Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PowerPoint® Lecture Presentations for

Biology Eighth Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp

Chapter 9 Cellular Respiration: Harvesting Chemical Energy

Overview: Life Is Work

• Living cells require energy from outside sources

• Some animals, such as the giant panda, obtain energy by eating plants, and some animals feed on other organisms that eat plants

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 9-1

A Can of Bull? Do Energy Drinks Really Provide a Source of Energy? Movie

vie

5

CQ#1: Which of the following best describes your use of energy drinks?

A. I have never tried an energy drink.

B. I drink an energy drink occasionally.

C. I drink an energy drink whenever I need a “boost” of energy.

D. I drink an energy drink almost every day.

6

CQ#2: I drink energy drinks because:

A. They do give me an energy boost.

B. They taste good.

C. They give me an energy boost and they taste good.

D. I don’t drink energy drinks.

7

CQ#3: The average cost of a canned energy drink is:

A. $1

B. $2

C. $3

D. $4

8 8

The Case

The job was fantastic! Since high school, where she had excelled in cross country, Rhonda had been a consistent runner, participating in local races and those assigned to her for her job. For her last assignment, she had run in and reported about the Leadwood, South Dakota marathon, and it was a blast!

After spending several years working at the

Sports Desk of the Lansing State Journal,

Rhonda found the job of her dreams as a writer for Running Magazine.

Rhonda’s Story

The day she returned, her boss Charley walked in her office with a can of Red Bull® in one hand and a list of several other energy drinks in the other. “We’ve been getting a lot of inquiries about the different energy drinks on the market. Do you know anything about them?” Charley asked.

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“I do know that people use them for various reasons,” replied Rhonda. “They’re primarily used by athletes to provide some “fuel” as they practice and compete. Other people use them more casually as a way to become more ‘energized.’ That’s about all I know.”

“For your next assignment,” Charley continued, “I want you to find out what each of the ingredients in these drinks is and what it does for a runner or for a non-athlete. You need to be very accurate in your analysis. Determine what each component really does for the body, not what the marketers want us to believe it does. Then look at the marketing claims to see if the scientific facts match up to them. Here are the marketing claims, a list of ingredients and nutrition facts provided on the cans for consumers.”

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12 12

As Charley left the office, Rhonda looked over the materials.

“Guess I’ll have to brush up on my biochemistry. No problem. I’m interested in knowing if my running would be improved by drinking this stuff.”

13 13

Rhonda perused the marketing claims for each drink on the list.

Red Bull® (from advertising materials)

• is a functional product developed especially for periods of increased mental and physical exertion.

• can be drunk in virtually any situation.

• improves performance, especially during times of increased stress or strain.

• improves concentration and reaction speed.

• stimulates the metabolism.

14 14

Lo-Carb Monster Energy® (from advertising materials)

• Tear into a can of the meanest energy supplement on the planet. We went down to the lab and cooked up a double shot of our killer energy brew.

• We hacked out the carbohydrates and calories, transplanted the “wicked buzz,” and dialed in the flavor.

• Lo-Carb MONSTER energy drink still delivers twice the BUZZ of a regular energy drink, but only has a fraction of the calories.

15 15

Sobe Adrenaline Rush® (from advertising materials)

• This maximum energy supplement delivers an energy boost with a natural passion fruit flavor. It’s lightly carbonated with a clean smooth feel.

• This maximum energy supplement delivers an energy boost with a unique blend of natural energizing elements, including d-ribose, l-carnitine and taurine. It’s pure, concentrated energy in an 8.3 fluid ounce can.

16 16

Impulse® (from advertising materials)

• Elevate Your Performance.

• Impulse® Energy Drink contains special supplements to immediately enhance mental and physical efficiency and give you the energy boost you deserve…replenishing your strength.

• Impulse® Energy Drink gets its energy from a simple source: nutrients, minerals, and vitamins that occur naturally in the body and foods we eat. Enjoy: the wake-up power of caffeine, the alertness-inducing properties of taurine, the lift you get from vitamin B6 and B12. Combined with Impulse’s other ingredients, these are known to increase mental focus and physical well being, enhance performance, and accelerate metabolism.

17 17

Rhonda recalled that a food’s calorie content was the simplest reflection of its energy content. Looking at Charley’s list, she saw that the different energy drinks contained the following calories per can:

– Lo-Carb Monster® 20

– Red Bull® 110

– Sobe Adrenaline Rush® 140

– Impulse® 110

For comparison

– Coca Cola® 140

18 18

Rhonda realized that before she could start analyzing the energy drinks, she needed to know the answer to the following questions:

When we say something gives us “energy” what does that mean?

What is a biological definition of energy?

What is energy?

• Energy is the capacity to cause change

• Energy exists in various forms, some of which can perform work

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20 20

CQ#4: Food energy is the amount of stored chemical energy in food that is available following digestion and metabolism. The most common value for expressing the amount of available energy in food is:

A. Calvins

B. Joules

C. Ounces

D. Calories

Answer: D

How is food used for energy? A brief review of metabolism

• Adenosine triphosphate (ATP) is the primary energy molecule of organisms

• The hydrolysis of ATP provides the chemical energy that powers most cell work.

• On the flip side, making ATP takes energy; this comes from the oxidation of sugars and other reduced compounds.

• This energy is used to phosphorylate adenine diphosphate (ADP) to make ATP

+ H20

ATP ADP + Pi

+ 7.3 kcal/mol of ATP

Energy 21

22

Energy use

Energy conversion Energy storage

CO2 + H2O + sunlight (Fats and carbohydrates) (Photosynthesis)

Glucose

O2 + (CH20)n

Respiration Glucose + O2 + ADP + Pi

CO2 + H2O + ATP (high yield!)

Fermentation Glucose + ADP + Pi

Small organic molecules + ATP (low yield) But it is fast!

Matter conversions that accompany energy transformations / transfers

• Energy flows into an ecosystem as sunlight and leaves as heat

• Photosynthesis generates O2 and organic molecules, which are used in cellular respiration

• Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24 24

CQ#5: ATP is used as an energy source for nearly all cellular metabolic processes. Which of the following macromolecules, if available, is used preferentially for ATP synthesis?

A. Amino acids

B. Caffeine

C. Proteins

D. Lipids

E. Carbohydrates

Answer: E

The Stages of Cellular Respiration: A Preview

• Cellular respiration has three stages:

– Glycolysis (breaks down glucose into two molecules of pyruvate)

– The citric acid cycle (completes the breakdown of glucose)

– Oxidative phosphorylation (accounts for most of the ATP synthesis)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26 26

Rhonda was determined to wade through the confusing labeling of the drinks. The first thing she needed to do was sort out the various ingredients on the labels- a task that consumers rarely undertake. She decided she to determine a few things:

– What is the nature (sugar, fat, amino acid, vitamin, etc.) of each ingredient listed on the cans?

– What is the physiological role of each in the human body?

– Which ingredients actually provide energy?

27 27

Rhonda started her research with Caffeine. She discovered that: – small to moderate amounts (50-300 mg) of caffeine act as a

mild stimulant.

– Caffeine increases heart rate and blood pressure.

– Athletes have taken advantage of the stimulant effect of caffeine for many years.

Rhonda also discovered that individuals differ in their sensitivity to caffeine. Some are sensitive to the effects of caffeine at very small doses, and pregnancy and age can affect this sensitivity. Even in people who consume caffeine regularly, the stimulant effect is not always consistent. This suggests that we may actually become less sensitive to the effects of caffeine over time.

28 28

Rhonda discovered that energy drinks typically contain large

doses of caffeine. In fact, she learned that energy drinks may

contain as much as 80 mg of caffeine, the equivalent of a cup

of coffee. Compared to the 37 mg of caffeine in a Mountain

Dew, or the 23 mg in a Coca-Cola Classic, that's a big punch!

She also found that many energy drinks add other legal stimulants

like ephedrine, guarana, and ginseng.

29 29

CQ#8: The most common ingredient in energy drinks is caffeine. Do you think caffeine is a source of energy?

A: Yes

B: No

Answer: B

30 30

Your Task:

• Research each ingredient found in one of the energy drinks (or in Coca Cola®) using the information provided in your handout. Work in groups of two or three so that one person can record the relevant information.

• Place each ingredient for your drink under the proper heading in the table provided.

• We will summarize the information on the boards in front of the room and then discuss the results.

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The combination of glycolysis, the Krebs cycle, and the electron transport chain is called cellular respiration.

Glycolysis Pyruvate processing

and Krebs Cycle Electron Transport

and Oxidative Phosphorylation

Glucose Pyruvate

ATP

CO2

NADH

CO2

NADH

Krebs Cycle

NADH FADH2

ATP

Electron transport chain establishes a proton

gradient that is used to produce ATP

O2 H20

ATP

http://www.mcgrawhill.ca/school/applets/abbio/quiz/ch05/how_nad_works.swf

33 33

Processing Glucose: Glycolysis • Glycolysis, a series of ten chemical reactions that take

place in the cytoplasm of the cell, is the first step in glucose oxidation.

• In glycolysis, glucose is broken down into two molecules of pyruvate.

• Nicotinamide adenine dinucleotide (NAD+) is reduced to NADH, an electron carrier that donates electrons to more oxidized molecules.

• At the end of glycolysis, each molecule of glucose yields a net gain of 2 ATP molecules.

• http://www.mcgrawhill.ca/school/applets/abbio/quiz/ch05/how_glycolysis_works.swf

Fig. 9-6-1

Substrate-level phosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electrons carried

via NADH

Fig. 9-7

Enzyme

ADP

P Substrate

Enzyme

ATP +

Product

37 37

CQ#6: The net products of glycolysis are:

A. 2 ATP, 2 CO2 , 2 ethanol

B. 2 ATP, 2 NAD+, 2 acetate

C. 2 ATP, 2 NADH, 2 pyruvate

D. 38 ATP, 6 CO2, 6 H2O

E. 4 ATP, 2 FADH2, 2 pyruvate

Answer: C

38 38

The Krebs Cycle

• In the presence of O2, the pyruvate of most cells enters the Krebs cycle (citric acid cycle), in which each pyruvate is oxidized to three molecules of CO2.

• 6 additional (NAD+) molecules are reduced to 6 NADH, and 2 FAD+ (a second electron carrier) are reduced to form 2 FADH2.

• 2 additional ATPs are formed as the 2 pyruvates are oxidized in the Krebs cycle.

• The Kreb’s cycle occurs in the mitochondria of eukaryotic cells.

Fig. 9-6-2

Mitochondrion

Substrate-level phosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electrons carried

via NADH

Substrate-level phosphorylation

ATP

Electrons carried via NADH and

FADH2

Citric acid cycle

• http://multimedia.mcb.harvard.edu/

41 41

Electron Transport

The high-potential-energy electrons carried by NADH and FADH2 participate in a series of redox reactions. These electrons are passed down an electron transport chain (ETC) in the inner mitochondrial membrane of eukaryotes (and in the cell membrane of prokaryotes).

Simultaneously, protons are pumped across the inner mitochondrial membrane generating a proton gradient with high potential energy.

• http://www.qcc.cuny.edu/BiologicalSciences/Faculty/DMeyer/respiration.html

• http://www.mcgrawhill.ca/school/applets/abbio/q

uiz/ch05/how_the_krebs_cycle_wor.swf

Fig. 9-5

(a) Uncontrolled reaction

H2 + 1/2 O2

Explosive release of

heat and light energy

(b) Cellular respiration

Controlled release of energy for

synthesis of ATP

2 H+ + 2 e–

2 H 1/2 O2 (from food via NADH)

1/2 O2

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw&feature=related

Fig. 9-16

Protein complex of electron carriers

H+

H+ H+

Cyt c

Q

Ι

ΙΙ

ΙΙΙ

ΙV

FADH2 FAD

NAD+ NADH (carrying electrons from food)

Electron transport chain

2 H+ + 1/2O2 H2O

ADP + P i

Chemiosmosis

Oxidative phosphorylation

H+

H+

ATP synthase

ATP

2 1

Fig. 9-6-3

Mitochondrion

Substrate-level phosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electrons carried

via NADH

Substrate-level phosphorylation

ATP

Electrons carried via NADH and

FADH2

Oxidative phosphorylation

ATP

Citric acid cycle

Oxidative phosphorylation: electron transport

and chemiosmosis

47 47

ATP Synthase

• The proton gradient drives the production of ATP through the mechanical rotation of the enzyme ATP synthase.

ADP + Pi ATP

Matrix

Intermembrane space

• http://www.youtube.com/watch?v=J8lhPt6V-yM

49 49

CQ#9: Based upon the class analysis, which of the following “energy drinks” actually provides more energy per can than a 12oz can of Coca Cola®?

A. Red Bull®

B. Impulse®

C. Lo-Carb Monster®

D. SoBe Adrenaline Rush®

E. None of the above

Answer: E

• Rhonda finished her research and started writing her article. She wanted her article for Running Magazine to be a real eye opener for the readers. Her overall message would be to “Know What You're Drinking.”

• Charley stopped by her office to see how everything was going. “Hey Rhonda, so what about those energy drinks? Are they good for you?”

• “Oh hi Charley. Well, based upon my research I don’t think they are necessarily bad for you, but they shouldn't be seen as "natural alternatives" either. Some of the marketing claims they make like "improved performance and concentration" are down right misleading.”

• “Really?” Charley sounded intrigued. 50 50

“Well, I think people should think of energy drinks more as highly-caffeinated beverages. They’ll

have a much more accurate picture of what they are and how they affect you.”

“These drinks are just loaded with stimulants – not

true sources of energy. I mean you wouldn't use Mountain Dew as a sports drink, and you shouldn’t

use most of the energy drinks as a sports drink either,” said Ronda.

Movie

38

52 52

“Sounds like good work, Rhonda.” Charley said as he headed out the door.

“Oh, I forgot. I am going to include in my article some information about the growing trend of

mixing energy drinks with alcohol. Apparently, a drink made with Red Bull and vodka is very much like mixing strong coffee and whiskey. Worse yet,

since energy drinks are stimulants and alcohol is a depressant, the combination may be dangerous.

53 53

“There is a nation-wide concern about the marketing of these mixed drinks. Moreover, both energy drinks and alcohol are very dehydrating (the caffeine in energy drinks is a diuretic). Dehydration hinders your body's ability to metabolize alcohol and will increase the toxicity, and therefore the hangover, the next day.” said Rhonda.

http://www.cbsnews.com/video/watch/?id= 3465186n%3fsource=search_video

“Sounds like a really important thing for young people to know. You’ve done a great job, Rhonda. This will be a super story for our magazine.”

54 54

CQ#10: Should you simply buy a soft drink rather than one of these energy drinks when you need an energy boost?

A. Yes

B. No

C. Still undecided

Catabolic Pathways and Production of ATP

• The breakdown of organic molecules is exergonic

• Fermentation is a partial degradation of sugars that occurs without O2

• Aerobic respiration consumes organic molecules and O2 and yields ATP

• Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2

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An Accounting of ATP Production by Cellular Respiration

• During cellular respiration, most energy flows in this sequence:

glucose → NADH → electron transport chain → proton-motive force → ATP

• About 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 ATP

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 9-17

Maximum per glucose: About 36 or 38 ATP

+ 2 ATP + 2 ATP + about 32 or 34 ATP

Oxidative phosphorylation: electron transport

and chemiosmosis

Citric acid cycle

2 Acetyl CoA

Glycolysis

Glucose 2

Pyruvate

2 NADH 2 NADH 6 NADH 2 FADH2

2 FADH2

2 NADH CYTOSOL Electron shuttles

span membrane or

MITOCHONDRION

Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen

• Most cellular respiration requires O2 to produce ATP

• Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions)

• In the absence of O2, glycolysis couples with fermentation or anaerobic respiration to produce ATP

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• http://www.youtube.com/watch?v=StXlo1W3Gvg&feature=related

• Anaerobic respiration uses an electron transport chain with an electron acceptor other than O2, for example sulfate

• Fermentation uses phosphorylation instead of an electron transport chain to generate ATP

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Types of Fermentation

• Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis

• Two common types are alcohol fermentation and lactic acid fermentation

• http://www.youtube.com/watch?v=-nIDGG0sYcg&feature=related

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• In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2

• Alcohol fermentation by yeast is used in brewing, winemaking, and baking

Animation: Fermentation Overview

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 9-18a

2 ADP + 2 P i 2 ATP

Glucose Glycolysis

2 Pyruvate

2 NADH 2 NAD+ + 2 H+

CO2

2 Acetaldehyde 2 Ethanol

(a) Alcohol fermentation

2

• In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2

• Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt

• Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 9-18b

Glucose

2 ADP + 2 P i 2 ATP

Glycolysis

2 NAD+ 2 NADH + 2 H+

2 Pyruvate

2 Lactate

(b) Lactic acid fermentation

Fermentation and Aerobic Respiration Compared

• Both processes use glycolysis to oxidize glucose and other organic fuels to pyruvate

• The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration

• Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule

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• Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2

• Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration

• In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes

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Fig. 9-19 Glucose

Glycolysis

Pyruvate

CYTOSOL

No O2 present: Fermentation

O2 present: Aerobic cellular respiration

MITOCHONDRION Acetyl CoA Ethanol

or lactate

Citric acid cycle

Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways

• Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways

• Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Versatility of Catabolism

• Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration

• Glycolysis accepts a wide range of carbohydrates

• Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle

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• Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA)

• Fatty acids are broken down by beta oxidation and yield acetyl CoA

• An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate

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Fig. 9-20 Proteins Carbohydrates

Amino acids

Sugars

Fats

Glycerol Fatty acids

Glycolysis

Glucose

Glyceraldehyde-3-

Pyruvate

P

NH3

Acetyl CoA

Citric acid cycle

Oxidative phosphorylation

74 74

CQ#7: You have a friend who lost 15 pounds of fat on a diet. Where did the fat go?

A. It was released as CO2 and H2O.

B. It was converted to heat and then released.

C. It was converted to ATP, which weighs less than fat.

D. It was broken down into amino acids and eliminated from the body.

E. It was converted to urine and eliminated from the body.

Answer: A

Biosynthesis (Anabolic Pathways)

• The body uses small molecules to build other substances

• These small molecules may come directly from food, from glycolysis, or from the citric acid cycle

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Regulation of Cellular Respiration via Feedback Mechanisms

• Feedback inhibition is the most common mechanism for control

• If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down

• Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway

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Fig. 9-21 Glucose

Glycolysis Fructose-6-phosphate

Phosphofructokinase

Fructose-1,6-bisphosphate Inhibits

AMP

Stimulates

Inhibits

Pyruvate

Citrate Acetyl CoA

Citric acid cycle

Oxidative phosphorylation

ATP

+

– –

• http://www.youtube.com/watch?v=hxTed-lTe7g&feature=related

• http://www.youtube.com/watch?v=YyN0wx2AHfE&feature=related

You should now be able to:

1. Explain in general terms how redox reactions are involved in energy exchanges

2. Name the three stages of cellular respiration; for each, state the region of the eukaryotic cell where it occurs and the products that result

3. In general terms, explain the role of the electron transport chain in cellular respiration

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4. Explain where and how the respiratory electron transport chain creates a proton gradient

5. Distinguish between fermentation and anaerobic respiration

6. Distinguish between obligate and facultative anaerobes

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