Transcript

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Chapter 8Chapter 8

Cellular Cellular Respiration:Respiration:

Harvesting Harvesting Chemical EnergyChemical Energy

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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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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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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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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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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

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-A to make Acetyl-enzyme Co-A to make 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 microorganismsmicroorganisms 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)

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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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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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