PhotosynthesisPhotosynthesis

Chapter 8 pp160-175Chapter 8 pp160-175

ReviewReview

What is photosynthesis?What is photosynthesis? Process by which energy from sunlight is used Process by which energy from sunlight is used

to convert water and carbon dioxide into high-to convert water and carbon dioxide into high-energy carbohydrates (sugars and starches) energy carbohydrates (sugars and starches) and oxygen as a waste productand oxygen as a waste product

Who uses photosynthesis?Who uses photosynthesis? Plants and other producers Plants and other producers

Key contributorsKey contributors

Big Question:Big Question: When a tiny seed grows into a tall tree with a When a tiny seed grows into a tall tree with a

mass of several tons, where does the tree’s mass of several tons, where does the tree’s increase in mass come from? From the soil? increase in mass come from? From the soil? From the water? From the air?From the water? From the air?

Jan van Helmont Jan van Helmont 16431643 Belgian physicianBelgian physician Do plants grow by taking material out of the Do plants grow by taking material out of the

soil?soil? Mass of soilMass of soil Mass of seedMass of seed Watered regularlyWatered regularly @ end of 5 yrs, tree was 75 g, soil the same@ end of 5 yrs, tree was 75 g, soil the same Conclusion: Mass came from waterConclusion: Mass came from water Accounts to the “hydrate” portion of Accounts to the “hydrate” portion of

carbohydrate produced but what made the carbohydrate produced but what made the “carbo-” portion“carbo-” portion

Joseph PriestlyJoseph Priestly

17711771 English ministerEnglish minister Bell jar, candle, plantBell jar, candle, plant Jar over candleJar over candle flame flame

died outdied out Jar over candle with live Jar over candle with live

sprig of mintsprig of mint flame flame didn’t diedidn’t die

Conclusion: Plant Conclusion: Plant releases oxygenreleases oxygen

Jan IngenhouszJan Ingenhousz

17791779 Dutch scientistDutch scientist Aquatic plants produce Aquatic plants produce

bubbles only when light is bubbles only when light is presentpresent

Conclusion: Plants need Conclusion: Plants need sunlight to produce oxygensunlight to produce oxygen

Julius Robert MayerJulius Robert Mayer

18451845 German scientistGerman scientist Proposed that plants Proposed that plants

convert light into energy convert light into energy into chemical energyinto chemical energy

Melvin CalvinMelvin Calvin 19481948 American chemistAmerican chemist Traces the chemical pathway Traces the chemical pathway

that carbon follows to form that carbon follows to form glucose…reactions known as glucose…reactions known as the Calvin Cycle the Calvin Cycle

Rudolph MarcusRudolph Marcus 19921992 Canadian chemistCanadian chemist Won Nobel Prize for Won Nobel Prize for

describing process in describing process in which electrons are which electrons are transferred from one transferred from one molecule to another in the molecule to another in the electron transport chainelectron transport chain

The experiments performed by van The experiments performed by van Helmont, Priestly, and Ingenhousz led to Helmont, Priestly, and Ingenhousz led to work by other scientists who finally work by other scientists who finally discovered that in the presence of light, discovered that in the presence of light, plants transform carbon dioxide and plants transform carbon dioxide and water into carbohydrates, and they also water into carbohydrates, and they also release oxygenrelease oxygen

Review SunlightReview Sunlight White lightWhite light

ROYGBIVROYGBIV Combo of all colorsCombo of all colors

PigmentsPigments Chemicals that absorb electromagnetic radiation Chemicals that absorb electromagnetic radiation

(visible light)(visible light) Light absorbing moleculesLight absorbing molecules

Electromagnetic spectrumElectromagnetic spectrum Electrons=energyElectrons=energy

Structures and moleculesStructures and molecules

ChloroplastChloroplast ChlorophyllChlorophyll ThylakoidsThylakoids

Chloroplast (found in Chloroplast (found in cells in leaves)cells in leaves)

Concentrated in the cells of the Concentrated in the cells of the mesophyll (inner layer of tissue) in mesophyll (inner layer of tissue) in leafleaf

StomataStomata Tiny pores on surface of leafTiny pores on surface of leaf Allows carbon dioxide and Allows carbon dioxide and

oxygen in and out of the leafoxygen in and out of the leaf VeinsVeins

Carry water and nutrients from Carry water and nutrients from roots to leavesroots to leaves

Deliver organic molecules Deliver organic molecules produced in leaves to other produced in leaves to other parts of the plantparts of the plant

ChloroplastChloroplast Cellular organelle where Cellular organelle where

photosynthesis takes photosynthesis takes placeplace Double membraneDouble membrane Outer membraneOuter membrane Stroma (fluid filled space)Stroma (fluid filled space) Inner membraneInner membrane ThylakoidsThylakoids GranumGranum Intermembrane spaceIntermembrane space

Contain chemical Contain chemical compound called compound called ChlorophyllChlorophyll This molecule gives This molecule gives

chloroplast its green colorchloroplast its green color

Structure of ChloroplastStructure of Chloroplast Structures organize the many Structures organize the many

reactions that take place in reactions that take place in photosynthesisphotosynthesis

StromaStroma Thick fluid enclosed by the inner Thick fluid enclosed by the inner

membranemembrane ThylakoidsThylakoids

Disc-like sacs suspended in the Disc-like sacs suspended in the stromastroma

Has membrane that surrounds Has membrane that surrounds inner thylakoid spaceinner thylakoid space

Grana (sing. Granum)Grana (sing. Granum) Stacks of thylakoidsStacks of thylakoids

ChlorophyllChlorophyll Plants principle pigmentPlants principle pigment 2 types2 types

Chlorophyll aChlorophyll a Absorbs light in the blue-violet and red regions of visible spectrumAbsorbs light in the blue-violet and red regions of visible spectrum

Chlorophyll bChlorophyll b Absorbs light in the blue and red regions of the visible spectrumAbsorbs light in the blue and red regions of the visible spectrum

Chlorophyll does NOT absorb light well in the green portion Chlorophyll does NOT absorb light well in the green portion of the visible spectrumof the visible spectrum

Green light reflected by leavesGreen light reflected by leaves This is why plants look green…they reflect green lightThis is why plants look green…they reflect green light

CaroteneCarotene Secondary plant pigmentSecondary plant pigment Red and orange pigmentsRed and orange pigments Absorb light in other regions of the spectrum other than red and Absorb light in other regions of the spectrum other than red and

orangeorange

2 main stages2 main stages Light Dependent RxnLight Dependent Rxn Light-Independent or Calvin CycleLight-Independent or Calvin Cycle

Photosynthesis OverviewPhotosynthesis Overview #1 “Light-Dependent” reactions#1 “Light-Dependent” reactions

Convert the E in sunlight to chemical energyConvert the E in sunlight to chemical energy Rxns depend on molecules made in membranes of Rxns depend on molecules made in membranes of

thylakoidsthylakoids Chlorophyll in membr. captures light EChlorophyll in membr. captures light E Chloroplast use E to remove e- from waterChloroplast use E to remove e- from water

Splits water into oxygen (waste) and hydrgen ionsSplits water into oxygen (waste) and hydrgen ions e- taken are used to make high-E molecule NADPH (similar to e- taken are used to make high-E molecule NADPH (similar to

NADH)NADH) Chloroplast also use captured E to make ATPChloroplast also use captured E to make ATP

Overall Product: convert light E into chemical energy Overall Product: convert light E into chemical energy stored in compounds ATP and NADPHstored in compounds ATP and NADPH

Photosynthesis OverviewPhotosynthesis Overview# 2 “Light- Independent” Reactions aka # 2 “Light- Independent” Reactions aka

The Calvin CycleThe Calvin Cycle Makes sugar from atoms of CO2 and H+ ions and High-E Makes sugar from atoms of CO2 and H+ ions and High-E

e- carried by NADPHe- carried by NADPH Enzymes for these reactions are dissolved in the stroma Enzymes for these reactions are dissolved in the stroma

(outside thylakoid)(outside thylakoid) ATP made by light Rxns provides E to make sugar ATP made by light Rxns provides E to make sugar

(glucose)(glucose) Called light independent, b/c unlike unlike the light Called light independent, b/c unlike unlike the light

reactions, these do NOT require light tp beginreactions, these do NOT require light tp begin However, this cycle does require two things made by the However, this cycle does require two things made by the

light reactions: ATP and NADPHlight reactions: ATP and NADPH This means that the calvin cycle cannot necessarily continue in This means that the calvin cycle cannot necessarily continue in

the darkthe dark