© 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 6 Cellular Respiration: Obtaining Energy from Food

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. The waste products of cellular respiration are: –CO 2 and H 2 O –Used in photosynthesis Animals perform only cellular respiration. Plants perform: –Photosynthesis and –Cellular respiration

Sunlight energy enters ecosystem Photosynthesis Cellular respiration C 6 H 12 O 6 Glucose O 2 Oxygen CO 2 Carbon dioxide H 2 O Water drives cellular work Heat energy exits ecosystem ATP Figure 6.2 Study the relationship of photosynthesis & cell respiration

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 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. © 2010 Pearson Education, Inc.

Breathing Cellular respiration Muscle cells Lungs CO 2 O2O2 O2O2 Figure 6.3a

C 6 H 12 O 6 CO 2 O2O2 H2OH2O GlucoseOxygenCarbon dioxide Water  6 6 Reduction Oxidation Oxygen gains electrons (and hydrogens) Glucose loses electrons (and hydrogens) Figure 6.UN02 The overall equation for what happens to glucose during cellular respiration:

© 2010 Pearson Education, Inc. 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.

© 2010 Pearson Education, Inc. 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 Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid ATP Figure 6.6a

© 2010 Pearson Education, Inc. 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. –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 Thus, glycolysis produces a net of two molecules of ATP per glucose molecule.

© 2010 Pearson Education, Inc. Stage 2: The Citric Acid Cycle The citric acid cycle completes the breakdown of sugar. The citric acid cycle: –Extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO 2 –Uses some of this energy to make ATP –Forms NADH and FADH 2

3 NAD  ADP  P 3 NADH FADH 2 FAD Acetic acid Citric acid Acceptor molecule Citric Acid Cycle ATP 2 CO 2 INPUT OUTPUT Figure 6.10

(from glycolysis)(to citric acid cycle) Oxidation of the fuel generates NADH Pyruvic acid loses a carbon as CO 2 Acetic acid attaches to coenzyme A Pyruvic acid Acetic acid Acetyl CoA Coenzyme A CoA CO 2 NAD  NADH INPUTOUTPUT Figure 6.9

© 2010 Pearson Education, Inc. Stage 3: Electron Transport 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. 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

1 2 Space between membranes Inner mitochondrial membrane Electron carrier Protein complex Electron flow MatrixElectron transport chain ATP synthase NADH NAD  FADH 2 FAD ATP ADP H2OH2O O2O2 HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH  2 P  Figure 6.11a

Cytoplasm Mitochondrion NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid 2 ATP 2 ATP NADH FADH 2 Maximum per glucose: 2 Acetyl CoA About 34 ATP by direct synthesis by direct synthesis by ATP synthase About 38 ATP Figure 6.13

© 2010 Pearson Education, Inc. 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

© 2010 Pearson Education, Inc. The Versatility of Cellular Respiration In addition to glucose, cellular respiration can “burn”: –Diverse types of carbohydrates –Fats –Proteins

© 2010 Pearson Education, Inc. 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. In human muscle cells, lactic acid is a by-product.

Glucose 2 ATP 2 NAD  2 NADH 2 NAD   2 H  2 ADP 2 Pyruvic acid 2 Lactic acid Glycolysis INPUTOUTPUT  2 P Figure 6.14

© 2010 Pearson Education, Inc. Yeast are a type of microscopic fungus that: –Use a different type of fermentation –Produce CO 2 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 NAD   2  2 P 2 Pyruvic acid 2 Ethyl alcohol Glycolysis INPUTOUTPUT 2 CO 2 released Bread with air bubbles produced by fermenting yeast Beer fermentation 2 ADP HH Figure 6.16