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Chapter 9 Cellular Respiration

9-1 Chemical Pathways

Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria.

Animal

Plant

Animal Cells

Plant Cells

Mitochondrion

Chemical Energy and Food

One gram of glucose (C6H12O6), when burned in the presence of oxygen, releases 3811 calories of heat energy. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius.

Overview of Cellular Respiration

Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

MatrixIntermembrane Space

Overview of Cellular Respiration*The equation for cellular respiration is:

6O2 + C6H12O6 → 6CO2 + 6H2O + Energyoxygen + glucose → carbon dioxide + water + Energy

Overview of Cellular Respiration*

Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place in the mitochondria.

CytoplasmMitochondrion

Glycolysis

Glycolysis*

ATP Production At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction.

2 ADP 4 ADP 4 ATP

2 Pyruvicacid

2 ATP

Glucose

Glycolysis*

When glycolysis is complete, 4 ATP molecules have been produced. This gives the cell a net gain of 2 ATP molecules.

4 ADP 4 ATP

Glucose

2 ADP2 ATP

2 Pyruvicacid

Glycolysis

Remember from Photosynthesis? High energy electron carrier NADP+ Cellular respiration uses different carriers to transport high energy electrons. NAD+ FAD

Glycolysis

NADH Production One molecule of glucose (6 carbons) is split into two molecules of pyruvic acid (3 carbons). Requires energy in the form of ATP. Yields 2 ATP Yields 2 NADH

Glucose

4 ADP 4 ATP2 ADP2 ATP

2NAD+2

Glycolysis*

The Advantages of Glycolysis The process of glycolysis is so fast that cells can produce thousands of ATP molecules in a few milliseconds. Glycolysis does not require oxygen.

Fermentation*

When oxygen is not present, glycolysis follows a different pathway, called fermentation. producing ATP in the absence of oxygen.

FermentationFermentation does not require oxygen—it is an anaerobic process. Two main types of fermentation.

Fermentation*Alcoholic Fermentation Yeasts and a few other microorganisms use alcoholic fermentation, forming ethyl alcohol and carbon dioxide as wastes. pyruvic acid + NADH → alcohol + CO2 + NAD+

Fermentation*Lactic Acid Fermentation Pyruvic acid that accumulates as a result of glycolysis can be converted to lactic acid. pyruvic acid + NADH → lactic acid + NAD+

9.1 Concept Assessment1. Describe the process of cellular respiration. 2. Key Concept What are the products of glycolysis? 3. Key Concept Name the two main types of fermentation. 4. What is a calorie? A Calorie? 5. How is the function of NAD + similar to that of NADP +? 6. Critical Thinking Comparing and Contrasting How are lactic acid fermentation and alcoholic fermentation similar? How are they different?

9.1 QUIZ

9.1 Vocabcalorie glycolysis cellular respiration NAD+ (nicotinamide adenine dinucleotide) fermentation anaerobic

1- The raw materials required for cellular respiration are

A. carbon dioxide and oxygen. B. glucose and water. C. glucose and oxygen. D. carbon dioxide and water.

Quiz 9.1

2- Glycolysis occurs in the

A. mitochondria. B. cytoplasm. C. nucleus. D. chloroplasts

Quiz 9.1

3- The net gain of ATP molecules after glycolysis is

A. 3 ATP molecules. B. 2 ATP molecules. C. 3 pyruvic acid molecules. D. 4 pyruvic acid molecules

Quiz 9.1

4- Fermentation releases energy from food molecules in the absence of

A. oxygen. B. glucose. C. NADH. D. alcohol.

Quiz 9.1

5- The two main types of fermentation are called

A. alcoholic and lactic acid. B. lactic acid and anaerobic. C. aerobic and anaerobic. D. alcoholic and aerobic.

Quiz 9.1

6- Which of the following acts as an electron carrier in cellular respiration?

A. NAD+ B. pyruvic acid C. ATP D. ADP

Quiz 9.1

7- Which of the following is NOT a product of glycolysis?

A. NADH B. pyruvic acid C. ATP D. glucose

Quiz 9.1

8- One cause of muscle soreness is

A. alcoholic fermentation. B. the Krebs cycle. C. glycolysis D. lactic acid fermentation

Quiz 9.1

9- The starting molecule for glycolysis is

A. pyruvic acid. B. glucose. C. ADP D. citric acid

Quiz 9.1

10- Which of these is a product of cellular respiration?

A. glucose. B. oxygen. C. water D. all of the above

Quiz 9.1

9-2 The Krebs CycleIn the presence of oxygen, Krebs cycle begins when pyruvic acid produced by glycolysis enters the mitochondrion.

The Krebs Cycle

The Krebs CyclePyruvic acid from glycolysis is converted into a usable form, Acetyl CoA.

The Krebs CycleOne carbon molecule is removed, forming CO2, and electrons are removed, changing NAD+ to NADH.

The Krebs CycleAcetyl-CoA then adds the 2-carbon acetyl group to a 4-carbon compound, forming citric acid.

The Krebs Cycle

Citric acid is broken down into a 5-carbon compound, then into a 4-carbon compound.

The Krebs CycleTwo more molecules of CO2 are released and electrons join NAD+ and FAD, forming NADH and FADH2

The Krebs CycleIn addition, one molecule of ATP is generated.

The Krebs Cycle

The Krebs Cycle

The energy tally from 1 molecule of pyruvic acid is 4 NADH 1 FADH2 1 ATP 3 CO2

The Krebs CycleHappens if oxygen is present. Pyruvates break down further so that the carbon and oxygen atoms end up in CO2.

The Krebs CycleHydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2 2 more ATP produced, but loads several electron carriers that will be used in the 3rd stage.

Electron TransportThe electron transport chain uses the high-energy electrons from the Krebs cycle to convert ADP into ATP.

Electron TransportHigh-energy electrons from NADH and FADH2 are passed along the electron transport chain from one carrier protein to the next.

Electron Transport

At the end of the chain, an enzyme combines these electrons with hydrogen ions and oxygen to form water.

Electron Transport

As the final electron acceptor of the electron transport chain, oxygen gets rid of the low-energy electrons and hydrogen ions.

Electron Transport

When 2 high-energy electrons move down the electron transport chain, their energy is used to move hydrogen ions (H+) across the membrane.

Electron TransportDuring electron transport, H+ ions build up in the intermembrane space, so it is positively charged.

Electron Transport

The other side of the membrane, from which those H+ ions are taken, is now negatively charged.

Electron Transport

ATP synthase

Channel

Electron Transport

As H+ ions escape through channels, the ATP synthase spins.

ATP

ATP synthase

Channel

Electron Transport

As it rotates, the enzyme grabs a low-energy ADP, attaching a phosphate, forming high-energy ATP.

The Totals

The breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

The Totals

The TotalsCells contain small No of ATP produced during glycolysis and cellular respiration. In a quick exercise muscles contain only enough of this ATP for a few seconds. That store of ATP is quickly gone. At this point, muscle cells are producing most of their ATP by lactic acid fermentation. That will last about 90 seconds. The only way to get rid of lactic acid is in a chemical pathway that requires extra oxygen. To repay, you have to do plenty of heavy breathing to get the O2. For anything longer cellular respiration is the only way to generate a continuing supply of ATP. Cellular respiration releases energy slower than fermentation, which is why even well-conditioned athletes have to pace themselves during a long race or over the course of a gam

9.2 Concept Assessment1. What happens to pyruvic acid during the Krebs cycle? 2. How does the electron transport chain use the high-energy electrons from the Krebs cycle? 3. Why is cellular respiration considered to be much more efficient than glycolysis alone? 4. How many molecules of ATP are produced in the entire breakdown of glucose? 5. Compare the energy flow in photosynthesis to the energy flow in cellular respiration. 6. How is the chemical energy in glucose similar to money in a savings account?

9.2 Quiz

9.2 Quiz

1. The Krebs cycle breaks pyruvic acid down into

A. oxygen. B. NADH. C. carbon dioxide. D. alcohol.

9.2 Quiz2. What role does the Krebs cycle play in the cell?

A. It breaks down glucose and releases its stored energy.

B. It releases energy from molecules formed during glycolysis.

C. It combines carbon dioxide and water into high-energy molecules.

D. It breaks down ATP and NADH, releasing stored energy.

9.2 Quiz3. In eukaryotes, the electron transport chain is located in the

A. cell membrane. B. inner mitochondrial membrane. C. cytoplasm. D. outer mitochondrial membrane.

9.2 Quiz

4. To generate energy over long periods, the body must use

A.stored ATP. B. lactic acid fermentation. C. cellular respiration. D.glycolysis

9.2 Quiz5. Which statement correctly describes photosynthesis and cellular respiration?

A. Photosynthesis releases energy, while cellular respiration stores energy.

B. Photosynthesis and cellular respiration use the same raw materials.

C. Cellular respiration releases energy, while photosynthesis stores energy.

D. Cellular respiration and photosynthesis produce the same products.

9.2 Quiz6. The Krebs cycle starts with

A. glucose and yields 32 ATPs. B. pyruvic acid and yields carbon dioxide. C. pyruvic acid and yields lactic acid or

alcohol. D. lactic acid and yields carbon dioxide.

9.2 Quiz

7. The starting molecule for the Krebs cycle is

A. NADH B. coenzyme C. pyruvic acid. D. glucose.

9.2 Quiz

8. The Krebs cycle produces

A. glucose B. lactic acid C. electron carriers D. oxygen

9.2 Quiz

9. Photosynthesis is to chloroplasts as cellular respiration is to

A. chloroplasts B. nuclei C. bytoplasm D. mitochondria

9.2 Quiz

10. The Krebs cycle does not occur if

A. glycolysis occurs B. carbon dioxide is present C. oxygen is present D. fermentation occurs

9.2 Quiz

11. Which of the following is the correct sequence of events in cellular respiration?

A. Krebs cycle —- glycolysis —- electron transport B. glycolysis —- fermentation —- Krebs cycle C. Krebs cycle —- electron transport —- glycolysis D. glycolysis —- Krebs cycle —- electron transport

9.2 Quiz

12. Cellular respiration is called an aerobic process because it requires

A. exercise B. light C. glucose D. oxygen

Chapter 9 Test