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Chapter 8Chapter 8

Energy & Life

Cell Energy

•Energy is essential to life. All living organisms must:

•be able to produce energy•store energy for future use, and use energy.

The need for energy

•Several cell processes require energy– Active transport– Cell division– Movement of flagella or cilia– Production and storage of

proteins– What else?

…more uses of cell energy

Making new molecules•Enzymes which carry out chemical

reactions•To build membranes and cell organellesMaintain homeostasis•Kidneys uses energy to move molecules

and ions in order to eliminate waste substances while keeping needed substances in the bloodstream

The need for energy (cont.)• When you finish strenuous activity,

your body wants a quick source of energy, so you may eat a candy bar.

• There is a molecule in your cells that is a quick source of energy for any organelle in the cell that needs it. This is stored in the chemical bonds of the molecule and can be used quickly and easily by the cell.

ATP and ADP• ATP is the molecule that stores energy

for easy use within the cell.(Adenosine triphosphate)– ATP is formed when a phosphate

group is added to ADP. When ATP is broken down, ADP and phosphate are formed and energy is released. (Adenosine Diphosphate)

– ATP is the main link between energy –releasing and energy –using reactions

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Cells Using Biochemical Cells Using Biochemical EnergyEnergy

Cells Use ATP For:• Active transport• Movement• Photosynthesis• Protein Synthesis• Cellular

respiration• All other cellular

reactions

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More on ATPMore on ATP• Cells Have Enough ATP Cells Have Enough ATP

To Last For A To Last For A Few Few SecondsSeconds

• ATP must ATP must constantlyconstantly be be mademade

• ATP ATP Transfers Energy Transfers Energy Very WellVery Well

• ATP Is ATP Is NOTNOT Good At Good At Energy StorageEnergy Storage

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AutotrophsAutotrophs

Plants and Plants and some other some other types of types of organisms that organisms that contain contain chlorophyllchlorophyll are are able to use able to use light energy light energy from the sunfrom the sun to produce to produce food.food.

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AutotrophsAutotrophs• Autotrophs Autotrophs

include include organismsorganisms that make that make their own foodtheir own food

• Autotrophs Autotrophs can use the can use the sun’s energy sun’s energy directlydirectly

EuglenaEuglena

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HeterotrophsHeterotrophs• HeterotrophHeterotroph

s are s are organisms organisms that can NOT that can NOT make their make their own foodown food

• HeterotrophHeterotrophs can NOT s can NOT directly use directly use the sun’s the sun’s energyenergy

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GlucoseGlucose•Glucose is a Glucose is a

monosaccharidemonosaccharide

•CC66HH1212OO66

•One Molecule of One Molecule of glucose Stores glucose Stores 90 90 TimesTimes More Chemical More Chemical Energy Than One Energy Than One Molecule of ATPMolecule of ATP

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History of History of Photosynthesis & Photosynthesis & Plant PigmentsPlant Pigments

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PhotosynthesisPhotosynthesis

• Involves the Use Of light Involves the Use Of light Energy to convert Energy to convert Water Water (H(H220)0) and and Carbon Dioxide Carbon Dioxide (CO(CO22)) into into Oxygen (OOxygen (O22)) and and High Energy CarbohydratesHigh Energy Carbohydrates (sugars, e.g. Glucose) & (sugars, e.g. Glucose) & StarchesStarches

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Investigating Investigating PhotosynthesisPhotosynthesis

•Many Scientists Have Many Scientists Have Contributed To Contributed To Understanding Understanding PhotosynthesisPhotosynthesis

•Early ResearchEarly Research Focused On Focused On The The Overall ProcessOverall Process

•Later ResearchersLater Researchers Investigated The Detailed Investigated The Detailed Chemical PathwaysChemical Pathways

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Early Questions on Early Questions on PlantsPlants

Several Centuries Ago, Several Centuries Ago, The Question Was:The Question Was:

Does the increase in Does the increase in mass of a plant come mass of a plant come from the air? The soil? from the air? The soil?

The Water?The Water?

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Van Helmont’s Van Helmont’s Experiment 1643Experiment 1643

• Planted a Planted a seedseed into into A pre-measured A pre-measured amount of soil and amount of soil and wateredwatered for 5 years for 5 years

• Weighed Plant & Weighed Plant & Soil.Soil. Plant Was 75 Plant Was 75 kg, Soil The Same.kg, Soil The Same.

• Concluded Mass Concluded Mass Came From WaterCame From Water

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Priestley’s Experiment Priestley’s Experiment 17711771

• Burned Candle In Bell Jar Until It Went Out.

• Placed Sprig Of Mint In Bell Jar For A Few Days.

• Candle Could Be Relit And Burn.

• Concluded Plants Released Substance (O2) Necessary For burning.

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Ingenhousz’s Ingenhousz’s Experiment 1779Experiment 1779

Repeated Priestly experiment with & without Repeated Priestly experiment with & without sunlightsunlight

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Results of Ingenhousz’s Results of Ingenhousz’s ExperimentExperiment

• Showed That Priestley’s Showed That Priestley’s Results Only Occurred In Results Only Occurred In The Presence Of The Presence Of SunlightSunlight..

• Light Was Necessary For Light Was Necessary For Plants To Produce The Plants To Produce The “Burning Gas” or “Burning Gas” or oxygenoxygen

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Julius Robert Mayer Julius Robert Mayer 18451845

Proposed That Proposed That Plants can Plants can Convert Convert Light Light Energy Into Energy Into ChemicalChemical EnergyEnergy

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Samuel Ruben & Martin Samuel Ruben & Martin KamenKamen19411941

Used Isotopes Used Isotopes To Determine To Determine That The That The OxygenOxygen Liberated In Liberated In PhotosynthesPhotosynthesis is Comes Comes From WaterFrom Water

KAMENKAMEN

RUBINRUBIN

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Melvin Calvin 1948Melvin Calvin 1948

•First to trace the path First to trace the path that that carbon (COcarbon (CO22)) takes takes in forming in forming GlucoseGlucose

•Does Does NOTNOT require require sunlightsunlight•Called the Called the Calvin CycleCalvin Cycle or or Light Independent Light Independent ReactionReaction•Also knownAlso known as the as the Dark Dark ReactionReaction

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Rudolph Marcus 1992Rudolph Marcus 1992•Studied the Studied the Light Light Independent Independent ReactionsReactions•First to First to describe the describe the Electron Electron transport transport ChainChain

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The Photosynthesis The Photosynthesis EquationEquation

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PigmentsPigments

• In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments

•Chlorophyll is the primary light-absorbing pigment in autotrophs

•Chlorophyll is found inside chloroplasts

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It Begins with Sunlight!It Begins with Sunlight!

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Photoautotrophs Absorb Photoautotrophs Absorb Light EnergyLight Energy

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Question:Question:

Where does Where does photosynthesiphotosynthesis take place?s take place?

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PlantsPlants• Autotrophs Autotrophs – produce their own food – produce their own food (glucose)(glucose)• Process called Process called photosynthesisphotosynthesis• Mainly occurs in the leaves:Mainly occurs in the leaves:

a.a. stoma - poresstoma - pores

b.b. mesophyll cellsmesophyll cells

Stoma

MesophyllCell

Chloroplast

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Stomata (stoma)Stomata (stoma)PoresPores in a plant’s cuticle through which in a plant’s cuticle through which

waterwater and and gasesgases are exchanged are exchanged between the plant and the between the plant and the atmosphere.atmosphere.

Guard CellGuard CellCarbon Dioxide (CO2)

Oxygen (O2)

Found on the underside of leavesFound on the underside of leaves

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Mesophyll Cell of LeafMesophyll Cell of Leaf

Cell Wall

NucleusNucleus

Chloroplast

Central Vacuole

Photosynthesis occurs in these cells!Photosynthesis occurs in these cells!

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Inside A ChloroplastInside A Chloroplast

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ChloroplastChloroplastOrganelleOrganelle where photosynthesisphotosynthesis takes

place.

GranumThylakoid

Stroma

Outer Membrane

Inner Membrane

Thylakoid stacks are connected togetherThylakoid stacks are connected together

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ThylakoidThylakoid

Thylakoid Membrane

Thylakoid SpaceGranum

Grana make up the inner membraneGrana make up the inner membrane

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Function of the StromaFunction of the Stroma

•Light IndependentLight Independent reactions occur herereactions occur here

•ATP usedATP used to make to make carbohydrates like carbohydrates like glucoseglucose

•Location of the Location of the Calvin Calvin CycleCycle

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Photosynthesis Photosynthesis OverviewOverview

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Harvesting Light energyWithin the inner membrane of the chloroplast, is the stroma which contains the thylakoid membrane.

This membrane produces flat, disc-like sacs called thylakoids that are arranged in stacks and contain molecules that absorb light energy for photosynthesis

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Light Reaction SummaryLight Reaction SummaryReactants:Reactants:

• HH22OO

• Light EnergyLight Energy

Energy Products:Energy Products:• ATPATP• NADPHNADPH

Products:Products:

• OO22

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Light Independent Reaction Light Independent Reaction summarysummary

• ATP and NADPH ATP and NADPH from light from light reactions used as energyreactions used as energy

• Atmospheric Atmospheric C0C022 is used is used to to make sugarsmake sugars like like glucose and fructoseglucose and fructose

• Six-carbon Sugars made Six-carbon Sugars made during the during the Calvin CycleCalvin Cycle

• Occurs in theOccurs in the stroma stroma

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The Calvin CycleThe Calvin Cycle

•Carbon Fixation Carbon Fixation (light independent (light independent reaction)reaction)•CC33 plants (80% of plants (80% of plants on earth)plants on earth)• Occurs in the Occurs in the stromastroma•Uses Uses ATP and ATP and NADPHNADPH from light from light reaction as energyreaction as energy•Uses Uses COCO22•To produce To produce glucoseglucose: it takes : it takes 2 2 turns and uses 18 turns and uses 18 ATP and 12 NADPH.ATP and 12 NADPH.

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Factors Affecting the Factors Affecting the Rate of PhotosynthesisRate of Photosynthesis

• Amount of Amount of available available waterwater

• TemperatureTemperature• Amount of Amount of

available available light energylight energy

Formula for Photosynthesis

Light–dependent reactions convert light energy into chemical energy (molecules of ATP)Light–independent reactions are fueled by the ATP produced to produce glucose .

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Question:Question:

During the fall, During the fall, what causes what causes the leaves to the leaves to

change colors?change colors?

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Fall ColorsFall Colors• In addition to the chlorophyll In addition to the chlorophyll

pigments, there are pigments, there are other other pigmentspigments present present

• During the fall, the During the fall, the green green chlorophyll pigments are greatly chlorophyll pigments are greatly reducedreduced revealing the other revealing the other pigmentspigments

• CarotenoidsCarotenoids are pigments that are pigments that are either are either redred, , orangeorange, or , or yellowyellow