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1 Teacher Ntes fr "Hw d muscles get the energy they need fr athletic activity?" 1 In this activity, students analyze hw aerbic cellular respiratin and anaerbic fermentatin cntribute t ATP prductin in muscle cells during different types f athletic activity. In additin, students gain understanding f general principles such as the cnservatin f energy and the imprtance f interactins between bdy systems t accmplish functins such as supplying the energy that muscles need fr physical activity. Students apply this knwledge t an analysis f hw the training effects f regular aerbic exercise cntribute t an increase in muscle cells capacity fr aerbic respiratin. Learning Gals In accrd with the Next Generatin Science Standards 2, this activity: helps students t learn the Disciplinary Cre Ideas: LS1.C, "Cellular respiratin is a chemical prcess whereby the bnds f fd mlecules and xygen mlecules are brken, carbn dixide and water are frmed, and the energy released is used in the prductin f ATP frm ADP and P. Then, the hydrlysis f ATP mlecules prvides the energy needed fr many bilgical prcesses. LS2.B, "Phtsynthesis and cellular respiratin (including anaerbic prcesses) prvide mst f the energy fr life prcesses." LS1.A, "Multicellular rganisms have a hierarchical structural rganizatin, in which any ne system is made up f numerus parts and is itself a cmpnent f the next level." engages students in recmmended Scientific Practices, including cnstructing explanatins and arguing frm evidence illustrates the Crsscutting Cncept, Energy and matter: Flws, cycles and cnservatin, including Energy cannt be created r destryed nly mves between ne place and anther place, between bjects and/r fields, r between systems. helps students t prepare fr Perfrmance Expectatins: HS-LS1-7, "Use a mdel t illustrate that cellular respiratin is a chemical prcess whereby the bnds f fd mlecules and xygen mlecules are brken and the bnds in new cmpunds are frmed resulting in a net transfer f energy." HS-LS2-3, "Cnstruct and revise an explanatin based n evidence fr the cycling f matter and flw f energy in aerbic and anaerbic cnditins." HS-LS1-2, "Develp and use a mdel t illustrate the hierarchical rganizatin f interacting systems that prvide specific functins within multicellular rganisms." Instructinal Suggestins and Backgrund Infrmatin Befre beginning this activity, students shuld have a basic understanding f cellular respiratin and the imprtance f ATP. Fr this purpse, I recmmend ur analysis and discussin activity "Hw d bilgical rganisms use energy?" ( T maximize student participatin and learning, I suggest that yu have yur students wrk in pairs (r individually r in grups f three) t cmplete grups f related questins and then have a class discussin after each grup f related questins. In each discussin, yu can prbe student thinking and help them t develp a sund understanding f the cncepts and infrmatin cvered befre mving n t the next grup f related questins. 1 By Dr. Ingrid Waldrn, Department f Bilgy University f Pennsylvania, These Teacher Ntes and the Student Handut are available at 2

2 The PDF f the Student Handut shws the crrect frmat, s yu will want t cnsult the PDF if yu use the wrd file t make revisins. A key fr this activity is available upn request t Ingrid Waldrn (iwaldrn@sas.upenn.edu). The fllwing paragraphs prvide additinal instructinal suggestins and backgrund infrmatin fr yur interest and pssible use in class discussins. This activity fcuses n energy metablism in skeletal muscle in humans. The fllwing figure illustrates the rle f ATP in muscle cntractin. ( ) Althugh this activity fcuses n the prductin and use f ATP during muscle cntractin, students shuld be aware that all f ur cells are cnstantly using cellular respiratin f rganic mlecules like glucse t make ATP and using hydrlysis f ATP t prvide the energy fr bilgical prcesses such as synthesizing mlecules, pumping ins int and ut f cells, and mving mlecules within cells. On average, each ATP mlecule in ur bdy is used and resynthesized mre than 30 times per minute when a persn is at rest and mre than 500 times per minute during strenuus exercise. The cnstant mlecular activity within bdy cells and cnstant changes within ur bdies can be illustrated using: the figure n page 1 f the Student Handut that shws the cnstant breakdwn and resynthesis f ATP the repeated breakdwn and resynthesis f glycgen (shwn n the tp f page 3 f the Student Handut) 2

3 questin 9 cncerning training effects, and questin 13 cncerning recvery prcesses. Bth anaerbic fermentatin and aerbic respiratin begin with glyclysis, when glucse breaks dwn t 2 pyruvate and prduces 2 ATP. (See tp part f this figure and left part f the figure n the next page.) ( In the prcess f glyclysis, NAD+ is reduced t NADH. Fr glyclysis t cntinue, NADH must be xidized back t NAD+. When O2 is available as an electrn acceptr, NADH enters the electrn transprt chain and is xidized t NAD+ in a prcess that cntributes t the prductin f ATP (as part f aerbic respiratin). When O2 is nt available, the pyruvate prduced by glyclysis reacts with NADH t prduce lactate (lactic acid) and NAD+ (in anaerbic fermentatin). Eventually, lactate can be used t prduce ATP, either when lactate is used by heart muscle cells as input fr aerbic respiratin r when lactate is cnverted back t glucse which can underg aerbic respiratin (see questin 13). Sme rganisms use a slightly different type f anaerbic fermentatin that prduces ethanl; see e.g. ur hands-n activity "Alchlic Fermentatin in Yeast" ( The figure n the next page f these Teacher Ntes summarizes the multiple steps f aerbic respiratin (als knwn as cellular respiratin); bviusly, many specific steps are mitted. Ntice that O2 des nt interact directly with glucse, but rather cmbines with an electrn and H+ at the end f the electrn transprt chain t frm water. Ntice als that aerbic respiratin generates ~29 mlecules f ATP fr each glucse mlecule; this number is less than previusly believed (and still ften errneusly stated in textbks). Brief explanatins are prvided in: "Cellular Respiratin and Phtsynthesis Imprtant Cncepts, cmmn Miscnceptins, and Learning Activities" (available at "Apprximate Yield f ATP frm Glucse, Designed by Dnald Nichlsn" by Brand, 2003, Bichemistry and Mlecular Bilgy Educatin 31:2-4 (available at These recent findings are interesting as an example f hw science prgresses by a series f successively mre accurate apprximatins t the truth. 3

(Frm "Bilgical Science" by Sctt Freeman, Benjamin Cummings, 2011) Creatine phsphate (als called phsphcreatine) can be used t make ATP during muscle cntractin (shwn n page 2 f the Student Handut).

4 (Frm "Bilgical Science" by Sctt Freeman, Benjamin Cummings, 2011) Creatine phsphate (als called phsphcreatine) can be used t make ATP during muscle cntractin (shwn n page 2 f the Student Handut). After muscle cntractin, ATP prduced by cellular respiratin is used t reverse these reactins and restre the muscle cell s creatine phsphate supply. Muscle cells have extreme increases in metablic demands, with up t 100 fld increases in the rate f hydrlysis f ATP when the muscles are active. Therefre, it is nt surprising that skeletal muscles cntain mst f the bdy s creatine phsphate (~95% f the ttal bdy creatine). Meat and fish prvide dietary surces f creatine. Use f ral creatine supplements can lead t increased creatine in skeletal muscles and ~10-15% imprvement in perfrmance in brief high-intensity athletic events; use f these supplements can als cntribute t imprved perfrmance in intermittent high-intensity sprts. Use f creatine supplements that d nt have cntaminants des nt appear t result in serius side effects, althugh weight gain (mainly lean bdy mass) is cmmn. ( ) Questin 6 prvides the pprtunity t emphasize the cnservatin f energy. Questin 7 reinfrces the imprtant pint that all types f energy transfrmatin are inefficient and result in the prductin f heat. The discussin f hw the muscles get glucse n page 3 f the Student Handut prvides the pprtunity t reinfrce the imprtant pint that interactins between bdy systems are imprtant fr accmplishing the activities f life. There is a relatively limited supply f glycgen in skeletal muscle (enugh fr less than an hur f mderate intensity activity). A slightly larger amunt f energy is available frm the fat in muscles. In cmparisn, there is three times as much glycgen in the liver and rughly 20 times as much fat in adipse tissue. Depletin f glycgen within skeletal muscles is assciated with fatigue, s it is imprtant t reduce the rate f utilizatin f muscle glycgen by having external surces f glucse fr aerbic respiratin in the muscle cells. In this cnnectin, yu may be interested in the evidence that carbhydrate ingestin befre and during endurance events lasting lnger than an hur can help t prevent fatigue and imprve perfrmance (see "Carbhydrate Cnsumptin, Athletic Perfrmance and Health Using Science Prcess Skills t Understand the Evidence"; In cntrast, cnsumptin f fats immediately befre r during athletic cmpetitins is nt recmmended, because lng chain fatty 4

acids take t lng t digest and medium chain fatty acids cause gastrintestinal distress when cnsumed in sufficient quantity t prvide significant energy.

5 acids take t lng t digest and medium chain fatty acids cause gastrintestinal distress when cnsumed in sufficient quantity t prvide significant energy. Fat mlecules are brken dwn t fatty acids (and glycerl) which muscle cells can use fr aerbic respiratin. Aerbic respiratin f fatty acids is especially imprtant fr lnger duratin, lw intensity r mderately vigrus physical activity. Fr high-intensity physical activity, the supply f O2 t the muscle is limiting, s muscle cells reduce aerbic respiratin f fatty acids which requires mre O2 per ATP mlecule prduced than aerbic respiratin f glucse. Fatty acids cannt be used fr anaerbic fermentatin; they are cnverted t Acetyl CA and enter the citric acid cycle in the mitchndria (after glyclysis). It appears that neither amin acids nr nucleic acids are a significant input fr aerbic respiratin in well-nurished individuals. ( Yu may want t relate aerbic respiratin f fatty acids t the cntributin f aerbic exercise t weight lss (r preventin f weight gain; see "Fd, Energy and Bdy Weight"; During weight lss, it appears that resistance exercise can help t ensure that lean bdy mass (including muscles) is maintained while adipse tissue mass is reduced; this is desirable fr bth health and athletic cmpetitin. 5

Increased capacity fr aerbic respiratin reduces the need fr anaerbic fermentatin; this cnserves glycgen stres and prevents the prductin f lactic acid, thus delaying fatigue and increasing endurance.

6 Training effects f regular aerbic exercise cntribute t increased capacity fr aerbic respiratin in muscle cells. Increased capacity fr aerbic respiratin imprves athletic perfrmance, especially in sprts that rely primarily n aerbic respiratin (e.g. lnger running, swimming, r bicycling races). Increased capacity fr aerbic respiratin reduces the need fr anaerbic fermentatin; this cnserves glycgen stres and prevents the prductin f lactic acid, thus delaying fatigue and increasing endurance. Other effects f regular aerbic exercise include increased bld vlume, strke vlume and maximum breathing capacity, and strnger bnes. There are multiple additinal effects f training which cntribute t bth imprved athletic perfrmance and health. Mre infrmatin n the effects f training, as well as are mre infrmatin n the cmplexities f energy metablism, is available in "The Surgen General's Reprt n Physical Activity and Health" ( Creatine phsphate, anaerbic fermentatin and aerbic respiratin all cntribute t ATP prductin during any physical activity, but the relative cntributins vary substantially ver time and between different types f physical activity. Fr high-intensity brief events, the supply f ATP is heavily dependent n the hydrlysis f creatine phsphate and anaerbic fermentatin which can supply ATP very rapidly and d nt require O2; when the intensity f muscle activity is very high, the rate f ATP use exceeds the capacity f the circulatry system t supply the muscles with O2 fr aerbic respiratin. Hwever, bth the hydrlysis f creatine phsphate and anaerbic fermentatin are limited t relatively shrt time perids, and aerbic respiratin is the primary energy surce after a minute r tw. PC = Phsphcreatine = Creatine phsphate = Anaerbic Fermentatin = Aerbic Respiratin ( Many sprts invlve intermittent high-intensity activity which depends n creatine phsphate and anaerbic fermentatin fr rapid supply f ATP. During the intervals between these bursts f high-intensity activity, aerbic respiratin prduces ATP which can be used t restre the supply f creatine phsphate. Lactate prduced by alchlic fermentatin is mainly secreted int the bld and carried t the liver (where it is cnverted back t pyruvate r glucse) and the heart (where it is used in aerbic respiratin). These rapid recvery prcesses are smewhat similar t the mre lng-term recvery prcesses after a marathn, as discussed in questin 13. 6

7 Pssible Extensin Activity If yur students have questins abut ther aspects f energy metablism and athletic activity, yu may want t encurage them t investigate these questins and engage in the NGSSrecmmended science practices f "asking questins" and "btaining, evaluating, and cmmunicating infrmatin". Pssible surces include thse already referred t in these Teacher Ntes, ther nline surces, and physilgy textbks. If yur students are unfamiliar with hw t evaluate the reliability f varius surces, this imprtant skill can be intrduced with resurces available at and Related Learning Activities "Cellular Respiratin and Phtsynthesis Imprtant Cncepts, Cmmn Miscnceptins, and Learning Activities" ( "Alchlic Fermentatin in Yeast A Biengineering Design Challenge" ( "Shuld yu drink sprts drinks? When? Why?" ( 7

Module 3. Chapter 5 Microbial Metabolism. Catabolic and Anabolic Reactions Metabolism Two general types of metabolic reactions: o :

Module 3. Chapter 5 Microbial Metabolism. Catabolic and Anabolic Reactions Metabolism Two general types of metabolic reactions: o : Mdule 3 Chapter 5 Micrbial Metablism Catablic and Anablic Reactins Metablism Tw general types f metablic reactins: : : Recall frm Chapter 2: Energy can be when bnds Energy can be when bnds Catablism Purpse