Chapter 6 Cellular Respiration: Obtaining Energy from Food Laua Coronado Chap 6 Bio 10.

Chapter 6Chapter 6

Cellular Respiration: Obtaining Energy from Food

Laua Coronado Chap 6 Bio 10

Biology and : Marathoners versuSocietys Sprinters

– Sprinters do not usually compete at short and long distances.

– Natural differences in the muscles of these athletes favor sprinting or long-distance running.


Muscle Fibers–The muscles that move our legs contain

two main types of muscle fibers: • Slow twitch fibers–Generate less power–Last longer–Generate ATP using oxygen

• Fast twitch fibers–Generate more power–Fatigue much more quickly–Can generate ATP without using oxygen


ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE

–Animals depend on plants to convert solar energy to:• Chemical energy of sugars • Other molecules we consume as food

– Photosynthesis:• Uses light energy from the sun to power a chemical

process that makes organic molecules.


Producers and Consumers

–Plants and other autotrophs (self-feeders):• Make their own organic matter from inorganic

nutrients.

–Heterotrophs (other-feeders):• Include humans and other animals that cannot make

organic molecules from inorganic ones.

–Autotrophs are producers because ecosystems depend upon them for food.–Heterotrophs are consumers because they eat

plants or other animals.Laua Coronado Chap 6 Bio 10

Figure 6.1Laua Coronado Chap 6 Bio 10

Chemical Cycling between Photosynthesis and Cellular Respiration

– The ingredients for photosynthesis are carbon dioxide and water.• CO2 is obtained from the air by a plant’s leaves.

• H2O is obtained from the damp soil by a plant’s roots.

– Chloroplasts in the cells of leaves:• Use light energy to rearrange the atoms of CO2 and H2O,

which produces– Sugars (such as glucose)–Other organic molecules–Oxygen


Cellular Respiration

–Plant and animal cells perform cellular respiration, a chemical process that:• Primarily occurs in mitochondria• Harvests energy stored in organic molecules• Uses oxygen• Generates ATP

– The waste products of cellular respiration are:• CO2 and H2O

• Used in photosynthesis


Cellular Respiration

–Animals perform only cellular respiration.–Plants perform:• Photosynthesis and• Cellular respiration


Sunlight energyenters ecosystem

Photosynthesis

Cellular respiration

C6H12O6

Glucose

O2

Oxygen

CO2

Carbon dioxide

H2O

Water

drives cellular work

Heat energy exits ecosystem

ATP


CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY

–Cellular respiration is:• The main way that chemical energy is harvested

from food and converted to ATP • An aerobic process—it requires oxygen


CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY–Cellular respiration and breathing are

closely related.• Cellular respiration requires a cell to

exchange gases with its surroundings.–Cells take in oxygen gas.–Cells release waste carbon dioxide gas.

• Breathing exchanges these same gases between the blood and outside air.


Breathing

Cellularrespiration

Musclecells

Lungs

CO2

CO2

O2

O2


C6H12O6 CO2O2H2O

Glucose Oxygen Carbondioxide

Water

6 66

Reduction

Oxidation

Oxygen gains electrons (and hydrogens)

Glucose loses electrons(and hydrogens)

Figure 6.UN02Laua Coronado Chap 6 Bio 10

The Role of Oxygen in Cellular Respiration

–Cellular respiration can produce up to 38 ATP molecules for each glucose molecule consumed.–During cellular respiration, hydrogen and its

bonding electrons change partners.• Hydrogen and its electrons go from sugar to

oxygen, forming water.• This hydrogen transfer is why oxygen is so vital to

cellular respiration.


Redox Reactions–Chemical reactions that transfer electrons

from one substance to another are called:• Oxidation-reduction reactions or• Redox reactions for short

– The loss of electrons during a redox reaction is called oxidation.

– The acceptance of electrons during a redox reaction is called reduction.

– During cellular respiration glucose is oxidized while oxygen is reduced.


CitricAcidCycle

ElectronTransportGlycolysis

ATP ATPATP


Why does electron transfer to oxygen release energy?

• When electrons move from glucose to oxygen, it is as though the electrons were falling.• This “fall” of electrons releases energy during

cellular respiration.• Cellular respiration is:–A controlled fall of electrons –A stepwise cascade much like going down a

staircase


Releaseof heatenergy

12H2 O2

H2OFigure 6.4


NADH and Electron Transport Chains– The path that electrons take on their way down from

glucose to oxygen involves many steps.– The first step is an electron acceptor called NAD+.• The transfer of electrons from organic fuel to NAD+

reduces it to NADH.– The rest of the path consists of an electron transport

chain, which:• Involves a series of redox reactions • Ultimately leads to the production of large amounts of

ATP


Electrons from food

Stepwise releaseof energy usedto make

Hydrogen, electrons,and oxygen combineto produce water

Electron transport chain

NADHNAD

H

H

ATP

H2O

O2

2 2

2

2

21

e e

e e

e

e


An Overview of Cellular Respiration

–Cellular respiration:• Is an example of a metabolic pathway, which is a

series of chemical reactions in cells

–All of the reactions involved in cellular respiration can be grouped into three main stages:• Glycolysis• The citric acid cycle• Electron transport


Cytoplasm

Cytoplasm

Cytoplasm

Animal cell Plant cell

Mitochondrion

Mitochondrion

High-energyelectronscarriedby NADH

High-energyelectrons carriedmainly byNADH

CitricAcidCycle

ElectronTransport

Glycolysis

Glucose2

Pyruvicacid

ATP ATP ATP


The Three Stages of Cellular Respiration– Stage 1: Glycolysis • A six-carbon glucose molecule is split in half to form

two molecules of pyruvic acid.• These two molecules then donate high energy

electrons to NAD+, forming NADH.• Three steps– Uses two ATP molecules per glucose to split the six-

carbon glucose –Makes four additional ATP directly when enzymes

transfer phosphate groups from fuel molecules to ADP• Produces a net of two molecules of ATP per glucose

molecule.


Energy investment phase

Carbon atomPhosphategroupHigh-energyelectron

Key

Glucose

2 ATP 2 ADP

INPUT OUTPUT

Figure 6.7-1Laua Coronado Chap 6 Bio 10



Key

Glucose

2 ATP 2 ADP

INPUT OUTPUT

Energy harvest phase

NADH

NADHNAD

NAD




Key

Glucose

2 ATP 2 ADP

INPUT OUTPUT

Energy harvest phase

NADH

NADHNAD

NAD 2 ATP

2 ATP

2 ADP

2 ADP

2 Pyruvic acid


ADPATP

P

P P

Enzyme


Stage 2: The Citric Acid Cycle

–Completes the breakdown of sugar.– In the citric acid cycle, pyruvic acid from

glycolysis is first “prepped.”– The citric acid cycle:• Extracts the energy of sugar by breaking the acetic

acid molecules all the way down to CO2

• Uses some of this energy to make ATP• Forms NADH and FADH2


(from glycolysis) (to citric acid cycle)Oxidation of the fuelgenerates NADH

Pyruvic acidloses a carbonas CO2

Acetic acidattaches tocoenzyme APyruvic acid

Acetic acidAcetyl CoA

Coenzyme A

CoA

CO2

NAD NADH

INPUT OUTPUT


3 NAD

ADP P

3 NADH

FADH2FAD

Aceticacid

Citricacid

Acceptormolecule

CitricAcidCycle

ATP

2 CO2

INPUT OUTPUT


Stage 3: Electron Transport

–Releases the energy your cells need to make the most of their ATP.– The molecules of the electron transport chain

are built into the inner membranes of mitochondria.• The chain functions as a chemical machine that uses

energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane.• These ions store potential energy.


Stage 3: Electron Transport

– When the hydrogen ions flow back through the membrane, they release energy.

• The hydrogen ions flow through ATP synthase.• ATP synthase:–Takes the energy from this flow–Synthesizes ATP


Space betweenmembranes

Innermitochondrialmembrane

Electroncarrier

Proteincomplex

Electronflow

Matrix Electron transport chain ATP synthase

NADHNAD

FADH2 FAD

ATPADP

H2OO2

H

12

HHH

H

H

H

H

H

H

H

HH

HH

HH

HH

H 2

P


ETC Inhibitor

–Cyanide is a deadly poison that:• Binds to one of the protein complexes in the

electron transport chain • Prevents the passage of electrons to oxygen• Stops the production of ATP


The Versatility of Cellular Respiration

– In addition to glucose, cellular respiration can “burn”:• Diverse types of carbohydrates• Fats• Proteins


Food

Polysaccharides Fats Proteins

Sugars Glycerol Fatty acids Amino acids

Glycolysis AcetylCoA

CitricAcidCycle

ElectronTransport

ATP


Cytoplasm

Mitochondrion

NADH

CitricAcidCycle

ElectronTransport

Glycolysis

Glucose2

Pyruvicacid

2ATP

2ATP

NADHNADH

FADH2

Maximumper

glucose:

2Acetyl

CoA

About34 ATP

by directsynthesis

by directsynthesis by ATP

synthase

2 2

2

6

About38 ATP


FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY

– Some of your cells can actually work for short periods without oxygen.

– Fermentation is the anaerobic (without oxygen) harvest of food energy.

– After functioning anaerobically for about 15 seconds:• Muscle cells will begin to generate ATP by the process of

fermentation

– Fermentation relies on glycolysis to produce ATP.


FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY

–Glycolysis:• Does not require oxygen • Produces two ATP molecules for each glucose

broken down to pyruvic acid

–Pyruvic acid, produced by glycolysis, is• Reduced by NADH, producing NAD+, which keeps

glycolysis going.

– In human muscle cells, lactic acid is a by-product.


Glucose

2 ATP

2 NAD 2 NADH 2 NADH 2 NAD

2 H

2 ADP

2 Pyruvicacid 2 Lactic acid

Glycolysis

INPUT OUTPUT

2 P


The Process of Science: Does Lactic Acid Buildup Cause Muscle Burn?

– Observation: Muscles produce lactic acid under anaerobic conditions.

– Question: Does the buildup of lactic acid cause muscle fatigue?

– Hypothesis: The buildup of lactic acid would cause muscle activity to stop.

– Experiment: Tested frog muscles under conditions when lactic acid could and could not diffuse away.


Battery

Forcemeasured

Battery

Forcemeasured

Frog musclestimulated byelectric current

Solution preventsdiffusion of lactic acid

Solution allowsdiffusion of lactic acid;

muscle can work fortwice as long


The Process of Science: Does Lactic Acid Buildup Cause Muscle Burn?

– Results: When lactic acid could diffuse away, performance improved greatly.

– Conclusion: Lactic acid accumulation is the primary cause of failure in muscle tissue.

– However, recent evidence suggests that the role of lactic acid in muscle function remains unclear.


Fermentation in Microorganisms

– Fermentation alone is able to sustain many types of microorganisms.– The lactic acid produced by microbes using

fermentation is used to produce:• Cheese, sour cream, and yogurt dairy products• Soy sauce, pickles, olives • Sausage meat products


Fermentation in Microorganisms– Yeast are a type of microscopic fungus that:• Use a different type of fermentation • Produce CO2 and ethyl alcohol instead of lactic acid

– This type of fermentation, called alcoholic fermentation, is used to produce:• Beer• Wine• Breads


Glucose

2 ATP

2 NAD 2 NADH 2 NADH 2 NAD

2

2 ADP

2 Pyruvicacid 2 Ethyl alcohol

Glycolysis

INPUT OUTPUT

2 CO2 released 2 P

H

Figure 6.16aLaua Coronado Chap 6 Bio 10

Evolution Connection:Life before and after Oxygen

– Glycolysis could be used by ancient bacteria to make ATP when little oxygen was available, and before organelles evolved.

– Today, glycolysis:• Occurs in almost all organisms • Is a metabolic heirloom of the first stage in the

breakdown of organic molecules


O2 p

rese

nt in

Eart

h’s

atm

osph

ere

First eukaryotic organisms

Origin of Earth

Atmospheric oxygen reaches 10% of modern levelsAtmospheric oxygenfirst appears

Oldest prokaryoticfossilsBi

llion

s of

yea

rs a

go

2.1

0

2.7

4.5

2.2

3.5


C6H12O6

CO2 H2O

ATPO2

Heat

Photosynthesis

Sunlight

Cellularrespiration


C6H12O6 CO2ATPO2 H2O 6 66 Approx. 38


C6H12O6 CO2

ATP

O2H2O

OxidationGlucose loses electrons(and hydrogens)

ReductionOxygen gainselectrons (andhydrogens)

Electrons(and hydrogens)


NADH

CitricAcidCycle

ElectronTransport

Glycolysis

Glucose2

Pyruvicacid

2ATP

2ATP

NADHNADH

FADH2

2Acetyl

CoA

About34 ATPby direct

synthesisby directsynthesis

by ATPsynthase

2 2

2

6

About38 ATP

2 CO2 CO2

O2

H2O4

Mitochondrion


Chapter 6 Cellular Respiration: Obtaining Energy from Food Laua Coronado Chap 6 Bio 10.

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Transcript of Chapter 6 Cellular Respiration: Obtaining Energy from Food Laua Coronado Chap 6 Bio 10.