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Chapter 9Chapter 9

Cellular Cellular Respiration:Respiration:

Harvesting Harvesting Chemical EnergyChemical Energy

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All the energy in all the food you eat can be traced back to sunlightsunlightIf you exercise too hard, your muscles shut down from a lack of oxygenlack of oxygen

Respiration Facts:

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When you exercise:Muscles need energy in order to perform workMuscles need energy in order to perform workYour cells use oxygen to release energy from the sugar glucoseYour cells use oxygen to release energy from the sugar glucoseBoth Both aerobic and anaerobicaerobic and anaerobic burning of glucose can take place burning of glucose can take place in your cellsin your cells

FEELING THE “FEELING THE “BURNBURN””

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Aerobic metabolismAerobic metabolism - When enough oxygen reaches cells to support energy needs - When enough oxygen reaches cells to support energy needs

- Maximum energy production- Maximum energy productionAnaerobic metabolismAnaerobic metabolism– When the demand for oxygen outstrips the body’s ability to deliver itWhen the demand for oxygen outstrips the body’s ability to deliver it– Low energy productionLow energy production

Aerobic & Anaerobic Metabolism

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Without enough oxygen, Without enough oxygen, muscle cells break down muscle cells break down glucose to produce glucose to produce lactic lactic acidacidLactic acidLactic acid is associated is associated with the “with the “burnburn” associated ” associated with heavy exercisewith heavy exerciseIf too much lactic acid If too much lactic acid builds up, your builds up, your muscles muscles give outgive out

Anaerobic MetabolismAnaerobic Metabolism

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Physical ConditioningPhysical Conditioning

Allows your body to Allows your body to adapt to increased adapt to increased activityactivityThe body can The body can increase its ability to increase its ability to deliver deliver oxygen to oxygen to musclesmusclesLong-distance Long-distance runners wait until the runners wait until the final sprint to exceed final sprint to exceed their aerobic capacitytheir aerobic capacity

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Only Only producersproducers are capable of are capable of PhotosynthesisPhotosynthesis

Light energy from the sun powers this chemical process that makes Light energy from the sun powers this chemical process that makes organic molecules (sugars)organic molecules (sugars)

This process occurs in the This process occurs in the mesophyll cells of leavesmesophyll cells of leaves of producers (plants & algae) of producers (plants & algae)

Why Photosynthesis?Why Photosynthesis?

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ENERGY FLOW IN THE ENERGY FLOW IN THE BIOSPHEREBIOSPHERE

Energy stored in food can be Energy stored in food can be traced back to the traced back to the sunsun

Fuel molecules in food store Fuel molecules in food store solar energy in solar energy in chemical bondschemical bonds

Animals depend on plants to Animals depend on plants to convert solar energy to chemical convert solar energy to chemical energyenergy

This chemical energy is in the This chemical energy is in the form of form of sugars and other organic sugars and other organic moleculesmolecules

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AutotrophsAutotrophs - Plants and other organisms that make - Plants and other organisms that make all their own organic matter from inorganic nutrientsall their own organic matter from inorganic nutrientsHeterotrophsHeterotrophs - Humans and other animals that - Humans and other animals that cannot make organic molecules from inorganic onescannot make organic molecules from inorganic ones

Autotrophs & Autotrophs & HeterotrophsHeterotrophs

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The Cycle of EnergyThe Cycle of EnergyProducersProducers - - Biologists refer to Biologists refer to plants and other plants and other autotrophs as the autotrophs as the producers in an producers in an ecosystemecosystem

ConsumersConsumers - - Heterotrophs are Heterotrophs are consumers, because consumers, because they eat plants or they eat plants or other animalsother animals

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The ingredients for photosynthesis The ingredients for photosynthesis are are carbon dioxide and watercarbon dioxide and water

COCO22 is obtained from the air by a is obtained from the air by a plant’s plant’s leavesleaves

HH22OO is obtained from the damp is obtained from the damp soilsoil by by a plant’s rootsa plant’s roots

ChloroplastsChloroplasts rearrange the atoms of rearrange the atoms of these ingredients to produce these ingredients to produce sugars sugars (glucose)(glucose) and other organic molecules and other organic molecules

OxygenOxygen gas is a by-product of gas is a by-product of photosynthesisphotosynthesis

Chemical CyclingChemical Cycling

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Both plants and animalsBoth plants and animals perform cellular respirationperform cellular respiration

Cellular respiration is a Cellular respiration is a chemical process that chemical process that harvests harvests energy from organic moleculesenergy from organic molecules and occurs in the and occurs in the mitochondriamitochondria

The The waste productswaste products of cellular of cellular respiration, respiration, COCO22 and H and H22OO, are , are used in photosynthesisused in photosynthesis

Chemical CyclingChemical Cycling

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Sunlightenergy

Ecosystem

Photosynthesis(in chloroplasts)

Glucose

Oxygen

Carbon dioxide

Cellular respiration(in mitochondria)

Water

Cellular energy

Heat energy

Sunlight supplies the energy!

Bonds of Glucose, made in chloroplasts, contain the stored energy

Raw materials for photosynthesis

Raw materials for cellular respiration

Glucose broken down to release energy for cellular work

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Cellular respiration is the main way that Cellular respiration is the main way that chemical energy is chemical energy is harvested from foodharvested from food and converted to ATP for cellular work and converted to ATP for cellular work

Cellular respiration is an Cellular respiration is an aerobicaerobic process requiring oxygen process requiring oxygen

AEROBIC HARVEST OF FOOD AEROBIC HARVEST OF FOOD ENERGYENERGY

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The Versatility of Cellular The Versatility of Cellular RespirationRespiration

Cellular respiration can “burn” other kinds of molecules besides glucose:

Diverse types ofDiverse types of carbohydratescarbohydrates

FatsFats

ProteinsProteins

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A common A common fuelfuel molecule for cellular respiration is molecule for cellular respiration is glucoseglucose

This is the This is the overall equationoverall equation for what happens to glucose during cellular respiration for what happens to glucose during cellular respiration

The Overall Equation for The Overall Equation for Cellular RespirationCellular Respiration

Glucose Oxygen Carbon dioxide Water Energy

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But Remember …But Remember …

Cellular Respiration is a Cellular Respiration is a metabolic pathway, metabolic pathway, not a single not a single reactionreaction

Many chemical reactionsMany chemical reactions, both , both aerobic and anaerobic, are aerobic and anaerobic, are involved in the process of involved in the process of cellular respirationcellular respiration

Lots of enzymesLots of enzymes are required for are required for the process to occurthe process to occur

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Cellular respiration and breathing are Cellular respiration and breathing are closely relatedclosely related

Cellular respiration requires a cell to Cellular respiration requires a cell to exchange gases with its surroundingsexchange gases with its surroundings

Breathing exchanges these gases Breathing exchanges these gases betweenbetween the blood and outside air the blood and outside air

The Relationship Between The Relationship Between Cellular Respiration and Cellular Respiration and

BreathingBreathing

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Breathing

Lungs

Musclecells

CellularRespiration

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During cellular respiration, During cellular respiration, hydrogen and its bonding electronshydrogen and its bonding electrons change partnerschange partners

Hydrogen and its electrons go Hydrogen and its electrons go from sugar to oxygenfrom sugar to oxygen, forming water, forming water

The Role of Oxygen in Cellular The Role of Oxygen in Cellular RespirationRespiration

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Chemical reactions that transfer electrons from one Chemical reactions that transfer electrons from one substance to another are called substance to another are called oxidation-reduction oxidation-reduction reactionsreactions

REDOXREDOX short for oxidation-reduction reactions short for oxidation-reduction reactions

Redox ReactionsRedox Reactions

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The The loss loss of electrons during a redox reaction is called of electrons during a redox reaction is called oxidationoxidationThe The acceptanceacceptance of electrons during a redox reaction is called of electrons during a redox reaction is called reductionreductionReducing agent:Reducing agent: e- donore- donorOxidizing agent:Oxidizing agent: e- acceptore- acceptor

Redox ReactionsRedox Reactions

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Oxygen gains electrons (and hydrogens)]

Oxidation

Glucose loses electrons (and hydrogens)

Glucose OxygenCarbondioxide

Water

Reduction

REDOX in Cellular REDOX in Cellular RespirationRespiration

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ComparisonComparison

RespirationRespiration PhotosynthesiPhotosynthesiss

Occurs in all Occurs in all organismsorganisms

Occurs in only Occurs in only chlorophyll chlorophyll containing containing organismsorganisms

Breaks down Breaks down glucoseglucose

Stores light energy Stores light energy as chemical energy as chemical energy

in the bonds of in the bonds of glucoseglucose

Releases carbon Releases carbon dioxide, water, & dioxide, water, &

ATPATP

Produces glucose Produces glucose and oxygenand oxygen

Exergonic ReactionExergonic Reaction Endergonic Endergonic reactionreaction

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Cellular respiration is an example of a Cellular respiration is an example of a metabolic pathwaymetabolic pathway

A series of chemical reactions in cells either building or breaking down A series of chemical reactions in cells either building or breaking down moleculesmolecules

The Metabolic Pathway of The Metabolic Pathway of Cellular RespirationCellular Respiration

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All of the reactions involved in cellular respiration can be grouped into All of the reactions involved in cellular respiration can be grouped into threethree main stages main stages

GlycolysisGlycolysis – occurs in cytoplasm – occurs in cytoplasm

The The Krebs cycleKrebs cycle – occurs in matrix of mitochondria – occurs in matrix of mitochondria

Electron transportElectron transport – occurs across the mitochondrial membrane – occurs across the mitochondrial membrane

The Metabolic Pathway of The Metabolic Pathway of Cellular RespirationCellular Respiration

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A Road Map for Cellular A Road Map for Cellular RespirationRespiration

CytosolMitochondrion

High-energyelectronscarried

by NADH

High-energyelectrons carried

mainly byNADH

Glycolysis

Glucose2

Pyruvicacid

KrebsCycle

ElectronTransport

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GlycolysisStage OneStage One

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Glycolysis takes place in the Glycolysis takes place in the cytoplasmcytoplasm

Oxygen NOT requiredOxygen NOT required

Process breaks a six-carbon glucose into two, Process breaks a six-carbon glucose into two, three-carbon moleculesthree-carbon molecules

A molecule of glucose is split into two molecules of A molecule of glucose is split into two molecules of pyruvic acidpyruvic acid

These molecules then donate These molecules then donate high energy electrons to NADhigh energy electrons to NAD+, forming NADH+, forming NADH

Stage 1: GlycolysisStage 1: Glycolysis

GlycolysisGlycolysis

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Glucose

2 Pyruvic acidMETABOLIC PATHWAY

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CoA

Pyruvicacid

Aceticacid

Coenzyme A

Acetyl-CoA(acetyl-coenzyme A)CO2

GlycolysisGlycolysis

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Glycolysis SummaryGlycolysis SummaryThe Krebs cycle extracts the The Krebs cycle extracts the energy of sugar by energy of sugar by breaking the breaking the acetic acid molecules all the way acetic acid molecules all the way down to COdown to CO22

The cycle The cycle uses some of this uses some of this energy to make ATPenergy to make ATP

The cycle also forms The cycle also forms NADHNADH and and FADHFADH22 ( 2 energy carrier ( 2 energy carrier molecules)molecules)

Krebs CycleKrebs CycleStage TwoStage Two

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Stage 2: The Krebs CycleStage 2: The Krebs Cycle

The Krebs cycle completes The Krebs cycle completes the the breakdown of sugarbreakdown of sugar

It occurs inside the It occurs inside the mitochondriamitochondria

In the Krebs cycle, In the Krebs cycle, pyruvic pyruvic acid from glycolysisacid from glycolysis is first is first “prepped” into a usable “prepped” into a usable form by combining it with form by combining it with enzyme Co-Aenzyme Co-A to make to make Acetyl-Acetyl-CoACoA

Input

Acetic acid

ADP

3 NAD

FAD

KrebsCycle

Output

2 CO2

1 2

3

4

5

6

ACETYL Co-A

Electron TransportElectron Transport

Stage 3

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Stage 3: Electron Stage 3: Electron TransportTransport

Electron transport releases Electron transport releases the energy your cells need the energy your cells need to make the most of their to make the most of their ATPATP

The molecules of electron The molecules of electron transport chains are built transport chains are built into the into the inner membranes of inner membranes of mitochondriamitochondria

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Stage 3: Electron Stage 3: Electron TransportTransport

The chain functions as a The chain functions as a chemical machine that uses chemical machine that uses energy released by the “fall” of energy released by the “fall” of electrons to electrons to pump hydrogen ions pump hydrogen ions across the inner mitochondrial across the inner mitochondrial membranemembrane

These These ions store potentialions store potential energyenergy

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Electron transport chainElectron transport chainCytochromes carry electron Cytochromes carry electron carrier molecules (NADH & carrier molecules (NADH & FADHFADH22) down to oxygen) down to oxygen

ChemiosmosisChemiosmosis: : energy coupling mechanismenergy coupling mechanism

ATP synthaseATP synthase: : produces ATP by using the H+ produces ATP by using the H+ gradient (proton-motive force) gradient (proton-motive force) pumped into the inner pumped into the inner membrane space from the membrane space from the electron transport chain; this electron transport chain; this enzyme harnesses the flow of enzyme harnesses the flow of H+ back into the matrix to H+ back into the matrix to phosphorylate ADP to ATP phosphorylate ADP to ATP (oxidative phosphorylation)(oxidative phosphorylation)

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Proteincomplex

Electroncarrier

Innermitochondrialmembrane

Electronflow

Electron transport chain ATP synthase

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Food

Polysaccharides Fats Proteins

Sugars Glycerol Fatty acids Amino acids

Amino groups

Glycolysis Acetyl-CoA

KrebsCycle Electron

Transport

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Adding Up the ATPAdding Up the ATP

Figure 6.14

Cytosol

Mitochondrion

Glycolysis

Glucose2

Pyruvicacid

2Acetyl-

CoA

KrebsCycle Electron

Transport

bydirectsynthesis

by directsynthesis

byATPsynthase

Maximumper

glucose:

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FERMENTATION: ANAEROBIC FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGYHARVEST OF FOOD ENERGY

Some of your cells can actually Some of your cells can actually work for short periods without work for short periods without oxygen (oxygen (anaerobic respirationanaerobic respiration))

For example, For example, muscle cellsmuscle cells can can produce ATP under anaerobic produce ATP under anaerobic conditionsconditions

Called Called FermentationFermentation

Involves The anaerobic harvest Involves The anaerobic harvest of food energyof food energy

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Human muscle cells can make ATP Human muscle cells can make ATP with and without oxygenwith and without oxygen

They have enough ATP to support They have enough ATP to support activities such as quick sprinting for activities such as quick sprinting for about about 5 seconds5 seconds

A secondary supply of energy A secondary supply of energy ((creatine phosphatecreatine phosphate) can keep ) can keep muscle cells going for muscle cells going for another 10 another 10 secondsseconds

To keep running, your muscles must To keep running, your muscles must generate ATP by the generate ATP by the anaerobic anaerobic process of fermentationprocess of fermentation

Fermentation in Human Fermentation in Human Muscle CellsMuscle Cells

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GlycolysisGlycolysis is the metabolic is the metabolic pathway that provides ATP pathway that provides ATP during fermentationduring fermentation

Pyruvic acidPyruvic acid is reduced by is reduced by NADH, producing NAD+, NADH, producing NAD+, which keeps glycolysis goingwhich keeps glycolysis going

In human muscle cells, In human muscle cells, lactic lactic acidacid is a by-product is a by-product

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2 ADP+ 2

Glycolysis

Glucose

2 NAD

2 Pyruvicacid

+ 2 H

2 NAD

2 Lacticacid

Lactic acid fermentation

Various types of Various types of microorganisms microorganisms perform fermentationperform fermentation

Yeast cellsYeast cells carry out a slightly different type of fermentation pathway carry out a slightly different type of fermentation pathway

This pathway produces This pathway produces COCO22 and ethyl alcohol and ethyl alcohol

Fermentation in Fermentation in MicroorganismsMicroorganisms

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2 ADP+ 2

2 ATPGlycolysis

Glucose

2 NAD

2 Pyruvicacid

2 CO2 released

+ 2 H

2 NAD

2 Ethylalcohol

Alcoholic fermentation

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The food industry uses yeast to produce various food products

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Related metabolic Related metabolic processesprocesses

Fermentation:Fermentation:alcohol~ pyruvate alcohol~ pyruvate to ethanolto ethanol lactic acid~ lactic acid~ pyruvate to lactatepyruvate to lactate

Facultative Facultative anaerobesanaerobes (yeast/bacteria)(yeast/bacteria)

Beta-oxidationBeta-oxidationlipid catabolismlipid catabolism

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Review: Cellular Review: Cellular RespirationRespiration

Glycolysis:Glycolysis:– 2 ATP (substrate-level phosphorylation)2 ATP (substrate-level phosphorylation)

Kreb’s Cycle:Kreb’s Cycle:– 2 ATP (substrate-level phosphorylation)2 ATP (substrate-level phosphorylation)

Electron transport & oxidative phosphorylation:Electron transport & oxidative phosphorylation: – 2 NADH (glycolysis) = 6ATP 2 NADH (glycolysis) = 6ATP – 2 NADH (acetyl CoA) = 6ATP 2 NADH (acetyl CoA) = 6ATP – 6 NADH (Kreb’s) = 18 ATP 6 NADH (Kreb’s) = 18 ATP – 2 FADH2 (Kreb’s) = 4 ATP2 FADH2 (Kreb’s) = 4 ATP

38 TOTAL ATP/glucose38 TOTAL ATP/glucose

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