chapter 6 · •natural differences in the muscles of these athletes ... •plant and animal cells...

© 2013 Pearson Education, Inc.Lectures by Edward J. Zalisko

PowerPoint® Lectures forCampbell Essential Biology, Fifth Edition, and

Campbell Essential Biology with Physiology,

Fourth Edition

– Eric J. Simon, Jean L. Dickey, and Jane B. Reece

Chapter 6Cellular Respiration: Obtaining

Energy from Food

20_02SeaLion_SV.mpg

Biology and Society: Marathoners versus 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.

© 2013 Pearson Education, Inc.

Figure 6.0

• The muscles that move our legs contain two main

types of muscle fibers:

1. slow-twitch and

2. fast-twitch.



• Slow-twitch fibers

– last longer,

– do not generate a lot of quick power, and

– generate ATP using oxygen (aerobically).



• Fast-twitch fibers

– contract more quickly and powerfully,

– fatigue more quickly, and

– can generate ATP without using oxygen

(anaerobically).

• All human muscles contain both types of fibers but

in different ratios.



ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE

• Animals depend on plants to convert the energy of

sunlight to

– chemical energy of sugars and

– other organic molecules we consume as food.

• Photosynthesis uses light energy from the sun to

– power a chemical process and

– make 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.


Producers and Consumers

• Autotrophs are producers because ecosystems

depend upon them for food.

• Heterotrophs are consumers because they eat

plants or other animals.


Figure 6.1

Chemical Cycling between Photosynthesis and Cellular Respiration

• The ingredients for photosynthesis are carbon

dioxide (CO2) and water (H2O).

– 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, and

– oxygen gas.



Figure 6.UN07

C6H12O6 CO2 ATPO2H2O 6 66 Approx. 32

• Plant and animal cells perform cellular

respiration, a chemical process that

– primarily occurs in mitochondria,

– harvests energy stored in organic molecules,

– uses oxygen, and

– generates ATP.



• The waste products of cellular respiration are

– CO2 and H2O,

– used in photosynthesis.



• Animals perform only cellular respiration.

• Plants perform

– photosynthesis and

– cellular respiration.



• Plants usually make more organic molecules than

they need for fuel. This surplus provides material

that can be

– used for the plant to grow or

– stored as starch in potatoes.



Figure 6.2

Sunlight energy

enters ecosystem

Photosynthesis

Cellular respiration

C6H12O6 CO2

drives cellular work

Heat energy exits

ecosystem

ATP

O2 H2O

Figure 6.UN06

C6H12O6

CO2 H2O

ATP

O2

Heat

Photosynthesis

Sunlight

Cellularrespiration

CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY

• Cellular respiration is

– the main way that chemical energy is harvested

from food and converted to ATP and

– an aerobic process—it requires oxygen.


• 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.


CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY

Figure 6.3

Breathing

Cellular

respiration

Muscle

cells

Lungs

CO2

CO2

O2

O2

The Simplified Equation for Cellular Respiration

• A common fuel molecule for cellular respiration is

glucose.

• Cellular respiration can produce up to 32 ATP

molecules for each glucose molecule consumed.

• The overall equation for what happens to glucose

during cellular respiration is

– glucose & oxygen CO2, H2O, & a release of

energy.


Figure 6.UN01

C6H12O6 CO2 ATPO2 H2O

Glucose Oxygen Carbon

dioxide

Water Energy

6 66

The Role of Oxygen in Cellular Respiration

• During cellular respiration, hydrogen and its

bonding electrons change partners from sugar to

oxygen, forming water as a product.


Redox Reactions

• Chemical reactions that transfer electrons from one substance to another are called

– oxidation-reduction reactions or

– redox reactions for short.


Redox Reactions

• The loss of electrons during a redox reaction is oxidation.

• The acceptance of electrons during a redox reaction is reduction.

• During cellular respiration

– glucose is oxidized and

– oxygen is reduced.


Figure 6.UN02

C6H12O6 CO2O2 H2O

Glucose Oxygen Carbon

dioxide

Water

6 66

Reduction

Oxidation

Oxygen gains electrons (and hydrogens)

Glucose loses electrons

(and hydrogens)

• 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.

Redox Reactions


Figure 6.4

Release

of heat

energy

1

2H2 O2

H2O

Figure 6.UN08

C6H12O6 CO2

ATP

O2H2O

Oxidation

Glucose loses electrons

(and hydrogens)

Reduction

Oxygen gains

electrons (and

hydrogens)

Electrons

(and hydrogens)

• Cellular respiration is

– a controlled fall of electrons and

– a stepwise cascade much like going down a

staircase.

Redox Reactions


• 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+.

– NAD is made by cells from niacin, a B vitamin.

– The transfer of electrons from organic fuel to NAD+ reduces it to NADH.

NADH and Electron Transport Chains


• The rest of the path consists of an electron transport chain, which

– involves a series of redox reactions and

– ultimately leads to the production of large amounts of ATP.

NADH and Electron Transport Chains


Figure 6.5

Electrons from food

Stepwise releaseof energy usedto make

Hydrogen, electrons,and oxygen combineto produce water

NADHNAD

H

H

ATP

H2O

O2

2 2

2

2

2

1

e e

e e

e

e

Figure 6.5a

Stepwise release

of energy used

to make ATP

Hydrogen, electrons, and oxygen combine to produce water

H

ATP

H2O

O2

2 2

2

2

2

1

e

e

Electron

transport chain

H

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:

1. glycolysis,

2. the citric acid cycle, and

3. electron transport.


Figure 6.6

Cytoplasm

Cytoplasm

Cytoplasm

Animal cell Plant cell

Mitochondrion

Mitochondrion

High-energy

electronsvia carrier

molecules

Citric

Acid

Cycle

Electron

Transport

Glycolysis

Glucose

2

Pyruvic

acid

ATP ATP ATP

The Three Stages of Cellular Respiration

• With the big-picture view of cellular respiration in

mind, let’s examine the process in more detail.


Stage 1: Glycolysis

1. A six-carbon glucose molecule is split in half to

form two molecules of pyruvic acid.

2. These two molecules then donate high energy

electrons to NAD+, forming NADH.


Figure 6.7

Energy investment phase

Carbon atom

Phosphate group

High-energy electron

Key

Glucose

2 ATP2 ADP

INPUT

P

–

Energy harvest phase

OUTPUT

NADH

NADH

NAD

NAD 2 ATP

2 ATP

2 ADP

2 ADP

2 Pyruvic acid

P

PP

P

PP

P

P

1

2

2

3

3

– –

– –

Figure 6.7a

2 Pyruvic acid

Glucose

INPUT OUTPUT

– uses two ATP molecules per glucose to split the

six-carbon glucose and

– makes four additional ATP directly when enzymes

transfer phosphate groups from fuel molecules to

ADP.

• Thus, glycolysis produces a net of two molecules

of ATP per glucose molecule.

3. _________

– ____ ___ _________ ___ _______ __ _____ ___ ___ ______ _______

___

– _____ ____ __________ ________ ____ _______ ________

_________ ______ ____ ____ _________ __

• ___ __________ ________ _ ___ __ ___ _________ __ ___

_______ ________

3. Glycolysis

Stage 1: Glycolysis


Figure 6.8

ADPATP

P

P P

Enzyme

Stage 2: The Citric Acid Cycle

• In the citric acid cycle, pyruvic acid from glycolysis

is first ―groomed.‖

– Each pyruvic acid loses a carbon as CO2.

– The remaining fuel molecule, with only two carbons

left, is acetic acid.

• Oxidation of the fuel generates NADH.


• Finally, each acetic acid is attached to a molecule

called coenzyme A to form acetyl CoA.

• The CoA escorts the acetic acid into the first

reaction of the citric acid cycle.

• The CoA is then stripped and recycled.



Figure 6.9

(from

glycolysis)

(to citric

acid cycle)

Oxidation of the fuel

generates NADH

Pyruvic acid

loses a carbon

as CO2

Acetic acid

attaches to

coenzyme APyruvic acid

Acetic acid Acetyl CoA

Coenzyme A

CoA

CO2

NAD NADH

INPUT OUTPUT2

31

– –

Figure 6.9a

(from

glycolysis) (to citric

acid cycle)

Pyruvic acidAcetyl CoA

CoA

INPUT OUTPUT

• 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, and

– forms NADH and FADH2.



Figure 6.10

3 NAD

ADP P

3 NADH

FADH2FAD

Aceticacid

Citricacid

Acceptormolecule

CitricAcidCycle

ATP

2 CO2

INPUT OUTPUT

3

12

4

5

– –

– –

6

Figure 6.10a

3 NAD

ADP P

3 NADH

FADH2FAD

Aceticacid

1

ATP

2 CO2

INPUT OUTPUT

4

2

3

5

– –

– –

• Electron transport releases the energy your cells need to make the most of their ATP.

• The molecules of the electron transport chainare built into the inner membranes of mitochondria.

• The chain

– functions as a chemical machine, which

– uses energy released by the ―fall‖ of electrons to pump hydrogen ions across the inner mitochondrial membrane, and

– uses these ions to 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 and

– synthesizes ATP.



Figure 6.11

Space betweenmembranes

Innermitochondrialmembrane

Electroncarrier

Proteincomplex

Electronflow

Matrix Electron transport chain ATP synthase

NADH NAD

FADH2 FAD

ATPADP

H2OO21

2

H

2

P

H

H

H

H

HH

H

H

H

H

H

H

H

H H

H

H

H

H1

2

4

6

53

– –

– –

1

2

Figure 6.11a

Space

betweenmembranes

Inner

mitochondrial

membrane

Electron

carrier

Protein

complex

Electron

flow

Matrix Electron transport chain ATP synthase

NADH NAD

FADH2 FAD

ATPADP

H2OO2 2

P

– –

– –

H

H

H

H

H

HH

H

H

H

H

H

H

H

H H

H

H

H1

2

4

6

53

H

1

2

Figure 6.11b

Space

betweenmembranes

Inner

mitochondrial

membrane

Electron

carrier

Protein

complex

Electron

flow

Matrix Electron transport chain

NADH NAD

FADH2 FAD

O2

H

2

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

––

––

1

2

3

4

1

2

Figure 6.11c

ATP synthase

ATPADP

H2OO2 2

P

H

5

4

6

H

H

H

H

H

H

H

H

• 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, and

– stops the production of ATP.



The Results of Cellular Respiration

• Cellular respiration can generate up to 32

molecules of ATP per molecule of glucose.


Figure 6.12

Cytoplasm

Mitochondrion

NADH

Citric

Acid

Cycle

Electron

Transport

Glycolysis

Glucose

2

Pyruvic

acid

2ATP

2ATP

NADHNADH

FADH2

Maximum

per

glucose:

2

Acetyl

CoA

About28 ATP

by direct

synthesis

by direct

synthesisby ATP

synthase

2 2

2

6

About32 ATP

– –– –

– –

– –

Figure 6.12a

Citric

Acid

Cycle

Electron

Transport

Glycolysis

Glucose

2

Pyruvic

acid

2ATP

2ATP

2

Acetyl

CoA

About28 ATP

by direct

synthesis

by direct

synthesisby ATP

synthase

• In addition to glucose, cellular respiration can

―burn‖

– diverse types of carbohydrates,

– fats, and

– proteins.

The Results of Cellular Respiration


Figure 6.13

Food

Polysaccharides Fats Proteins

Sugars Glycerol Fatty acids Amino acids

Glycolysis Acetyl

CoA

Citric

Acid

Cycle

ElectronTransport

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.


Fermentation in Human Muscle Cells

• After functioning anaerobically for about 15

seconds, muscle cells begin to generate ATP by

the process of fermentation.

• Fermentation relies on glycolysis to produce ATP.

• Glycolysis

– does not require oxygen and

– 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.

Fermentation in Human Muscle Cells



Fermentation Overview

Figure 6.14

Glucose

2 ATP

2 NAD 2 NADH 2 NADH 2 NAD

2 H

2 ADP

2 Pyruvic acid2 Lactic acid

Glycolysis

INPUT OUTPUT

2 P

– – – –

• Observation: Muscles produce lactic acid under anaerobic conditions.

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

The Process of Science: What Causes Muscle Burn?


• 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.



Figure 6.15

Battery

Forcemeasured

Battery

Force

measured

Frog muscle

stimulated by electric

current

Solution preventsdiffusion of lactic acid

Solution allowsdiffusion of lactic acid;

muscle can work fortwice as long

– –

• 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,

– soy sauce, pickles, and olives, and

– sausage meat products.


• Yeast is a microscopic fungus that

– uses a different type of fermentation and

– produces CO2 and ethyl alcohol instead of lactic

acid.

• This type of fermentation, called alcoholic

fermentation, is used to produce

– beer,

– wine, and

– breads.

Fermentation in Microorganisms


Figure 6.16

Glucose

2 ATP

2 NADH 2 NAD

2

2 P

2 Pyruvicacid

2 Ethyl alcohol

Glycolysis

INPUT OUTPUT

2 CO2 released

2 ADP

H

2 NADH2 NAD

– –– –

Figure 6.UN09

NADH

Citric

Acid

Cycle

Electron

Transport

Glycolysis

Glucose

2Pyruvic

acid

2ATP

2ATP

NADHNADH

FADH2

2

Acetyl

CoA

About28 ATPby direct

synthesis

by direct

synthesis

by ATP

synthase

2 2

2

6

About32 ATP

2 CO2 CO2

O2

H2O4

Mitochondrion

– – – –– –

– –

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 and

– is a metabolic heirloom of the first stage in the

breakdown of organic molecules.


Figure 6.17

O2

pre

se

nt

in

Ea

rth

’s a

tmo

sp

he

re

First eukaryotic organisms

Origin of Earth

Atmospheric oxygen reaches 10% of modern levels

Atmospheric oxygen

first appears

Oldest prokaryotic

fossilsBil

lio

ns

of

ye

ars

ag

o 2.1

0

2.7

4.5

2.2

3.5

chapter 6 · •natural differences in the muscles of these athletes ... •plant and animal cells...

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