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Interest Grabber

Feel the Burn Do you like to run, bike, or swim? These all are good ways to exercise. When you exercise, your body uses oxygen to get energy from glucose, a six-carbon sugar.

Section 9-1

1. How does your body feel at the start of exercise, such as a long, slow run? How do you feel 1 minute into the run; 10 minutes into the run?

2. What do you think is happening in your cells to cause the changes in how you feel?

3. Think about running as fast as you can for 100 meters. Could you keep up this pace for a much longer distance? Explain your answer.

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Section Outline

9–1 Chemical Pathways A. Chemical Energy and Food B. Overview of Cellular Respiration C. Glycolysis

1. ATP Production 2. NADH Production

D. Fermentation 1. Alcoholic Fermentation 2. Lactic Acid Fermentation

Section 9-1

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Chemical Energy and Food

•  How much energy is in food??? •  calorie – the amount of energy needed to raise the

temperature of 1g of water 1 degree Celsius. •  1g of glucose releases 3811 calories •  Food is measured in Calories which equals 1000 calories.

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Cellular Respiration

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

•  Cellular Respiration has three main steps: 1.  Glycolysis 2.  Krebs Cycle 3.  Electron Transport Chain

•  The equation for Cellular Respiration is as follows:

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Glucose Glycolysis

Cytoplasm

Pyruvic acid

Electrons carried in NADH

Krebs Cycle

Electrons carried in

NADH and FADH2 Electron

Transport Chain

Mitochondrion

Figure 9–2 Cellular Respiration: An Overview

Mitochondrion

Section 9-1

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Glucose

To the electron transport chain

Figure 9–3 Glycolysis

Section 9-1

2 Pyruvic acid

Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound.

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Fermentation •  Fermentation releases energy from food molecules by producing

ATP in the absence of oxygen. •  The cell take the high energy electrons from NADH and sends them

back to the pyruvic acid. •  NADH is transformed back to NAD+, thus allowing glycolysis to

continue. •  Because fermentation does not require oxygen, it is called

Anaerobic (not in air). •  There are two types of fermentation:

1.  Alcoholic Fermentation 2.  Lactic Acid Fermentation

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Alcoholic Fermentation

•  Yeasts and a few other microorganisms use AF, forming ethyl alcohol and carbon dioxide as wastes.

•  AF causes bread dough to rise. When the yeast runs out of oxygen, it begins to ferment giving off bubbles of carbon dioxide.

•  The alcohol evaporates as the bread is baked. •  The equation is as follows:

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Lactic Acid Fermentation

•  Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues.

•  So to continue the production of ATP, pyruvic acid takes excited electrons from NADH and produces lactic acid and NAD+.

•  The NAD+ can then reenter glycolysis to produce ATP.

•  Some prokaryotes are used to make some foods such as cheese, yogurt, buttermilk, and sour cream.

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Glucose Pyruvic acid Lactic acid

Figure 9–4 Lactic Acid Fermentation

Section 9-1

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Glucose

Glycolysis Krebs cycle

Electron transport

Fermentation (without oxygen)

Alcohol or lactic acid

Chemical Pathways

Section 9-1

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Interest Grabber

Rolling and Folding Some of the steps in cellular respiration take place in the membrane inside the cell structure called the mitochondrion, which has a folded inner membrane. What purpose do these folds serve? To find out the answer to this question, perform this activity.

Section 9-2

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Interest Grabber continued

1. Obtain two sheets of paper and a metric ruler. What is the surface area of the paper?

2. Roll one sheet of paper into a tube lengthwise. What is the surface area of the rolled paper?

3. Fold the second sheet of paper into a fan. Then, roll the first sheet of paper around the folded paper so it is inside the rolled paper. What has happened to the surface area of the inside of the rolled paper?

4. What would be the value of increasing the surface area of the membrane inside a mitochondrion?

Section 9-2

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Section Outline

9–2 The Krebs Cycle and Electron Transport A. The Krebs Cycle B. Electron Transport C. The Totals D. Energy and Exercise

1. Quick Energy 2. Long-Term Energy

E. Comparing Photosynthesis and Cellular Respiration

Section 9-2

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Flowchart

Section 9-2

Glucose (C6H1206)

+ Oxygen

(02)

Glycolysis Krebs Cycle

Electron Transport

Chain

Carbon Dioxide (CO2)

+ Water (H2O)

Cellular Respiration

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Krebs Cycle

•  In the presence of oxygen, pyruvic acid enters the second stage of Cellular Respiration, the Krebs Cycle.

•  The Krebs Cycle was discovered by Hans Krebs in 1937.

•  During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reaction.

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Steps of the Krebs Cycle

1. Pyruvic acid enters into the mitochondria. 2. One carbon atom of the pyruvic acid becomes

part of a carbon dioxide molecule, which will enter into the air.

3. The remaining two carbons join another compound called coenzyme A to form acetyl-CoA.

4. Acetyl-CoA then adds the 2-carbon acetyl group to a 4-carbon molecule, producing a 6-carbon molecule called citric acid.

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Citric Acid Production

Figure 9–6 The Krebs Cycle

Section 9-2

Mitochondrion

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Steps of the Krebs Cycle

5. Citric Acid is then broken down into a 4-carbon releasing 2 molecules of carbon dioxide and electrons that are picked up by the electron carriers NADH and FADH2.

6. An ADP molecule is also converted into an ATP molecule.

7. The electron carriers then travel to the electron transport chain.

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Citric Acid Production

Figure 9–6 The Krebs Cycle

Section 9-2

Mitochondrion

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Electron Transport Chain

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

-This process takes place in the inner membrane of the mitochondria.

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Electron Transport Chain

1.  High-energy electrons from NADH and FADH2 are passed along the ETC. These electrons are passed from one carrier protein until it reaches the end where they are combined with H+ ions and oxygen to form a water molecule.

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Electron Transport Chain

2. Every time 2 high-energy electrons transport the ETC, their energy is used to pump H+ ions into the mitochondrial intermembrane space causing it to become positively charged.

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Electron Transport Chain

3.  Through diffusion, the H+ ions in the intermembrane space pass through ATP synthase causing it to spin. Every time it spins, ATP synthase transforms ADP into a high-energy ATP. For every pair of electrons that goes down the ETC, there is enough energy to produce 3 ATP molecules.

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Figure 9–7 Electron Transport Chain

Section 9-2

Electron Transport Hydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Mitochondrion

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ETC Totals

Video Contents

Video Contents

Click a hyperlink to choose a video. Aerobic Respiration Glycolysis Krebs Cycle, Part 1 Krebs Cycle, Part 2 Electron Transport Chain, Part 1 Electron Transport Chain, Part 2

Video 1

Click the image to play the video segment.

Video 1

Aerobic Respiration

Video 2

Click the image to play the video segment.

Video 2

Glycolysis

Video 3

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Video 3

Krebs Cycle, Part 1

Video 4

Click the image to play the video segment.

Video 4

Krebs Cycle, Part 2

Video 5

Click the image to play the video segment.

Video 5

Electron Transport Chain, Part 1

Video 6

Click the image to play the video segment.

Video 6

Electron Transport Chain, Part 2

Internet

Links from the authors on Creatine

Share kimchi lab data Interactive test For links on cellular respiration, go to www.SciLinks.org and enter the Web Code as follows: cbn-3091. For links on the Krebs cycle, go to www.SciLinks.org and enter the Web Code as follows: cbn-3092.

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Section 1 Answers

Interest Grabber Answers

1. How does your body feel at the start of exercise, such as a long, slow run? How do you feel 1 minute into the run; 10 minutes into the run? Students may answer that they feel no fatigue at the start of a run; however, after 1 minute and more so after 10 minutes, they are breathing hard, their heart rate has increased significantly, and their muscles may hurt.

2. What do you think is happening in your cells to cause the changes in how you feel? Students may say that the increase in heart rate and breathing rate are a response that gets extra oxygen to the cells. The pain may be attributed to the cells becoming fatigued.

3. Think about running as fast as you can for 100 meters. Could you keep up this pace for a much longer distance? Explain your answer. Students may know that very high levels of performance can be sustained only very briefly even among the best of athletes. Students may say that the body runs out of readily available energy, food, or oxygen, or that the body builds up too many waste products in the cells.

Section 2 Answers

Interest Grabber Answers

1. Obtain two sheets of paper and a metric ruler. What is the surface area of the paper? The area will vary depending on the size of paper used. A sheet of notebook paper has an area of approximately 600 cm3.

2. Roll one sheet of paper into a tube lengthwise. What is the surface area of the rolled paper? The surface area is the same as the original sheet of paper.

3. Fold the second sheet of paper into a fan. Then, roll the first sheet of paper around the folded paper so it is inside the rolled paper. What has happened to the surface area of the inside of the rolled paper? The surface area has increased (surface area of rolled paper + surface area of folded paper).

4. What would be the value of increasing the surface area of the membrane inside a mitochondrion? Increasing the surface area increases the amount of space where chemical reactions can take place.

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