Cellular Respiration: Obtaining Energy from Food

Chapter 6 Cellular Respiration: Obtaining Energy from Food PowerPoint Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko 2013 Pearson Education, Inc.

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

Biology and Society: Marathoners versus Sprinters The muscles that move our legs contain two main types of muscle fibers: 1. slow-twitch and 2. fast-twitch. 2013 Pearson Education, Inc.

Biology and Society: Marathoners versus Sprinters Slow-twitch fibers last longer, do not generate a lot of quick power, and generate ATP using oxygen (aerobically). 2013 Pearson Education, Inc.

Biology and Society: Marathoners versus Sprinters 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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Producers and Consumers Autotrophs are producers because ecosystems depend upon them for food. Heterotrophs are consumers because they eat plants or other animals. 2013 Pearson Education, Inc.

Figure 6.1

Chemical Cycling between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide (CO 2 ) and water (H 2 O). CO 2 is obtained from the air by a plant s leaves. H 2 O is obtained from the damp soil by a plant s roots. 2013 Pearson Education, Inc.

Chemical Cycling between Photosynthesis and Cellular Respiration Chloroplasts in the cells of leaves use light energy to rearrange the atoms of CO 2 and H 2 O, which produces sugars (such as glucose), other organic molecules, and oxygen gas. 2013 Pearson Education, Inc.

Chemical Cycling between Photosynthesis and Cellular Respiration 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. 2013 Pearson Education, Inc.

Chemical Cycling between Photosynthesis and Cellular Respiration The waste products of cellular respiration are CO 2 and H 2 O, used in photosynthesis. 2013 Pearson Education, Inc.

Chemical Cycling between Photosynthesis and Cellular Respiration Animals perform only cellular respiration. Plants perform photosynthesis and cellular respiration. 2013 Pearson Education, Inc.

Chemical Cycling between 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. 2013 Pearson Education, Inc.

Figure 6.2 Sunlight energy enters ecosystem Photosynthesis C 6 H 12 O 6 CO 2 O 2 H 2 O Cellular respiration ATP drives cellular work Heat energy exits ecosystem

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. 2013 Pearson Education, Inc.

CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY 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. 2013 Pearson Education, Inc.

Figure 6.3 O 2 CO 2 Breathing Lungs O 2 CO 2 Cellular respiration Muscle cells

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

Figure 6.3b

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 CO 2, H 2 O, & a release of energy. 2013 Pearson Education, Inc.

Figure 6.UN01 C 6 H 12 O 6 6 6 CO 2 6 H 2 O ATP O 2 Glucose Oxygen Carbon dioxide Water Energy

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. 2013 Pearson Education, Inc.

Redox Reactions Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions or redox reactions for short. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Figure 6.UN02 Oxidation Glucose loses electrons (and hydrogens) C 6 H 12 O 6 6 O 2 6 CO 2 6 Glucose Oxygen Carbon dioxide H 2 O Water Reduction Oxygen gains electrons (and hydrogens)

Redox Reactions 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. 2013 Pearson Education, Inc.

Figure 6.4 1 2 H 2 O 2 Release of heat energy H 2 O

Redox Reactions Cellular respiration is a controlled fall of electrons and a stepwise cascade much like going down a staircase. 2013 Pearson Education, Inc.

NADH and Electron Transport Chains 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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Figure 6.5 e e Electrons from food NAD + e e NADH Stepwise release of energy used to make 2 2 e ATP 2 e 2 1 2 O 2 Hydrogen, electrons, and oxygen combine to produce water H 2 O

Figure 6.5a 2 2 e ATP Stepwise release of energy used to make ATP Electron transport chain 2 e 2 1 2 O 2 Hydrogen, electrons, and oxygen combine to produce water H 2 O

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. 2013 Pearson Education, Inc.

2013 Pearson Education, Inc. BioFlix Animation: Cellular Respiration

Figure 6.6 Mitochondrion Cytoplasm Cytoplasm Animal cell Plant cell Cytoplasm Mitochondrion High-energy electrons via carrier molecules Glycolysis 2 Glucose Pyruvic acid Citric Acid Cycle Electron Transport ATP ATP ATP

Figure 6.6a Cytoplasm Mitochondrion Glycolysis 2 Glucose Pyruvic acid Citric Acid Cycle High-energy electrons via carrier molecules Electron Transport 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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Figure 6.7 INPUT NADH OUTPUT P NAD + P 2 ADP 2 ATP 2 ATP 2 ADP P 2 P 3 2 Pyruvic acid 1 P P 2 P 3 Glucose NAD + NADH P 2 ADP 2 ATP Energy investment phase Key Carbon atom P Phosphate group High-energy electron Energy harvest phase

Figure 6.7a INPUT OUTPUT 2 Pyruvic acid Glucose

Figure 6.7b-1 P 2 ATP 2 ADP 1 P Energy investment phase

Figure 6.7b-2 NADH P NAD + P 2 ATP 2 ADP P 2 P 1 P P 2 P NAD + NADH P Energy investment phase Energy harvest phase

Figure 6.7b-3 NADH P NAD + P 2 ADP 2 ATP 2 ATP 2 ADP P 2 P 3 1 P P 2 P 3 NAD + NADH P 2 ADP 2 ATP Energy investment phase Energy harvest phase

Stage 1: Glycolysis 3. Glycolysis 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. 2013 Pearson Education, Inc.

Figure 6.8 Enzyme P ADP ATP P P

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 CO 2. The remaining fuel molecule, with only two carbons left, is acetic acid. Oxidation of the fuel generates NADH. 2013 Pearson Education, Inc.

Stage 2: The Citric Acid Cycle 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. 2013 Pearson Education, Inc.

Figure 6.9 INPUT (from glycolysis) 2 NAD + Oxidation of the fuel generates NADH NADH OUTPUT (to citric acid cycle) CoA Pyruvic acid 1 Pyruvic acid loses a carbon as CO 2 CO 2 Acetic acid Coenzyme A 3 Acetic acid attaches to coenzyme A Acetyl CoA

Figure 6.9a INPUT (from glycolysis) OUTPUT (to citric acid cycle) CoA Pyruvic acid Acetyl CoA

Figure 6.9b 2 NAD + Oxidation of the fuel generates NADH NADH OUTPUT 1 Pyruvic acid loses a carbon as CO 2 CO 2 Acetic acid Coenzyme A 3 Acetic acid attaches to coenzyme A

Stage 2: The Citric Acid Cycle 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, and forms NADH and FADH 2. 2013 Pearson Education, Inc.

Blast Animation: Harvesting Energy: Krebs Cycle Select Play 2013 Pearson Education, Inc.

Figure 6.10 INPUT Citric acid OUTPUT 1 Acetic acid 2 CO 2 2 ADP + P 3 NAD + Citric Acid Cycle ATP 3 NADH 3 4 FAD FADH 2 5 6 Acceptor molecule

Figure 6.10a INPUT OUTPUT 1 Acetic acid 2 CO 2 2 ADP + P ATP 3 3 NAD + FAD 3 NADH FADH 2 4 5

Figure 6.10b INPUT Citric acid OUTPUT Citric Acid Cycle Acceptor molecule

Stage 3: Electron Transport Electron transport releases the energy your cells need to make the most of their ATP. The molecules of the electron transport chain are 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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Figure 6.11 Space between membranes Protein complex Electron carrier 3 5 Inner mitochondrial membrane Electron flow FADH 2 NADH NAD + 1 FAD 2 2 H 2 O 6 4 Matrix Electron transport chain ATP synthase 1 2 O 2 ADP P ATP

Figure 6.11a Space between membranes Electron carrier Protein complex 3 5 Inner mitochondrial membrane Electron flow FADH 2 NADH NAD + 1 FAD + H H+ H+ 2 Matrix Electron transport chain ATP synthase 1 2 O 2 2 4 H 2 O ADP P 6 ATP

Figure 6.11b Space between membranes H Electron carrier Protein complex 3 Inner mitochondrial membrane Electron flow FADH 2 2 FAD 1 2 O 2 2 NADH NAD + 4 1 H+ Matrix Electron transport chain

Figure 6.11c + 5 1 2 O 2 2 H 2 O 6 4 ADP P ATP ATP synthase

Stage 3: Electron Transport 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. 2013 Pearson Education, Inc.

The Results of Cellular Respiration Cellular respiration can generate up to 32 molecules of ATP per molecule of glucose. 2013 Pearson Education, Inc.

Figure 6.12 Cytoplasm Mitochondrion 2 NADH 2 NADH 6 NADH 2 FADH 2 Glycolysis 2 Glucose Pyruvic acid 2 Acetyl CoA Citric Acid Cycle Electron Transport Maximum per glucose: 2 ATP 2 ATP About 28 ATP About 32 ATP by direct synthesis by direct synthesis by ATP synthase

Figure 6.12a Glycolysis 2 Glucose Pyruvic acid 2 Acetyl CoA Citric Acid Cycle Electron Transport 2 ATP 2 ATP About 28 ATP by direct synthesis by direct synthesis by ATP synthase

The Results of Cellular Respiration In addition to glucose, cellular respiration can burn diverse types of carbohydrates, fats, and proteins. 2013 Pearson Education, Inc.

Figure 6.13 Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Glycolysis Acetyl CoA Citric Acid Cycle Electron Transport 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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Fermentation in Human Muscle Cells 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. 2013 Pearson Education, Inc.

Animation: Fermentation Overview Right click slide / select Play 2013 Pearson Education, Inc.

Figure 6.14 INPUT 2 ADP 2 P 2 ATP OUTPUT Glycolysis Glucose 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Pyruvic acid 2 2 Lactic acid

Figure 6.14a INPUT 2 ADP 2 P 2 ATP OUTPUT Glycolysis 2 NAD + 2 NADH 2 NADH 2 NAD + Glucose 2 Pyruvic acid 2 2 Lactic acid

Figure 6.14b

The Process of Science: What Causes Muscle Burn? Observation: Muscles produce lactic acid under anaerobic conditions. Question: Does the buildup of lactic acid cause muscle fatigue? 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Figure 6.15 Battery + Force measured Battery + Force measured Frog muscle stimulated by electric current Solution prevents diffusion of lactic acid Solution allows diffusion of lactic acid; muscle can work for twice as long

The Process of Science: What Causes Muscle Burn? 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. 2013 Pearson Education, Inc.

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. 2013 Pearson Education, Inc.

Fermentation in Microorganisms Yeast is a microscopic fungus that uses a different type of fermentation and produces CO 2 and ethyl alcohol instead of lactic acid. This type of fermentation, called alcoholic fermentation, is used to produce beer, wine, and breads. 2013 Pearson Education, Inc.

Figure 6.16 INPUT 2 ADP + 2 P 2 ATP 2 CO 2 released OUTPUT Glycolysis Glucose 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Pyruvic acid + 2 2 Ethyl alcohol

Figure 6.16a INPUT 2 ADP + 2 P 2 ATP 2 CO 2 released OUTPUT Glycolysis Glucose 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Pyruvic acid +2 2 Ethyl alcohol

Figure 6.16b

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. 2013 Pearson Education, Inc.

Figure 6.17 0 Billions of years ago 2.1 2.2 2.7 3.5 O 2 present in Earth s atmosphere First eukaryotic organisms Atmospheric oxygen reaches 10% of modern levels Atmospheric oxygen first appears Oldest prokaryotic fossils 4.5 Origin of Earth

Figure 6.17a 0 Billions of years ago 2.1 2.2 2.7 3.5 O 2 present in Earth s atmosphere First eukaryotic organisms Atmospheric oxygen reaches 10% of modern levels Atmospheric oxygen first appears Oldest prokaryotic fossils 4.5 Origin of Earth

Figure 6.17b

Figure 6.UN03 Glycolysis Citric Acid Cycle Electron Transport ATP ATP ATP

Figure 6.UN04 Glycolysis Citric Acid Cycle Electron Transport ATP ATP ATP

Figure 6.UN05 Glycolysis Citric Acid Cycle Electron Transport ATP ATP ATP

Figure 6.UN06 C 6 H 12 O 6 Heat Sunlight O 2 ATP Photosynthesis Cellular respiration CO 2 H 2 O

Figure 6.UN07 C 6 H 12 O 6 + 6 6 CO 2 + 6 H 2 O + Approx. 32 ATP O 2

Figure 6.UN08 Oxidation Glucose loses electrons (and hydrogens) C 6 H 12 O 6 CO 2 Electrons (and hydrogens) ATP O 2 Reduction Oxygen gains electrons (and hydrogens) H 2 O

Figure 6.UN09 Mitochondrion O 2 6 NADH 2 NADH 2 NADH 2 FADH 2 Glycolysis 2 Glucose Pyruvic acid 2 Acetyl CoA Citric Acid Cycle Electron Transport 2 CO 2 4 CO 2 H 2 O 2 ATP by direct synthesis by direct synthesis 2 ATP About 28 ATP by ATP synthase About 32 ATP