Cellular Respiration 3.2 CAN YOU EXPLAIN IT?

Transcription

1 3.2 Cellular Respiration Cars need energy to move. A mixture of oxygen and gasoline, when ignited by a spark, produes a small, ontrolled explosion in the engine s ylinder that moves the axle. Gather Evidene As you explore the lesson, gather evidene that bonds are broken and new bonds are formed in the proess of ellular respiration. CAN YU EXPLAIN IT? Both ars and your body need fuel. Most ars use gasoline as a fuel, whih often inludes ethanol in addition to gasoline. For a ar or a human body to use fuel, the energy in the hemial bonds of the fuel must be released. A ombustion reation in a ar s engine releases this energy. Your body uses a similar reation in whih it releases the energy ontained in the hemial bonds of the food you eat. FIGURE 1: The ignition of a mixture of ethanol and oxygen in the Explore nline air produes a ombustion reation, whih releases energy in the forms of heat and light. Predit ow is the proess of fuel ombustion in a ar engine similar to the way the ells in your body release energy stored in fuel? Image Credits: (t) Cultura/Eho/Getty Images; (b) oughton Mifflin arourt 128 Unit 3 Matter and Energy in Living Systems

2 EXPLRATIN 1 Matter and Energy in Cellular Respiration Fuel is any material that reats to release energy to be used for work. Not all fuels are alike. They have many different hemial strutures. C C C C C C C C FIGURE 2: Ethanol is a fuel made from plant material, suh as orn. As a renewable energy soure, it helps redue petroleum use. Gluose is a simple sugar that living things use for energy. Analyze ow are gluose and ethanol similar in struture and funtion? ow do they differ? Gluose Ethanol Energy in Living Systems Whether food for organisms or fuel for ars, almost all the energy on Earth has its origins in the sun. In the proess of photosynthesis, plants transform light energy from the sun into hemial energy in the form of gluose. When an organism eats a plant, any energy the plant has not used an be used by the onsumer. Anient plants and animals that died deomposed and were buried under soil, rok, and sometimes sea water. These organisms deomposed into organi materials that ontain unused stored energy. ver millions of years, heat and pressure transformed these remains into the fossil fuels we use today. Chemial bonds must be broken for the stored energy to be released. In ars, a ombustion reation provides the energy needed to break these bonds and release energy. In ells, a similar proess alled ellular respiration releases hemial energy from sugars and other arbon-based moleules to make when oxygen is present. Exothermi Reation Energy reatants ativation energy differene in energy FIGURE 3: Ativation energy is the energy needed to start a hemial reation. An exothermi reation releases more energy than it absorbs. Cellular respiration is an exothermi reation. produts Reation progress Gather Evidene Explain why ellular respiration is an exothermi reation. Cite evidene from the graph shown in Figure 3 to support your explanation. Lesson 2 Cellular Respiration 129

3 ands-n Lab Cellular Respiration and Exerise Burning fuel through either ombustion or ellular respiration requires oxygen. In eah proess, bonds break and new bonds form. In this lab, you will use an indiator alled bromothymol blue to gather evidene to support a laim about the inputs and outputs of ellular respiration. Bromothymol blue hanges olor in the presene of an aid. Predit What evidene ould there be to support the laim that during ellular respiration, hemial bonds are broken and new bonds are formed? SAFETY Do not onsume any of the materials used in this lab. Be areful not to breathe in through the straw. MATERIALS bromothymol blue solution ups or beakers (2) straw timer PRCEDURE 1. Plae the amount of bromothymol blue solution speified by your teaher in a up or beaker. 2. Get the timer ready. Slowly blow through the straw into the bromothymol blue solution, and reord how long it takes for the solution to hange from blue to yellow. Be sure not to inhale when the straw is in the solution. 3. Plae the amount of bromothymol blue solution speified by your teaher in a seond up or beaker. 4. Run in plae for approximately one minute. 5. Get the timer ready again. Slowly blow through the straw into the bromothymol blue solution, and reord how long it takes for the solution to turn yellow. ANALYZE The water turned aidi when you blew into it beause arbon dioxide in your breath reated with water to form arboni aid. 1. ow do your findings support the laim that bonds were broken and new bonds were formed to produe the gas you breathed out? 2. When you exerised, what was different about the time it took the solution to hange olor? Explain why this happened. FIGURE 4: Bromothymol blue is an indiator that hanges olor in the presene of an aid. Image Credits: oughton Mifflin arourt 130 Unit 3 Matter and Energy in Living Systems

4 The Proess of Cellular Respiration During ellular respiration, the breakdown of gluose and other arbon-based moleules releases energy stored in their hemial bonds. The stored energy is transferred to, whih we an think of as the ell s energy urreny. Energy in the form of heat is also released in the proess. The release of heat aounts for why the body temperatures of mammals range from 36 to 39 C ( F). Cellular respiration is an aerobi proess, whih means that it requires oxygen to take plae. Some organisms an produe small amounts of through anaerobi proesses, or proesses that do not require oxygen. owever, the presene of oxygen allows ellular respiration to produe far more from eah gluose moleule. The inputs and outputs of ellular respiration are shown in Figure 5. oxygen ( 2 ) gluose (C ) arbon dioxide (C 2 ) water ( 2 ) FIGURE 5: Inputs and utputs of Cellular Respiration Explain What is the role of the organism in this model of ellular respiration? Explain your answer. heat Energy and Matter The balaned hemial equation for ellular respiration is: C C heat + 1. ow does this equation represent the law of onservation of matter that matter annot be reated or destroyed? 2. ow does this equation represent the law of onservation of energy that energy annot be reated or destroyed? Consider the role of photosynthesis in your answer. Mitohondria Cellular respiration takes plae inside an organelle alled the mitohondrion (plural mitohondria), shown in Figure 6. Mitohondria release the hemial energy required to make. Both plant and animal ells ontain mitohondria, beause both plants and animals arry out ellular respiration. ristae intermembrane spae outer membrane mitohondrion inner membrane matrix FIGURE 6: The mitohondrion has an inner membrane with many folds, alled ristae. The outer membrane separates the mitohondrion from the rest of the ell. The spae between the two membranes is alled the intermembrane spae. Collaborate With a partner, ite evidene that supports the laim that mitohondria are the powerhouses of the ell. Lesson 2 Cellular Respiration 131

5 Explore nline ands-n Lab Investigating Photosynthesis and Cellular Respiration Design an experiment to determine whih organisms (pond snails or Elodea) produe arbon dioxide and whih use arbon dioxide. Cellular Respiration and Photosynthesis Almost all energy for living things omes from photosynthesis, either diretly or indiretly. Produers absorb light energy from the sun and transform it using photosynthesis to a usable form of energy, or food. This energy is then passed from produers to onsumers. Although only produers arry out photosynthesis, both produers and onsumers arry out ellular respiration. Photosynthesis stores energy from sunlight as hemial energy. In ontrast, ellular respiration releases stored energy as and heat. FIGURE 7: A Comparison of Photosynthesis and Cellular Respiration Photosynthesis light energy REACTANTS PRDUCTS C 2 C Analyze What is the relationship between the inputs and outputs of photosynthesis and ellular respiration? Cellular Respiration PRDUCTS REACTANTS C 2 C heat Model Sort the following terms into those that our during photosynthesis and those that our during ellular respiration. Then plae the terms in the orret order. absorption of sunlight prodution prodution of sugars breakdown of sugars 132 Unit 3 Matter and Energy in Living Systems

6 EXPLRATIN 2 Using Chemial Energy ne way that organisms maintain homeostasis is through ellular respiration, whih releases energy to arry out ell proesses and helps maintain body temperature. Bonds in food moleules and oxygen moleules are broken and new moleules are formed that transfer energy in forms that the organism an use. Cellular respiration transfers hemial energy stored in the bonds of gluose and other moleules to. Analyze Identify the inputs and outputs of glyolysis and the two stages of ellular respiration. gluose eletrons arried in NAD pyruvate glyolysis Krebs yle eletrons arried in NAD and FAD 2 2 eletron transport hain FIGURE 8: The proess of glyolysis ours before the two main stages of ellular respiration: the Krebs yle and the eletron transport hain. mitohondrion C 2 2 Glyolysis and the Stages of Cellular Respiration Cellular respiration ours in mitohondria. Before it an take plae, however, gluose must be broken down into ompounds the mitohondria an use. This proess ours in the ytoplasm of the ell. Glyolysis, shown in Figure 9, is an anaerobi proess that uses a series of enzyme-atalyzed reations to break gluose into two three-arbon moleules, alled pyruvate. Mitohondria use the pyruvate moleules to fuel ellular respiration. FIGURE 9: Glyolysis ADP ADP gluose NAD + NAD 2 pyruvate Gather Evidene Summarize evidene that bonds are broken and new bonds are formed in glyolysis. Lesson 2 Cellular Respiration 133

7 Krebs Cyle The Krebs yle, sometimes alled the itri aid yle, is the first set of reations in ellular respiration. The funtion of the Krebs yle is to omplete the breakdown of gluose started in glyolysis and fuel the prodution of. This is done by transferring high-energy eletrons to the eletron transport hain. FIGURE 10: The Krebs Cyle 1 NAD + pyruvate NAD C 2 2 NAD CoA CoA Coenzyme A NAD + itri aid 3 FAD 2 C 2 FAD 6 ADP 4-arbon ompound 5-arbon ompound NAD + NAD 4 NAD NAD + C 2 5 The Krebs yle is summarized in the steps below. Analyze ow is the Krebs yle a bridge between the energy in sugars and energy-arrying moleules? 1. Pyruvate is broken down A 3-arbon pyruvate moleule is split into a 2-arbon moleule and a arbon dioxide moleule, whih is given off as waste. igh-energy eletrons are transferred to NAD +, forming a moleule of NAD. The NAD moves to the seond stage of ellular respiration, the eletron transport hain. 2. Coenzyme A is added A moleule alled oenzyme A bonds to the 2-arbon moleule, forming an intermediate moleule. 3. Citri aid is formed The 2-arbon part of the intermediate moleule is added to a 4-arbon moleule to form the 6-arbon moleule alled itri aid. 4. Citri aid is broken down The itri aid moleule is broken down by an enzyme, and a 5-arbon moleule is formed. A moleule of NAD is made, whih moves out of the Krebs yle. A moleule of arbon dioxide is given off as a waste produt. 5. Five-arbon moleule is broken down The 5-arbon moleule is broken down by an enzyme. A 4-arbon moleule, a moleule of NAD, and one are formed. Carbon dioxide is given off as a waste produt. 6. Four-arbon moleule is rearranged Enzymes rearrange the 4-arbon moleule, releasing high-energy eletrons. Moleules of NAD and FAD 2, another eletron arrier, are made. They leave the Krebs yle, and the 4-arbon moleule remains. Explain During the hands-on lab, whih produt of the Krebs yle aused the bromothymol blue solution to hange olor? 134 Unit 3 Matter and Energy in Living Systems

8 The Krebs yle is a ontinual series of reations. All the arbon atoms in gluose eventually end up as arbon dioxide, a waste produt expelled from the ell. The role of the eletron arriers NAD and FAD 2 is to transfer eletrons to the eletron transport hain in the next stage of respiration. The transferred eletrons will fuel the formation of. The Eletron Transport Chain The seond stage of ellular respiration, the eletron transport hain, uses proteins embedded in the inner membrane of the mitohondrion. It is similar to the eletron transport hain stage of photosynthesis. The energy arried by the NAD and FAD 2 moleules produed in the Krebs yle is used to make. A number of enzymes are involved in this proess. Model Make a simple flow hart to summarize the energy transfer from energyarrying moleules to. FIGURE 11: The Eletron Transport Chain eletron transport hain Explore nline synthesis intermembrane spae synthase inner membrane e- e- e- e- matrix NAD + NAD + FAD 2 FAD ½ 2 2 ADP + The eletron transport hain is summarized in the steps below. 1. Eletrons are transferred Proteins inside the inner membrane of the mitohondrion take high-energy eletrons from NAD and FAD ydrogen ions are transported igh-energy eletrons travel from protein to protein in the eletron transport hain. The proteins use energy from the eletrons to pump hydrogen ions aross the inner membrane to produe a gradient, just as in photosynthesis. The hydrogen ions build up in the intermembrane spae. 3. is produed Like in photosynthesis, the flow of hydrogen ions is used to make. ydrogen ions diffuse through a protein hannel in the inner membrane of the mitohondrion. The hannel is part of the synthase enzyme. synthase adds phosphate groups to ADP to make moleules. 4. Water is formed xygen piks up eletrons and hydrogen ions to form water. The water moleules are given off as a waste produt. Together, glyolysis and ellular respiration produe up to 38 moleules for every gluose moleule. Collaborate With a partner, disuss how the eletron transport hain depends on the Krebs yle. Consider the role of energy in your disussion. Lesson 2 Cellular Respiration 135

9 Fermentation Analyze What is the role of anaerobi respiration in organisms? What is the role in eosystems? FIGURE 13: Bifidobateria live in the digestive trats of animals, inluding humans. The ells in your body annot store large amounts of oxygen for ellular respiration. The amount of oxygen that is provided by breathing is enough for your ells during normal ativities. When you are doing high levels of ativity, suh as playing a game of basketball as shown in Figure 12, your body annot bring in enough oxygen for your ells, even though you breathe faster. ow do your ells funtion without oxygen to keep ellular respiration going? The prodution of without oxygen ontinues through the anaerobi proesses of glyolysis and fermentation. Fermentation does not make, but it allows glyolysis to ontinue. Fermentation removes eletrons from NAD moleules and reyles NAD + moleules for glyolysis. Why is this proess important? Beause glyolysis, just like ellular respiration, needs a moleule that piks up eletrons. It needs moleules of NAD +. The role of fermentation is simply to provide the proess of glyolysis with a steady supply of NAD +. If you ve ever felt your musles burn during hard exerise, that is a result of fermentation. Lati aid is a waste produt of fermentation that builds up in musle ells and auses that burning feeling. ne oxygen is available again, your ells return to using ellular respiration. The lati aid is quikly broken down and removed from the ells. FIGURE 12: During strenuous or prolonged ativity, athletes may not be able to sustain the oxygen levels their bodies need. If not enough oxygen is supplied to the ells, anaerobi respiration takes over. Not all organisms rely on oxygen for respiration. rganisms that use anaerobi respiration have an important role in an eosystem, beause they an live in plaes where most other organisms annot. For example, miroorganisms, suh as the bifidobateria shown in Figure 13, live in the digestive trats of animals and help in the proess of digestion. They must get their from anaerobi proesses beause oxygen is not available. Explain Summarize the evidene that you have gathered to explain how moleules are rearranged and energy is transferred in the proess of ellular respiration. 1. Cite evidene to support the laim that bonds are broken and new bonds are formed in eah stage of ellular respiration. 2. Explain how energy is transferred from the bonds of food moleules to ellular proesses. Image Credits: (r) MCMXCV/Larry Dale Gordon/ Image Bank/ Getty Images; (l) SCIMAT/Siene Soure 136 Unit 3 Matter and Energy in Living Systems

10 CNTINUE YUR EXPLRATIN ands-n Lab Aerobi and Anaerobi Proesses in Yeast The speies used in this investigation, Saharomyes erevisiae, like other speies of yeast, is a faultative anaerobe. It an break down sugars using either aerobi or anaerobi proesses, depending on the presene of oxygen. When oxygen is not present, yeast arry out ethanol fermentation. This proess produes arbon dioxide and ethanol, a type of alohol. FIGURE 14: Yeast are singleelled organisms that belong to the group of organisms alled fungi. Predit ow will you know whether aerobi or anaerobi proesses are ourring in the bottle? SAFETY btain and wear goggles for this lab. Do not eat any materials used in this lab. PRCEDURE 1. Blow up the balloon a few times to streth it. 2. Using the funnel, pour 150 ml of warm water into the bottle. Dry the funnel. 3. Using the dry funnel, add 1 paket of yeast to the water. Swirl the mixture gently. 4. Using the funnel, add 1 tablespoon (12 g) of sugar to the yeast solution, swirl, and quikly over the bottle with the balloon. Allow the mixture to reat for 5 minutes. 5. After 5 minutes have passed, use the string, marker, and ruler to measure the irumferene of the balloon. 6. In a data table, reord the irumferene of the balloon, along with all of your observations of what is happening in the bottle. Continue making and reording observations every 5 minutes for the next 30 minutes. 7. Dispose of waste aording to your teaher s instrutions. MATERIALS ative dry yeast (1 pakage) balane (optional) balloon, round funnel graduated ylinder marker ruler, metri string, 30 m sugar, granulated tablespoon (optional) Image Credits: Andrew Syred/Siene Soure ANALYZE 1. Desribe evidene, if any, that aerobi respiration took plae in the bottle. 2. ow does matter yle during aerobi respiration? Explain how the reatants are rearranged to form the produts. What is the soure of energy, how is the energy transferred, and how is it used in the ell? 3. Desribe evidene, if any, that fermentation took plae in the bottle. 4. ow does matter yle during fermentation? Explain how the reatants are rearranged to form the produts. What is the soure of energy, how is the energy transferred, and how is it used in the ell? EVIDENCE FR ENDSYMBISIS INVESTIGATING PTSYNTESIS AND CELLULAR RESPIRATIN timer water, very warm (40 C) water bottle, plasti, 500 ml weighing boat (optional) Go online to hoose one of these other paths. Lesson 2 Cellular Respiration 137

11 EVALUATE Lesson Self-Chek CAN YU EXPLAIN IT? FIGURE 15: Beause ethanol burns more leanly than gasoline, Explore nline it is added to gasoline to help redue the emission of greenhouse gases produed by ombustion engines in ars. Like gasoline, ethanol ontains energy in its hemial bonds that an be released by the proess of ombustion. Combustion and ellular respiration are both exothermi reations that result in the release of energy. The energy is released when hemial bonds that store energy are broken. Combustion is a fast proess that results in the prodution of energy in the forms of heat and light. C 3 C C heat In ontrast, ellular respiration is a slow proess, with energy being released over a series of several steps. This makes energy available for use whenever ells of the body need it to arry out ellular ativities. C C heat + Explain A sientist named Antoine Lavoisier demonstrated that ellular respiration is a ombustion proess. Reall that ar engines use a ombustion reation to release energy. Construt an explanation for how the breakdown of fuel in a ar engine ompares to the breakdown of fuel in your body s ells. Answer the following questions: 1. Look arefully at the equations for both ombustion and ellular respiration, and ompare the inputs and outputs. ow an the different inputs result in the same outputs based on what you know about hemial bonds and atoms? 2. What is missing from the proess of ombustion that makes it an imperfet model for ellular respiration? Explain your answer. Image Credits: oughton Mifflin arourt 138 Unit 3 Matter and Energy in Living Systems

12 CECKPINTS Chek Your Understanding 1. ow does arbon flow between photosynthesis and ellular respiration? a. Photosynthesis produes arbon dioxide from gluose generated by the proess of ellular respiration. b. Cellular respiration produes arbon dioxide from gluose generated by the proess of photosynthesis.. Photosynthesis produes arbon dioxide from generated by the proess of ellular respiration. d. Cellular respiration produes arbon dioxide from generated by the proess of photosynthesis. 2. Whih of the following are the main inputs, or reatants, in ellular respiration? Selet all orret answers. a. pyruvate b. gluose. arbon dioxide d. oxygen 3. Whih of the following are the main outputs, or produts, of ellular respiration? Selet all orret answers. a. water b. energy. oxygen d. arbon dioxide 4. Before ellular respiration, gluose must be broken down by the proess of a. photosynthesis. b. glyolysis.. eletron transport. d. fermentation. 5. During whih proess is lati aid formed when there is not enough oxygen present for ellular respiration to take plae? a. fermentation b. glyolysis. Calvin yle d. Krebs yle 6. Use the following terms to omplete the statement:, ellular respiration, eletron transport hain, glyolysis, Krebs yle, photosynthesis Living things require energy to grow and reprodue and to arry out different ell proesses. Certain ells an apture energy from the sun through the proess of. Through a series of reations, that energy is transferred to organisms. Through the proess of, the energy urreny of the ell,, is produed. This is a three-part proess, beginning with in the ell ytoplasm and proeeding within the mitohondrion with the and, finally, the. 7. ow do you know that energy and matter are onserved during the proess of ellular respiration? Explain. 8. Energy is transferred in several different ways during the proess of ellular respiration. Give two examples of ways that energy is transferred during this proess. 9. Is oxygen neessary for the prodution of in your ells? Why or why not? 10. ow are photosynthesis and ellular respiration related? MAKE YUR WN STUDY GUIDE In your Evidene Notebook, design a study guide that supports the main idea from this lesson: Cellular respiration is a proess that breaks down food moleules to release energy to fuel ellular proesses in organisms. Remember to inlude the following information in your study guide: Use examples that model main ideas. Reord explanations for the phenomena you investigated. Use evidene to support your explanations. Your support an inlude drawings, data, graphs, laboratory onlusions, and other evidene reorded throughout the lesson. Consider how moleules are rearranged and energy is transferred during the proess of ellular respiration. Lesson 2 Cellular Respiration 139