Unit 3 – ENERGY Conversion

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The Sun is the ultimate source of energy on Earth

Then what?• Plants convert the SOLAR ENERGY into CHEMICAL

ENERGY (glucose and other high-energy carbs) • Julius Mayer discovered this conversion in 1845

Energy flow through ecosystems

• Autotrophs (Producers) – organisms that can make their own food (glucose)

• Ex. Plants, algae

• Heterotrophs (Consumers) – Organisms that obtain energy from the food they eat

• Ex. Fungi, Animals… anything that has to EAT to get ENERGY

Why do plants and animals need energy?

1.Mechanical functions (muscle contractions – animals, turning toward the sun – plants)

2.Protein synthesis3.Active transport

PHOTOSYNTHESIS AND CELLULAR RESPIRATION ARE COMPLIMENTARY PROCESSES

PS and CR: Chloroplasts and Mitochondria

Can PRODUCERS do both? Can CONSUMERS do both?

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ATP = Energy Currency of the Cell• Adenosine TriPhosphate – most

important energy storing compound used by every cell

• Even used during PS to make glucose… which is used to make ATP!

Question

Why are eukaryotes able to be larger and more complex than prokaryotes?

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Theory of Endosymbiosis• Lynn Margulies and many other scientists• The theory of Endosymbiosis explains the origin of

chloroplasts and mitochondria and their double membranes.• This concept postulates that chloroplasts and mitochondria

are the result of years of evolution initiated by the endocytosis of bacteria and blue-green algae.

• According to this theory, blue green algae and bacteria were not digested; they became symbiotic instead.

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Support for Endosymbiotic TheoryMitochondria and chloroplasts…•reproduce like bacteria do (binary fission)•have their own ribosomes that resemble bacterial ribosomes (70S)•are double membrane-bound•have their own DNA which is different than the DNA in the nucleus, but similar to bacterial DNA•…

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History of History of PhotosynthesisPhotosynthesis

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PhotosynthesisPhotosynthesis

• Involves the Use Of light Energy Involves the Use Of light Energy to convert to convert Water (6HWater (6H220)0) and and Carbon Dioxide (6COCarbon Dioxide (6CO22)) into into Oxygen (6OOxygen (6O22)) and and High Energy High Energy CarbohydratesCarbohydrates (sugars, e.g. (sugars, e.g. Glucose) & StarchesGlucose) & Starches

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FORMULA for PS

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Investigating Investigating PhotosynthesisPhotosynthesis

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

•Early Research: Overall Early Research: Overall ProcessProcess

•Later Later Researchers:Detailed Researchers: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:

Plants tend to grow… Plants tend to grow… WHY?WHY?

Does the increase in mass Does the increase in mass of a plant come from the of a plant come from the

air? The soil? The air? The soil? The Water?Water?

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

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

• Weighed Plant & Soil.Weighed Plant & Soil. • Van Helmont dried and weighed the soil. • The plant gained approx. 74 kg of mass…

but the dried soil weighed almost the same (lost ~2 ounces)

• Concluded Mass Came From WaterConcluded Mass Came 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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Priestley = O2 is the burning gas and plants release it

• Thinking questions: • Do all types of plants

release the same amount of oxygen gas? How could you test that?

• What factors, if any, might have an effect on the production of oxygen?

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Ingenhousz’s Experiment Ingenhousz’s Experiment 17791779

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

Results of Results of Ingenhousz’s Ingenhousz’s ExperimentExperiment

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

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

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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 Chemical Chemical EnergyEnergy

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Samuel Ruben & Martin Samuel Ruben & Martin KamenKamen19411941

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

25KAMENKAMEN

RUBINRUBIN

Isotope = rare form of an atom

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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•Used radioactive Used radioactive isotope Carbon-14isotope Carbon-14•Does Does NOTNOT require require sunlightsunlight•Called the Called the Calvin CycleCalvin Cycle or or Light Independent Light Independent Reaction Reaction or or 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 Transport Chain

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Recap• Van Helmont = mass of a plant comes

from water• Preistley = plants produce oxygen (the

gas necessary for combustion)• Ingenhousz = plants only produce

oxygen in the LIGHT (is a product of the light rnxs, NOT the calvin cycle)

• Mayer = plants convert light into chemical energy

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• Ruben and Kamen = the O’s in oxygen gas comes from the O’s in water (breaking water molecules during light rxns). Used isotope of oxygen to trace its path.

• Calvin = the C’s in glucose/ sugars comes from the C’s in carbon dioxide. Glucose/ sugars can be made in the absence of light. Used isotope of carbon.

• Marcus = first to describe the ETC

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PhotosynthesisPhotosynthesis

• Anabolic (small molecules combined)Anabolic (small molecules combined)• Light energy is converted into Light energy is converted into

chemical energy.chemical energy.• Endergonic (stores energy)Endergonic (stores energy)• Carbon dioxide (COCarbon dioxide (CO22)) requiring process requiring process

that uses that uses light energy (light energy (photons-photons-particles of lightparticles of light)) and and water (Hwater (H22O)O) to to produce produce organic macromolecules organic macromolecules (glucose).(glucose).

6CO2 + 6H2O C6H12O6 + 6O2glucoseglucose

SUNphotonsphotons

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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 – produce their own

food food (glucose)-Known as (glucose)-Known as Producers. Examples plants, Producers. Examples plants, algae, and some bacteria.algae, and some bacteria.

• Process called Process called photosynthesisphotosynthesis• Mainly occurs in the Mainly occurs in the leaves:leaves:

a.a.stoma - poresstoma - pores

b.b.mesophyll cellsmesophyll cells

StomaMesophyllCell

Chloroplast

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Stomata (stoma)Stomata (stoma)

PoresPores in a plant’s leaves through in a plant’s leaves through which which waterwater and and gasesgases are are exchanged between the plant exchanged between the plant and the atmosphere.and the atmosphere.

Carbon Dioxide (CO2)

Oxygen (O2)

Found on the underside of leavesFound on the underside of leaves

Adaptations

• Why are stomata usually located on the bottom/ underside of a leaf?

• Where would a water lily’s stomata probably be located?

• How would desert plants adapt? They need to avoid losing water from stomata BUT need to open the stomata to allow CO2 in and O2 out…

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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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ChloroplastChloroplastOrganelleOrganelle where

photosynthesisphotosynthesis takes place.

GranumThylakoid

Stroma

Outer Membrane

Inner Membrane

Thylakoid stacks are connected togetherThylakoid stacks are connected together

Stroma is a solution surrounding thylakoidsStroma is a solution surrounding thylakoids

Where in a plant does most PS occur?

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Question:Question:

Why are Why are plants plants green?green?

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Chlorophyll MoleculesChlorophyll Molecules

Pigment-Light absorbing Pigment-Light absorbing moleculemolecule

Often stored in vacuolesOften stored in vacuoles• Plants are Plants are greengreen because the because the green green

wavelength is reflectedwavelength is reflected, not absorbed, not absorbed.

• CHLOROPHYLLCHLOROPHYLL – reflects green light, – reflects green light, absorbs light of other wavelengths. absorbs light of other wavelengths. Found in chloroplastsFound in chloroplasts

• CarotenoidsCarotenoids, , AnthocyaninsAnthocyanins, , XanthophyllsXanthophylls accessory pigments. Absorbs different accessory pigments. Absorbs different wavelengths of light than chlorophyllwavelengths of light than chlorophyll

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Wavelength of Light (nm)Wavelength of Light (nm)

Short wave Long wave(more energy) (less energy)

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Absorption of Light by Absorption of Light by ChlorophyllChlorophyll

wavelengthwavelength

Absorption

Shade Tolerant Plants

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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 chlorophyll pigments are greatly reducedgreatly reduced revealing the revealing the other pigmentsother pigments

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

PS = a two part process

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Light Reactions

1.Light Reaction or Light 1.Light Reaction or Light Dependent Reaction - Dependent Reaction -

• Occurs within the thylakoid Occurs within the thylakoid membranesmembranes

• Reactant: HReactant: H22OO

• Product: OProduct: O2 (and ATP)2 (and ATP)

Remember Ingenhousz?

48Plant + Light = OXYGEN!

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Dark ReactionsDark Reactions2. Calvin Cycle or Light 2. Calvin Cycle or Light

Independent Reaction Independent Reaction• Also called Carbon Fixation Also called Carbon Fixation

or Cor C33 Fixation Fixation• Reactant: COReactant: CO2 (ATP is used)2 (ATP is used)

• Product: Glucose and other Product: Glucose and other high-energy carbohydrateshigh-energy carbohydrates

Remember Calvin?• The 6 Carbons in Glucose comes from 6

molecules of CO2

• How do plants get CO2? STOMATA = SITE OF GAS EXCHANGE IN PLANTS

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Cyclic Electron Flow during Cyclic Electron Flow during Light RXNsLight RXNs

P700

PrimaryElectronAcceptor

e-

e-

e-

e-

ATPATPproducedby ETC

Photosystem I

AccessoryPigments

SUN

Photons

Pigments absorb light energy & excite e- of Pigments absorb light energy & excite e- of Chlorophyll a to produce ATP Chlorophyll a to produce ATP

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. Energy stored in the bonds between phosphate molecules is released when a phosphate molecule breaks off.

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ChemiosmosisChemiosmosis• Powers Powers ATP synthesisATP synthesis• Located in the Located in the thylakoid thylakoid

membranesmembranes• Uses Uses ETC ETC and and ATP ATP

synthase (enzyme)synthase (enzyme) to to make ATPmake ATP

• Photophosphorylation:Photophosphorylation: addition of phosphate to addition of phosphate to ADP to make ATPADP to make ATP

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ChemiosmosisChemiosmosisH+ H+

ATP Synthase

H+ H+ H+ H+

H+ H+ high Hhigh H++

concentrationconcentration

H+ADP + P ATP

PS II PS IE

TC

low Hlow H++

concentrationconcentration

H+ThylakoidThylakoidSpaceSpace

ThylakoidThylakoid

SUN (Proton Pumping)

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ChloroplastChloroplast

GranumThylakoid

STROMA– where Calvin Cycle occursOuter Membrane

Inner Membrane

Huh?

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Rate of Photosynthesis• What factors affect the rate of PS?1.Temperature2.Light Intensity3.Amount of CO2

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Cellular Respiration• Why do we eat? Why can’t we make energy

like plants (producers/ autotrophs) do?

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Pulmonary Respiration VERSUS Cellular Respiration• PULMONARY RESPIRATION AKA Breathing:

– Alternation of inhalation and exhalation.– Exchange of gases in which organisms obtain oxygen

from the air (or water) and release carbon dioxide.– Exchange occurs in lungs (or gills).

• CELLULAR RESPIRATION: – Harvesting of energy from food molecules by cells. – Aerobic process (requires oxygen). – Occurs inside cells (cytoplasm and mitochondria).

“Respiration” comes from Latin word for breathing.

Pulmonary and cellular respiration are closely related, but not the same processes.

Breathing versus Cellular Respiration

Where Does Cellular Respiration Take Place?

• It actually takes place in two parts of the cell:

Glycolysis Glycolysis occurs in the occurs in the CytoplasmCytoplasmKrebs Cycle & Krebs Cycle & ETC TakeETC Take place place in the in the MitochondriaMitochondria

CELLULAR RESPIRATION BANKS ATPCELLULAR RESPIRATION BANKS ATP

REACTIONREACTION::

CC66HH1212OO66 + 6O + 6O22 ----> 6CO ----> 6CO22 + 6H + 6H22O + O + ENERGYENERGY(Glucose) (Oxygen) (Carbon dioxide) (Water)(Glucose) (Oxygen) (Carbon dioxide) (Water)

What happens to the energy in glucose or other What happens to the energy in glucose or other food molecules?food molecules? Only about 40% of energy is turned into ATPOnly about 40% of energy is turned into ATP The rest is lost as metabolic heat (think: The rest is lost as metabolic heat (think:

CALORIES)CALORIES) One One ATPATP molecule has about molecule has about 1%1% of the of the

chemical energy found in glucose.chemical energy found in glucose.

ENERGY CONVERSIONS ARE INEFFICIENTSecond Law of Thermodynamics

By Comparison Living Organisms Are Efficient

ATP = adenosine triphosphateATP = adenosine triphosphate The phosphates are attached by The phosphates are attached by

high energy bondshigh energy bonds Enzymes break off the last high energy bond and Enzymes break off the last high energy bond and

energy is released to do cell work leaving ADP energy is released to do cell work leaving ADP (Adenosine Diphosphate)(Adenosine Diphosphate)

In an ATP molecule:In an ATP molecule:where’s the energy where’s the energy stored?stored?

PO–

O–

O

–O PO–

O–

O

–O PO–

O–

O

–O energyPO–

O–

O

–O +

ATP is recycled

Fully charged batteryATP

Half charged batteryADP

CATABOLISMCATABOLISM::

Process of splitting larger molecules to smaller Process of splitting larger molecules to smaller ones. Catabolic reactions are exergonic and ones. Catabolic reactions are exergonic and release free energyrelease free energy..

THREE MAJOR CATABOLIC PATHWAYS IN THREE MAJOR CATABOLIC PATHWAYS IN LIVING ORGANISMSLIVING ORGANISMS

A. A. Cellular respirationCellular respiration (Aerobic) (Aerobic)

B.B. Anaerobic respirationAnaerobic respiration

C.C. FermentationFermentation

MAJOR CATABOLIC PATHWAYSMAJOR CATABOLIC PATHWAYS

A. A. Cellular respiration (AKA Oxidative or Cellular respiration (AKA Oxidative or Aerobic respiration)Aerobic respiration):: Requires Requires oxygenoxygen.. Occurs in Mitochondria (steps 2 and 3)Occurs in Mitochondria (steps 2 and 3) Most commonly used catabolic pathway.Most commonly used catabolic pathway. Used to extract energy from glucose molecules.Used to extract energy from glucose molecules. Most Most efficientefficient: : 1 glucose = 36 net ATP.1 glucose = 36 net ATP.

Cellular Respiration

REACTION:REACTION:CC66HH1212OO66 + 6O + 6O22 ---> 6CO ---> 6CO22 + 6H + 6H22O + O + ENERGYENERGY

GlucoseGlucose Oxygen Oxygen Carbon dioxide Water ATP Carbon dioxide Water ATP

CR vs PS

THREE MAJOR CATABOLIC THREE MAJOR CATABOLIC PATHWAYSPATHWAYS

B. B. Anaerobic respirationAnaerobic respiration:: Does Does notnot require require oxygenoxygen.. Used by bacteria that live in anoxic Used by bacteria that live in anoxic

environments.environments. 1 glucose = 2 ATP1 glucose = 2 ATP Final productsFinal products: Carbon dioxide, water, and : Carbon dioxide, water, and

other other inorganicinorganic compounds. compounds.

THREE MAJOR CATABOLIC PATHWAYSTHREE MAJOR CATABOLIC PATHWAYS

C. C. FermentationFermentation:: Does Does notnot require require oxygenoxygen.. Used by yeast, bacteria, and other cells when Used by yeast, bacteria, and other cells when

oxygen is not available.oxygen is not available. Final electron acceptor:Final electron acceptor: OrganicOrganic molecule.molecule. 1 glucose = 2 ATP1 glucose = 2 ATP Products depend on type of fermentation:Products depend on type of fermentation:

Lactic acid fermentationLactic acid fermentation: Used to make cheese and : Used to make cheese and yogurt. Carried out by muscle cells if oxygen is low.yogurt. Carried out by muscle cells if oxygen is low.

Alcoholic fermentationAlcoholic fermentation: Used to make alcoholic : Used to make alcoholic beverages. Produces alcohol and carbon dioxide. beverages. Produces alcohol and carbon dioxide.

FERMENTATION OCCURS WHEN OXYGEN FERMENTATION OCCURS WHEN OXYGEN IS NOT AVAILABLEIS NOT AVAILABLE

Yeasts normally use aerobic respiration to Yeasts normally use aerobic respiration to process food.process food.

If oxygen is not available, they use fermentation, If oxygen is not available, they use fermentation, which is which is less efficientless efficient..

Types of fermentation:

Alcoholic fermentationAlcoholic fermentation

Glucose ----> 2 pyruvate ----> Glucose ----> 2 pyruvate ----> 2 Ethanol + 2 CO2 Ethanol + 2 CO22

Lactic acid fermentationLactic acid fermentation

Glucose ----> 2 pyruvate ----> Glucose ----> 2 pyruvate ----> 2 Lactic acids2 Lactic acids

In a 2 minute footrace… All your stored ATP is used up, so you begin lactic All your stored ATP is used up, so you begin lactic

acid fermentationacid fermentation

Fermentation Occurs When Oxygen is Unavailable

Why do you breathe heavily after AEROBIC activity?

Alcoholic and Lactic Acid Fermentation: An Alternative to Aerobic Respiration

Three Stages of Cellular Respiration

Glycolysis (in cytoplasm)Glycolysis (in cytoplasm) Krebs Cycle (in mitochondria)Krebs Cycle (in mitochondria) Electron Transport Chain (in mitochondria)Electron Transport Chain (in mitochondria)

Three Stages of Aerobic Respiration

A. A. Glycolysis: “Splitting sugar”Glycolysis: “Splitting sugar” Occurs in the Occurs in the cytoplasmcytoplasm of the cell of the cell DOES NOT require oxygenDOES NOT require oxygen Net result: 2 ATPNet result: 2 ATP

IF OXYGEN IS PRESENT, Cellular Respiration will IF OXYGEN IS PRESENT, Cellular Respiration will proceed and more ATP can be made.proceed and more ATP can be made.

IF NO OXYGEN PRESENT, fermentation occurs and IF NO OXYGEN PRESENT, fermentation occurs and you ONLY GET 2 ATP.you ONLY GET 2 ATP.

Glycolysis: “Splitting” of Glucose into Two Molecules of Pyruvic Acid

B. B. Kreb’s Cycle (Citric Acid Cycle)Kreb’s Cycle (Citric Acid Cycle)

Occurs in the Occurs in the matrixmatrix of the mitochondrion of the mitochondrion

Carbons are released asCarbons are released as CO CO22

Yield per glucose molecule:Yield per glucose molecule:

2 ATP2 ATP

Electron carrying molecules (NADH, Electron carrying molecules (NADH, FADHFADH22), and H+), and H+

Analogy: Kreb’s Cycle is to CR as Calvin Analogy: Kreb’s Cycle is to CR as Calvin Cycle is to PSCycle is to PS

C. C. Electron Transport Chain & ChemiosmosisElectron Transport Chain & Chemiosmosis

Most ATP is produced at this stageMost ATP is produced at this stage Occurs on inner mitochondrial membraneOccurs on inner mitochondrial membrane Electrons fromElectrons from NADH and FADHNADH and FADH22 are transferred to are transferred to

electron acceptors, which produces aelectron acceptors, which produces a proton gradientproton gradient Proton gradientProton gradient used to drive synthesis of ATP.used to drive synthesis of ATP. ChemiosmosisChemiosmosis: ATP synthase allows H: ATP synthase allows H++ to flow across to flow across

inner mitochondrial membrane down concentration inner mitochondrial membrane down concentration gradient, which produces ATP.gradient, which produces ATP.

Ultimate acceptor of HUltimate acceptor of H++ and electrons is and electrons is OXYGENOXYGEN, , producing producing waterwater..

Analogy: ETC is to CR as Light RXNs are to PS

Electron Transport & Chemiosmosis: GeneratesMost ATP Produced During Cellular Respiration

Electron Transport Chain Animation

NOTENOTE:: The electron transport chain ONLY The electron transport chain ONLY

works when OXYGEN is available at the end works when OXYGEN is available at the end

of the chain to accept the electrons and Hof the chain to accept the electrons and H++ to to

form water.form water.

So… in order to make LOTS of ATP, what So… in order to make LOTS of ATP, what

GAS is necessary?GAS is necessary?

Net Total Energy from cellular respirationNet Total Energy from cellular respiration

~36 ATP from 1 glucose molecule~36 ATP from 1 glucose molecule

(Approx. 38 made, BUT 2 are used for (Approx. 38 made, BUT 2 are used for active transport of pyruvate across active transport of pyruvate across mitochondrial membrane)mitochondrial membrane)