Cellular Respiration: Obtaining Energy from Food PDF

# Campbell Essential Biology and Campbell Essential Biology with Physiology - Sixth Edition ## Chapter 6 - Cellular Respiration: Obtaining Energy from Food ### The Cells of Your Brain Burn Through a Quarter Pound of Glucose Each Day A colorful image of the brain is displayed and a caption reads *...

# Campbell Essential Biology and Campbell Essential Biology with Physiology - Sixth Edition ## Chapter 6 - Cellular Respiration: Obtaining Energy from Food ### The Cells of Your Brain Burn Through a Quarter Pound of Glucose Each Day A colorful image of the brain is displayed and a caption reads *"The Cells of Your Brain Burn Through a Quarter Pound of Glucose Each Day"* . ### Biology and Society: Getting the Most Out of Your Muscles (1 of 2) - For many endurance athletes, the rate at which oxygen is provided to working muscles is the limiting factor in their performance. - Your aerobic capacity is - the maximum rate at which oxygen can be taken in and used by your muscle cells and - therefore the most strenuous exercise that your body can maintain aerobically. ### The Science of Exercise A picture of an athlete running out of the water on a beach is displayed. ### Biology and Society: Getting the Most Out of Your Muscles (2 of 2) - If you work even harder and exceed your aerobic capacity, - the demand for oxygen in your muscles will outstrip your body's ability to deliver it, - metabolism then becomes anaerobic (without oxygen), and - your muscle cells switch to an “emergency mode" in which they - break down glucose very inefficiently and - produce lactic acid as a by-product (hurts when it builds up in your muscles). ### Energy Flow and Chemical Cycling in the Biosphere - All life requires energy. - In almost all ecosystems on Earth, this energy originates from the sun. - During photosynthesis, plants convert the energy of sunlight to the chemical energy of sugars and other organic molecules. - All animals depend on this conversion for food and more. ### Producers and Consumers (1 of 3) - Plants and other **autotrophs** ("self-feeders") are organisms that make all their own organic matter from nutrients that are entirely inorganic: - carbon dioxide from the air and water - minerals from the soil. - **Heterotrophs** (other-feeders) - include humans and other animals and - cannot make organic molecules from inorganic ones. ### Heterotroph and Autotroph (3 of 3) A picture of a koala eating leaves is displayed. ### Chemical Cycling Between Photosynthesis and Cellular Respiration (1 of 3) - The chemical reactants for photosynthesis are - carbon dioxide which passes from the air into a plant via tiny pores - water which is absorbed from the soil by the plant's roots - Inside leaf cells, chloroplasts use light energy to rearrange the atoms of these ingredients to produce sugars, most importantly **glucose** and other organic molecules. - A by-product of photosynthesis is oxygen gas. ### *****Energy Flow and Chemical Cycling in Ecosystems***** A diagram depicting the flow of energy within an ecosystem is displayed. The diagram shows the sun providing energy for photosynthesis, which is then used by a fox for cellular respiration. ### Chemical Cycling Between Photosynthesis and Cellular Respiration (2 of 3) - Cellular respiration uses oxygen to convert the energy stored in the chemical bonds of sugars to another source of chemical energy called **adenosine triphosphate (ATP)**. - In plants and animals, the production of ATP during cellular respiration occurs mainly in mitochondria. - The waste products of cellular respiration are carbon dioxide and water, the very same ingredients used for photosynthesis. ### Chemical Cycling Between Photosynthesis and Cellular Respiration (3 of 3) - Plants usually make more organic molecules than they need for fuel. This photosynthetic surplus - provides material for the plant to grow or - can be stored, as starch in potatoes, for example. **Checkpoint:** What is misleading about the following statement? *"Plants perform photosynthesis, whereas animals perform cellular respiration."* ### ****Cellular Respiration: Aerobic Harvest of Food Energy**** - Cellular respiration is - aerobic harvesting of chemical energy from organic fuel molecules, - the main way that chemical energy is harvested from food and converted to ATP, and - an aerobic process - it requires oxygen. - Cellular respiration requires that a cell exchange two gases with its surroundings: - The cell takes in oxygen in the form of the gas oxygen - It gets rid of waste as carbon dioxide ### How Breathing Is Related to Cellular Respiration An image of a runner is displayed. The runner's lungs are depicted as taking in oxygen and releasing carbon dioxide. The runner's muscles are depicted as releasing carbon dioxide. ### An Overview of Cellular Respiration (1 of 7) - All living organisms depend on transformations of energy and matter. - **Cellular respiration** - consists of many chemical steps using a specific enzyme to catalyze each reaction, - constitutes one of the most important metabolic pathways for nearly every eukaryotic cell, and - provides the energy these cells need to maintain the functions of life. ### *****An Overview of Cellular Respiration***** (2 of 7) A diagram of the chemical equation for cellular respiration is displayed: $C_6H_{12}O_6 + 6O_2 \longrightarrow 6CO_2 + 6H_2O + \text{Approx.} 32 \text{ ATP}$ ### An Overview of Cellular Respiration (3 of 7) - The many chemical reactions that make up cellular respiration can be grouped into three main stages: 1. **glycolysis** 2. **the citric acid cycle** 3. **electron transport** ### *****A Road Map for Cellular Respiration***** A diagram depicting the flow of reactions involved in cellular respiration is displayed. Glycolysis is depicted as occurring in the cytoplasm. The citric acid cycle and electron transport are depicted as occurring in the mitochondria. Arrows between the cytoplasm and the mitochondria indicate the movement of pyruvic acid from the cytoplasm to the mitochondria and high-energy electrons from the mitochondria to the cytoplasm. ### An Overview of Cellular Respiration (4 of 7) 1. During **glycolysis**, a molecule of glucose is split into two molecules of a compound called pyruvic acid, located in the cytoplasm. 2. The **citric acid cycle** (also called the **Krebs cycle**) completes the breakdown of glucose all the way to carbon dioxide, which is then released as a waste product. The enzymes for the citric acid cycle are dissolved in the fluid within **mitochondria**. ### An Overview of Cellular Respiration (5 of 7) 1 and 2. Glycolysis and the citric acid cycle generate a small amount of ATP directly and much more ATP indirectly, via reactions that transfer electrons from fuel molecules to a molecule called **nicotinamide adenine dinucleotide**. - The electron transfer forms a molecule called **NADH**, which acts as a shuttle carrying high-energy electrons from one area of the cell to another. ### An Overview of Cellular Respiration (6 of 7) 3. The third stage of cellular respiration is **electron transport**. - Electrons captured from food by NADH are stripped of their energy, a little bit at a time, until they are finally combined with oxygen to form water. - The proteins and other molecules that make up electron transport chains are embedded within the inner membrane of the **mitochondria**. - Electron transport from NADH to oxygen releases the energy your cells use to make most of their ATP. ### An Overview of Cellular Respiration (7 of 7) - The overall equation for cellular respiration shows that the atoms of the reactant molecules glucose and oxygen are rearranged to form the products carbon dioxide and water. - The main function of cellular respiration is to generate ATP for cellular work. - The process can produce around 32 ATP molecules for each glucose molecule consumed. **Checkpoint:** Which stages of cellular respiration take place in the mitochondria? Which stage takes place outside the mitochondria? ### BioFlix Animation: Cellular Respiration https://mediaplayer.pearsoncmg.com/assets/Wj_9NI2ur_4lbzbNg8BleE4f943wprq4 ### Stage 1: Glycolysis - During glycolysis, a six-carbon glucose molecule is split in half to form two molecules of pyruvic acid. - This initial split requires an energy “investment” of two ATP molecules per glucose. - The three-carbon molecules then donate high-energy electrons to **NAD+**, forming NADH. - Glycolysis also generates four ATP molecules. - Glycolysis thus produces a net gain of two molecules of ATP per molecule of glucose. ### ☑ Glycolysis A diagram depicting the reactions involved in glycolysis is displayed. The diagram shows glucose as the input and 2 pyruvic acid as the ouutput. The diagram depicts the use and output of ATP and NADH and the movement of electrons. ### ② Stage 2: The Citric Acid Cycle (1 of 3) - Before pyruvic acid can be used by the citric acid cycle, it must be converted to a form the citric acid cycle can use. 1. Each pyruvic acid loses a carbon as carbon dioxide, forming acetic acid. 2. Electrons are stripped from these molecules and transferred to **NAD+**, forming more NADH. 3. Finally, each acetic acid is attached to coenzyme A (CoA) to form acetyl CoA. ### **The Link Between Glycolysis and the Citric Acid Cycle: The Conversion of Pyruvic Acid to Acetyl CoA** A diagram depicting the conversion of pyruvic acid to acetyl CoA is displayed. The diagram shows pyruvic acid as the input and acetyl CoA as the output. The diagram depicts the release of carbon dioxide and the generation of NADH. ### ② Stage 2: The Citric Acid Cycle (2 of 3) - The citric acid cycle finishes extracting the energy of sugar by dismantling the acetic acid molecules all the way to carbon dioxide. 1. Acetic acid joins a four-carbon acceptor molecule to form a six-carbon product called citric acid (for which the cycle is named). 2. For every acetic acid molecule that enters the cycle as fuel, two carbon dioxide molecules eventually exit as a waste product. Along the way, the citric acid cycle harvests energy from the fuel. ### ② The Citric Acid Cycle A diagram depicting the citric acid cycle is displayed. The diagram shows the input of acetic acid, ADP, NAD+ and FAD. The diagram shows the output of carbon dioxide, ATP, NADH and FADH2. The diagram shows the citric acid cycle as a series of reactions that cycle around a central orange circle. ### Stage 2: The Citric Acid Cycle (3 of 3) 3. Some of the energy is used to produce ATP directly. 4. However, the cycle captures much more energy in the form of NADH and a second, closely related electron carrier called **FADH2**. 5. All the carbon atoms that entered the cycle as fuel are accounted for as **carbon dioxide**, and the four-carbon acceptor molecule is recycled. ### ② Stage 3: Electron Transport (1 of 4) - During cellular respiration, the electrons gathered from food molecules gradually "fall,” losing energy at each step. - Electrons are transferred from glucose in food molecules to **NAD+**, forming **NADH**. - Then NADH releases two electrons that enter an **electron transport chain**, a series of electron carrier molecules. With each exchange, the electron gives up a bit of energy. ### Cellular Respiration Illustrated Using a Hard-Hat Analogy An illustration of a worker transferring electrons from glucose to NAD+ and then to the electron transport chain is displayed. At the top of the chain is a worker at a machine that generates ATP. ### Stage 3: Electron Transport (2 of 4) - The overall effect of all this transfer of electrons during cellular respiration is a “downward” trip for electrons - from glucose, - to NADH, - to an electron transport chain, and - to oxygen. ### ? The Role of Oxygen in Harvesting Food Energy A diagram depicting the electron transport chain is displayed. The diagram shows electrons moving from NAD to the electron transport chain and then to oxygen. ### Stage 3: Electron Transport (3 of 4) - The **molecules of electron transport chains** are built into the inner membranes of **mitochondria**. - Because these membranes are highly folded, their large surface area can accommodate thousands of copies of the electron transport chain - a good example of how biological structure fits function. - The energy stored by electron transport behaves something like the water behind a dam. ### The Mitochondrion: Site of Cellular Respiration An illustration depicting the mitochondria is displayed. The inner, outer, and cristae membranes of the mitochondria are labeled. A TEM image of the mitochondria is displayed. ### Stage 3: Electron Transport (4 of 4) - Mitochondria have structures that act like turbines. - Each of these miniature machines, called an **ATP synthase**, is constructed from proteins built into the inner mitochondrial membrane, adjacent to the proteins of the electron transport chains. - **Figure 6.10** shows a simplified view of how the energy previously stored in NADH and FADH2 can now be used to generate ATP. ### How Electron Transport Drives ATP Synthase Machines A diagram depicting electron transport and the generation of ATP is displayed. The diagram shows electrons moving from NADH and FADH2 through the electron transport chain and then to oxygen. The movement of electrons through the transport chain drives the generation of ATP by ATP synthase machines. ### The Results of Cellular Respiration (1 of 2) - Cellular respiration can generate up to **32 molecules of ATP** per molecule of glucose. - **Figure 6.11** will help you keep track of the ATP molecules generated. ### ? A Summary of ATP Yield During Cellular Respiration ****** A diagram depicting the flow of reactions involved in cellular respiration is displayed. ### The Results of Cellular Respiration (2 of 2) - Respiration is a versatile metabolic furnace that can “burn” many other kinds of food molecules. - **Figure 6.12** diagrams some metabolic routes for the use of carbohydrates, fats, and proteins as fuel for cellular respiration. - The interplay between these pathways provides a clear example of the theme of system interactions; in this case, all of these interactions contribute to maintaining a balanced metabolism. ### Energy From Food An illustration depicting the breakdown of food molecules is displayed. The illustration shows the breakdown of carbohydrates, fats, and proteins into sugars, fatty acids, and amino acids. These food molecules are further broken down via glycolysis, the citric acid cycle, and the electron transport chain, resulting in the production of ATP. ### Fermentation: Anaerobic Harvest of Food Energy - Some of your cells can work for short periods without oxygen. This **anaerobic** ("without oxygen") harvest of food energy is called **fermentation**. - **Fermentation relies on glycolysis**, the first stage of cellular respiration. - Glycolysis does not require oxygen, but does **produce two ATM molecules for each glucose** molecule broken down to pyruvic acid. ### Fermentation in Human Muscle Cells - To harvest food energy during glycolysis **oxygen** must be present to receive electrons. - This is no problem under aerobic conditions, because the cell regenerates NAD+ when NADH drops its electron cargo down electron transport chains to oxygen. - However, this recycling of NAD+ cannot occur under anaerobic conditions because there is no oxygen present. - Instead, NADH disposes of electrons by adding them to the pyruvic acid produced by glycolysis, producing a waste product called **lactic acid**. ### Fermentation: Producing Lactic Acid A diagram depicting the production of lactic acid is displayed. The diagram shows glucose as the input and 2 lactic acid as the output. The diagram depicts the use and output of ATP and NADH. ### Animation: Fermentation Overview https://mediaplayer.pearsoncmg.com/assets/secs-campbell-fermentation ### Fermentation in Microorganisms - **Yeast** and some other organisms can survive with or without oxygen. - Wastes from fermentation can be ethyl alcohol, lactic acid, or other compounds, depending on the species. ### Fermentation: Producing Ethyl Alcohol A diagram depicting the production of ethyl alcohol is displayed. The diagram shows glucose as the input and 2 ethyl alcohol and 2 carbon dioxide as the output. The diagram depicts the use and output of ATP and NADH. ### Evolution Connection: The Importance of Oxygen (1 of 2) - Aerobic and anaerobic respiration start with glycolysis. Glycolysis is thus the universal energy-harvesting process of life. - The role of glycolysis in respiration and fermentation has an evolutionary basis. - Between 3.5 and 2.7 billion years ago, before significant levels of oxygen were present in Earth's atmosphere, ancient prokaryotes probably used glycolysis to make ATP and generated ATP exclusively from glycolysis. ### A Time Line of Oxygen and Life on Earth A timeline depicting the evolution of life on Earth is displayed. The timeline depicts notable milestones including: - The origin of Earth - The appearance of the oldest prokaryotic fossils - The first appearance of oxygen in the atmosphere - The appearance of the first eukaryotic organisms. ### Evolution Connection: The Importance of Oxygen (2 of 2) - The fact that glycolysis occurs in almost all organisms suggests that it evolved very early in ancestors common to all the domains of life. - The location of glycolysis within the cell also implies great antiquity. The pathway does not require any of the membrane-enclosed organelles of the eukaryotic cell, which evolved more than a billion years after the prokaryotic cell. ### Copyright This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching their courses and assessing student learning. Dissemination or sale of any part of this work (including on the World Wide Web) will destroy the integrity of the work and is not permitted. The work and materials from it should never be made available to students except by instructors using the accompanying text in their classes. All recipients of this work are expected to abide by these restrictions and to honor the intended pedagogical purposes and the needs of other instructors who rely on these materials.