #5 where the e-’s are re-energizedPut a #6 where hydrolysis occursPut a #7 where active transport is occurring.
33 The Dark Reaction: Key Concepts LT7The Dark Reaction: Key ConceptsThe second part of PS is called the Dark Reaction,the Calvin Cycle, or the Light Independent CycleIt is called the Dark Rxn because this part can take place without light (that is not to say it must be dark,but if it were,this part couldstill proceed)
34 The Dark Reaction: Key Concepts The two products from the Light Reaction, NADPH and ATP go to the Dark ReactionNADPH and ATP have lots of energy in their bonds but they can only hold it for a few minutesIf the cell wants to hold the energy long-term, they will have to build high energy molecules that can hold it…like GLUCOSE (savings account!)This process takes place in the stRoma (outside of chloroplast)
35 1 exits and will become GLUCOSE The Dark ReactionFrom Light Rxn3-RuBP’s5 C’s6-ATP3 -CO23-6C Compound-Unstable!6-3C PGA’s6-NADPH6-3C PGAL’s3-5C RuBP’s3-ATPCalvin Cycle Video1 exits and will become GLUCOSE5 stay in cycle
36 There are factors that limit the amount of PS LT8Limiting Factors to PSThere are factors that limit the amount of PSH2O –slow or decrease PSTemperatureRecall that enzymes have particular optimaltemperaturesFunctions best between °CTemperatures above or below these temps slow PSVery low temps STOP PSLight Intensity- increase intensity = increase PSColor of Light – RO and BV preferred
37 Photosynthesis Review LT’s1-8Photosynthesis ReviewTwo rxns: Light and DarkReactants: H2O, CO2, and LightProducts: O2 and GlucoseTwo Locations:Light –Thylakoid MembraneDark- StRoma
38 Photosynthesis Review Word BankPhotosynthesisATP (2)ThylakoidStromaLight Energy from the sunHigh energy sugarsNADPH (2)OxygenLight-depentdent reactionCalvin CycleChloroplast22.214.171.124.126.96.36.199.188.8.131.52.13.